Resource Hub
CRAC resources
and frequently asked questions.
Sizing guides, refrigerant types, set-point recommendations, ASHRAE TC 9.9 envelope, AS/NZS 5149 compliance, high-density / liquid-cooling decision tree, and the questions our team answers most often.
Topology
What is a CRAC unit?
A CRAC unit (Computer Room Air Conditioning) is a precision cooling system designed specifically for data centres, server rooms, and telecommunications environments. Unlike standard comfort air conditioning, CRAC units maintain tight temperature and humidity tolerances, operate continuously, and handle the high sensible heat loads from IT equipment. They typically include redundancy options (N+1, 2N) for concurrently-maintainable operation.
CRAC vs CRAH — what is the difference?
CRAC stands for Computer Room Air Conditioner and refers to direct-expansion (DX) units with refrigerant compressors. CRAH stands for Computer Room Air Handler — uses chilled water from a centralised plant with no compressor in the indoor unit. CRAH is more efficient at scale but requires chiller plant; CRAC is simpler to deploy without central plant. Modern CHW perimeter units (e.g. Vertiv Liebert PCW) are technically CRAH but are commonly grouped under "CRAC" in industry vernacular.
DX vs CDW vs CHW — which CRAC topology is right for my site?
DX (Direct Expansion) is best for small to mid sites (<500kW IT load) where per-unit air-cooled condensers are economical. CDW (Condenser Water) suits mid sites with centralised heat rejection via cooling tower. CHW (Chilled Water) is best for large data centres (>1MW IT) where central chiller plants drive part-load efficiency. AI/high-density sites increasingly mix CHW with rear-door heat exchangers and direct-to-chip liquid cooling.
What set-point should I run my data centre at?
ASHRAE TC 9.9 recommended envelope spans 18-27°C supply air, with most modern IT comfortable at the warmer end. Operating in the 24-27°C range substantially reduces cooling energy with no reliability impact for current-generation equipment. Older equipment (pre-2010) may benefit from 22-24°C. We can audit your set-points and advise.
Sizing
How do I calculate sensible heat load for a server room?
Take the IT load draw in watts (from UPS output meter or rack PDUs), add lighting and occupancy contribution (~5W/m² lighting, 80W per occupant), add external gain (10-15% of IT for an internal room). Convert to kW. Add 25% growth headroom and round up to the nearest practical CRAC unit size.
Maintenance
How often should CRAC units be serviced?
Quarterly servicing is the industry standard for mission-critical CRAC, with annual comprehensive services adding refrigerant leak detection, coil cleaning, and electrical IR scans. Sites with high-density loads (>10kW/rack) or heavy dust exposure may require monthly filter checks.
What does CRAC servicing include?
Compressor and condenser performance test, refrigerant pressure and superheat checks, air filter replacement, airflow balancing, coil cleaning, humidifier service and water-treatment check, electrical connection inspection (IR), control system diagnostics, alarm review, and setpoint validation against ASHRAE TC 9.9.
Do you also maintain cooling towers and chillers?
We can service cooling towers and chiller plant under a coordinated programme, or work with your existing mechanical-services contractor for that scope. Either way, we provide the AS/NZS 3666 compliance review on the water side that ties the indoor and outdoor scopes together.
Compliance
What refrigerants do you support?
We service all common DX CRAC refrigerants in Australian use: R410A (legacy), R32 (mid-life), and R513A (current low-GWP CRAC, e.g. Vertiv CoolPhase). We do not handle R22 except for emergency leak repair pending replacement, in line with the phase-out.
Are you ARC-licensed?
Yes. All our refrigeration technicians hold current ARCtick licences (RAC1 / RAC2) issued by the Australian Refrigeration Council, which is a legal requirement for any refrigerant handling work in Australia. We maintain a refrigerant logbook for each site as part of compliance records.
What Australian Standards apply to CRAC work?
AS/NZS 5149 (refrigerating systems safety) is mandatory for DX work. AS/NZS 1668.2 (mechanical ventilation) applies to all data hall designs. AS/NZS 3666 (Legionella control) covers cooling tower / chilled-water plant. ARCtick licensing is a federal regulatory requirement for refrigerant handling.
Commissioning
Why is manufacturer commissioning required?
Most CRAC manufacturers require their factory-trained engineers to perform initial commissioning to activate the full warranty. Manufacturer commissioning also ensures firmware, control logic, and refrigerant charge are configured per the validated reference build.
High-Density / AI
When should I consider liquid cooling?
Liquid cooling becomes economically attractive above ~30kW per rack — typical thresholds for AI training, GPU clusters, and HPC nodes. Below that, optimised air cooling with hot-aisle containment usually wins on capex.
Direct-to-chip vs rear-door vs immersion — which retrofit is easiest?
Rear-door heat exchangers (RDHx) are the easiest retrofit — they bolt onto existing racks and remove ~80% of rack heat at the door. Direct-to-chip handles the highest-density GPU loads (60-100kW/rack). Single-phase immersion is best for very-high-density / ultra-low-PUE deployments but requires significant facility change.