100% rated breakers and cable
- Thread starter lsclonch
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Re: 100% rated breakers and cable
100% rated breakers can be used in place of standard breakers but must be applied as if they were standard breakers. So, no big deal.
Unless......
you interested in the 100% factor which begins here:
The circuit breaker must be 100% rated and listed as such by UL. But, it cannot be applied magically for 100% operation in a panel, switchboard, or enclosure unless they have been successfully tested as an assembly per UL testing requirements.
Then, instead of using the 80% of the continuous load and 100% of the noncontinuous load to size the cable, you can calculated the size of the cable at 100% plus 100%, ref 2002 NEC art. 210.20(A) Continuous and Noncontinuous Loads, and the exception.
Also, 90c rated cable must be used according to the breaker manufacture's instructions for 100% application but must be applied at 75degC.
Of course this does not take any additional derating factors the make also influence the selection of the cable size.
The goal n the application of a 100% rated breaker is the possibility of downsizing the breaker as well a using a smaller cable which
So, if the cable was rated 75deg and 380a it was sized selected based upon the 80% + 100% rule. If the breaker and enclosure were 100% rated then you would reconsider the cable to assure that it is also rated 90degC. If so then the cable ampacity would be based on 100% + 100%, or 380a continuous without any derating factors for the cable considered.
In addition it is of interest to note that the 100% rated breakers have solid state trip units.
I trust that this sheds some light on the subject.
100% rated breakers can be used in place of standard breakers but must be applied as if they were standard breakers. So, no big deal.
Unless......
you interested in the 100% factor which begins here:
The circuit breaker must be 100% rated and listed as such by UL. But, it cannot be applied magically for 100% operation in a panel, switchboard, or enclosure unless they have been successfully tested as an assembly per UL testing requirements.
Then, instead of using the 80% of the continuous load and 100% of the noncontinuous load to size the cable, you can calculated the size of the cable at 100% plus 100%, ref 2002 NEC art. 210.20(A) Continuous and Noncontinuous Loads, and the exception.
Also, 90c rated cable must be used according to the breaker manufacture's instructions for 100% application but must be applied at 75degC.
Of course this does not take any additional derating factors the make also influence the selection of the cable size.
The goal n the application of a 100% rated breaker is the possibility of downsizing the breaker as well a using a smaller cable which
So, if the cable was rated 75deg and 380a it was sized selected based upon the 80% + 100% rule. If the breaker and enclosure were 100% rated then you would reconsider the cable to assure that it is also rated 90degC. If so then the cable ampacity would be based on 100% + 100%, or 380a continuous without any derating factors for the cable considered.
In addition it is of interest to note that the 100% rated breakers have solid state trip units.
I trust that this sheds some light on the subject.
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