Calculating The Size of Server Room Air Conditioning
This guide will show you how to calculate your requirements for an air conditioning system for your computer room or computer server center.
In principle it’s easy to calculate the size of an air conditioning unit you will need for your computer room, just add together all the sources of heat and install an air conditioning unit that can remove that much.
In practice it’s rather more complicated.
Fire regulations often require that computer rooms have levels of insulation far higher than that of a normal office or commericial space. Providing sufficient air conditioning cooling is essential to ensure reliable running of computer servers, routers, switches and other key equipment. Failure of the air conditioning can have serious consequences for the equipment itself and for your company. Early warning of cooling problems and spare capacity in the cooling system are both highly desirable.
Calculating heat load in a server room
The amount of heat generated is known as the heat gain or heat load. Heat is measured in either British Thermal Units (BTUs) or Kilowatts (KW). 1KW is equivalent to 3412 BTUs.
The heat load depends on a number of factors, by taking into account those that apply in your circumstances and adding them together a reasonably accurate measure of the total heat may be calculated*.
When looking air conditioning for a server room, consider the following:
- The floor area of the room
- The size and position of windows if any, and whether they have blinds or shades
- The number of room occupants (if any)
- The heat generated by equipment
- The heat generated by lighting
Floor area of the computer room
The amount of cooling required depends on the area of the room. To calculate the area in square metres:
Room Area BTU = Length (m) x Width (m) x 337
Window Size and Position
If, as is quite common, your Server Room has no windows, you can ignore this part of the calculation. If, however there are windows you need to take the size and orientation into account.
South Window BTU = South Facing window Length (m) x Width (m) x 870
North Window BTU = North Facing windows Length (m) x Width (m) x 165
If there are no blinds on the windows multiply the result(s) by 1.5.
Obviously if you are in the southern hemisphere you would swap the conversion factors as the heat on North facing windows is then greatest.
Add together all the BTUs for the windows.
Windows BTU = South Window(s) BTU + North Window(s) BTU
People
Purpose built Server Rooms don’t normally have people working in them, but if people do regularly work in your Server Room you will have to take that into account. The heat output from a simgle person is around 400 BTU per person, per hour.
Total Occupant BTU = Number of occupants x 400
Computer equipment
Clearly most heat in a Server Room is generated by the equipment. This is trickier to calculate that you might think. The wattage on equipment is the maximum power consumption rating, the actual power consumed may be less. However it is probably safer to overestimate the wattage than underestimate it.
Add together all the wattages for Servers, Switches, Routers and multiply by 3.5.
Equipment BTU = Total wattage for all equipment x 3.5
Lighting
Take the total wattage of the lighting and multiply by 4.25.
Lighting BTU = Total wattage for all lighting x 4.25
Consider switching off lights in computer or server rooms when not in use. Lights are for people to see what they are doing. Computers don't need lights. This will reduce your heat load considerably and save you money on your electricty bill too.
Total cooling required
Add all the BTUs together.
Total Heat Load = Room Area BTU + Windows BTU + Total Occupant BTU + Equipment BTU + Lighting BTU
This is the amount of cooling required so you need one or more air conditioning units to handle that amount of heat.
What size computer room air conditioning system do I need?
Small air conditioning units have a cooling capacity of between 5000 and 10000 BTUs. Small units may fit in windows, venting to the outside world.
Larger units may be rated in tons of cooling. 1 ton of cooling is equivalent to 12 thousand BTUs.
Disclaimer:
This calculation is intended as a rough guide only. Complete accuracy cannot be guaranteed.
Before you decide on an air conditioning system for your computer server room, you should commission a cost-free survey from ourselves.
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