Telecommunications Mobile Tower BTS, Microwave Radio Site, Edge Data Centre, Exchange, NBN POI & Submarine Cable Landing Station HVAC Duct Guide

Why this guide collects every telecommunications built-form into one reference

From the SBKJ Group office in Box Hill North, Victoria, we look at the Australian telecommunications HVAC market as a single ecosystem rather than a stack of separate verticals. A fabricator supplying ductwork to an Amplitel BTS rollout this quarter will be supplying ductwork to a NEXTDC edge node next quarter, an NBN POI room the quarter after that and a Telstra exchange refurbishment in the same calendar year. The customers are different, the rack densities are different, the standards overlays are different, but the underlying duct fabrication is one body of work that responds to one capital investment in machinery, one trained workforce and one quality system. The engineer who understands the full telecommunications built-form quotes faster, fabricates with less rework and wins more competitive tenders than the engineer who treats each room type as a brand-new problem.

This guide is the engineering reference our team uses when an Australian fabricator asks us how a single SBKJ machine fleet covers the spread — a 6 kW BTS hut in regional Victoria, a 1.5 MW edge data centre node in metro Sydney, a 50 MW carrier hotel in Macquarie Park, a 600-rack NBN POI in Brisbane, and a 200-square-metre submarine cable landing station on the Western Australian coast feeding the Indian Ocean. The technical content covers each built-form in turn, the standards overlay that applies to it, the duct material selection that survives the local atmospheric environment, and the SBKJ machine configuration that produces the duct package profitably. The commercial content covers the operator landscape — Telstra, Optus, TPG Telecom, the three TowerCos, NBN Co, the five major carrier-neutral data centre operators, the submarine cable consortia — and the procurement reality of bidding into each customer.

The Australian telecommunications landscape in 2026

Before the engineering, a quick map of the operators. The Australian telecommunications market sits on three layers of infrastructure ownership — active radio and core network, passive towers and built-form, and the data centre and submarine cable layer that connects everything to the outside world.

Mobile carriers

Three carriers operate active radio infrastructure across the continent. Telstra Group (ASX:TLS) is the largest, with the deepest regional footprint, the highest macro-cell count and the largest installed base of legacy copper and fibre exchange buildings of any operator anywhere in the Southern Hemisphere. Telstra's passive tower portfolio sits in Amplitel, a separately incorporated subsidiary in which Brookfield Asset Management and the Canada Pension Plan Investment Board together hold 49 percent. Amplitel manages more than 16,000 active sites across Australia. Optus, owned by Singapore Telecommunications, operates the second-largest network from its Sydney headquarters with roughly 9,000 active sites; its tower portfolio was divested to Indara Digital Infrastructure, which now consolidates the former Stilmark, APT, Crown Castle Australia and ANZ Stadium Tower assets and the ATC (American Tower Corporation) Australian portfolio. TPG Telecom (ASX:TPG), formed from the 2020 merger of Vodafone Hutchison Australia and TPG, operates the third active network from Sydney with around 7,000 sites and retains the iiNet retail brand inside the same corporate group. Network sharing arrangements between Telstra and TPG cover meaningful slices of regional and outer-suburban coverage.

Tower companies

Australian passive tower infrastructure has consolidated into a TowerCo layer that sits between the network operators and the local civil contractors. Amplitel holds the Telstra-derived portfolio, the largest single tower owner in the country. Indara Digital Infrastructure holds the Optus-derived portfolio and the legacy Crown Castle Australia portfolio sold by Crown Castle International in 2023 to Brookfield and OMERS, plus the former Axicom and APT portfolios. Broadcast Australia (BAI) retains the broadcasting transmission portfolio with growing mobile co-tenancy. Together these three TowerCos own the great majority of macro-cell tower assets on the continent; the HVAC ductwork specification a fabricator builds against is increasingly written by the TowerCo rather than the active operator, harmonised across multiple tenants, calibrated to the most demanding tenant's environmental envelope.

NBN Co and the Points of Interconnect

NBN Co Limited — the Federal Government corporation that built and operates the National Broadband Network — is the single largest telecommunications infrastructure deployment in Australian history and the single largest customer for telecommunications-grade HVAC ductwork in the country over the past 15 years. The NBN architecture is anchored on 121 Points of Interconnect (POIs) distributed across the continent, with every retail service provider connecting to NBN at the nearest POI to deliver service into its end customers. Each POI is a purpose-built telecommunications room within a Telstra or commercial exchange building, hosting optical transmission equipment, fibre splitters and the cross-connect infrastructure that hands off traffic between NBN and the carriers. POI rooms vary in size from a single rack inside a regional Telstra exchange to dozens of racks in the major metropolitan exchanges. The HVAC envelope is mid-tier telecommunications grade — 22 to 24 degrees Celsius dry bulb, 40 to 60 percent relative humidity, N+1 cooling redundancy, dedicated outdoor air to AS 1668.2 and 24/7 alarm monitoring.

Telecommunications exchange buildings

The Australian exchange building stock is a legacy of more than a century of telecommunications infrastructure investment. Telstra Exchange buildings — numbered in the thousands, distributed across every metropolitan, regional and rural population centre — host copper, hybrid fibre-coax, fibre-to-the-node, full fibre, 4G core, 5G core, business-grade services, NBN POI tenancy and an increasing population of edge computing nodes co-located with the existing telecommunications plant. The major metro exchanges — the Lonsdale Exchange in Melbourne, the Pitt Street Exchange in Sydney, the Wickham Exchange in Brisbane — are multi-storey purpose-built telecommunications buildings with 24/7 N+1 redundancy on every mechanical, electrical and security subsystem. Optus retains a smaller exchange footprint focused on metropolitan and major regional centres. TPG consolidates the legacy Optus, Vodafone and iPrimus exchange holdings. The HVAC ductwork market across the exchange estate is large and steady — refurbishment, capacity uplift and equipment retrofit drive continuous installation work that runs alongside the new-build rollout.

Data centres — the telecommunications-adjacent layer

Although technically a separate market with its own engineering canon (covered in data centre HVAC duct manufacturing and Australia data centre HVAC and AS/NZS 4254), the Australian carrier-neutral data centre operators sit so close to the telecommunications layer that the HVAC fabrication overlap is substantial. NEXTDC (ASX:NXT), the largest Australian-owned data centre operator, runs facilities across Sydney (SY1, SY2, SY3, SY4), Melbourne (M1, M2, M3, M4), Perth (PE1, PE2, PE3), Brisbane (B1, B2), Canberra (C1) and Adelaide (AD1), with a growing edge data centre programme at sub-3 MW IT load served from regional centres. Equinix, the Singapore-international operator, runs Sydney SY1, SY2, SY4, SY6, Melbourne ME1, ME2, Perth PE1, PE2 with strong carrier-neutral interconnect density. AirTrunk, the Singapore-headquartered hyperscale specialist, runs Sydney SYD1, SYD2, Melbourne MEL1, MEL2 with the largest single-site IT load in the country. DCI Data Centers, the Toronto-headquartered operator, runs Sydney SYD1, SYD2. Macquarie Telecom runs an established carrier-neutral colocation portfolio across Sydney, Melbourne, Brisbane, Canberra, Perth and Adelaide.

Beyond the majors, the edge and regional layer hosts iSEEK Communications in Brisbane edge, HostCo in Sydney, ICEdrop in Adelaide, Pacific Data Centres in Brisbane, Australian Data Centre in Brisbane and StackCT in Canberra serving Federal Government cloud workloads under the Hosting Certification Framework. The hyperscale customer layer — AWS Sydney, AWS Melbourne, Microsoft Azure Sydney, Microsoft Azure Melbourne, Google Cloud Sydney — sits inside leased capacity within the operator portfolios and drives the bulk of new-build capex.

Submarine cable landing stations

The Australian submarine cable landing station population is small in absolute count — fewer than 30 active terrestrial landings — but unusually demanding in technical specification because each landing station terminates one or more international fibre cables carrying tens of terabits per second of traffic that cannot be re-routed within Australia in the event of failure. The major cable systems active or recently commissioned in 2026 are the Pacific Light Cable Network (Telstra Subsea and consortium partners, Australia-United States), Indigo Central and Indigo West (Vocus, Google and Subsea Networks JV, Perth-Singapore-Indonesia and Sydney-Perth domestic), the Australia-Singapore Cable (Vocus), the Telstra Global Network TGN-W and TGN-S (Perth-South Africa and Sydney-United States via Asia), the Hawaiki Submarine Cable (BW Group, Sydney-Auckland-Pacific-United States), the Coral Sea Cable System (Australian Government funded, Papua New Guinea-Solomon Islands), the Bifrost Cable System (Telstra and Indosat consortium, Singapore-Australia-United States, commissioned 2024), the SEA-ME-WE-3 and SEA-ME-WE-5 international consortium cables with Perth landings, the Australia-Japan Cable (AJC) and the Papua New Guinea Telco landings. The major Australian landings cluster around Sydney (Tamarama, Bondi), Perth (Two Rocks, Mullaloo), Brisbane (Maroochydore) and the Northern Territory (Darwin), with smaller landings on the Western Australian coast feeding Asian routes.

Industry bodies and the regulatory layer

The Australian telecommunications regulatory and standards layer is anchored on the Australian Communications and Media Authority (ACMA), which administers the Carrier Class facility standards and the Carriage Service Provider reliability requirements that apply to operators of declared facilities. The Communications Alliance is the telecommunications industry peak body. The Telecommunications Industry Ombudsman (TIO) handles consumer-grade dispute resolution. The Mobile Carriers Forum and the Australian Information Industry Association (AIIA) are the major industry consultations bodies for new-build standards and procurement frameworks. For Federal Government clients, the Digital Transformation Agency (DTA) administers the Hosting Certification Framework with three tiers — Certified (general government workload), Assured (sensitive workload, security overlay) and Strategic (most sensitive workload, ASIO T4 Protective Security policy overlay). HVAC ductwork that crosses a HCF Strategic security compartment line has substantially heavier construction, testing and documentation requirements than commercial colocation. The Box Hill North office maintains current familiarity with each regulatory layer because we quote into all of them in any given quarter.

The applicable Australian standards canon

The Australian standards canon that governs HVAC ductwork across the telecommunications-adjacent built-form spectrum sits on top of the National Construction Code and pulls in references from the AS, AS/NZS, ASHRAE and international standard families. The design that passes audit applies the strictest envelope from each family.

AS 1668.2 — mechanical ventilation in buildings

AS 1668.2 is the foundation Australian standard for outdoor-air ventilation rates by occupancy category. For a telecommunications exchange the equipment room attracts the machinery-room category rate (a low base for unmanned spaces, raised significantly when staffed for maintenance), the battery room attracts a higher dedicated rate driven by hydrogen dispersion calculation, the generator room follows the diesel-engine combustion-air rate from manufacturer plus the standard human-occupancy supplement, and the office or NOC areas attract the commercial-occupancy rate of 7.5 litres per second per person. Edge data centre and carrier hotel rooms typically attract the same machinery-room category, with raised supplementary outdoor air when the room is occupied by maintenance staff. The detail of the standard is unpacked at HVAC commissioning and air balancing.

AS 4254 — ductwork construction

AS 4254 is the binding Australian ductwork construction standard. Part 1 covers low-pressure ductwork below 500 Pa, which is the great majority of telecommunications HVAC. Part 2 covers high-pressure ductwork above 500 Pa, which is found in large carrier hotels and the trunk segments of major hyperscale builds. The standard prescribes sheet-metal gauge tables by duct width and pressure class, reinforcement spacing, seam construction, flange types, support spacing and acceptance leakage class. Australian leakage classes A (tightest), B and C (loosest) align with the AS/NZS framework; SMACNA classes are often referenced by US-led hyperscale operators on Australian builds (AWS, Microsoft Azure, Google Cloud) and the fabricator builds to the tighter of the two specifications. The standards comparison is at international duct standards compared.

AS 1530.4 — fire-rated construction

AS 1530.4 governs fire-resistance testing for elements of building construction including ductwork. Any duct crossing a fire-resistant compartment line — the UPS room boundary, the generator room boundary, the gaseous fire suppression integrity envelope, the security compartment line in an HCF Strategic facility — receives a tested and certified fire-rated construction at the crossing. The default solution is standard galvanised duct wrapped with fire-rated insulation board (Promat 25 or 50 mm board, Cafco K150 spray or 3M Interam wrap) at the penetration point, with the wrap rated to AS 1530.4 for the required fire-resistance level (FRL) of the compartment — typically 60/60/60 or 90/90/90 minutes for telecommunications buildings. Fire-rated duct sections that pass through compartment lines require certified penetration seals and AS 1851-compliant fire dampers; the integration is unpacked at fire and smoke damper HVAC duct integration.

AS 4072.1 and AS 4072.3 — service penetrations through fire barriers

AS 4072.1 sets the service penetration test requirements for fire-resistant compartment lines. AS 4072.3 covers smoke-control penetrations specifically. The pair drive the intumescent fire-and-smoke barrier assemblies used at duct penetrations — collared intumescent strips, mortar-filled penetration seals and pillows for cable trays running alongside duct. Hosting Certification Framework Strategic facilities typically require certified penetration seals at every security compartment crossing, with the seal traceable to the original AS 4072.1 test certificate.

AS 1530.4 fire damper combined with AS 1851 — routine service

AS 1851 sets the routine inspection and service intervals for fire-protection systems including fire dampers. Telecommunications facility operators with declared ACMA Carrier Class status maintain an AS 1851 service register on every fire damper in the building, with quarterly visual inspections and annual functional tests. The duct fabricator's role is to supply fire dampers with commissionable reset access — meaning the damper actuator and reset mechanism are accessible from inside the protected envelope without breaking the duct seal.

AS 1657 — access platforms

AS 1657 governs fixed platforms, walkways, stairways and ladders for safe access to equipment. The standard is invoked wherever HVAC equipment requires routine inspection or service from elevated position — rooftop economiser plants, gantry-mounted CRAH units, ceiling-void supply duct. The fabricator builds duct that integrates with the AS 1657 access platforms without obstructing routine service paths.

AS 4214 — gaseous fire suppression

AS 4214 is the binding Australian standard for gaseous fire-extinguishing systems — FM-200 (HFC-227ea), Novec 1230 (FK-5-1-12), INERGEN (IG-541), Argonite (IG-55) and the carbon dioxide systems still occasionally found on legacy installations. Almost every Australian telecommunications exchange, edge data centre and submarine cable landing station equipment room is protected by a gaseous suppression system rather than wet sprinkler. The standard prescribes the design concentration, the discharge time, the soaking time and the room integrity test (the pressure-decay test that verifies the protected room holds the suppression agent at design concentration for the required hold time). HVAC ductwork plays a structural role in passing the integrity test — every duct entering or leaving the protected room receives an automatic gas-tight damper that closes on suppression activation, preventing agent dilution and re-flash through the duct path. The damper specification is gas-tight at AS 4214 integrity-test pressure, which is substantially higher than the routine fire-damper class.

AS 2118 — wet sprinkler systems

AS 2118 applies to wet sprinkler systems and is rare in telecommunications equipment rooms but ubiquitous in the office, corridor and amenity spaces of telecommunications facilities. Where sprinkler is fitted in an equipment room, the design is typically pre-action (the pipework is dry, with the head requiring both heat-detector activation and individual head activation before water release) to prevent accidental discharge onto live electronic equipment. The ductwork interface is the smoke-detector and aspirating smoke detection (VESDA) system integration, which often runs in parallel with the supply duct.

AS/NZS 60079 — explosive atmospheres

AS/NZS 60079 is the binding Australian standard for hazardous-area classification and equipment selection. The standard applies in two places inside a typical telecommunications facility — the diesel generator room and the lead-acid battery room. Inside the generator room, the area immediately around the day-tank or fuel piping where diesel vapour may accumulate is classified Zone 2 for the duration of any leak event; the duct-mounted extract fans serving this zone require ATEX-rated or AS/NZS 60079-compatible motors and spark-resistant centrifugal fan housings. Inside the lead-acid battery room, the volume immediately above the cell bank where hydrogen accumulates during overcharge is classified Zone 2; the dedicated battery exhaust duct serves this zone, the extract fan runs continuously, and the fan motor is again spark-resistant. The standard also applies in a residual sense to the diesel fuel storage compound, where AS 1940 takes the lead for the storage itself.

AS 1940 — flammable and combustible liquids

AS 1940 governs the storage and handling of flammable and combustible liquids, including the bulk diesel storage that serves backup generators at every Australian telecommunications exchange, edge data centre, NBN POI and submarine cable landing station. The storage compound is a separate hazardous-area envelope with its own ventilation requirements, drainage to oil-water separator and Zone classification.

AS 4036 and AS 4037 — pressure vessels for generators

AS 4036 and AS 4037 govern the design, testing and routine service of pressure vessels associated with generator installations — the surge tank in the radiator coolant circuit, the compressed-air starter air receiver, the lubricating oil reservoir. These are not strictly HVAC ducts, but the duct fabricator who supplies the generator-room ductwork understands the AS 4036/AS 4037 layout because the pressure vessels share the same generator-room space and the same maintenance access plan.

AS 3008 — electrical wiring

AS 3008 sets cable sizing and selection for electrical wiring. The standard applies to the cable runs that power the HVAC plant, the cable runs that connect the HVAC controllers to the building management system and the cable runs that connect the supply-temperature, return-temperature and humidity sensors back to the controller. The duct fabricator's interface is the cable tray layout that shares the ceiling void with the HVAC supply and return ducts — the trays are coordinated with the duct routing so the cables do not interfere with duct service access.

ASHRAE Standard 90.4 — datacom energy efficiency

ASHRAE Standard 90.4, first published in 2016 and now in regular revision, is the dedicated energy-efficiency standard for data centre and telecommunications-equivalent facilities. It overlays ASHRAE 90.1 (the general commercial building energy standard) with datacom-specific provisions on mechanical load component, electrical loss component and total annualised Power Usage Effectiveness (PUE). Where a NABERS Data Centre or Green Star Data Centre rating is targeted, ASHRAE 90.4 is the de facto engineering reference for the mechanical design. HVAC ductwork plays directly into the energy efficiency through the air-side economiser fraction, the fan-power efficiency (which scales as a cube of duct velocity), the leakage class (which scales linearly with annual recirculation loss) and the temperature reset strategy.

ASHRAE TC 9.9 — thermal guidelines for datacom

ASHRAE TC 9.9 Technical Committee 9.9 publishes the canonical Thermal Guidelines for Data Processing Environments, now in its fourth or fifth edition depending on the equipment vendor reference date. The four classes A1 through A4 widen progressively. Class A2 (18 to 27 degrees Celsius inlet, 30 to 70 percent RH, 21-degree dew point ceiling) is the recommended envelope for mainstream colocation and edge data centre rooms. Class A3 (5 to 40 degrees inlet, same RH band) widens to support free-cooling-favoured architectures and is increasingly the architecture-of-choice for new Australian sub-3 MW edge builds. Class A4 widens further to 5 to 45 degrees but is rarely specified in colocation because the equipment-vendor warranty on high-density servers commonly tightens at the wider band. ASHRAE TC 9.9 also publishes the canonical Datacom Equipment Power Trends and Cooling Applications volume, which the duct fabricator uses to size supply diffuser quantities to high-density rack populations.

ASHRAE Standard 62.1 — ventilation for acceptable indoor air quality

ASHRAE Standard 62.1 is the international ventilation IAQ standard, used as a cross-reference where the Australian project is designed by US consultants or where the equipment vendor specifies ASHRAE rather than AS. The duct fabricator builds to the tighter of AS 1668.2 and ASHRAE 62.1 where both are invoked, with the practical answer almost always being AS 1668.2 because the rates are broadly aligned.

NEBS — Network Equipment-Building System

The Network Equipment-Building System (NEBS) is the United States Telcordia (formerly Bellcore) generic-requirements framework for outside-plant and central-office equipment, with NEBS Level 3 the certification level commonly referenced by international equipment vendors. NEBS is not enforceable as Australian law, but it is widely referenced in vendor specifications as an internationally recognised benchmark for outside-plant tolerance and is invoked by some operators — particularly Telstra Subsea on submarine cable landing stations — as the reference envelope for terminating equipment. An HVAC system designed to hold the room inside the NEBS Level 3 envelope under the Australian climatic extreme is a defensible specification across all three mobile operators, NBN Co and the major data centre operators.

NABERS Data Centre and Green Star Data Centre ratings

For ratings-targeted builds, the NABERS Data Centre Energy Efficiency rating (1 to 6 stars, with 5+ stars increasingly the bid-qualifying threshold for hyperscale colocation tenders) and the Green Star Data Centre design and as-built rating drive the energy-performance specifications that the HVAC ductwork has to satisfy. Tight duct leakage class (Class A or better), high free-cooling fraction (60 to 75 percent in Sydney and Melbourne climates), low fan velocity to suppress fan power and integrated economiser scheduling are the standard answers. The fabrication discipline that supports the ratings is the same AS 4254 discipline, but the FAT testing is more rigorous and the as-built leakage acceptance is tighter than the commercial baseline.

Facility classification — eight built-form categories

With the standards laid out, we move to the engineering content. Across the telecommunications-adjacent spectrum, eight distinct built-form categories drive eight distinct HVAC ductwork solutions. The fabricator who maps the customer's brief to the correct category at the start of the engagement avoids the common mistake of over-specifying or under-specifying by a wide margin.

Category 1 — Cell tower BTS equipment hut

The mobile carrier base transceiver station (BTS) equipment hut is the highest-volume telecommunications HVAC built-form by site count. A modern Australian macro-cell hut is 4 to 6 metres long by 2 to 3 metres wide, internal volume 8 to 25 cubic metres, with 6 to 15 kilowatts of continuous equipment heat load from base band units, remote radio heads, microwave point-to-point backhaul radios, transmission switches, power amplifiers, DC rectifiers and a 48 V battery bank (LFP or VRLA). The setpoint is 22 to 24 degrees Celsius dry bulb with plus or minus 2 degrees tolerance, 35 to 65 percent RH non-condensing, and the cooling strategy is a hybrid free-cooling-plus-DX economiser with the free cooling fraction tracking the local climate — 60 to 80 percent across the populated coastal and inland metropolitan corridor, falling to 25 to 40 percent in the Top End and Far North Queensland tropics. The HVAC ductwork inside the hut runs to a supply trunk along the ceiling, branch ducts to each equipment rack, a return trunk on the cool-side wall, a dedicated battery-room exhaust to the highest practical roof penetration and the economiser intake-and-exhaust dampers on the cool-side wall. Material selection is galvanised steel inland, aluminium or 304 stainless within 1 kilometre of the coast. This category is treated in detail at telecom BTS and equipment shelter HVAC duct guide.

Category 2 — Outdoor cabinet (small cell, pico cell, mmWave)

The outdoor cabinet is a separate category from the walk-in BTS hut, with internal volume under 5 cubic metres and 1 to 5 kilowatts of heat load. The cooling strategy is one of three — sealed cabinet with thermosiphon heat exchanger (passive, capacity-limited to 2 kW), filtered direct-air cabinet (IP55 or IP65 filtered intake louvres with internal fan), or monobloc DX cabinet air conditioner (3 to 5 kW, wall-mounted). Ductwork inside an outdoor cabinet is minimal — short rectangular plenums or sheet-metal baffles directing air across hot RF cards, no full distribution. The category has exploded in volume across Australian metro markets since 2024 with the 5G mmWave densification rollout, generating tens of thousands of installed units. Material selection favours aluminium or 304 stainless for corrosion resistance because the cabinet sits in continuous outdoor exposure. The same SBKJ machinery suite that builds the BTS hut ductwork produces the outdoor cabinet internal plenums with minor tooling adjustment.

Category 3 — Microwave radio repeater site

Microwave radio repeater sites are a specialised category, distinct from cell tower BTS huts because the dominant equipment is the point-to-point microwave radio rather than the cellular base station. Repeater sites are sited on hilltops, ridges, water towers and isolated mountain peaks for line-of-sight propagation; they typically host 4 to 10 microwave radios feeding the cell-site backhaul network, plus a small power and battery plant. The HVAC envelope is similar to the BTS hut but with tighter temperature stability on the microwave shelf because microwave oscillator stability degrades with rate-of-change above 1 degree per hour. The 4G/5G/6G base station equipment co-located in the same shelter follows the BTS envelope. Repeater sites are often off-grid solar-plus-diesel hybrids, with HVAC engineering optimised for passive ventilation and minimal compressor load.

Category 4 — Telecommunications exchange building (legacy and modern)

The telecommunications exchange building is a purpose-built telecommunications facility, typically 500 to 5,000 square metres of floor area distributed across one to four storeys. Legacy exchanges date from the 1950s through the 2000s and host a stratified mix of copper distribution frame (MDF), fibre optic terminating equipment (FOTE), 4G core and 5G core equipment, NBN POI tenancy and edge computing co-location. Modern exchanges are purpose-built to host 4G/5G core, fibre transmission and a meaningful population of edge computing racks at 5 to 15 kilowatts per rack. The HVAC envelope sits in the range 22 to 24 degrees Celsius dry bulb at 40 to 60 percent RH, with N+1 redundancy on every mechanical and electrical subsystem and 24/7 alarm monitoring through the carrier NOC. The ductwork is bulk rectangular galvanised duct for supply and return, with dedicated battery-room exhaust, dedicated generator-room ventilation and the gaseous-suppression integrity dampers at each protected enclosure boundary. The exchange category is the largest single market for HVAC ductwork by total fabrication volume across the Australian telecommunications layer.

Category 5 — NBN Point of Interconnect

An NBN POI is a discrete room or rack suite inside a Telstra or commercial exchange building, hosting NBN Co's optical transmission and cross-connect equipment plus the retail service provider hand-off racks. POI rooms range from a single rack inside a regional Telstra exchange to dozens of racks in the major metropolitan exchanges. The HVAC envelope is identical to the exchange building — 22 to 24 degrees Celsius, 40 to 60 percent RH, N+1 cooling redundancy, dedicated outdoor air to AS 1668.2 and 24/7 alarm monitoring. The ductwork is integrated into the host exchange building's HVAC system where possible, or supplied by dedicated NBN POI HVAC plant where the host building cannot accommodate the POI load. The 121 POIs nationally drove a sustained ductwork installation programme through the NBN build-out and remain a steady refurbishment market.

Category 6 — Sub-3 MW edge data centre

The sub-3 MW edge data centre is the rising category — Cogent, Megaport, NEXTDC's regional edge programme, the AirTrunk regional builds, the Equinix metro builds, the Macquarie Telecom regional Adelaide and Perth builds. Edge data centres sit closer to the end user than the hyperscale carrier hotels, with the architecture deliberately distributed to reduce latency for time-sensitive applications — autonomous-vehicle support, low-latency gaming, content delivery network caching, edge AI inference. The HVAC envelope is ASHRAE TC 9.9 Class A2 or A3 (18 to 27 degrees Celsius inlet for A2, widening to 5 to 40 degrees for A3), with N+1 cooling redundancy minimum and 30 to 70 percent RH. The cooling architecture is increasingly indirect adiabatic (Munters, Stulz or Vertiv platform) because the Sydney and Melbourne climates support 60 to 70 percent free cooling availability on Class A3 envelopes. The ductwork is bulk rectangular galvanised duct for supply and return at AS 4254.1 below 500 Pa, with selected high-pressure trunks at AS 4254.2 above 500 Pa where the air-side economiser bypass demands it. Hot-aisle and cold-aisle containment is universal, with blank panels at every U not occupied by equipment.

Category 7 — Hyperscale carrier hotel

The hyperscale carrier hotel — Equinix SY1, SY2, ME1, PE1, NEXTDC S5, M3, B2, AirTrunk SYD1, SYD2, MEL1, MEL2 — is the apex of the Australian telecommunications-adjacent built-form spectrum. IT loads run 30 to 200 megawatts per site, the building is purpose-built carrier-neutral with hundreds of customers cross-connected through dense meet-me-rooms, and the redundancy is N+1 on every subsystem with selected N+2 on the most critical paths. The HVAC ductwork engineering is the data-centre canon laid out at data centre HVAC duct manufacturing and Australia data centre HVAC and AS/NZS 4254. From the fabricator's perspective, the carrier hotel is the largest single ticket on offer — AUD 5 to 15 million HVAC duct supply across the project, distributed over 12 to 18 months — and the SBAL-V multi-shift configuration is the appropriate machinery answer.

Category 8 — Submarine cable landing station

The submarine cable landing station is the smallest category by site count (fewer than 30 active landings on the continent) and one of the most technically demanding. The landing station consists of a beach manhole where the submerged cable comes ashore, a cable conduit running to the landing station building (typically 100 to 1,000 metres inland), and the landing station building itself — a purpose-built telecommunications facility containing the cable terminating equipment, the dense wavelength-division-multiplexing (DWDM) optical chassis that converts the submarine wavelengths to terrestrial wavelengths, the cross-connect infrastructure that hands off to the terrestrial backhaul network and the power and battery plant. The HVAC envelope is tighter than the typical exchange — plus or minus 1 degree from setpoint, 45 to 55 percent RH controlled to a tight band — because the DWDM optical chassis has narrow temperature stability requirements and the cable terminating equipment is the single most critical infrastructure on the continent for international connectivity. Material selection is 304 stainless throughout because the landing station is by definition coastal (ISO 9223 C3 to C4 or C5) and the 30-year design life is non-negotiable. The redundancy is N+2 or 2N on mechanical and electrical subsystems. The security envelope is heavy — many landing stations are declared critical infrastructure under the Security of Critical Infrastructure Act and the duct construction reflects the security overlay.

Thermal envelope by room type

Inside each facility, the rooms break down into a consistent set of room types. The HVAC ductwork serving each room type is calibrated to the room's specific failure modes and operating envelope. The numbers below are the consensus Australian targets used by NEXTDC, Equinix, AirTrunk, NBN Co, Telstra and the major operators in 2026.

IT load rooms — ASHRAE TC 9.9 envelope

The data hall, the colocation hall, the central office hall and the NBN POI room all sit inside the ASHRAE TC 9.9 envelope. Inlet air at the cold-aisle face is held at 18 to 27 degrees Celsius dry bulb (Class A2) widening to 5 to 40 degrees (Class A3 for free-cooling-favoured architectures). Relative humidity is 30 to 70 percent with a dew-point ceiling of 21 degrees on Class A2. Hot-aisle return temperature runs 35 to 45 degrees Celsius depending on rack density and containment effectiveness. Temperature rate-of-change is held below 5 degrees Celsius per hour to prevent condensation on cold equipment surfaces when warm air is introduced from outside air during economiser cycling.

DC plant room (telco -48 VDC battery and rectifier)

The DC plant room is the distinctive telecommunications subsystem, almost ubiquitous in legacy and modern Telstra-style exchange buildings. It houses the -48 VDC rectifier bank that converts incoming AC mains to the telco-standard -48 VDC distribution voltage, plus the battery bank (lead-acid or LFP) that holds the load through a mains outage until the diesel generator stabilises. The thermal envelope is held cooler than the IT load rooms — 18 to 22 degrees Celsius — because battery Arrhenius-life economics dominate. The atmosphere is potentially aggressive — hydrogen evolution on overcharge for lead-acid chemistry, sulphuric acid mist for VRLA cells under heavy charge, low-level off-gassing of organic vapours from the LFP electrolyte under thermal stress. The HVAC ductwork serving the DC plant is dedicated — never shared with IT load recirculation — with a continuous-run extract fan moving the room volume through the duct on a calibrated air-change rate. Material selection is 304 stainless for the exhaust ductwork to resist sulphuric acid corrosion. The Safe Work Australia Workplace Exposure Standards apply to the DC plant room — hydrogen 25 percent of LEL alarm threshold, sulphuric acid mist 1 mg/m³ TWA, ozone 0.1 ppm STEL.

UPS room (AC redundancy)

The UPS room hosts the AC uninterruptible power supply that holds the IT and HVAC load through a mains outage until the diesel generator stabilises (typically 30 to 60 seconds at full load). The thermal envelope is held at 20 to 24 degrees Celsius dry bulb, with humidity controlled to 40 to 60 percent RH non-condensing. UPS efficiency is 92 to 98 percent depending on technology and load fraction; the waste heat dissipates entirely as sensible heat into the room, so the cooling load is 2 to 8 percent of the UPS throughput. The HVAC ductwork serves the UPS room from the main IT load supply with a balancing damper or from a dedicated CRAC unit. The UPS room is typically a separate fire-resistant compartment with its own gaseous suppression to AS 4214, so the duct boundary at the room wall receives the gas-tight integrity damper.

Diesel generator room

The diesel generator room is sized to host the backup generator and its day tank. Combustion air enters through a dedicated intake duct sized for the worst-case wide-open-throttle airflow rate; radiator-discharge air exits through a discharge duct without recirculation to the combustion intake; engine exhaust gas exits through a silencer-and-insulated-pipe assembly to outdoor termination at a height clear of any air intake on the site. The room is AS/NZS 60079 Zone 2 classified around the day tank, requiring spark-resistant fan housings and ATEX or AS/NZS 60079-compatible motors on the duct-mounted extracts inside the classified envelope. The generator-room HVAC ductwork interfaces with the diesel storage compound (AS 1940) and the generator pressure vessel infrastructure (AS 4036 and AS 4037) without crossing them. The standard reference is NFPA 110 for emergency-power-system mechanical detail.

Fuel storage compound

The bulk diesel storage compound is a separate hazardous-area envelope, typically AS/NZS 60079 Zone 1 around the storage tank (where flammable diesel vapour is expected during normal operation including transfer events) and Zone 2 around the tank vents and breather pipes. The compound is bunded to contain a full tank failure, drained to an oil-water separator and ventilated to prevent vapour accumulation. The HVAC ductwork serving the compound is minimal — the compound is typically an outdoor or semi-outdoor space with natural ventilation supplemented by intumescent fire-rated extract that activates on fire detection.

Mechanical and chiller plant room

The mechanical and chiller plant room hosts the primary cooling plant — chiller compressors (for chilled-water-served sites), CRAH (computer room air-handler) banks (for raised-floor cooling), CRAC (computer room air-conditioning) banks (for direct-expansion cooling), and the indirect adiabatic units (for free-cooling-favoured sites). The room is typically held at 18 to 30 degrees Celsius depending on plant heat rejection strategy. The HVAC ductwork serving the plant room is bulk rectangular galvanised, with supply runs feeding the room air-handlers and return runs leaving via roof-mounted heat-rejection equipment. Refrigerant leak detection is mandatory under the Safe Work Australia framework — R32, R410A, R744 (CO2), R1234ze (HFO) refrigerants all have specific exposure standards.

Free cooling air handler (outdoor air economiser)

The free cooling air handler is the dominant cooling-strategy element for Australian edge data centres and modern exchange buildings. Filtered outdoor air enters through a louvred intake, passes through a pre-filter (G4) and a fine filter (F7), routes through the economiser damper, mixes with return air at the controller-determined ratio and delivers to the IT load rooms. The bin-hour distribution of Sydney and Melbourne outdoor air temperatures against the ASHRAE Class A3 inlet envelope supports 60 to 70 percent free cooling availability annually. The ductwork is large-section, low-velocity (4 to 6 metres per second in the trunk) to minimise pressure drop and fan power. The intake louvre is sized generously to keep face velocity under 3 metres per second, suppressing rain ingress and noise.

Indirect adiabatic cooling and humidification

Indirect adiabatic cooling is the dominant new-build cooling architecture for sub-3 MW Australian edge data centres. The Munters, Stulz and Vertiv platforms deliver heat rejection to outdoor air via a cross-flow polymer plate heat exchanger, with the outdoor-air side adiabatically pre-cooled by water spray when outdoor temperature exceeds the threshold. The architecture delivers free cooling 60 to 75 percent of operating hours in Sydney and Melbourne, with the remaining hours satisfied by adiabatic pre-cooling alone — no mechanical compression at all on the cooling side, dramatic energy savings over DX. Adiabatic humidification on the IT-load side maintains RH inside the ASHRAE TC 9.9 envelope without compressor work. The ductwork serving the indirect adiabatic plant is large-section bulk rectangular at the IT-load side and high-flow round spiral at the outdoor-air discharge side; the SBKJ machinery configuration covers both with the SBAL-V for the rectangular and the SBFB-1500 spiral tubeformer for the round.

Hot-aisle and cold-aisle containment

Containment is universal in new Australian sub-3 MW edge and hyperscale builds. Racks are laid out in alternating cold and hot aisles, with cold-aisle doors or hot-aisle chimneys preventing the supply air and return air from mixing in the room. Blank panels fill every unused U inside every rack to prevent recirculation through the rack. The HVAC ductwork delivers supply to the cold aisle (via raised-floor plenum, supply diffusers above the cold aisle, or in-row cooling units) and removes return from the hot aisle (via ceiling plenum, return diffusers above the hot aisle, or in-row cooling units). Containment effectiveness is measured by the Return Temperature Index (RTI) and the Rack Cooling Index (RCI); well-contained rooms hit RTI 95 to 105 percent and RCI 100 percent across the rack population.

Cable tray and server-rack air management

Cable trays and the air management inside the server rack are coordinated with the HVAC ductwork. Cable trays run along the ceiling void typically alongside the supply and return duct, separated by the duct service-access clearance. Inside the rack, blank panels, brush strips and chimney kits ensure the cold supply air entering the rack does not recirculate to the hot return without passing through the server. The fabricator's role is to coordinate the duct routing with the cable tray routing so neither obstructs the other.

Access control and security room

The access control and security room is a small clean space typically held at the same envelope as the office (20 to 24 degrees Celsius, 40 to 60 percent RH) with a low cooling load (2 to 5 kilowatts). The HVAC ductwork serves the room from a small dedicated branch off the main office system. For HCF Strategic facilities the room is a separate security compartment with its own dedicated outdoor air to AS 1668.2 and an acoustic-attenuating duct construction at the compartment boundary to suppress acoustic-based side-channel attacks.

Fire suppression cylinder room

The gaseous fire suppression cylinder room hosts the FM-200, Novec 1230 or INERGEN cylinders that protect the IT load rooms. The room is held at 15 to 30 degrees Celsius dry bulb (within the agent storage temperature range) with low humidity to prevent corrosion of the cylinder valves. The HVAC ductwork is small — a single branch from the main office supply, with the cylinder-room boundary receiving an integrity-class damper if the cylinder room sits inside the protected-enclosure envelope.

Network Operations Centre (NOC)

The NOC is the staffed operations control room from which the facility is monitored and controlled. It is held at office envelope (20 to 24 degrees Celsius, 40 to 60 percent RH) with full N+1 redundancy because the NOC is mission-critical for operations. The HVAC ductwork serves the NOC from a dedicated subsystem of the main office or from a small dedicated plant; the NOC is typically held at slight positive pressure to suppress dust ingress from corridors.

Office, admin and amenity spaces

The office, administration and amenity spaces (kitchenettes, toilets, break rooms) follow the standard commercial-building envelope. AS 1668.2 outdoor air at 7.5 litres per second per person, AS/NZS 4254 ductwork construction, and the standard commercial ratings (Green Star Office, NABERS Energy for Offices) where applicable. The duct fabricator's role is to supply the bulk rectangular ductwork at the standard AS 4254.1 specification.

Worker amenity (24/7 shift)

For 24/7 staffed facilities (carrier hotels, hyperscale data centres, ACMA Carrier Class exchanges) the worker amenity zones — break rooms, lockers, showers, sleep rooms for technicians on shift — require continuous ventilation at AS 1668.2 occupied rates, with the supply held inside the comfort envelope. Toilet and shower extract is dedicated and discharges to outdoor.

Calculating cooling load — the practical method

The fabricator does not usually do the cooling load calculation — that is the consulting engineer's responsibility — but understanding how the load is built up clarifies why specific duct geometries appear on the drawings.

The sensible cooling load decomposes as follows. IT load is the dominant term in a data hall or central office, calculated from nameplate kilowatts per rack times the number of populated racks. For a 1.5 MW edge data centre with 200 racks at 7.5 kilowatts average and a diversity allowance of 10 percent, the IT load is approximately 1.35 MW sensible. UPS waste heat adds 6 to 8 percent of the UPS throughput, typically 80 to 100 kilowatts on a 1.5 MW facility. Battery waste heat on float charge is small — 0.5 to 2 percent of the float-charge wattage, so 10 to 30 kilowatts — rising under outage to a higher value as the battery discharges. Lighting at 10 to 12 watts per square metre across the active operational floor adds 5 to 15 kilowatts typically. Envelope and solar gain through external walls, roof and any glazing varies by site orientation and climate; for a windowless central data hall this term is negligible, for an exchange-building office annexe it can reach 30 percent of the office cooling load. Diversity reduces the sum slightly because not every load runs at peak simultaneously, but on a critical-IT facility the design assumes near-zero diversity on the IT and DC plant rooms.

The latent cooling load is dominated by humidity introduced via the outdoor air. AS 1668.2 ventilation rates bring in 5 to 20 litres per second per occupant times the typical maintenance occupancy, plus the economiser load when the free-cooling intake is open. For a Sydney summer day at 28 degrees dry bulb and 65 percent RH, the latent load from 1,000 litres per second of economiser intake air is approximately 8 kilowatts. The latent fraction is small compared with the sensible IT load in a data centre but becomes significant in spaces with high human occupancy (offices, NOCs, worker amenity).

The fabricator's downstream interest is the supply air volume that drops out of the cooling load. Supply air volume is calculated as cooling load divided by the temperature differential between supply and return; with a 14-degree differential typical for a Class A2 envelope and a 1.35 MW IT load, the supply air volume is approximately 80 cubic metres per second, equivalent to a 4-by-5 metre trunk at 4 metres per second velocity. That number drives the duct cross-section, the gauge selection per AS 4254 and the SBKJ machine setting for the fabrication run.

Cooling architecture — the six options

Six cooling architectures dominate the Australian telecommunications-adjacent built-form spectrum. The architecture choice drives the ductwork geometry.

Direct expansion CRAC (computer room air conditioner)

Direct expansion CRAC is the traditional architecture — one or more in-room air-handlers with internal DX evaporator coils, connected to outdoor condensers. CRACs are sized at 30 to 200 kilowatts cooling capacity each, with N+1 redundancy on the room count. The ductwork is bulk rectangular under the raised floor and overhead in the ceiling void, distributing supply from the CRAC discharge to the cold aisles and returning from the hot aisles back to the CRAC. The architecture is energy-inefficient compared with chilled water but mechanically simpler, and remains the default for sub-1 MW deployments where the chilled-water plant capital cannot be justified.

Chilled water CRAH (computer room air handler)

Chilled water CRAH is the dominant architecture above 1 MW IT load. A central chilled-water plant (electric chillers with rooftop heat-rejection towers, or air-cooled chillers, or magnetic-bearing oil-free chillers for energy-efficiency targets) circulates chilled water through CRAH coils in each IT-load room. The CRAH discharges supply air to the cold aisle and returns hot-aisle air. The ductwork is bulk rectangular under the raised floor or overhead, identical in geometry to the CRAC architecture; the difference is the cooling-side plant. Energy efficiency is markedly better than DX CRAC at scale because the chiller plant can be sized for higher COP and the heat-rejection is centralised.

In-row cooling

In-row cooling places cooling units between rack rows inside the IT-load hall, with the unit discharging cold supply at the cold aisle and drawing hot return from the hot aisle. The unit is fed by chilled water or DX from the main plant. The ductwork is minimal — the in-row unit is self-contained and only the chilled-water or DX piping crosses to the unit. The architecture is energy-efficient because the cooling is delivered close to the load with minimal duct loss and is the default for very-high-density rack deployments (15 to 50 kilowatts per rack).

Free cooling air-side economiser

Free cooling air-side economising routes filtered outdoor air directly into the IT load rooms whenever outdoor temperature is below the inlet setpoint. The architecture works as a standalone (rare) or as a hybrid with DX or chilled-water backup. The ductwork is large-section bulk rectangular at the intake side, with the intake louvre sized for low face velocity to suppress rain ingress and noise. The architecture delivers dramatic energy savings in Sydney and Melbourne but introduces the contamination risk from outdoor pollutants — salt aerosol in coastal sites, dust in mining-adjacent sites, smoke in bushfire-affected sites — managed by the filter regime.

Indirect adiabatic cooling

Indirect adiabatic cooling, covered above, is the architecture of choice for new Australian sub-3 MW edge builds. The Munters, Stulz and Vertiv platforms deliver free cooling for 60 to 75 percent of operating hours in Sydney and Melbourne, with adiabatic pre-cooling of the outdoor air for the remaining hours, and minimal mechanical compression on the cooling side. The ductwork is bulk rectangular at the IT-load side with high-flow round spiral at the outdoor-air discharge side.

Rear-door heat exchanger

Rear-door heat exchanger places a chilled-water coil at the back of each high-density rack, absorbing the rack's hot-aisle discharge directly. The architecture is energy-efficient and allows very high rack densities (up to 100 kilowatts per rack) but requires chilled water piping to every rack. The ductwork is minimal — the rack is self-cooling and only the chilled water piping crosses to the rack.

Material selection — galvanised, aluminium or stainless

The duct material decision is driven by atmospheric corrosivity, ductwork pressure class, fire-rating requirement and the room's contamination tolerance. The ISO 9223 framework is the canonical reference.

ISO 9223 classification

The ISO 9223 framework classifies atmospheric corrosivity at a site into six categories — C1 (very low, indoor air-conditioned spaces), C2 (low, indoor unheated spaces, dry rural), C3 (medium, urban and industrial, low salinity coastal), C4 (high, industrial, moderate salinity coastal), C5 (very high, industrial, high salinity coastal), CX (extreme, offshore platforms, surf-zone). For the Australian telecommunications-adjacent built-form spectrum the relevant categories are C1 (interior of an air-conditioned data hall), C2 to C3 (the great majority of metropolitan and regional inland sites), C4 (coastal sites within 1 kilometre of an exposed coast, the typical submarine cable landing station inland of the beach manhole), and C5 (submarine cable landing stations within 200 metres of mean high-water facing the Southern Ocean or directly exposed to monsoonal salt aerosol).

Galvanised steel

Galvanised steel with G275 zinc coating (275 grams per square metre of zinc, both faces) is the standard Australian HVAC duct material. Service life in C2 environments is 30+ years, in C3 environments 15 to 25 years, in C4 environments 5 to 8 years, in C5 environments under 5 years. Material thickness ranges from 0.5 mm to 1.2 mm depending on duct cross-section and pressure class per AS 4254. The galvanised duct is fabricated on the SBAL-V auto duct line with TDF flange forming at line speed.

Aluminium

Aluminium duct (typically grade 5052 H32) is specified for coastal sites within 1 kilometre of the ocean, for remote-site logistics where transport weight matters, and for some shelter OEMs who standardise on aluminium for production simplicity. Service life in C3 to C4 environments is 15 to 25 years, with the aluminium developing a protective passive oxide layer that resists further attack. Material thickness is similar to galvanised steel (0.6 mm to 1.5 mm for equivalent strength). Aluminium is fabricated on the same SBKJ tooling as galvanised steel with minor adjustment to forming pressure and lubrication routine.

304 stainless steel

304 stainless steel (with 18 percent chromium and 8 percent nickel) is the SBKJ default for coastal sites within 100 metres of the ocean, for submarine cable landing stations, for DC plant battery exhaust where sulphuric acid is present, for HEPA-filtered plenums where outgassing must be minimal, and for low-leakage class A duct where the seam quality is critical. Service life in C4 environments is 30+ years; in C5 environments 20 to 30 years. Material thickness ranges from 0.6 mm to 1.5 mm. Fabrication uses the SBKJ SB-ZF1500 stitchwelder for the longitudinal seam, delivering the continuous-weld geometry that supports low-leakage class A acceptance. The SBPC1500 plasma cutter blanks the fittings.

316 stainless steel

316 stainless steel (with 2 to 3 percent molybdenum on top of the 304 alloy base) is reserved for the most severe corrosion environments — submarine cable landing stations within 200 metres of mean high-water, offshore-platform telecommunications duct, and the most demanding battery exhaust duty. Service life in C5 environments is 30+ years. Material thickness is similar to 304. Fabrication is on the same SB-ZF1500 stitchwelder with a minor adjustment to weld parameters because 316 has higher heat conductivity than 304.

Material decision matrix

The fabricator's working rule for the telecommunications-adjacent spectrum: galvanised G275 for all inland metropolitan, regional and rural sites at ISO 9223 C1 to C2; galvanised G275 for ISO 9223 C3 sites with a 15-year design life expectation; aluminium 5052 H32 or 304 stainless for ISO 9223 C3 sites with a 25-year design life expectation; 304 stainless mandatory for ISO 9223 C4 sites; 304 stainless or 316 stainless for ISO 9223 C5 sites; 316 stainless for all submarine cable landing stations within 200 metres of mean high-water regardless of formal corrosivity classification.

Pressure class, gauge and seam construction

AS 4254 prescribes the duct gauge and reinforcement by pressure class and cross-section. The standard divides into Part 1 (low pressure, below 500 Pa, the great majority of installations) and Part 2 (high pressure, above 500 Pa, large carrier hotels and hyperscale trunk segments).

Typical AS 4254.1 low-pressure gauges for telecommunications HVAC: up to 300 mm wide, 0.5 to 0.6 mm galvanised; 300 to 600 mm wide, 0.6 to 0.7 mm; 600 to 1,200 mm wide, 0.8 to 1.0 mm; 1,200 to 1,500 mm wide, 1.0 to 1.2 mm; above 1,500 mm wide, 1.2 mm with reinforced cross-bracing at 1.2-metre intervals.

Typical AS 4254.2 high-pressure gauges for the larger carrier hotel and hyperscale trunk segments: up to 600 mm wide, 0.8 mm galvanised; 600 to 1,200 mm wide, 1.0 mm; 1,200 to 2,000 mm wide, 1.2 mm; above 2,000 mm wide, 1.5 mm with reinforced cross-bracing at 0.9-metre intervals.

Seam construction is Pittsburgh lock or button-punch snaplock on the SBAL-V auto duct line for the longitudinal seam, with TDF flange or angle flange on the transverse joints. For 304 stainless plenum duct on the SB-ZF1500 stitchwelder, the longitudinal seam is a continuous stitch weld at 25 to 50 mm pitch, with welded transverse joints or bolted flanges depending on the room cleanliness specification. The seam construction reference is at Pittsburgh lock versus snaplock and the flange comparison is at TDF versus angle flange.

Duct leakage class and the FAT

AS 4254 references three leakage classes. Class A is the tightest, with a leakage rate under 0.5 percent of design airflow at design pressure. Class B is moderate, under 1.5 percent. Class C is loose, under 3 percent. The default for commercial telecommunications HVAC is Class C; the default for sub-3 MW edge data centre is Class B; the default for hyperscale carrier hotel and submarine cable landing station is Class A. The fabricator runs a Factory Acceptance Test (FAT) on the first 200 metres of duct fabrication against the specified leakage class, with a calibrated pressure-test rig that pressurises a sample duct section to design pressure and measures the leak-off rate. SBKJ machines hold Class C by default on the SBAL-V output; tuning to Class A requires the SB-ZF1500 stitchwelder for continuous-weld longitudinal seams and bolted-flange transverse joints. The FAT discipline is unpacked at HVAC commissioning and air balancing.

Fire-rated construction and compartmentation

Telecommunications buildings are heavily compartmented for fire-resistance. The fire-rated construction at duct penetrations follows AS 1530.4 with one of two strategies. Wrap-in-place uses standard galvanised duct wrapped with fire-rated insulation (Promat 25 or 50 mm board, Cafco K150 spray or 3M Interam wrap) at the penetration, achieving the required Fire Resistance Level (FRL) of 60/60/60 or 90/90/90 minutes. The wrap is installed on site by the HVAC fitter; the fabricator supplies the duct only. Fire-rated duct uses a duct constructed from inherently fire-rated material (Promat-DUR, Hardie SystemFire) with no additional wrap; the duct is more expensive but installs more cleanly in tight ceiling voids.

Fire dampers cross the compartment line in parallel with the duct, with the damper to AS 1530.4 fire-resistance and AS 1851 routine service requirements. Fire dampers are commissionable from inside the protected envelope, with reset access through an inspection panel that the fabricator coordinates with the duct routing. Penetration seals follow AS 4072.1 and AS 4072.3 with certified intumescent fire-and-smoke barrier assemblies traceable to the original test certificate.

DC plant, generator and battery room engineering

The DC plant, generator and battery rooms are the most distinctive HVAC subsystems inside a telecommunications facility, each calibrated to specific failure modes and regulatory envelopes.

DC plant and battery room

The DC plant is the -48 VDC battery and rectifier room. Inside the room, the rectifier bank converts incoming AC to -48 VDC distribution, and the battery bank holds the load through any outage in the rectifier chain or the upstream AC supply. Heat dissipation is moderate — a 200 kilowatt rectifier bank loses 10 to 15 kilowatts of heat continuously; a fully discharging battery on outage transient can dump tens of kilowatts of heat for a short period. The HVAC ductwork is a dedicated subsystem — never shared with IT load recirculation — with continuous-run extract sized to the worst-case sustained heat-rejection rate.

For lead-acid battery chemistry, the hydrogen evolution on float and overcharge drives an additional dedicated extract sized per AS/NZS 60079 Zone 2 calculation with the worst-case overcharge gas rate. The Zone 2 extract is on a spark-resistant centrifugal fan with an ATEX-rated motor, runs continuously and discharges to the highest practical roof termination, accounting for hydrogen's positive buoyancy. For LFP chemistry, the AS/NZS 5139 thermal-runaway extract takes the lead, sized to the worst-case vent-gas rate from cell damage and discharging to a similar high-roof termination.

The duct material is 304 stainless throughout the DC plant exhaust because of the sulphuric acid mist from VRLA chemistry and the residual aggressiveness of the LFP electrolyte off-gas. The seam is continuous-weld on the SB-ZF1500 stitchwelder. The Safe Work Australia exposure limits apply — hydrogen 25 percent of LEL alarm at 1 percent volume in air, sulphuric acid mist 1 mg/m³ TWA, ozone 0.1 ppm STEL.

Generator room

The diesel generator room hosts the backup generator that holds the facility through extended mains outages. The room HVAC ductwork serves three distinct flow paths — combustion air, radiator discharge and engine exhaust. Combustion air enters through a dedicated intake duct sized for the worst-case wide-open-throttle airflow rate, with a filter cassette appropriate to the site environment (G4 standard, F7 for high-dust sites). Radiator discharge air exits through a discharge duct without recirculation back to the combustion intake. Engine exhaust gas exits through a silencer and insulated-pipe assembly to outdoor termination at a height clear of any air intake on the site.

The room is AS/NZS 60079 Zone 2 classified around the day tank, with spark-resistant centrifugal fan housings and ATEX-rated motors on the duct-mounted extracts inside the classified envelope. The Safe Work Australia exposure standards apply during generator run-up — diesel particulate matter elemental carbon at 0.1 mg/m³ TWA, carbon monoxide at 30 ppm TWA, nitrogen dioxide at 5 ppm STEL. The duct material is galvanised steel for the bulk runs with 304 stainless on selected sections close to the engine exhaust where temperatures exceed the galvanised service envelope. NFPA 110 governs the mechanical detail because there is no native Australian standard at the same level of detail.

Diesel fuel storage compound

The bulk diesel storage compound sits as a separate hazardous-area envelope. The storage tank, the day tank inside the generator room and the fuel transfer pipework are all AS 1940 governed. The compound is AS/NZS 60079 Zone 1 around the tank vents and Zone 2 around the tank itself during normal operation. The HVAC ductwork serving the compound is minimal — natural ventilation supplemented by intumescent fire-rated extract that activates on fire detection.

Gaseous fire suppression and integrity dampers

Gaseous fire suppression is universal in Australian telecommunications equipment rooms because the IT and central-office load cannot tolerate water-based suppression. The agents in service in 2026 are FM-200 (HFC-227ea, the legacy agent, being phased out of new builds under the AS/NZS HFC management regime), Novec 1230 (FK-5-1-12, the dominant new-build agent, low GWP, fast knockdown), INERGEN (IG-541, an inert-gas blend, oxygen depletion mechanism, lower toxicity at design concentration), and Argonite (IG-55, similar inert blend). All are designed and tested to AS 4214.

The HVAC ductwork interfaces with the gaseous suppression integrity envelope at every duct that crosses the protected enclosure boundary. The damper at the boundary is an automatic gas-tight integrity damper — closing on suppression activation with a leakage rate substantially tighter than the routine fire damper class. The damper specification is integrity-class to AS 4214, with seals that maintain agent concentration during the design hold time (typically 10 minutes at design concentration after discharge). The integrity test is the room pressure-decay test at 50 Pa or 100 Pa, with the integrity damper closed; the room is acceptable when the pressure decay rate corresponds to an estimated hold time at design concentration that exceeds the required hold time.

The duct fabricator's role is to supply the duct sections that interface with the integrity dampers with the correct flange profile and sealing geometry. The flange profile is typically bolted with full-perimeter gasket for the integrity-class connection rather than the simpler TDF flange for the bulk duct. The SBKJ machinery accommodates the bolted-flange geometry with a small change to the flange-forming tooling.

Aisle containment and ASHRAE Standard 90.4 compliance

For sub-3 MW edge data centres and larger, hot-aisle and cold-aisle containment is universal in new builds. The architecture decision is between cold-aisle containment (CAC, the cold aisle is enclosed with doors and ceiling panels, the room volume runs at hot-aisle temperature, return air is unducted) and hot-aisle containment (HAC, the hot aisle is enclosed with doors and ceiling chimneys, the room volume runs at cold-aisle temperature, supply air is unducted). HAC has gained dominance in new Australian builds because it leaves the room volume at the cooler operating temperature, which is more comfortable for technicians and reduces the cooling load on lighting and ancillary equipment.

ASHRAE Standard 90.4 drives the efficiency thresholds that the HVAC ductwork has to support. The Mechanical Load Component (MLC) and Electrical Loss Component (ELC) are each calculated for the design and compared to the standard's allowable values. The mechanical load component drives fan power directly, which scales as the cube of duct velocity — halving the duct velocity reduces fan power by a factor of eight. The standard's allowable MLC drives the duct cross-section in new builds toward larger, lower-velocity geometries than the historical baseline. The fabricator who can deliver the larger cross-section without rework or seam-quality compromise wins on the energy-rated tender.

Acoustic considerations

Telecommunications buildings are typically sited in industrial or fringe-commercial zoning, but a meaningful subset sit in mixed-use precincts with residential proximity. The acoustic compliance at the site boundary is typically NC-35 daytime and NC-30 night-time for sites within 50 metres of residential receivers, with state-specific regulations (EPA Victoria, NSW EPA, Queensland Environmental Protection Act) setting the legal threshold. The dominant noise sources are the rooftop heat-rejection equipment (chiller condensers, indirect adiabatic discharge plenums) and the generator under load test. The HVAC ductwork contributes through fan-noise transmission down the supply trunks, with duct silencer insertion in the supply and return runs and lined plenums at intake and exhaust meeting the boundary target. The night-time NC-30 constraint drives larger ductwork (lower velocity, lower regenerated noise), heavier louvre construction and acoustic lining inside selected duct sections. The acoustic ductwork reference is at acoustic HVAC duct lining and attenuator guide.

Security overlays for Hosting Certification Framework and Carrier Class facilities

Hosting Certification Framework Strategic and Assured facilities operated for Federal Government clients carry security overlays that materially affect the duct fabrication discipline. The ASIO T4 Protective Security policy framework, administered through the Digital Transformation Agency, drives the supplementary requirements. The duct construction at security compartment lines is tested to AS 4072.1 and AS 4072.3 with certified intumescent fire-and-smoke barriers. The penetration seals are inspectable from inside the protected envelope. The outdoor air intakes are hardened against contaminant introduction (typical mitigation is a multi-stage gas-phase filter cassette between the standard particulate filters and the room supply, plus chemical-bonding panels at the intake plenum to mitigate chemical, biological and radiological introduction). The intake louvres are physically protected by perimeter security and located in positions that cannot be observed from outside the building perimeter.

ACMA Carrier Class facilities (Telstra, Optus and TPG declared facilities) follow a similar but commercially calibrated overlay. The Carrier Class facility regime requires 99.99 percent annual availability on declared services, which drives the redundancy on the mechanical and electrical subsystems including the HVAC. N+1 redundancy on chillers, AHUs and pumps is the minimum standard; N+2 is common on the most critical paths. Dual-path supply ductwork from independent AHUs with automatic isolation dampers and changeover sequences is the standard architecture for the central office hall and the DC plant. The Carrier Class regime is enforced through ACMA audit and operator self-attestation.

Submarine cable landing station engineering in depth

The submarine cable landing station is the most demanding category in the telecommunications-adjacent built-form spectrum. The landing station building hosts the cable terminating equipment (the optical line amplifiers and the cable termination box that takes the submarine wavelengths and converts them to terrestrial form), the dense wavelength-division-multiplexing (DWDM) optical chassis (typically Ciena, Infinera or Nokia-Alcatel platforms running 96 to 192 wavelengths per fibre at 100 to 400 gigabits per wavelength), the cross-connect to the terrestrial backhaul network, the power and battery plant (sized for substantially longer hold times than a typical exchange because the cable cannot be re-routed on outage), and the security and access control infrastructure.

The HVAC envelope is plus or minus 1 degree from setpoint at 22 degrees Celsius, 45 to 55 percent RH controlled to a tight band. The cooling architecture is typically chilled-water CRAH with N+2 redundancy and 2N on the most critical paths, supplemented by indirect adiabatic for the free-cooling fraction. The ductwork is 304 stainless throughout the protected envelope because of the ISO 9223 C4 to C5 corrosivity classification. The seam construction is continuous-weld on the SB-ZF1500 stitchwelder with bolted-flange transverse joints for the integrity-class connections. The leakage class is A at AS 4254 test pressure.

Each major Australian landing station is a critical infrastructure asset under the Security of Critical Infrastructure Act, with the operator required to maintain a Critical Infrastructure Risk Management Program (CIRMP) registered with the Cyber and Infrastructure Security Centre. The HVAC fabricator working on a landing station refurbishment or new-build receives security clearance and may be inspected and audited as part of the operator's CIRMP. The procurement is correspondingly heavyweight — multi-month pre-qualification, panel arrangements, multi-party reviews of the duct fabrication discipline and the as-built leakage acceptance.

The major Australian landing stations active in 2026 sit at Tamarama and Bondi (Sydney), Mullaloo and Two Rocks (Perth), Maroochydore (Queensland) and Darwin (Northern Territory), with smaller landings on the Western Australian coast for Asian routes. The Coral Sea Cable System landing at Sydney serves the Papua New Guinea and Solomon Islands cable backbone. The Bifrost cable (Telstra and Indosat consortium, commissioned 2024) landed at Darwin for the Singapore-Australia-United States route. The Indigo Central landing at Perth feeds the Perth-Singapore-Indonesia link with Vocus, Google and Subsea Networks as consortium partners. The Australia-Singapore Cable (Vocus) lands at Perth, with the SEA-ME-WE-3 and SEA-ME-WE-5 international consortium cables also landing at Perth for shared use. The Hawaiki cable (BW Group) lands at Sydney for the Pacific and US route; the Pacific Light Cable Network (Telstra Subsea consortium) similarly Sydney. The Telstra Global Network TGN-W and TGN-S systems land at Perth (south Africa route) and Sydney (Asia-US route). The Australia-Japan Cable lands at Sydney.

Australian climate spread — designing for the full envelope

The Australian telecommunications operator that runs a national network builds HVAC to one specification family that covers the full continental climate envelope. Alpine sites in the Snowy Mountains and Tasmanian highlands see winter ambient at minus 10 degrees Celsius and below, with the HVAC challenge inverting to preventing the inside dropping below the equipment minimum — heating is provided by the equipment itself supplemented by trim electric resistance heaters in the ductwork. Temperate sites across southern Victoria, Tasmania, the ACT and southern NSW swing from minus 2 degrees winter to 38 degrees summer, with free cooling availability 85 to 95 percent and the intake filter blockage with pollen and shoulder-season dust the dominant failure mode. Sub-tropical sites across Sydney, central NSW and southern Queensland see 5 to 42 degrees with summer-dominance, free cooling 60 to 75 percent and harmonised carrier specifications calibrated to this band. Tropical sites in the Top End and Far North Queensland face high temperature and humidity year round with free cooling only 25 to 40 percent available, condensate management constant, the envelope built to IP65 against monsoonal rain and 304 stainless or aluminium ductwork preferred for coastal corrosion. Arid sites in the Pilbara, western WA and central Australia see 45 to 48 degree summers with very low humidity, with dust ingress the dominant failure mode, addressed by larger pre-filter areas, more frequent filter changes and dust-tight louvres.

SBKJ machinery configuration for the telecommunications HVAC fabricator

For Australian fabricators serving the telecommunications-adjacent built-form spectrum, the SBKJ machinery configuration recommendation tracks the build mix. Most fabricators carry a single SBAL-V auto duct line for the bulk rectangular work, a single SBFB-1500 spiral tubeformer for risers and branches, a single SB-ZF1500 stitchwelder for stainless plenum and a single SBPC1500 plasma cutter for fitting blanks — sufficient for AUD 4 to 8 million annual HVAC duct revenue across the telecommunications sector.

SBAL-V auto duct line — bulk rectangular galvanised duct for general telco

The SBAL-V auto duct line is the SBKJ workhorse for the bulk rectangular galvanised duct that dominates the general telecommunications HVAC fabric — BTS equipment huts, NBN POI rooms, telecommunications exchange buildings and sub-3 MW edge data centres. SBAL-V galvanised duct output is the default specification for these built-form categories at ISO 9223 C1 and C2 sites where the 30-year design life of galvanised G275 zinc coating is acceptable. Available in SBAL-V-1250J (up to 1,250 mm coil width) and SBAL-V-1500J (up to 1,500 mm coil width) configurations, the line runs at 16 metres per minute single-shift, with TDF flange forming, longitudinal seaming and end-cut integrated. Single-shift output covers the major sub-3 MW edge data centre build at 5,500 square metres per month; multi-shift output covers concurrent projects at up to 16,000 square metres per month. The line handles galvanised steel, aluminium and 304 stainless within the same tooling envelope, with minor adjustment to forming pressure and lubrication for non-galvanised. Power is 380V 3-phase 50Hz (60Hz on request). The SBAL-V comparison against the SBAL-III is unpacked at SBAL-V versus SBAL-III.

SBSF-1525 round-duct flanging machine

The SBSF-1525 round-duct flanging machine handles the round-duct flange forming for spiral return riser duct, branch lines and supply diffuser connections. Working diameter ranges 200 to 1,525 mm. The machine pairs with the SBFB-1500 spiral tubeformer (below) to deliver the complete round-duct package for the supply and return risers in larger sub-3 MW edge and carrier hotel installations.

SBFB-1500 spiral tubeformer — round spiral risers and branches

The SBFB-1500 spiral tubeformer produces round spiral duct in diameters from 100 mm to 1,500 mm for risers, supply branches and return runs. Spiral duct is preferred for round-duct content because it has lower pressure drop than longitudinally-seamed round duct, easier cleaning for IAQ-sensitive applications and faster installation. The SBFB-1500 handles galvanised steel, aluminium and 304 stainless within the same tooling envelope. For larger trunk and main risers up to 2,000 mm diameter, the SBTF-2020 extends the diameter range. The spiral duct forming reference is at spiral duct forming guide.

SB-ZF1500 stitchwelder — 304 stainless plenum duct

The SB-ZF1500 automatic stitchwelder produces the continuous longitudinal seam required for 304 stainless plenum duct serving HEPA-filtered rooms, submarine cable landing stations, DC plant battery exhaust and any application requiring AS 4254 low-leakage class A acceptance. Maximum working length 1,500 mm, with stitch pitch adjustable from 5 mm to 50 mm depending on seam quality requirement. The machine handles 304 and 316 stainless, plus galvanised and aluminium where the continuous-weld geometry is required for sealed plenum or low-leakage acceptance. Power 380V 3-phase 50Hz.

SBPC1500 plasma cutter — fitting blank development

The SBPC1500 plasma cutter is a CNC plasma table with a 1,500 by 3,000 mm bed (or 1,500 by 6,000 mm extended-bed version) for blanking the developments of fittings, transitions, reducers, cones and elbows from coil or sheet. The plasma technology handles galvanised steel, 304 and 316 stainless, aluminium and mild steel within the same machine envelope. Cutting speed varies with material thickness and grade; typical 1 mm galvanised cuts at 8 to 10 metres per minute. The SBPC1500 is the upstream feed for the SBLR-600 longitudinal seam welder (below) that closes the fitting cones and elbows.

SBLR-600 longitudinal seam welder — fitting closure

The SBLR-600 longitudinal seam welder closes the longitudinal seams of cone-shaped fittings, elbows, transitions and Y-pieces blanked from the SBPC1500 plasma cutter. Working length up to 600 mm, with the SBLR-600A variant extending the working envelope. The welder handles galvanised, 304 and 316 stainless and aluminium with minor parameter adjustment between materials. The SBLR welds deliver a clean, leak-tight longitudinal seam suitable for AS 4254 class A acceptance on fittings serving sealed plenum applications.

Spark-resistant fans and ATEX motors for hazardous-area duty

For the AS/NZS 60079 Zone 2 fans inside the diesel generator room and the lead-acid battery room, the SBKJ duct package extends to spark-resistant centrifugal fan housings and ATEX-rated motors. These are not strictly SBKJ-manufactured (the fans are supplied by SBKJ partners including Howden Australia, Greenheck, Soler & Palau or Fantech) but they are specified inside the SBKJ duct package because the duct geometry has to accommodate the fan flange and access. The fan housing is non-ferrous (aluminium or stainless steel) to suppress spark risk on impeller contact, with the motor IIB T3 or IIC T3 rating depending on the specific hazardous gas group.

Commissioning and the duct fabrication acceptance

The HVAC commissioning of an Australian telecommunications facility is a multi-week protocol that runs in parallel with the building handover. The duct fabrication acceptance is a subset of the commissioning, focused on the leakage class, the supply balancing and the temperature stability.

The duct leakage acceptance test pressurises a representative sample of the installed duct system to the design pressure and measures the leak-off rate against the specified AS 4254 leakage class. For an exchange building or edge data centre at Class C, the test is straightforward and most fabrication runs pass on first attempt. For a hyperscale carrier hotel or submarine cable landing station at Class A, the test requires substantially tighter seam quality and the FAT discipline catches any sections that would otherwise fail at site acceptance.

The supply balancing brings every supply diffuser at every rack cold-aisle terminal to within plus or minus 5 percent of design airflow, with the return path balanced symmetrically. The balancing is the air-balancer's responsibility but the duct fabricator's role is to supply the duct with the correct geometry — turning vanes at every right-angle elbow, balancing dampers at every branch take-off, splitter dampers at every Tee — that the balancer can adjust without rework.

The temperature stability acceptance runs a 24-hour trace of supply temperature, return temperature, room temperature and outdoor temperature at design IT load, with the room held inside the ASHRAE TC 9.9 envelope across the trace. The acceptance is typically a plus or minus 0.5 degree band around setpoint for an A2 room, widening to plus or minus 2 degrees for an A3 free-cooling-favoured room.

The gaseous fire suppression integrity test pressurises the protected enclosure to 50 Pa or 100 Pa and measures the pressure-decay rate, calculating the estimated agent hold time at design concentration and comparing to the required hold time. The duct integrity dampers contribute to the protected-enclosure envelope and any leak at a damper seal will degrade the calculated hold time. The fabricator's discipline is to supply the dampers with full-perimeter gasket and bolted-flange connection so the integrity test passes on first attempt.

Cost model — worked examples for the four major built-form categories

To anchor the engineering content in commercial reality, here are four worked HVAC ductwork cost models for representative Australian telecommunications-adjacent builds at 2026 metropolitan pricing.

Cost model 1 — NBN POI room in a regional Telstra exchange

A typical NBN POI room is 50 to 200 square metres of floor area inside a host exchange building, with 4 to 20 racks at 5 to 10 kilowatts each. The HVAC ductwork is integrated into the host exchange building's HVAC where possible, with a dedicated 50 to 200 kilowatt CRAC unit serving the POI room directly. Duct content runs 15 to 40 linear metres of rectangular galvanised supply trunk (typically 600 by 400 mm cross-section), 10 to 30 metres of rectangular return trunk (typically 500 by 400 mm), 12 to 25 metres of round spiral supply branch (250 to 400 mm diameter) and assorted plenums, transitions and fittings. Total ductwork content 200 to 500 kilograms of galvanised sheet. At AUD 14 to 18 per kilogram finished, the duct content runs AUD 3,000 to 9,000 ex factory; installed and commissioned runs AUD 8,000 to 25,000 once labour, transit and balancing are loaded. Across the 121 POIs nationally the addressable HVAC ductwork market over the build-out and refurbishment cycle ran into eight figures.

Cost model 2 — Sub-3 MW edge data centre in metro Sydney

A typical sub-3 MW edge data centre is 600 to 1,500 square metres of net IT space distributed across two to four data halls, with 200 to 500 racks at 5 to 10 kilowatts each. The HVAC ductwork is bulk rectangular galvanised with selected stainless plenum at HEPA-filtered rooms. Duct content runs 250 to 600 linear metres of rectangular galvanised supply trunk (typically 1,200 by 800 mm), 200 to 500 metres of return trunk (typically 1,000 by 800 mm), 80 to 200 metres of round spiral supply riser (500 to 1,000 mm diameter), 60 to 150 metres of round spiral return riser, the 304 stainless plenum for the HEPA-filtered NOC and the security room, the dedicated DC plant exhaust in 304 stainless, the generator combustion air intake duct, the generator radiator discharge duct, the gaseous suppression integrity dampers at every protected-enclosure boundary, and the bulk fittings, transitions, balancing dampers and fire-rated penetrations. Total ductwork content 3,500 to 8,500 square metres of finished duct. At AUD 90 to 130 per square metre finished, the duct content runs AUD 320,000 to 1.1 million ex factory; installed and commissioned runs AUD 800,000 to 2.5 million once site labour, lifting, fire wrap and balancing are loaded.

Cost model 3 — Hyperscale carrier hotel in Macquarie Park

A 50 MW hyperscale carrier hotel is approximately 8,000 to 20,000 square metres of net IT space distributed across multiple data halls, with the HVAC ductwork at AS 4254.1 low-pressure for the bulk supply and return, AS 4254.2 high-pressure for selected trunk segments and 304 stainless plenum for HEPA-filtered rooms and the integrity-class boundaries. Total ductwork content 8,000 to 15,000 square metres of finished duct over the 12 to 18 month construction window. At AUD 110 to 160 per square metre finished, the duct content runs AUD 900,000 to 2.4 million ex factory; installed and commissioned runs AUD 5 to 15 million once site labour, lifting, fire wrap, integrity-class dampers, balancing and ratings-validation are loaded. The fabrication throughput required to satisfy the project justifies the SBAL-V multi-shift configuration. Across the projected AUD 30 billion Australian hyperscale capex through 2030, the addressable HVAC duct market is approximately AUD 300 to 600 million.

Cost model 4 — Submarine cable landing station on the WA coast

A submarine cable landing station building is typically 200 to 500 square metres of floor area, with the equipment hall housing 10 to 30 racks of cable terminating equipment and DWDM optical chassis. The HVAC ductwork is 304 stainless throughout the protected envelope because of the ISO 9223 C4 to C5 corrosivity. Duct content runs 80 to 200 linear metres of rectangular 304 stainless supply trunk (typically 800 by 600 mm), 60 to 150 metres of 304 stainless return trunk (typically 700 by 600 mm), 30 to 80 metres of 304 stainless round spiral branch (300 to 500 mm diameter), the integrity-class dampers at the gaseous suppression boundary, the dedicated battery exhaust and the security-overlay penetrations. Total ductwork content 800 to 1,800 square metres of finished 304 stainless duct. At AUD 280 to 420 per square metre finished (304 stainless premium over galvanised), the duct content runs AUD 220,000 to 750,000 ex factory; installed and commissioned runs AUD 600,000 to 2.0 million once site labour, security clearance, integrity-class dampers, balancing and CIRMP-aligned acceptance are loaded. The 304 stainless content drives the SB-ZF1500 stitchwelder to the centre of the fabrication line.

Common failure modes and how to avoid them

Across the SBKJ customer base of Australian telecommunications HVAC fabricators, six ductwork-related failure modes account for the great majority of reported field issues.

Galvanised duct corrosion at coastal sites is the most common — pinhole corrosion at flange joints within 5 to 8 years of service for galvanised duct within 1 kilometre of an exposed coast, accelerating to under 5 years for sites within 200 metres of mean high-water. The mitigation is to default to 304 stainless on ISO 9223 C4 and C5 sites from day one rather than retrofitting after corrosion appears.

DC plant exhaust sulphuric acid attack on galvanised duct downstream of VRLA battery banks shows as accelerated zinc loss and base-metal attack within 3 to 7 years. The mitigation is to specify 304 stainless throughout the DC plant exhaust regardless of the broader building corrosivity classification.

Gaseous suppression integrity test failure at first acceptance is the most common ductwork-related project delay, caused by integrity damper seal leakage at the protected enclosure boundary. The mitigation is to specify integrity-class dampers with full-perimeter gasket and bolted-flange connection rather than the simpler TDF connection used elsewhere in the building.

Leakage class A failure on 304 stainless plenum is the second most common project delay, caused by skip-welding in the longitudinal stitch seam or incomplete penetration at flange welds. The mitigation is the SB-ZF1500 stitchwelder discipline with FAT-tested sample sections at the start of every fabrication run.

Free-cooling intake filter blockage manifests as supply temperature drift in summer, with the economiser unable to deliver the design flow because the filters are loaded. The mitigation is dual pressure-drop monitoring with network alarming plus generous filter cassette sizing.

Fire-rated penetration failure at compartment lines is the AS 1530.4 acceptance failure that surfaces during commissioning. The mitigation is the certified intumescent fire-and-smoke barrier assembly traceable to the original AS 4072.1 test certificate, installed by the trained subcontractor under the fabricator's site supervision.

Procurement and tendering across the operator landscape

Each operator family has its own procurement procedure, and the Australian HVAC ductwork fabricator that wins consistent work understands the distinctions.

Telstra and Amplitel maintain a panel arrangement for HVAC contractors and a sub-panel for HVAC ductwork fabricators, with multi-year framework agreements rolling at three-year cycles. The qualification process is heavyweight — pre-qualification documents, financial covenant, insurance evidence, AS/NZS quality management evidence, ISO 9001:2015 certification, site visit by the Telstra or Amplitel technical assurance team. Once on the panel, the fabricator quotes against discrete project releases with the operator setting the AS 4254 leakage class, the ASHRAE TC 9.9 envelope and the integrity test acceptance criteria. Payment terms run 30 to 60 days post-acceptance, with milestone payments tied to FAT acceptance and site delivery.

Optus and Indara run a similar panel arrangement, with the qualification process slightly lighter than Telstra and the project release pattern more concentrated — multi-site batched releases rather than the discrete-site pattern. TPG Telecom runs a more centralised procurement with the main contract awarded to a major HVAC contractor who sub-contracts the ductwork supply.

NBN Co procures through the major HVAC contractor, with the ductwork fabricator sub-contracted on standard commercial terms. The 121 POIs are typically aggregated into regional packages of 8 to 25 POIs released over a 6 to 18 month delivery window.

NEXTDC, Equinix and AirTrunk procure through the major construction contractor on the carrier hotel build, with the ductwork fabricator typically on a 6 to 18 month sub-contract for the full build. The hyperscale operator's brand-specific HVAC specification is typically layered on top of AS 4254 and the qualification requires evidence of multi-shift production capability and FAT-tested leakage acceptance. The major Sydney and Melbourne contractors maintain pre-qualified sub-contractor panels.

The submarine cable consortia (Telstra Subsea, Vocus, the consortia) procure through specialist telecommunications contractors with security clearance, with the ductwork fabricator typically requiring National Security Clearance Negative Vetting Level 1 or higher for site work. The procurement is heavyweight — multi-month pre-qualification, panel arrangements and multi-party reviews.

Future direction — what 2026 to 2030 brings

Five structural changes are reshaping the Australian telecommunications HVAC market through to 2030.

5G to 6G transition. The 5G to 6G transition begins in earnest from 2027 onwards, with the early 6G base stations deploying alongside existing 5G infrastructure at the major macro-cell sites. The HVAC implication is incremental rather than transformational — 6G base stations dissipate similar heat to 5G with marginally higher per-channel power, and the BTS hut envelope continues to be sized to the 22 to 24 degree, 35 to 65 percent RH target. The ductwork fabricator's response is to maintain the SBAL plus SBFB-1500 configuration that covers both generations.

Edge data centre acceleration. The sub-3 MW edge data centre category accelerates sharply through 2027 and 2028 as the major operators (NEXTDC, AirTrunk, Equinix, Macquarie Telecom) build out their regional edge programmes. The cumulative new-build edge capacity over 2026 to 2030 is forecast at 200 to 400 megawatts of IT load distributed across 30 to 60 sites. The HVAC ductwork market addressable to fabricators is AUD 60 to 120 million over the period.

Carrier hotel hyperscale capex. The hyperscale carrier hotel capex programme continues at AUD 4 to 6 billion per year across the projected window, with the major sites concentrated at Macquarie Park (Sydney), Tullamarine (Melbourne) and Avalon Park (Geelong emerging hyperscale precinct). The HVAC ductwork market is approximately AUD 80 to 140 million per year.

Submarine cable build-out. Three new major submarine cables are forecast to land in Australia over 2026 to 2030 — the Echo Cable (Telstra and partners, US-Singapore route landing Sydney), the Hawaiki Nui Cable (BW Group, Pacific extension landing Sydney), and the Project Apricot Cable (Google and Facebook, Asia-US route landing in Australia at a yet-to-be-confirmed site). Each landing station drives a new-build HVAC ductwork project at AUD 600,000 to 2 million each.

Hosting Certification Framework expansion. The Federal Government Hosting Certification Framework is expected to extend its remit through 2027 to 2030 with additional sensitive workloads moving to HCF Strategic and Assured hosting. The HVAC ductwork market addressable to fabricators with the security overlay capability is approximately AUD 30 to 60 million over the period.

Across all five drivers, the fabricator positioning that performs best is vertically integrated — AS 4254 galvanised duct supply, 304 stainless plenum duct supply, fire-rated penetration coordination, integrity-class damper supply and the site-installation labour under one commercial roof. SBKJ Group machinery supports the central two components: SBAL-V covers the galvanised bulk rectangular work, SBFB-1500 covers the spiral riser and branch work, SB-ZF1500 covers the 304 stainless plenum, SBPC1500 plus SBLR-600 covers the fitting and transition work.

How SBKJ supports the Australian telecommunications HVAC market

SBKJ Group operates from Box Hill North in Victoria, supplying ductwork machinery and engineering support to telecommunications HVAC fabricators, mobile tower contractors, exchange building refurbishment contractors, NBN POI specialists, edge data centre construction contractors, carrier hotel HVAC sub-contractors, submarine cable landing station specialist contractors and Federal Government cleared contractors across Australia and 100+ export markets.

Our telecommunications-sector activity covers five service lines. Machinery supply for the full HVAC ductwork fabrication line — SBAL-V auto duct line, SBFB-1500 spiral tubeformer, SBSF-1525 round-duct flanging, SB-ZF1500 stitchwelder, SBPC1500 plasma cutter, SBLR-600 longitudinal seam welder — with single-shift and multi-shift configurations depending on the customer's throughput target. Engineering review of a customer's exchange building, edge data centre, NBN POI or submarine cable landing station HVAC drawings against the AS 4254, AS 1530.4, AS 4214, AS/NZS 60079, ASHRAE TC 9.9, ASHRAE Standard 90.4 and Hosting Certification Framework canon laid out in this guide; the review takes one to two engineering days, is done at no charge to the prospective customer, and identifies the SBKJ machine configuration that delivers the customer's throughput target with the smallest capital outlay. Fabrication throughput consulting for fabricators pursuing multi-site rollouts or hyperscale frameworks, with detailed planning of multi-shift staffing, FAT acceptance discipline and site-delivery logistics. After-sales support for SBKJ machinery installed at Australian customer sites, with a 12-month warranty and lifetime parts continuity. Industry liaison with the Communications Alliance, AIIA, Mobile Carriers Forum and the major operator technical assurance teams.

Our standard practice is to review a customer's drawings before a machinery quote is issued. The review identifies the bottleneck in the customer's intended fabrication flow, the SBKJ machine configuration that resolves the bottleneck, and the operator-tier qualification requirements (Telstra, Amplitel, NEXTDC, Equinix, AirTrunk panel arrangements) that the customer needs to satisfy. The customer leaves the review with a clear capital plan, a clear qualification plan and a clear throughput projection.

Discuss an SBKJ machine configuration for telecommunications HVAC ductwork →

FAQ

Which Australian standards govern HVAC ductwork for a telecommunications exchange, edge data centre or NBN POI?

Five families. AS 1668.2 governs ventilation rates by occupancy. AS 4254 governs ductwork construction, leakage class and pressure class. AS 1530.4 governs fire-rated construction for any duct crossing a fire-resistant compartment line. AS 4214 governs gaseous fire suppression (FM-200, Novec 1230, INERGEN). AS/NZS 60079 applies in the generator and lead-acid battery rooms. ASHRAE Standard 90.4 datacom energy efficiency and ASHRAE TC 9.9 thermal guidelines overlay where invoked. HCF Strategic facilities add the ASIO T4 security overlay.

What inlet air envelope applies to a typical Australian edge data centre?

ASHRAE TC 9.9 Class A2 or A3. A2 is 18 to 27 degrees Celsius dry bulb at the IT inlet with 30 to 70 percent RH and a 21-degree dew-point ceiling. A3 widens to 5 to 40 degrees with the same RH band, supporting free-cooling-favoured architectures that dominate new Sydney and Melbourne builds.

Why are 304 stainless and aluminium specified for coastal submarine cable landing stations?

ISO 9223 classifies coastal landing station sites as C4 (high corrosivity) or C5 (very high). Galvanised duct service life in C4 is 5 to 8 years, in C5 under 5 years — unacceptable for a critical infrastructure landing. 304 stainless lifts the design life to 30 years even in C4. 316 stainless extends it further for direct ocean-exposure sites within 200 metres of mean high-water.

How does HCF Strategic differ from commercial carrier-neutral edge data centre?

HCF Strategic overlays the ASIO T4 Protective Security policy on top of the commercial HVAC canon. Duct penetrations across security compartment lines require certified intumescent fire-and-smoke barriers to AS 4072.1 and AS 4072.3 with acoustic transmission attenuation. Outdoor air intakes are hardened against contaminant introduction. Generator and UPS plant have dedicated outdoor air with TUV or UL listed fire dampers. Inspection and traceability documentation is substantially heavier than commercial colocation.

What SBKJ machinery configuration is recommended for telecommunications HVAC fabrication?

SBAL-V auto duct line for bulk rectangular galvanised duct serving exchanges, edge data centres and NBN POI rooms. SBSF-1525 round-duct flanging plus SBFB-1500 spiral tubeformer for risers and branches. SB-ZF1500 stitchwelder for 304 stainless plenum serving HEPA-filtered rooms or AS 4254 low-leakage class A acceptance, plus 304 stainless DC plant battery exhaust and submarine cable landing station envelope. SBPC1500 plasma cutter for fitting blank development, SBLR-600 longitudinal seam welder for closing fitting cones and elbows. Spark-resistant fan housings and ATEX motors for the AS/NZS 60079 Zone 2 fans inside generator and lead-acid battery rooms.

What duct leakage class is acceptable for an Australian sub-3 MW edge data centre?

AS 4254 class B is the default for sub-3 MW edge data centre, with class A increasingly specified by hyperscale-targeted operators (NEXTDC, AirTrunk, Equinix). Submarine cable landing stations and HCF Strategic facilities specify class A. Class C is acceptable for older legacy exchange building refurbishment but no longer the default for new build.

How is the gaseous fire suppression integrity test acceptance achieved?

The protected enclosure is pressurised to 50 Pa or 100 Pa with all integrity-class dampers closed; the pressure-decay rate is measured over 60 to 300 seconds. The calculated agent hold time at design concentration is compared to the required hold time (typically 10 minutes for Novec 1230 and FM-200, 5 to 7 minutes for INERGEN). The duct fabricator's role is to supply integrity-class dampers with full-perimeter gasket and bolted-flange connection that hold the protected enclosure envelope.

What is the addressable HVAC ductwork market across the Australian telecommunications sector over 2026 to 2030?

Approximately AUD 600 million to 1.2 billion across the full spectrum. Hyperscale carrier hotel build accounts for AUD 300 to 600 million; sub-3 MW edge data centres AUD 60 to 120 million; NBN POI refurbishment AUD 30 to 60 million; mobile tower BTS and outdoor cabinet rollouts AUD 50 to 100 million; legacy exchange building refurbishment AUD 80 to 150 million; submarine cable landing stations AUD 10 to 20 million; HCF Strategic and Assured government hosting AUD 30 to 60 million.