Panel Selection - Main Lug Only or Main Circuit Breaker? 4

[ck2013]

I understand there are two different type of panels: Main lug only type and main circuit breaker type.

Can you give me some general suggestions about which to use in different scenarios? Thanks in advance.

 

[mesutphen]

You can use a main lug panel when you have an upstream breaker to protect the panel. If you do not have an upstream breaker, you should use the main circuit breaker panel.

 

[jraef]

Assuming you are in the US (based on the vernacular you use), and assuming fuses are not part of the discussion here.

You must have a Main Breaker if the panel is the Service Entrance for a location (or if there are 6 or less breakers in it, the so-called "6 hand rule").

You may want to have a Main CB if the breaker feeding it is in another part of the facility that is not readily accessible and you want to have a local main device so that you can service the panel without making another trip. An example is a tall building where the Service Entrance gear is in the basement and there is an individual Feeder Circuit Breaker in the gear for the panelboards on each floor. You could technically use an MLO panel on the floors since the circuit is protected by the Feeder CB. But if you wanted to add a breaker to the panel on the 35th floor, you would have to go down to the basement, turn off, lock out and tag out the Feeder Breaker feeding the 35th floor, go back up, add the breaker, go back down, turn the Feeder back on, go back up and test it, then repeat if you screwed up. Or you could use a Main Breaker in that 35th floor anelboard and avoid the elevator rides.

"Will work for (the memory of) salami"

 

[unclebob]

A panel on the secondary side of a transformer may give you arc flash worries. Adding a main breaker may help reduce incident energy in that panel.

 

[dpc]

Adding a main breaker may help reduce incident energy in that panel

But if the main breaker is in the panel, it doesn't really count for arc-flash, since we have to assume the arcing could occur on the line side of the main breaker.

Also, I think JRaef might have meant "more than 6 breakers", unless I'm parsing the sentence incorrectly.

 

[jraef]

Actually, I think I meant unless there are 6 or less breakers in the panel.

I think. Heck, that was an early morning pre-coffee post, I wasn't really there yet...

"Will work for (the memory of) salami"