BTU Rating for a UPS

[Naveen Chenoli]

Hi,

WE have a 42Kw UPS to be installed in the Server room. Does anyone know how to calculate the BTU rating for a UPS?? I could not get any details from the web site ( Its a BPC Power pro RT)

thanks

[Pedro Albuquerque]

I dont understand your question, BTU is a measurement unit for cooling, it has nothing to do with electricity, so what do you really want to know??

[Darren Prior]

Hi,

I'm afraid I don't know the answer to your question, but I'm assuming that you need to know the BTU rating so that you can calculate how much extra cooling is required for your server room. The BTU (British Thermal Unit) is a unit of energy, kW is a unit of power.

The following website has a conversion factor between kW and BTU/hr:

http://www.coxhardware.com/usefulinfo/charts/3a_engtbl.htm

which shows that 42Kw ~143000 BTU/hr

There's also some useful info on BTU and conversion here: http://www.eia.doe.gov/kids/btudef.html

regards,

Darren.

[Pedro Albuquerque]

Assuming that you need to know the BTU rating so that you can calculate how much extra cooling is required for your server room, you can'tdo the caculations like that, 143000 BTU is an excesive value. An UPS with 42Kw doesn't mean that you will need that kind of refrigerention. You must see on the UPS specifications, what's the thermal dissipation to calculate what you need, example; for a room with 30 square meters, 18000Btu is a very good value. Also, an UPS like yours is not suposed to dissipate so much heat unless, when charging batterys, an Alpha server GS80 probably generates more heat.

[Joshua Scott]

A UPS doesn't generate much heat. If you figure out how much the protected equipment generates, then that will be the main determinate for how much cooling you will need for the room.

-Josh

[A. Clay Stephenson]

Actually BTU's are units of energy (can be thermal, electrical, kinetic, ...) and KW's are units of Power. You really need to know a BTU/HR rating so that you are comparing apples to apples.

What you don't say is the efficiency of the UPS and that is really the crux of the problem. Modern UPS's typically have an efficiency of 93-96%. Let's use 95% as a good round value (and the efficiency typically also varies as a function of fraction of rated load).

43 KW(out) / .95 = 45.3 KW(in)
The difference between input power and output power 45.3 KW - 43 KW = 2.3KW is the power that is dissapated as heat and that is your additional cooling load -- at full load.

2.3 KW X 3413 BTU / HR - KW = 7850 BTU/HR

You therefore need to make sure that your existing HVAC unit can handle the additional 7850 BTU/HR thermal load. If the efficiency rating is known, you can , of course, may more refined calculations but 95% should be "close enough".