PANEL SIDE FED MAIN BREAKERS 1

[TWW]

What are the NEC requirements in regard to using a normal circuit breaker as a panel main disconnect. That is with a single power source and the normal main lugs are left open. It is a common practice in the field, but, I need to double check if there are restrictions on this practice. In this case the side fed main is sized to the amperage requirement of the feed conductor. The power source is a 460/208 transformer with a primary and secondary side fused disconnects. There is no thermal (6 versus 3 spaces) issue in the case also as this is only a 30A aplication.

 

[busbar]

Someone else may need to confirm this, but you should be OK as long as the breaker is not marked with specific "line" and "load" terminals.

 

[davidbeach]

"Back Feed Mains" are allowable by the NEC, but there are requirements for additional mechanical connection of the breaker to the panel. NEC 408.16(F).

 

[dpc]

As mentioned, this is generally allowed, but the circuit breaker must be listed for reverse feed application.

 

[CHDean]

Normally not a problem, exception would be electronic trip breakers not designed for back feed. UL and NEC just require a mechanical attachment to prevent unintentional removal of energised breaker

 

[busbar]

I believe that molded-case circuit breakers with interchangeable trip units have terminals that are marked “line” and “load.”

 

[davidbeach]

"Line" and "load" depends on the manufacturer. Square D refers to the "on" and "off" ends of the breaker without any reference to "line" or "load" while Cutler-Hammer refers just to "line" and "load".

Like some many other things, the real answer is "it depends".

 

[TWW]

Ok, so bolt on circuit breakers are easy to get. However, say, squared QOB circuit breakers appear to be UL listed for many things however no UL listing for "back fed operation". The purpose of this was look and cost. These restrictions drive me to a seperate disconnect and regular snap in breakers. Looks like a dork designed it, but, that appears to be the most prudent approach. By the way, are all the 3R rated switch gear going to need to be surrounded with plactic bubbles in 2005?

 

[resqcapt19]

Listed circuit breakers are suitable for back feeding unless marked otherwise on the breaker by the use of the words "line" and "load". The quote below is from the UL Guide Information for Circuit Breakers, Molded-case and Circuit Breaker Enclosures (DIVQ).

"Line and load markings on a circuit breaker are intended to limit connections thereto as marked."

http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073985604&sequence=1

Don

 

[peebee]

I'd check with your panel manufacturer. They should be able to give you a definitive answer.