Raul Postigo
Member
What hazards will create the wrong connection (back feed) of Molded Case Circuit Breaker, (3 phases 600V. 800A.), that is marked Line/ Load?
Molded Case Circuit Breakers Connection
- Thread starter Raul Postigo
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bphgravity
Senior Member
- Location
- Florida
Who knows? When equipment is connected or used in a method for which it is not intended nor designed for, the result may be anything from unnoticeable to catastrophic.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
My guess, and it is only that, is that a breaker so marked does not have the back feed kit available that would allow you to safely use it in such a configuration. It may not be that such a configurations is especially dangerous, just that so few people would want to do it that it is not economical for the CB manufacturer to come up with a back feed kit.
davidr43229
Senior Member
- Location
- Columbus, Oh
Other than the hazzards ( which are valid) you are violating UL 489 and thus violating the entire panel.
Just my $.02
Last edited:
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
One possibe catastrophic probelm is a line-line short circuit on the incoming cables.
Every time a circuit breaker "opens" under load an arc is created. The hot gasses from the arc need to be vented out of the breaker case. If the breaker is marked with line and load it is possible the gasses are vented towards the "load" side of the breaker.
Every time a circuit breaker "opens" under load an arc is created. The hot gasses from the arc need to be vented out of the breaker case. If the breaker is marked with line and load it is possible the gasses are vented towards the "load" side of the breaker.
bphgravity
Senior Member
- Location
- Florida
You can make this generalized statement for just about any materials or equipment. Take for example a standard breaker (not 100% rated) loaded continuously.
What will happen? Maybe nothing or maybe it will blow up or maybe something in between. The bottom line is a violation is a violation regardless of what the consequences of the violation may be.
What will happen? Maybe nothing or maybe it will blow up or maybe something in between. The bottom line is a violation is a violation regardless of what the consequences of the violation may be.
boboelectric
Senior Member
- Location
- Eighty Four,Pa.15330
Jim,
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Bob O.Eighty Four,Pa.15330
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Bob O.Eighty Four,Pa.15330
This is the way I have understood it:
I don't know of any reason a breaker can not provide the protection that it has been designed for if feed form the line or load end. Breakers don't care which way the current flows through them.
Now, for the safety issue.
With breakers that are marked line and load one would trust that the load end of the breaker would be de-energized when the breaker is in the open position. If fed from the load end one would trust that the load end would be de-energized but it isn't.
Also, there is the question of accessories. Breakers that are physically thermal magnetic that have interchangeable trip units are marked line and load. With the breaker in the open position it is de-energizer at the line end of the breaker when feed from the line end which makes the moving contacts and the parts through the trip unit to the load end terminals de-energized. This allows the trip unit to the changed or accessories added or removed w/o de-energizing the line end of the breaker.
With regards to breakers with non-interchangeable trip units, such a residential plug-on breakers, if fed from the load end it would be hazardous to attempt to remove one if it was being reverse fed.
I don't know of any reason a breaker can not provide the protection that it has been designed for if feed form the line or load end. Breakers don't care which way the current flows through them.
Now, for the safety issue.
With breakers that are marked line and load one would trust that the load end of the breaker would be de-energized when the breaker is in the open position. If fed from the load end one would trust that the load end would be de-energized but it isn't.
Also, there is the question of accessories. Breakers that are physically thermal magnetic that have interchangeable trip units are marked line and load. With the breaker in the open position it is de-energizer at the line end of the breaker when feed from the line end which makes the moving contacts and the parts through the trip unit to the load end terminals de-energized. This allows the trip unit to the changed or accessories added or removed w/o de-energizing the line end of the breaker.
With regards to breakers with non-interchangeable trip units, such a residential plug-on breakers, if fed from the load end it would be hazardous to attempt to remove one if it was being reverse fed.
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