Server room air conditioning

A server room is not an office

An office is cooled for people for part of the day. A server room is cooled for equipment that never switches off. Nearly every watt of electricity your servers, switches, storage and UPS draw ends up as heat in the room, all day and all night, in January as well as July. If the cooling stops, the temperature climbs and the equipment either throttles back, shuts itself down or fails.

That changes how the cooling has to be chosen. It needs to run 24/7, cope with cold outdoor weather (because it still has to cool in winter), and have a plan for when a unit breaks down. A standard home-style split thrown on the wall can work for a while, but it is rarely the right long-term answer for a room the business depends on.

Sizing from the heat load, not the floor area

We size server room cooling from what is in the room. On the survey we look at the power drawn by the racks and UPS (your IT team or the UPS display usually knows this), any heat coming through walls, windows or the ceiling, and the plans for growth. A small room with a lot of kit can need far more cooling than a large office.

We also look at where the air goes. Servers take cool air in at the front and push hot air out of the back. If the cooling blows straight onto the hot side, or the hot air is drawn back into the front of the rack, the room thermometer can read fine while the equipment runs hot. Placing the indoor units with the rack layout in mind makes a real difference.

Comfort units, technical splits and close control

There are broadly three kinds of equipment used in IT rooms:

• Comfort air conditioning: the wall or ceiling units you see in offices. Built for people and part-time use. Fine for a room that is occupied and has a small comms cabinet in the corner.
• Commercial splits suited to technical cooling: several manufacturers offer splits and controls meant for all-year cooling, including low outdoor temperatures. We check the manufacturer’s data for the exact model before we recommend it. This is the usual choice for small and medium server rooms.
• Close control units: floor-standing precision units that hold temperature and humidity within tight limits. They suit larger, denser rooms and data halls. They are specialist plant: if your room needs close control, we will say so on the survey and tell you honestly whether it is a job for us.

N+1: planning for the day a unit fails

Every unit needs servicing and every unit can fail. N+1 means fitting one more cooling unit than the room needs, so if one stops or is switched off for a service, the others carry the load. For a small room that often means two units, each able to cool the room on its own.

The units need a controller that shares the running hours between them and switches to the standby automatically on a fault. Without that, the spare unit may sit unused for years and fail the day it is needed. We set up the changeover and test it at commissioning, then again at each service.

Alarms and monitoring

A failed unit at 2am on a Saturday is only a problem if nobody knows. We can fit a high-temperature alarm and connect the system’s fault outputs, where the equipment supports it, to your building management system, your IT monitoring or a simple alerting device. Many UPS units and racks also have their own temperature sensors, and it is worth setting alerts on those too. If an alarm goes off, our 24/7 emergency line takes the call.

Electrics, condensate and access

Server room cooling should have its own supply, protected so that a fault elsewhere does not trip it. We are NICEIC approved, so we can fit the circuits and isolators as part of the job. Condensate needs a safe route away from the racks: we avoid running drains over equipment and fit a pump with an alarm where gravity drainage is not possible. Outdoor units need clear airflow and a secure position, and we plan pipe routes so the room stays sealed.

We can do the work out of hours and keep the existing cooling running while the new system is connected, so the room is never left without cooling.

Leak checks, TM44 and maintenance

A system that runs 24/7 needs regular care. A maintenance contract covers filter and coil cleaning, changeover tests, electrical checks and the F-Gas leak checks the law requires for larger refrigerant charges. If the cooling in the building adds up to more than 12 kW, it also needs a TM44 inspection at least every five years. Prices for server room systems and contracts are set after the survey, on a fixed-price quote.