Electrical Room AC Sizing 3

[JPippet]

I need to determine the BTUs contributed to our electrical room from all of the equipment. We have 3 phase transformers with KVA values of 112.5, 300, 500, and 2500. There are also electrical control cabinets with motor drives ranging from 1 to 200 HP. I know I can't get an exact answer, I just need to be pointed in the right direction.

 

[Wareagl487]

The control cabinet heat is negligible. Assume 3% heat reject for the transformers.

 

[tys90]

VFDs give off heat too, roughly 115W per HP. Check the manufacturer for actual dissipated power numbers for mounting drives in an enclosure.

 

[cdxx139]

Add up the KVA's of the transformers
multiply by inefficiency (0.03) as stated wareagl487
convert to BTU's (3413 Btu/Kw)
and that is the sensible cooling load (not total cooling load) of the transformers.
add solar load of space
add other equipment (as stated by tys90)

if using outdoor air,
divide by 1.08
divide by delta T of 9 (104-95 for northeast US)
divide by 1.2 (safety factor)
which comes to over 8000 cfm of OA.

 

[JPippet]

This is excelent info. Thank you so much.