100% Rated Breakers

[mull982]

I've seen a number of One-Line drawings lately that indicte the use of 100% rated breakers for particular breakers.

Can someone explain the resaon behind specifying or using 100% rated breakers in a design.

I believe I read an article some time back that explained that a sysmes installation cost could be cheaper using 100% rated breakers becuase you did not have to de-rate cables and thus could use smaller cables and reduce the installation cost of the system. Is this typically why 100% rated breakers are used?

 

[petersonra]

I've seen a number of One-Line drawings lately that indicte the use of 100% rated breakers for particular breakers.

Can someone explain the resaon behind specifying or using 100% rated breakers in a design.

I believe I read an article some time back that explained that a sysmes installation cost could be cheaper using 100% rated breakers becuase you did not have to de-rate cables and thus could use smaller cables and reduce the installation cost of the system. Is this typically why 100% rated breakers are used?

Sometimes you can only effectively use 80% of the rating of a breaker. however, you can use 100% if it is listed as a 100% breaker. There is often a big difference in cost between a 100% breaker that would be adequate, and the next size up. In addition, you might well have to increase the wire size if you went to a larger breaker.

I personally do not like doing so because it leaves you with little room to work with down the road, but sometimes it is cost effective, and in some cases, future capacity needs are not an issue.