Tap rules and overcurrent protection

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JoeNorm

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WA
I don't have my code book in front of me at the moment and I am trying to clear up a "tap rules" question.

I'll be tapping off the service entrance conductors(not feeders) of a residence to supply a small 100 amp panel for a solar back-feed combiner. I am wondering if I can land the tap conductors on the main lugs of this panel or do I have to land on a breaker? The tap will be less than 10 feet.

The only advantage I see to the main breaker is being able to de-energize the bus bar of the 100 amp panel. But it's a solar combiner that will have a sticker saying "Solar combiner Only". So the idea is nobody will be working in it anyway.

Thanks
 
IMHO, since your not tapping a feeder this is being described as a 2nd service and as such, tap rules would not apply.
Panelboards require OCPD - 408.36
 
Normally, a line side tap is done with a fused disconnect. I would have to look it up to confirm your conformity. But a fused disconnect is def the norm in this area for a line side tap for a PV installation.
 
One reason for a main is AIC and fault current. A main would likely be rated 22K and the branches would series rate with it. You could also just get 22kaic branch breakers and no main, but it would likely be cheaper to go the series rating route. This may not even be an issue for small residential.

Whether there is a main or not effects the interconnection/bus bar rules that apply. In practice you can get the same benefits as the supply side rules with a main breaker and the load side rules by using the "sum of all breakers excluding the main" rule.
 
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