Panel w/ no main breaker

[andrew.tkelly]

Hi,

I frequently see electrical panels with no main breaker. What do you call this kind of configuration? I've heard some say "line-side panels" or even "hot bus panels". Is there a universal term?

Also, how does this affect the 120% rule since there is no main breaker? Can I just pile on solar as long as I stay within the ampacity of the service entrance conductors?

Regards,
Andy

 

[Carultch]

Hi,

I frequently see electrical panels with no main breaker. What do you call this kind of configuration? I've heard some say "line-side panels" or even "hot bus panels". Is there a universal term?

Also, how does this affect the 120% rule since there is no main breaker? Can I just pile on solar as long as I stay within the ampacity of the service entrance conductors?

Regards,
Andy

Main Lug Only, or MLO panelboard, is how you would see it in a manufacturer's catalog.

As for applying the 120% rule, there still would be an OCPD somewhere upstream of the panelboard that would serve the same purpose as a main breaker. That value would be what you'd use in this calculation.

If there is no OCPD upstream of the panel, then each of the branch breakers classify as service disconnects, and you are under the 6-disconnect rule unless you can find an exception.

 

[kwired]

Main Lug Only, or MLO panelboard, is how you would see it in a manufacturer's catalog.

As for applying the 120% rule, there still would be an OCPD somewhere upstream of the panelboard that would serve the same purpose as a main breaker. That value would be what you'd use in this calculation.

If there is no OCPD upstream of the panel, then each of the branch breakers classify as service disconnects, and you are under the 6-disconnect rule unless you can find an exception.

And AFAIK most if not all of your "loadcenters" are only suitable for use as service equipment when there is a main breaker installed, need to read the instructions that come with the listing

 

[ggunn]

Main Lug Only, or MLO panelboard, is how you would see it in a manufacturer's catalog.

As for applying the 120% rule, there still would be an OCPD somewhere upstream of the panelboard that would serve the same purpose as a main breaker. That value would be what you'd use in this calculation.

If there is no OCPD upstream of the panel, then each of the branch breakers classify as service disconnects, and you are under the 6-disconnect rule unless you can find an exception.

A solar interconnection would not count as a seventh handle, but whether your AHJ would allow you to land a solar BFB in a MLO panel that is a service entrance is up to the AHJ. I encountered exactly that on a commercial site here in Austin; the AHJ acknowledged that the solar was not a seventh handle (there were six breakers in the panel), but they had me install a bladed fused disco next to the panel and tap the bus rather than land on a breaker even though there was room in the panel for another breaker.

 

[jaggedben]

And AFAIK most if not all of your "loadcenters" are only suitable for use as service equipment when there is a main breaker installed, ...

That's hardly true around here. However, with those that are suitable for multiple service disconnecting means, every one I have ever seen is limited to six disconnects by design and/or labeling. I don't think you'll find a panel with more than 12 full spaces that doesn't require a main to be SUSE. Some of the ones with 12 spaces can be incorrectly used with single-pole breakers, but that clearly violates the label.

need to read the instructions that come with the listing

Yes, regardless.