Stormy01
New member
- Location
- Bayfield, Co, USA
Can you, according to the NEC, feed a 200 amp main breaker panel with a 100 amp breaker from another MCC? If so please provide NEC references.
It's a good question and one thats come up before with me. It's commonplace to use a panelboard or loadcenter that is rated for more than the feeder, ie, 200a 42 ckt MLO panel feed by a 100a feed. Personally, I've never thought it's a good idea to have a main breaker in that panel that is oversized simply to avoid confusion. 408.30 and 36 give some guidelines but it's not prohibited that I know of.
Confusing or not, you can't have a 100 Amp feeder on a 100A OCPD and a 200Amp main in the subpanel.
You have some explaining to do before most of us will buy that theory. Like I said you could supply that panel with a 15 amp breaker if the connected load is less than 15 amps. There is probably better and less expensive ways if that is the case but is otherwise NEC compliant.
I think I understood, you still haven't told us why you make that claim. If the supply is protected by a lower level overcurrent device what harm is there having the higher rated device?What I mean, is if your feeder is rated at 100Amps, you can not have a 200Amp main breaker in the sub panel.
You can have a 100Amp feeder that has 100A OCPD that will feed a 200A subpanel.
You have some explaining to do before most of us will buy that theory.
Can you, according to the NEC, feed a 200 amp main breaker panel with a 100 amp breaker from another MCC? If so please provide NEC references.
You also have to remember to treat the 2nd panel as a sub-panel and not bond the EGC's and neutral together (just in case that wasn't understood).I think I understood, you still haven't told us why you make that claim. If the supply is protected by a lower level overcurrent device what harm is there having the higher rated device?
You could even replace that main breaker with a molded case switch with no internal overcurrent protection if you wanted, as the 100 amp feeder device is providing the protection, or even convert to a main lug panel if a disconnecting means isn't required (say a separate building application). If there is an overload the 100 amp feeder is tripping. If there is a ground fault, it could be a crapshoot as to which responds first, all depends on the trip curves of each breaker and how much current flows during the fault event.
The article that confirms this statement is 408.30.Supply it with a 15 amp breaker if you so desire - as long as the connected load is less than 15.
Supply it with a 15 amp breaker if you so desire - as long as the connected load is less than 15.
Is there a code requiring the connected load to be less than 15?
(I do realize that common sense and not wanting the breaker to constantly trip apply)
230.23(A), 230.31(A), 230.42(A) for conductors. 230.90(A) for ocp.Yes, 210.20(A) - but that is for branch circuits, 215.3 says about the same thing and would apply to feeders. I don't see similar language in art 230 for services though.
230.23(A), 230.31(A), 230.42(A) for conductors. 230.90(A) for ocp.
No, you did not miss it. I had looked at it as you describe before... but it got lost somewhere up top.Conductors must be able to carry the load, just like feeders or branch circuits. But the requirements for OCP in 230.90 is not worded like it is for feeders or branch circuits. It just says not higher than the allowable ampacity of the conductor and never mentions an overcurrent device needing to be not less than 100% non continuous/ 125% continuous load like the sections covering feeders and branch circuits says.
I don't see that a 15 amp service overcurrent device is in violation of any code being connected to a 20 amp load. Not a good design though. The conductors need to be 20 amp conductors, but nothing says the overcurrent device needs to be a minimum rating, just that it can not exceed the conductor ampacity. Or did I miss it somewhere?