Heat loss calculations

[mshields]

Lets say you have a 2500kVA double ended lineup with transformers outside. And off of the double ended switchgear you've got multiple DP's. to find heat loss to hand over to our HVAC guys, I typically use various data I've received from manufacturer's over the years based on number and size of breakers plus bus size. But I'm wondering if I could just do the following:

Assume a load of 80% of a single 2500kVA service (since system is a 2N).

assume no more than average Voltage drop for loads off that system is 2%.

Take the KVA using 480V subtract the KVA using 480V x 98%.

Use the difference as the maximum heat loss.

Is there anything wrong with this logic?

I suppose that one thing would be the fact that much of the losses are occuring in the cable outside of the room. So your attributing more loss to the main room than there will actually be. But still - it's a safe approach is it not?

Thanks,

Mike

 

[Besoeker]

In the absence of actual data, I usually work on 1.8% to 2% of the kVA rating.
I've used this for calculating system losses for variable speed drives which have their own unit transformer - it's often something we have to provide at the bid stage of a project with financial penalties if you get it wrong.