80% vs 100% LV Circuit Breaker
80% vs 100% LV Circuit Breaker
(OP)
The circuit breaker is 800 A frame and 80% rated, which is 640 A, The adjustable rating plug, can be easily set to say 500 A. The trip unit, which is separate, can be set as a multiple of 500 A. Can the breaker carry 500 A as that is less than 640 A, or does it now become limited to 400 A?






RE: 80% vs 100% LV Circuit Breaker
If you are asking if the breaker is going to actually trip at exactly 500 A, I'd say probably not.
If you are asking if the NEC/UL will let you consider the 500 A a 100% rating, I'd say probably not since the 100% rating depends on the combination of the breaker, the trip unit and the enclosure. In addition, wiring must be done with 90 deg C insulation applied at the 75 deg C rating.
Also, the "80% rating" applies to continuous loads only.
RE: 80% vs 100% LV Circuit Breaker
http://www.eatoncanada.ca/ecm/groups/public/@pub/@...
My location is industrial, well controlled, and that is supervised. I don't know what is inside, but perhaps the sensor is like a CT with a transformer tap. I would think that the 80% rating relates to thermal at a max 640 amp and the main current paths. That would suggest 500 A is less of a thermal effect on a 500 A plug setting.
RE: 80% vs 100% LV Circuit Breaker
Also, when you buy a 100% rated breaker, you get a specific 100% rated trip unit. There are two different trip units, IIRC. Whether there is any actual difference, I don't know.
You could contact GE or Eaton and ask them. They have specialists in MCCBs who can give you their opinion.
RE: 80% vs 100% LV Circuit Breaker
RE: 80% vs 100% LV Circuit Breaker
http://www.eaton.com/ecm/groups/public/@pub/@elect...
Even if the cb is taking the lower current of the lower plug setting, but the conductor was sized for that lower current, the conductor may be at the same temperature.