residential riser

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bwyllie

Senior Member
Location
MA
Using 220.84 I have a load of 700A for a residential riser, am I ok to use a 800A breaker to feed this riser or do I need to goto a 1000A circuit breaker and riser for the 80% rating (or 100% rated 800A breaker). I think 800A would be fine as a residential load is not continuous, but interested in what others think.
 
A breaker can be loaded to 100% of its rated ampacity as long as the load is not continuous. Since you have non-continuous loads the 800 amp breaker would be fine.
 
What are your conductors or bus duct or wiring method rated at?

You can't upsize your overcurrent protection from 700-800 if the wiring method is only rated at 700. See 240.4(B).

You do your load calculation first.
Choose your conductor that will be able to carry the load of your calc.
Choose your overcurrent protection. You are allowed to upsize if your conductor and load are not a standard size and you are under 800 amps.

80% has nothing to do with this calculation. That should all be figured in on your load calculation.
 
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