Server room cooling designed for 24/7 duty, not office hours.
From 5 kW edge cabinets to 100 kW comms rooms — precision cooling with the redundancy, monitoring and SLA response that critical IT actually requires.
Server rooms need dedicated 24/7 cooling sized at IT load × 1.1 + headroom, delivered at 18–27 °C inlet with N+1 redundancy. Office VRF isn't the right answer — precision DX (CRAC), in-row or split-with-redundancy is.
Four architectures, chosen by density and load.
Split-system dedicated cooling
One outdoor condenser to one wall-mount or ceiling cassette, sized for 24/7 duty. Right answer up to ~14 kW IT load. Redundancy achieved by installing N+1 units on independent circuits.
DX close-control (CRAC)
Purpose-built precision cooling with tight temperature (±1 °C) and humidity (±5 %RH) control. Downflow or upflow, from 5 kW to 100 kW. Industry standard for comms rooms and edge cabinets.
In-row cooling
Chilled-water or DX units mounted between racks, drawing hot aisle air and returning cold aisle air. Efficient above 15 kW/rack — the density point where perimeter cooling stops working.
Free cooling & economiser
For sites above 30 kW IT load, air-side or water-side economisers can deliver PUE below 1.3 for 6+ months of the UK year. Retrofit-able onto existing CRAC where floor void allows.
What we build into every server room contract.
- —N+1 redundancy on every kW of IT load
- —Independent electrical supplies for each unit
- —Leak-detection cables under raised floor
- —24/7 remote monitoring with SMS/email alerting
- —SLA-backed 4-hour engineer response
- —F-Gas record and TM44 lodgement kept current
Related: emergency response, F-Gas compliance, TM44 inspections, VRF vs split, all sectors.
The questions IT and facilities ask before signing off.
What temperature should a server room be?
ASHRAE recommends 18–27 °C at the equipment inlet, with 20–25 °C the sweet spot for reliability and PUE. Humidity should sit between 40 % and 60 % RH. Room ambient can be higher than inlet — what the cooling system controls is inlet air, not room air.
How do you calculate server room cooling requirements?
Total kW of IT load × 1.1 for lighting and lookup + 5–10 % headroom = required kW of cooling. A 10 kW cabinet needs about 12 kW of cooling. Never size on floor area alone — a 6 m² comms room can carry 40 kW of IT load and need commercial-grade CRAC.
What is CRAC and CRAH?
CRAC (Computer Room Air Conditioning) is a DX precision cooling unit with its own compressor. CRAH (Computer Room Air Handler) is a chilled-water unit fed from a central chiller plant. CRAC suits standalone rooms up to ~80 kW; CRAH scales better in dedicated data centre environments.
Do server rooms need N+1 cooling?
For any business-critical IT load, yes. N+1 means one extra cooling unit beyond what's needed at peak load, so a single unit can fail or be serviced without downtime. For revenue-generating platforms and regulated data (finance, health), 2N is the standard.
Can office VRF cool a server room?
For a small comms room (≤ 8 kW), sometimes — but it's rarely the right answer. Office VRF is scheduled around occupancy, has no humidity control, and shares a condenser with zones that shut off overnight. Server rooms need independent 24/7 dedicated cooling with redundancy.