Panelboard Minimum Main Breaker Size per UL

J

jbt260

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Ohio
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Electrical Engineer
Is there a minimum main circuit breaker size for a 120/240V panel per UL? I was told that "Per UL, the smallest size main breaker we can install at the factory is 50 Amps."
 
I don't have a code article section or a UL reference for your question but I have used a 30 amp for a main
 
Seeing how you can backfeed a Main Lug Only panel with a 15A breaker, I would think the minimum main breaker size (non -plugin style) is determined by the manufacturer. There is probably not much demand for low ampacity non plugin style mains.
 
I don't know the answer to this but I installed a panel (for emergency circuits) and wanted to put in a 30A breaker to back feed the panel (for a generator). The panel had a 100 amp main breaker that was also a back feed. I bought the correct generator interlock. Problem I found was these "BR" circuit breakers the 100 amp 2 pole had a hole in to secure the breaker. The 30 amp did not. I found that BR 2 pole breakers from 50 or 60 (I forgot which one) and up have the hole the smaller breakers do not so maybe the 50-amp restriction on main breaker size posted above is correct.
 
Eddie702 said:
I don't know the answer to this but I installed a panel (for emergency circuits) and wanted to put in a 30A breaker to back feed the panel (for a generator). The panel had a 100 amp main breaker that was also a back feed. I bought the correct generator interlock. Problem I found was these "BR" circuit breakers the 100 amp 2 pole had a hole in to secure the breaker. The 30 amp did not. I found that BR 2 pole breakers from 50 or 60 (I forgot which one) and up have the hole the smaller breakers do not so maybe the 50-amp restriction on main breaker size posted above is correct.
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There are brands/series that have a clip or clamp that hold back fed breakers and would hold any standard sized breaker (but not AFCIs/GFCI's though those can't exactly be back fed and work properly anyway) that is listed for the panel.
 
kwired said:
There are brands/series that have a clip or clamp that hold back fed breakers and would hold any standard sized breaker (but not AFCIs/GFCI's though those can't exactly be back fed and work properly anyway) that is listed for the panel.
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The panel I had was a Bryant BR and of course the breakers were BR. The 100 amp main breaker had a hole in the breaker with a factory screw in the breaker. No problem their. I also bought the bryant breaker interlock for this panel and I intended to use a 2 pole 30 amp for that (4kw) gen. I also bought the Bryant "back feed breaker kit" that had a screw to go through the hole in the breaker just like the 100 amp main with a clip or something to screw into (forgot exactly how it went).


The problem was the 30 a 2 pole BR does not have a hole in it like the larger breakers do. I went to HD and looked at the BR breakers and it's either 50 or 60 amp and up have the hole for the screw the smaller breakers 20s 30s 40s do not
 
Eddie702 said:
The panel I had was a Bryant BR and of course the breakers were BR. The 100 amp main breaker had a hole in the breaker with a factory screw in the breaker. No problem their. I also bought the bryant breaker interlock for this panel and I intended to use a 2 pole 30 amp for that (4kw) gen. I also bought the Bryant "back feed breaker kit" that had a screw to go through the hole in the breaker just like the 100 amp main with a clip or something to screw into (forgot exactly how it went).


The problem was the 30 a 2 pole BR does not have a hole in it like the larger breakers do. I went to HD and looked at the BR breakers and it's either 50 or 60 amp and up have the hole for the screw the smaller breakers 20s 30s 40s do not
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I got that the first time.

I was pointing out other manufacturers do have methods that will hold down most if not all breakers that are accepted by their panels. and this is a bit of a consequence of using that series.

Apparently Eaton does make another style hold down according to letgomywago.

I had a situation one time with BR, that I rarely use, where I was connecting a dishwasher and unit was in location that wasn't adjacent to sink cabinet as is fairly typical. Adjacent cabinet was lazy Susan cabinet with no reasonable method of placing receptacle in there and I believe a drawer base on other side with no reasonable method of placing a receptacle in it either. I thought no problem I'll just use a breaker padlock attachment and direct wire the dishwasher. Come trim time and I find out their padlock attachment doesn't really fit on AFCI/GFCI or dual function breakers. Close but not close enough and no good apparent reason why the breaker couldn't been made so it would fit. It wasn't because the test button was in way or anything like that, just a difference in molding of the breaker case.
 
kwired said:
I got that the first time.

I was pointing out other manufacturers do have methods that will hold down most if not all breakers that are accepted by their panels. and this is a bit of a consequence of using that series.

Apparently Eaton does make another style hold down according to letgomywago.

I had a situation one time with BR, that I rarely use, where I was connecting a dishwasher and unit was in location that wasn't adjacent to sink cabinet as is fairly typical. Adjacent cabinet was lazy Susan cabinet with no reasonable method of placing receptacle in there and I believe a drawer base on other side with no reasonable method of placing a receptacle in it either. I thought no problem I'll just use a breaker padlock attachment and direct wire the dishwasher. Come trim time and I find out their padlock attachment doesn't really fit on AFCI/GFCI or dual function breakers. Close but not close enough and no good apparent reason why the breaker couldn't been made so it would fit. It wasn't because the test button was in way or anything like that, just a difference in molding of the breaker case.
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They have 2 styles of those as well. The one that works is set up like a 1 pole breaker lock but does both
 
LarryFine said:
I would simply drill a similar hole.
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BR 2 pole breakers seem to generally consist of two single pole moldings riveted together. On the ones with a hole for the hold down have a half-round slot on both sides of each single pole section, such that when riveted together a full round hole passes through the 2-pole assembly. The ones manufactured without the hole have the side walls of each single-pole section in that same area. So if you drill a hole there, you're drilling through the side walls of the molded cases and most likely opening up the interiors to the air. How you could know that you have drilled precisely enough not to damage interior parts, or send debris into the interiors of the breaker that might compromise its operation, is rather beyond me.

So that's pretty terrible advice you gave, IMHO.
 
Now I'm going to have to try it. I figure a 1/16" bit first, to drill a path straight between the bodies.

Then I'll try to follow with 1/8" and then 3/16". I'll let you know what happens.
 
LarryFine said:
Now I'm going to have to try it. I figure a 1/16" bit first, to drill a path straight between the bodies.

Then I'll try to follow with 1/8" and then 3/16". I'll let you know what happens.
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are you going to get that re-citified afterward? :cool:
 
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