Cal, I think you were pretty clear in what you want to do. I am not sure about the retrofitting of the panel.
Originally Posted by cal.interiors
What size is the feeder to the 480 panel? Depending on the feeder size you might be able to just tap into it ahead of the panel to feed the transformer.
Another thought I have is to keep the 45 KVA and 125 amp sub and add a second 45 with 125 sub, this eliminates the need for a breaker over 100 amps. If space is tight stack the transformers with a unistrut rack.
100 amp breaker is large enough
Unless I am missing something a 3P100 amp breaker is large enough to feed a 3phase 75kva transformer at 480v and get 200amp 120/208 on the secondary.
Can you guys please correct my misinterpretation of the problem.
Originally Posted by cpinetree
Using a 100 to feed a 75 can work, or it can trip out when you go to energize it due to inrush. The more energy efficient the transformer the more likely there will be a problem.
This is a classic example of a lot of nuisance tripping when you use this combination. The contractor is backed into a corner when limited to a 100a breaker. Since tthe pri FLA is 90 you are likely to have problems with energizing the transforner using a 100a breaker. The mag. of the breaker will not bew high enough.
Originally Posted by iwire
I thought about adding another transformer but room is limited although didnt think about stacking.. I finally talked to someone at eaton that half way knows what they are talking about and assured me that I was ok with the breaker kit I was looking into and verifying my panel specs. I then found a great deal on the kit which included the breaker, lugs and mounting hardware. Im thinking this is the safest and best bet. I looked into other options that were put in front of me but never could verify if it was 100% correct. Its always funny how you can get 20 different options or points of view from 20 different vendors yet there is usually only one or two correct methods.
Thanks for the opinions!!!