continuous load rating of main lug panels

[jeffovermyer]

Is a 125 amp main lug only panel rated to deliver 125 amps continuously? I understand that if it were a 125 amp main breaker panel it would only be rated for 80% of 125 amps because of the breaker, but lugs only?

 

[iceworm]

(1) Is a 125 amp main lug only panel rated to deliver 125 amps continuously? (2) I understand that if it were a 125 amp main breaker panel it would only be rated for 80% of 125 amps because of the breaker, (3) but lugs only?

My current understanding (pun intended) is:
1. yes
2. yes
3. 100% (but limited by the feeder CB)

Hummmm - conflict.
Essentially the main lug panel is rated for 125A continuous, but the feeder CB will be no greater than 125A and it will be limited to 80% continuous.

Although, I suspose one might find/spec a 100%CB, I've never seen one in that size range.

ice

 

[petersonra]

Is a 125 amp main lug only panel rated to deliver 125 amps continuously? I understand that if it were a 125 amp main breaker panel it would only be rated for 80% of 125 amps because of the breaker, but lugs only?

The bus itself is good for 125A.

Most breakers are not 100% rated, although they are sometimes available.

The individual breakers in a MLO panel have the same 80% rating issue, but conceivably you could have enough breakers running at 80% to get to 125A.

 

[electrofelon]

Is a 125 amp main lug only panel rated to deliver 125 amps continuously? I understand that if it were a 125 amp main breaker panel it would only be rated for 80% of 125 amps because of the breaker, but lugs only?

There is no "80% rule" for panelboards. The 80% rule is one of those things that its easy to get in the habit of applying it to anything carrying a continuous load. As other have said, you would have to get creative in supplying 125 amp continuous to the panel considering 408.36. The 100% rated breaker is the only way I can think of.

One could argue that the bus of the panelboard is a feeder and thus subject to the 80% rule for feeders.