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transfer switch sizing
#1

with our 20kw generators, what amperage should the transfer switch be rated to.  i know how to convert to amps, but am interested in the real world approach.  

tom

2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

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#2

I think here one should adhere to the National Electric Code.  The feeder from the shore power connection is protected by a 50 amp over current device.  The cabling is sized accordingly, therefore the switch, by code, doesn’t need to have a currrent carrying capacity greater than the feeder over current protection.  In other words, the nearest sized contactor to 50A is 60A.  There is nothing stated that prohibits using a larger sized switch so, if you have a 70A or larger rated switch, you are in compliance.

There is some advantage to an increased sized switch in that the contact points aren’t as likely to fail because of their robust size.

In a post put up by Nebster, I elaborated on the feeder from the generator to the xfer switch being the same size as the shore power cord even though the generator’s breaker is 80A for a 20KW set.  I have never seen a Newell with a feeder from the generator to the xfer sw sized for 80A.   Of course, I certainly have not seen all the Newells.   

I hope I have addressed you question.

Gordon Jones
2000-45'-2slide-#567
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