Mr. Chippers
Member
- Location
- Illinois
- Occupation
- Electrical Engineer
I have an existing ATS, protected on the normal and emergency side by a 1600A breaker. It feeds an existing chiller. This chiller will be disconnected and the contractor wants to use the load side of the ATS to feed a temporary chiller while work is being performed. The temporary chiller requires 2 circuits, with MCA of 490A & 561A, MOCP of 600 & 700A, and FLA of 442A & 511A. There are circuit breakers for each circuit on the temp chiller. It will be a couple hundred feet away.
My question is can we run 2 circuits off the load side of the ATS to the temp chiller? I worry about the branch wiring overheating before the 1600A upstream breaker would trip.
We could run 5 sets of #400kcmil for each but that seems overkill. Do we treat this as a tap off the ATS and provide a fused disconnect within 10 feet for each circuit?
Or does this follow the requirements of a multi-motor branch circuit, where the MOCP would be up to 250% of the largest motor FLA plus FLA of the other motor? Which would equal 1719A, so a 1600A breaker would suffice.
My question is can we run 2 circuits off the load side of the ATS to the temp chiller? I worry about the branch wiring overheating before the 1600A upstream breaker would trip.
We could run 5 sets of #400kcmil for each but that seems overkill. Do we treat this as a tap off the ATS and provide a fused disconnect within 10 feet for each circuit?
Or does this follow the requirements of a multi-motor branch circuit, where the MOCP would be up to 250% of the largest motor FLA plus FLA of the other motor? Which would equal 1719A, so a 1600A breaker would suffice.
