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Author Topic: Still trying to wrap my head around 3 phase 100 amp distro  (Read 6232 times)

Stephen Swaffer

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Re: Still trying to wrap my head around 3 phase 100 amp distro
« Reply #20 on: September 14, 2017, 07:20:36 pm »

Actually, since this is 3 phase, there are 18/3 or 6 20 amp circuits per leg. 

It is interesting to note that code in general requires branch circuits serving continuous loads (loads that obviously create signifiacnt heat and defines as expected to last 4 hours or longer) at 125%-or in other words you can load a circuit continuously to 80% of its "ampacity".  80% of 20 amps is 16 amps.  Six 16 amp circuits works out to 96 amps per leg-within the capacity of the panel.

If loads are NOT continuous, most electrical installations have a "demand" consideration-it is assumed that not every connected load would be on at the same time.  To exceed the ampacity of the panel, you would have to max nearly every circuit.  (Wire is a different story). 

That is not to say that I don't think a main sized for the feeder wire would be a good idea-the best place for this is at the source of energy.  If this was built to be used in a specific location, then that could easily have been a part of the master plan.

Also, anyone building a number of these likely purchased them as a panel+breaker package.  If you quote something like that, there is virtually no cost penalty to filling a panel with breakers vs putting in half of its capacity.  The pricing structure when you start doing that is crazy-the markup on service equipment on the manufacturing end must be very high-at least for materials sold individually.
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Steve Swaffer

TJ (Tom) Cornish

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Re: Still trying to wrap my head around 3 phase 100 amp distro
« Reply #21 on: September 14, 2017, 09:51:51 pm »

Actually, since this is 3 phase, there are 18/3 or 6 20 amp circuits per leg. 
Yikes - you are right, of course.  Brain fart.  I corrected my post.
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Re: Still trying to wrap my head around 3 phase 100 amp distro
« Reply #21 on: September 14, 2017, 09:51:51 pm »


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