Panelboard Minimum Main Breaker Size per UL

[kwired]

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.

Sounds like a fun challenge. If you are off by just a little bit or your hole isn't perfectly straight you won't hit the right spot in the panel with the screw.

 

[Jraef]

"Per UL, the smallest size main breaker we can install at the factory is 50 Amps."

Someone is making that up...

UL standard 67 does not in fact even require a Main breaker at all! It only requires that IF you use a breaker as the Main, it is marked "Main". In that section, it specifically states that ANY branch breaker can BE the "Main", so long as it is marked as such (and has a hold-down). In addition, when you have a "6 handle panel" in which there are up to 6 "Mains", one of them can be a 15A single pole breaker as far as the UL standard is concerned.

One thing that is possible is that IF it is a "Service Entrance" rated panel, new rules require that the Line Lugs of breakers, INCLUDING back-fed branch breakers used as Mains, have protective guards on the line terminals. It might be that some brands do not provide a line lug guard kit for anything smaller than a 50A breaker.