Server room and comms cupboard air conditioning

Why comms rooms are different

A London office might need cooling from May to September, during working hours. A server room or comms cupboard needs it every hour of every day. Network switches, servers, storage and power supplies turn almost all the electricity they use into heat, and they do it constantly. In a small, closed cupboard that heat builds fast.

The usual problems are:

• the comms cupboard sharing the office system, which switches off at 7pm
• a unit that heats in winter because the office system is set to heat
• a cupboard with no cooling at all, just a door left open
• a unit sized years ago, before more equipment was added

Sizing it properly

Equipment heat output is the starting point. As a rule of thumb, the heat given off is close to the electrical power the equipment draws. Add to that:

• lighting
• any people working in the room
• heat gain through walls, especially an outside wall or a wall next to a kitchen
• sun on any windows

Then allow room for growth. Comms rooms rarely get smaller.

Factor	Why it matters
Equipment power draw	the main heat source, running all the time
Room size and walls	small rooms heat up faster
Outside walls or windows	add heat in summer
Future equipment	avoid undersizing in two years
Target temperature	follow the equipment makers’ guidance

Choosing a unit for year round cooling

Home split systems are designed mostly for summer cooling. A comms room needs cooling in January too, when the outdoor temperature is low. Not every unit is happy cooling when it is cold outside. Choose a unit the manufacturer rates for low ambient cooling, so it keeps working through a London winter.

Other features worth having:

• auto restart after a power cut, so cooling resumes without anyone pressing a button
• a high temperature alarm or a link to your building management or monitoring system
• dedicated controls that office staff cannot change by accident

Resilience

If a business depends on its comms room, a single unit is a single point of failure. Common approaches are:

• two units with a controller that runs one as duty and one as standby, swapping over regularly
• a temperature alarm that alerts someone if the room gets too warm
• a service plan with visits more frequent than for office cooling, since the unit runs constantly

Condensate and leaks

A unit running all year makes condensate for much of it. Water and IT equipment do not mix, so the condensate route matters more here than anywhere. Avoid mounting the indoor unit directly above racks if you can. If the drain relies on a pump, consider a pump with an alarm or a cut out that stops the unit if water backs up. Our guide to air conditioning leaking water explains the common causes.

Landlord and building rules

In the City of London, most offices are let floor by floor, and the outdoor unit for a comms room usually has to go on a roof plant deck, a terrace or a designated plant area controlled by the landlord. Expect to need a licence for alterations and the landlord’s agreement on the outdoor unit location, pipe routes through risers and the condensate connection. Some buildings provide a dedicated cooling supply for tenant comms rooms, which can be simpler. Our City of London page explains how City buildings handle this.

New outdoor plant on commercial property normally needs planning permission, because the heat pump permitted development rules apply to homes only (Planning Portal).

Legal checks

The refrigerant work must be done by an engineer with an F-gas qualification, working for a company certified by an approved body listed on gov.uk. If the comms room units and the office system together exceed 12kW, the building needs a TM44 inspection at least every five years, explained in our TM44 guide. Larger systems may also need F-gas leak checks.

Getting it right

The steps are straightforward: measure the load, choose a unit built for constant cooling, plan the drain, add an alarm and keep it serviced. Our office air conditioning page explains how a commercial survey and install run.

Questions to ask before you install

Before choosing a system for a comms room, it helps to answer:

Question	Why it matters
What is the total power draw of the equipment?	sets the cooling load
Will more equipment be added in the next few years?	avoids undersizing
Is there an outside wall or window?	adds heat in summer
Where can the outdoor unit go, and who controls that space?	landlord consent and planning
Where will condensate drain?	water near IT equipment is a risk
Who gets alerted if the room overheats?	a fault at the weekend can go unnoticed
Is a standby unit justified?	depends on what the business can tolerate

The answers shape the design and the quote, and they are what the landlord’s engineer will want to see too.