Reverse feeding

[terrygrills]

I have not been able to see any reference to the reverse feeding of say a circuit breaker or switch in the NEC or in NEMA documentation. Is there any rule covering this practice, what I would like to know is it legal to say feed a MCCB from the bottom and take the load out from the top, that is providing the manufacture of the MCCB or other piece switchgear approves reverse feeding?

 

[charlie b]

Re: Reverse feeding

In general, what the NEC does not forbid is, by default, permitted. In specific, if the manufacturer says it?s OK, then it?s OK. But out of curiosity, why would you need to do this?

 

[jim dungar]

Re: Reverse feeding

Circuit breakers may always be "reverse" fed unless they are marked with specific LINE and LOAD terminals.

 

[ryan_618]

Re: Reverse feeding

See 408.16

(F) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type-main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.

 

[BAHTAH]

Re: Reverse feeding

You mentioned back feeding a breaker or switch. In the case of the switch the NEC requires the blades (knife switches) be de-energized when the switch is in the open position. The NEC does require that on a breaker the load-side terminations be de-energized when the breaker is in the open position, however with no load-line identification the load lugs can be top or bottom. Breakers are typically approved to be back fed except as stated where the Line-Load are indicated. I have found for example when installing a service with a CT-Can where the load is off the bottom of the CT-Mounting base it is eaiser to feed the main breaker from the bottom and allow the load to go out the top/side of the main breaker enclosure to the gutter for distribution to other disconnects. This makes it easier to align the CT-Can with the MCB enclosure and gutter.

 

[terrygrills]

Re: Reverse feeding

As mentioned sometimes it's a lot easier to wire the breaker from the bottom. I do know that one has to be carefull when one does this if you are dealing with DC as the polarity of the breaker in question is important and you can not simply reverse feed it. One must connect it only as indicated on the breaker. Failer to adhere to this could cause the breaker to fail on breaking a fault current.

 

[mclain]

Re: Reverse feeding

Back feeding a breaker might be allowed by code but it can be dangerous to maintenance personnel. I encountered this once at an industrial site where we had 1000?s of breakers top fed and someone installed one that was bottom fed. Due to changes at the site it was necessary to replace the cable that was fed from this breaker. The worker conditioned to having all of the breakers top fed opened the breaker and went to remove the cable from the bottom of the breaker. Luckily he wasn?t injured just surprised.

 

[paul]

Re: Reverse feeding

I posted this very same question two weeks ago. While, yes I did bottom feed the breaker, it will have plaque on the outside of the disconnect can stating that it is bottom fed along with labels on the breaker lug covers. The last thing I want is a fellow electrician getting bit.