Com Room Heat Loss
Com Room Heat Loss
(OP)
Can anyone point me to a standard for estimating heat loss (or heat added to a room) in say Watts/ft^2 for a communications room in a research building? This information will be used by the mechanical folk to determine HVAC requirements.
Thanks!
Thanks!





RE: Com Room Heat Loss
Heat gain is simply the heat load from your equipment plus body heat.
Additional heat load from solar or whatever, they can figure out.
TTFN
RE: Com Room Heat Loss
RE: Com Room Heat Loss
If these people are actually qualified to do A/C, they should only be asking for the heat dissipation values for your equipment.
TTFN
RE: Com Room Heat Loss
People: 74 W/person sensible and 58 W/person latent
Lights: 2.5 W/ft2
Equipment: 1.0 W/ft2
Hope this is usefull.
RE: Com Room Heat Loss
The task of determining the load in such a situation is the heart of the problem. If possible, obtain cut sheets of catalog data on every piece of equipment. Always compare the electrical load data with the heat rejection values - if listed. If they don't make sense, find out why. If you can't resolve the discrepancy, then count on the higher number. If none of that is available, then tally the nameplate data yourself: 1W = 3.41 Btuh - burn that into your memory. If needed, I have actually taken amprobe readings on the power lines to get a better idea on the load.
There are a lot of pitfalls with sizing the A/C equipment, too.
RE: Com Room Heat Loss
Not all of the 75kVA turns into heat added to an area. Of course the transformer has heat losses associated with operation, but 100% of its rating certainly not transfered into heat. Furthermore....small transformers often operate at 20-40% of the rating.
Is it common practice for HVAC designers to assume full rating heat gain from electrical equipment when sizing A/C units? If so...its a good thing I'm not a mech engineer, as the idea behind such practice makes no sense to me.
Thanks,
RE: Com Room Heat Loss
I would always recommend tallying the specific load, but in some cases (perhaps yours?) the customer knowledge is of little help. Resorting to this ultimate case may be useful in that type of environment.
No offense, but I can understand why some of these things make no sense to you. That's why there are "mech engineers."
RE: Com Room Heat Loss
RE: Com Room Heat Loss
Technically speaking, your example of the fan is correct. Practically speaking, fan motors are usually inside the air handler and in the airstream, which means it's a "coil" load, not a "room" load. You are right to say that's off topic, and it's not useful to digress further.
Back to the x-fmr analogy, you were also correct, but you weren't seeing the full scope of the problem. A transformer - minus some judgment on safety factor - may be a reasonable estimate of connected load in the absence of other information. If someone was simply trying to cool the transformer, then the load would simply be the heat rejected due to the winding losses. I was offering a very real alternative to your conclusion that the ME didn't know what he/she was doing.
Back on topic, you said "Com" for communications, aka electronics, digital devices, computerized switching, etc., etc. Ever see a communications device convert electrical energy to mechanical energy? Ever hear of an electric heater or load bank? Except for the trivial amount of mechanical energy spent on disk drives or printers shuffling paper, the product of all that connected load is 100% HEAT.