USE OF MAIN LUG PANELS

[Casey the Electrician]

Hello all,

Please forgive the lack of due diligence on my own. There seems to have always been a level of uncertainty around this subject in the group of coworkers that I have always been around.

The situation would be this: A fused service disconnect outside that its lockable. The feeders enter the building that the service disconnecting means is attached to and terminate into a main lug panel in the basement of that building.

Is this permissible? I have never had an issue in the past with any inspector as long as the above conditions were met.

Thank you for any help you can provide.

 

[infinity]

The feeder OCPD is at the origin of the feeder so a MLO panel is permitted.

 

[electrofelon]

Hello all,

Please forgive the lack of due diligence on my own. There seems to have always been a level of uncertainty around this subject in the group of coworkers that I have always been around. .

A while back I wrote up a list of cases where a main breaker would need to be used (although note it is never required to be integral to the panel board, it could be a separate ocpd, but just going under the assumption that's the most economical way to do it).

1. When the panel is the first piece of equipment in a detached structure.

2. Of course, when it's a service panel, to meet your service conductor ocpd and disconnect requirement.

3. When needed for 408.36 purposes

4. When needed for 450.3( B) transformer protection) purposes.

5. When needed for 240.21 tap rule purposes.

6. When used to achieve a series rating for the branch devices.

There is no requirement for a "local means of disconnect" for a panel board. Some people like to spec main breakers for perceived safety and practical purposes, but in my opinion it doesn't gain you anything and is a waste of money.