Electrical Room cooling load 1

[atlas06]

Does anyone know of published data for sizing electrical rooms cooling loads (heat from switch gear equipment and tranformers), besides the 2% rule (some say 1.5%) of total load (KW) is heat radiated to the room.
Others will say use 50 btu per KVA for enclosed transformers (dry type).
We typically oversize cooling equipment (for large swicth gear rooms) for future expansion.
If it is a main electrical room, we provide an AC unit for operation above 80F ambient and an exhaust fan for operation below 80F ambient. Energy savings and redundancy are thus accomplished. For small electrical closets, we provide an exhaust fan only.

What do you guys use to estimate your electrical room cooling loads?

 

[ChrisConley]

I usually try to get the exact numbers from the electrical engineer, preferably written down.

The 2% rule hold fairly close as most transformers seem to be rated at 98%.

You can also ask the electrical engineer about operating temperatures, some equipment will allow a higher ambient, some lower.

 

[AbbyNormal]

I think the 50 btu rule is the same as 1.5%.

Equipment room is a big sensible load anyways, 2% on a transformer is pretty good.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[atlas06]

Glad to see that we are with the industry practice. Good to have confirmation from your peers.
Thanks

 

[AbbyNormal]

And I doubt those those transformers are loaded much more than 70%.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[wsuengineer]

What about the cooling load for a MCC BUS 1200 AMPS 277/480 VOLTS?

 

[wsuengineer]

IGNORE THE ABOVE REPLY. I USED 98% EFFICIENCY.

 

[lilliput1]

Single Phase Transformers
KVA Watts Full Load Loss
3 158
6 246
9 292
15 455
Three Phase Transformers
KVA Watts Full Load Loss
15 852
30 1675
45 2188
75 3379
112.5 4023
150 5090
225 6394
300 8700
400 10800
500 13000
750 15650
1000 18720
1500 27400
2000 32000
2500 38000
Locate exhaust high above the transformers. blow supply down at the floor.

 

[atlas06]

Thank you so much for taking time to type all this data. It is getting copied and saved.