Computer Room

[spark master]

I'm dealing with a server room. 3 servers, phone system, video camera systems, etc, etc.
3 phase 20amp circuit feeding the room.

Is there a way to take the amp measurements from all 3 phases... and figure out the BTU's of heat produced by the computer equipment?

The A/C unit in the room needs to be replaced, as it is too small. So we're trying to size the A/C unit by the current draw.

 

[zbang]

Sure- 3500 watts is about one ton of cooling; there are many on-line calculators for this. Or just give the info the the HVAC company and let them size it.

 

[Julius Right]

See:
http://apcmedia.com/salestools/NRAN-5TE6HE/NRAN-5TE6HE_R3_EN.pdf?sdirect=true
http://citeseerx.ist.psu.edu/viewdo...00CF4A4?doi=10.1.1.583.5605&rep=rep1&type=pdf

 

[Julius Right]

See:
Heat Loss from Electrical and Control Equipment in Industrial Plants: Part ll-Results and Comparisons
https://www.researchgate.net/public...strial_Plants_Part_ll-Results_and_Comparisons

 

[spark master]

Each phase is drawing 5 amps...
so 15x120= 1800 watts.

So technically... I should only need 1/2 ton of cooling, but a 12,000 BTU (1 ton) mini split isn't doing it....

 

[drktmplr12]

Each phase is drawing 5 amps...
so 15x120= 1800 watts.

So technically... I should only need 1/2 ton of cooling, but a 12,000 BTU (1 ton) mini split isn't doing it....

Not to over-complicate the task here.. but your best bet is to find some kind of published the heat loss data (watts) for the major equipment and add it all up. Also include any UPS and lighting. If any walls are exterior, the insulation value of the walls, windows, and/or ceiling will need to be considered as well.

The square D worksheet is probably a good place to start and see where it gets you.

edit: If you know an HVAC person, run the result past them.

 

[ron]

So technically... I should only need 1/2 ton of cooling, but a 12,000 BTU (1 ton) mini split isn't doing it....

We always urge folks to bring on an electrical person to do electrical things, it might make sense to do the same for HVAC.

Generally my HVAC colleagues get involved in issues related to enough tonnage but not the proper airflow, or the difference between sensible cooling and (maybe its latent or something like that hokus pokus). But it might not be straight forward formula.

Sort of like when the UPS might be rated for enough KVA (printed big on the smaller UPSs to trick the IT guys), but not enough kW to carry the load and it keeps bouncing over to bypass and they can't figure out why. Hokus pokus unless you know the magic item called power factor.

 

[drktmplr12]

We always urge folks to bring on an electrical person to do electrical things, it might make sense to do the same for HVAC.

Agree on this point. The only input electrical should have into HVAC sizing is the amount of wattage dissipated as heat from electrical equipment (edit: and lighting). Unless you are a MEP or ME and you know how to size HVAC, you should enlist the expertise of someone who regularly sizes this stuff. That way you aren't stuck holding the basket when the unit is short cycling or not adequately cooling.