Main Feeder Protection

[AWinston]

If I have a feeder rated for 180A going to a panel with an MCB rated for 225A but the total load on the panel is 100A....is this ok? All of the loads are protected by their individual branch circuit breakers.

 

[kwired]

If I have a feeder rated for 180A going to a panel with an MCB rated for 225A but the total load on the panel is 100A....is this ok? All of the loads are protected by their individual branch circuit breakers.

Yes, but no on the answer.

As long as the load never goes above 180 amps you sort of never should have a problem, but overcurrent protection rules are still in violation as that 180 amp conductor needs protected at it's ampacity - or for 800 amps and less can be next standard size up which is 200 amps.

I guess next question is to clarify exactly what you have - a feeder needs proper overcurrent protection on it's supply side - where it appears you are describing a 225 amp device on the load end of the feeder. That wouldn't be any violation as long as there were 200 amp or less device on the supply end.

 

[Fitzdrew516]

Yes, but no on the answer.

As long as the load never goes above 180 amps you sort of never should have a problem, but overcurrent protection rules are still in violation as that 180 amp conductor needs protected at it's ampacity - or for 800 amps and less can be next standard size up which is 200 amps.

I guess next question is to clarify exactly what you have - a feeder needs proper overcurrent protection on it's supply side - where it appears you are describing a 225 amp device on the load end of the feeder. That wouldn't be any violation as long as there were 200 amp or less device on the supply end.

Agreed 100% with kwired. It depends on the OCP on the supply side not the load end. That's why it's common to see MLO panels (without main breakers in them) being fed from a breaker in another panel/switchboard/etc. Although what you're describing isn't necessarily the best way to do things because it gets confusing when surveying an existing facility, etc. It's completely legal as long as the feeders are protected. Usually I see this when there's an extra panel laying around that they want to re-use so it's understandable. If you're not reusing panels/breakers/wire/etc. IDK why this would ever be done as it seems the cost differential to run a 225A feed vs a 180A feed isn't much and that way you'd be able to utilize the 225A panel's full capacity down the road if you needed it.

 

[kwired]

Agreed 100% with kwired. It depends on the OCP on the supply side not the load end. That's why it's common to see MLO panels (without main breakers in them) being fed from a breaker in another panel/switchboard/etc. Although what you're describing isn't necessarily the best way to do things because it gets confusing when surveying an existing facility, etc. It's completely legal as long as the feeders are protected. Usually I see this when there's an extra panel laying around that they want to re-use so it's understandable. If you're not reusing panels/breakers/wire/etc. IDK why this would ever be done as it seems the cost differential to run a 225A feed vs a 180A feed isn't much and that way you'd be able to utilize the 225A panel's full capacity down the road if you needed it.

Or when the owner is buying materials, had one guy buy a 225 amp main breaker panel once for his home (he worked at supply house and wanted "his price" on equipment), because apparently bigger is better - yet he knew it has 200 amp protection upstream - and a main lug panel would have cost him less anyway.:slaphead:

 

[Fitzdrew516]

Or when the owner is buying materials, had one guy buy a 225 amp main breaker panel once for his home (he worked at supply house and wanted "his price" on equipment), because apparently bigger is better - yet he knew it has 200 amp protection upstream - and a main lug panel would have cost him less anyway.:slaphead:

Gotta love it :thumbsup:

 

[AWinston]

Thanks guys!