Service / Precision Cooling Maintenance
Chilled Water CRACand CRAH Maintenance Australia
Direct answer
A chilled water CRAC unit, also called a CRAH (computer room air handler), cools a data hall by passing room air across a coil fed with chilled water from a central chiller plant, and it needs maintenance on three separate systems: the air side, the water side, and the controls.
Indigi Power and Cooling services CHW CRAC and CRAH units across Australia from Brisbane, Sydney and Melbourne hubs, with one-off maintenance from $720 ex GST and annual plans from $1,940 ex GST.
The problem
Failures youcannot hear
Chilled water precision cooling behaves differently to the direct expansion equipment in most Australian comms rooms. A CHW CRAC or CRAH unit has no compressor and no refrigerant circuit of its own. It is a coil, a fan array, a control valve and a controller, and everything it does depends on the chiller plant upstream delivering water at the right temperature, the right flow rate and the right quality.
The typical symptom is not a hard fault. It is a unit that still runs, still reports healthy, and quietly stops holding setpoint on the hottest afternoon of the year because its coil has fouled, its two-port valve is passing, or its return water temperature has drifted so far that the coil no longer has the delta T to reject the load. By the time the alarm sounds, the rack inlet temperatures have already moved.
Indigi Power and Cooling is an Indigenous and Veteran-owned critical infrastructure service provider, Supply Nation and ICN Gateway registered. We maintain Vertiv Liebert, Schneider Electric Uniflair, STULZ, Emerson and Daikin Applied chilled water precision cooling across data centres, hospital plant rooms, government data halls and enterprise server rooms nationally.
Terminology
Is a CHW CRACthe same as a CRAH?
Refrigerant
on site
- Compressor inside the unit
- Capacity trimmed by compressor staging or inverter
- ARC licence required for any refrigerant work
- Maintenance risk sits in the unit itself
- Comms rooms, switch rooms, small to mid server rooms
Chilled water
from plant
- No compressor, cooling produced by the central chiller
- Modulating two-port or three-port valve plus EC fan speed
- No ARC licence at the unit, required at the plant
- Risk split between the unit and the chiller plant, pumps and pipework
- Large data centres, colocation halls, hospital and campus plant
In practice the two terms describe the same equipment from two different vocabularies. Australian mechanical contractors and building services documentation usually say CHW CRAC unit or chilled water CRAC. Data centre operators, hyperscale design documents and equipment datasheets from Vertiv and STULZ usually say CRAH, which stands for computer room air handler.
The distinction purists draw is that a true CRAC contains its own refrigeration cycle, so a chilled water unit is technically an air handler rather than an air conditioner. That is correct, and it is also why you will see the same physical cabinet in a Sydney data hall labelled a CRAH on the drawings and a CHW CRAC on the maintenance schedule. If you are pricing maintenance, the two words mean the same visit.
Operating principle
How a chilledwater unit works
Two numbers tell you whether the system is healthy: chilled water supply temperature, and delta T between supply and return.
Plant produces chilled water
A central chiller plant circulates chilled water through primary and secondary pumping to each CRAH in the data hall. Legacy building systems run around 6 to 7 degrees Celsius. Modern data centre designs deliberately raise this to 10 to 18 degrees, because a warmer loop lets the chiller run more efficiently and opens up hours of free cooling.
Air crosses the coil
EC fans draw warm return air from the hot aisle across a finned cooling coil. Heat transfers from the air into the water, and the cooled supply air is discharged into the underfloor plenum or directly into the cold aisle.
A valve trims capacity
Capacity is trimmed by a modulating chilled water control valve rather than by cycling a compressor. The controller measures return or supply air temperature and opens or closes the valve to hold setpoint. That is why a CRAH holds a very tight tolerance, and why a valve that no longer seats properly is such a serious fault.
Delta T tells you the truth
A falling delta T is the single clearest early warning that a coil is fouling or a valve is passing, and it is visible in the BMS trend long before a temperature alarm fires.
Scope of works
What a CHW service covers
A CHW service is not a filter change. Because the unit sits between a chiller plant and a data hall, the visit has to prove three things independently: that air moves correctly, that water arrives correctly, and that the controls are telling the truth.
| Task | What it prevents |
|---|---|
| Air side | |
| Filter inspection, differential pressure check and replacement | Restricted airflow, increased fan energy, loss of usable capacity |
| Chilled water coil inspection, fin comb and clean | Fouled coil, falling delta T, silent capacity loss |
| EC fan and motor inspection, vibration and current draw | Bearing failure, fan array imbalance, underfloor pressure loss |
| Supply and return airflow and underfloor plenum pressure check | Hot spots, air bypass, recirculation at the rack face |
| Water side | |
| CHW supply and return temperature verification against design | Chiller plant drift going undetected at the unit |
| Water flow rate and coil pressure drop measurement | Under-flow, blocked strainer, hydronic imbalance across the hall |
| Two-port and three-port control valve stroke and seating test | Passing valve, loss of modulation, overcooling and wasted chiller energy |
| Isolation valve, flexible connection and strainer inspection | Leaks into a live data hall, inability to isolate for repair |
| Water quality, glycol concentration and corrosion inhibitor sampling | Scale, biofilm, internal coil corrosion, pinhole leaks |
| Air venting and expansion vessel pressure check | Air locked coil, noisy circuit, uneven cooling across the coil face |
| Controls, electrical and safety | |
| Temperature and humidity sensor calibration | Controller acting on false readings, setpoint drift |
| BMS and SCADA point verification, alarm and teamwork mode test | Units fighting each other, alarms not reaching the NOC |
| Electrical termination inspection and thermographic scan | Loose terminations and hot joints, in line with AS/NZS 3000 |
| Humidifier, condensate tray and pump service | Water on the floor of a live data hall, blocked condensate line |
| Leak detection tape and float switch test | Undetected coil or pipework leak beneath the raised floor |
Where we work
Environments we maintain
Frequency
Service intervals
| Interval | Tasks |
|---|---|
| Monthly | Visual filter check, condensate tray and pump check, alarm log review, walk the hall for leaks and hot spots |
| Quarterly, professional | Filter replacement, fan and motor inspection, CHW flow and valve testing, delta T verification, sensor calibration, humidifier service |
| Annually, comprehensive | Full coil clean, thermographic scan of electrical terminations, water sample and analysis, glycol and inhibitor top up, capacity verification against design load, controls and BMS audit |
| Pre-summer, QLD, WA and NT | Complete the annual service before October. Chiller plant capacity falls as ambient rises, and a fouled CRAH coil that coped in July will not cope in January |
| After any chiller plant work | Re-verify supply temperature, flow and delta T at every CRAH. Plant changes routinely shift hydronic balance across the hall |
Diagnostics
Faults we attend
| Symptom | Likely cause | Where to look first |
|---|---|---|
| Runs continuously but will not reach setpoint | Fouled coil, low water flow, or CHW supply temperature higher than design | Compare supply and return water temperature against the design delta T |
| Room overcools and chiller energy climbs | Control valve passing or failed open | Command the valve closed and check for continued flow and coil surface temperature |
| Delta T falling month on month in BMS trends | Progressive coil fouling on the air side or water side | Coil differential pressure and a water sample |
| Uneven cooling across the coil face | Air locked coil, partially blocked strainer | Vent the coil, inspect and clean the strainer |
| Water under the raised floor | Condensate blockage, flexible connection failure, or internal coil corrosion | Condensate tray and pump, then flexible connections, then coil pressure test |
| Units in the same hall fighting each other | Teamwork or unit-to-unit control not configured, or sensors out of calibration | Controller configuration and sensor calibration across the group |
| Humidity swinging outside the ASHRAE envelope | Humidifier fault, or coil running below dew point and dehumidifying unintentionally | Humidifier service plus a review of chilled water supply temperature strategy |
Commercial
Maintenance pricing
Full inspection across air side, water side and controls, with a written service report and recommendations.
Scheduled visits, priority breakdown response and consumables included. The standard choice for a single critical unit.
Multi-unit and multi-site. Chiller plant, pumps and pipework can be bundled into the same schedule and the same report.
Coverage
Australia widefrom three hubs
Brisbane and QLD
Brisbane CBD, Tingalpa, Woolloongabba, Eight Mile Plains, Port of Brisbane, Gold Coast, Sunshine Coast, Ipswich, Townsville, Cairns
Our HQ hub. Complete the annual coil clean and water sample before October, when Queensland ambient starts eroding chiller plant capacity.
Sydney and NSW
Sydney CBD, Parramatta, North Ryde, Macquarie Park, Western Sydney, Alexandria, Newcastle, Wollongong, Canberra
The largest concentration of chilled water data halls in Australia. We work to site access, permit and change-control requirements in colocation environments.
Melbourne and VIC
Melbourne CBD, Port Melbourne, Docklands, Dandenong, Tullamarine, Geelong, Ballarat, regional Victoria
CRAH maintenance across the Port Melbourne to Tullamarine corridor, plus hospital and university campus chilled water plant.
Perth and WA
Perth CBD, Fremantle, Kewdale, Kalgoorlie, Pilbara, regional WA
Resources and government sites, where water quality and make-up water chemistry need closer monitoring than on the east coast.
Adelaide and SA
Adelaide CBD, Port Adelaide, Salisbury, Edinburgh, Whyalla, regional SA
Defence, government and health facility chilled water plant, including campus loops serving multiple data halls from shared chillers.
Darwin and NT
Darwin CBD, Palmerston, Katherine, Alice Springs, remote NT sites
The most demanding cooling conditions in Australia. High humidity year-round makes condensate management and dew point control critical.
Western Australia, Tasmania and Pacific Islands: we service chilled water precision cooling in Hobart, regional Tasmania, Papua New Guinea, Fiji and other Pacific Island nations, and can combine CHW servicing with UPS and battery maintenance in a single mobilisation to keep travel costs down. Contact us to discuss scheduling.
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Questions
CHW CRACand CRAH FAQs
The questions data centre and facilities teams ask us most. If yours is not here, call 1800 046 344.
What is a CRAH unit?
A CRAH (computer room air handler) is a data centre cooling unit that removes heat from room air using a cooling coil supplied with chilled water from a central chiller plant. It has no compressor and no refrigerant circuit of its own. Fans draw warm return air across the coil, heat transfers into the water, and the cooled air is delivered to the cold aisle or underfloor plenum. In Australian building services documentation the same unit is often called a CHW CRAC or chilled water CRAC unit.
What is the difference between CRAC and CRAH?
A CRAC unit contains its own refrigeration cycle and cools air using refrigerant expanded inside the unit. A CRAH has no compressor and cools air using chilled water produced by a central chiller. Practically, a CRAC needs ARC-licensed refrigerant work and a CRAH does not, but a CRAH depends entirely on the chiller plant, pumps and pipework upstream of it.
What is the maintenance of a CRAH unit?
CRAH maintenance covers three systems. Air side: filter replacement and differential pressure, coil cleaning, EC fan and motor inspection, airflow and plenum pressure. Water side: chilled water supply and return temperature verification, flow rate and coil pressure drop, control valve stroke and seating, strainer inspection, and water quality with glycol and corrosion inhibitor sampling. Controls: sensor calibration, BMS point and alarm verification, thermographic scan of electrical terminations, and humidifier, condensate and leak detection testing.
How does a chilled water CRAC unit work?
A central chiller produces chilled water, typically at 6 to 7 degrees Celsius in legacy building systems and 10 to 18 degrees Celsius in modern data centre designs, and pumps circulate it to each unit. Fans draw warm return air across the finned coil, heat transfers from the air into the water, and the cooled supply air is discharged into the cold aisle or underfloor plenum. Capacity is trimmed by a modulating chilled water control valve rather than by cycling a compressor.
How often should a chilled water CRAC unit be serviced?
Twice per year is the minimum for a standard server room. Quarterly professional servicing is recommended for data centres, colocation halls, hospitals and telecommunications infrastructure. Sites in Queensland, Western Australia and the Northern Territory should complete their annual comprehensive service before October, and every site should re-verify supply temperature, flow and delta T at each unit after any chiller plant works.
What are the maintenance requirements for the chilled water plant itself?
The chiller plant needs condenser and evaporator inspection, refrigerant pressure and leak checks by an ARC-licensed technician, water treatment and quality testing, pump and strainer servicing, electrical and control verification, and annual professional service. Where the plant is served by a cooling tower, Legionella risk management under AS/NZS 3666 applies as a separate compliance obligation.
What does CHW CRAC maintenance cost in Australia?
A one-off chilled water CRAC or CRAH maintenance visit is $720 ex GST for a single unit, including full inspection and a written service report. A standard annual maintenance plan is $1,940 per year ex GST. Multi-unit data halls and multi-site fleets are quoted individually, with the per-unit rate falling as fleet size increases.
Related services
Equipment
Brands and modelswe service
Our technicians work across every major chilled water precision cooling platform deployed in Australian data centres and plant rooms. If your unit is not listed, it is very likely we still service it. Tell us the model and we will confirm.
We also supply genuine replacement coils, EC fans, control valves, actuators and sensors. If you are specifying or replacing chilled water plant rather than maintaining it, see CRAC installation and commissioning.
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