pirate77
Member
- Location
- California
The data on a circuit breaker states "rated 60 deg.C/75 deg.C" Which temp do I use when calculating the conductor size(using THHN, THWN)?
CB data
- Thread starter pirate77
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bphgravity
Senior Member
- Location
- Florida
Re: CB data
The code requires you to load conductors and equipment to the lowest rating of any terminal. As long as everything else is at least 75 degrees C, you can use that column of the code. You can still use 90 degree conductors, but they can only be loaded to the 75 degree clomun. There is hardly anything rated at 90 degree C.
The code requires you to load conductors and equipment to the lowest rating of any terminal. As long as everything else is at least 75 degrees C, you can use that column of the code. You can still use 90 degree conductors, but they can only be loaded to the 75 degree clomun. There is hardly anything rated at 90 degree C.
BAHTAH
Senior Member
- Location
- United States
Re: CB data
It depends on where the circuit breaker is mounted. If the breaker is marked 60/75-deg C and located in a panel, the breakers are group mounted (next to one another) and you must use the 60-deg c lug rating. If the breaker is mounted in its own enclosure or in an industrial control panel with no other component next to it, you can use the 75-deg c rating. Breakers rated 125 amps and less and group mounted have the load applied based on the 60-deg c rating, breakers rated over 125 amps are suitable for use using the 75-deg rating.
It depends on where the circuit breaker is mounted. If the breaker is marked 60/75-deg C and located in a panel, the breakers are group mounted (next to one another) and you must use the 60-deg c lug rating. If the breaker is mounted in its own enclosure or in an industrial control panel with no other component next to it, you can use the 75-deg c rating. Breakers rated 125 amps and less and group mounted have the load applied based on the 60-deg c rating, breakers rated over 125 amps are suitable for use using the 75-deg rating.
Re: CB data
As I recall breakers 100a and below, or is it below 100a, were to be rated with 60degC terminals and 75degC above 100a, or 100a and above.
Beakers marked with 60degC terminals must be applied with 60degC rated wire or 75degC, 90degC rated wited applied at 60degC.
However, breakers 100a and below (or below 100A) for quite soe time have been commonly available with terminals marked 60/75degC. This means that the breaker can be applied with 60degC rated wire applied at 60degC or 75degC rated wire applied at 75degC with the exception as indicated 240.4(D) of the 2002 NEC. Of course 90degC rated wire and above are applied at 75degC.
There is no division as to how the breaker is mounted or installed.
As I recall breakers 100a and below, or is it below 100a, were to be rated with 60degC terminals and 75degC above 100a, or 100a and above.
Beakers marked with 60degC terminals must be applied with 60degC rated wire or 75degC, 90degC rated wited applied at 60degC.
However, breakers 100a and below (or below 100A) for quite soe time have been commonly available with terminals marked 60/75degC. This means that the breaker can be applied with 60degC rated wire applied at 60degC or 75degC rated wire applied at 75degC with the exception as indicated 240.4(D) of the 2002 NEC. Of course 90degC rated wire and above are applied at 75degC.
There is no division as to how the breaker is mounted or installed.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: CB data
Grant, can you provide a UL listing reference for the above?
BAHTAH
Senior Member
- Location
- United States
Re: CB data
Take a look in the UL-Green Book and you will find where molded case breakers labeled 60/75-deg C are to be applied based on temp rating and if installed in groups (panelboard) or separate enclosure or industrial panel. I am not in my office now, but monday if no one has found it I will site the location in the UL-Green Book.
[ March 21, 2003, 11:50 PM: Message edited by: grant ]
Take a look in the UL-Green Book and you will find where molded case breakers labeled 60/75-deg C are to be applied based on temp rating and if installed in groups (panelboard) or separate enclosure or industrial panel. I am not in my office now, but monday if no one has found it I will site the location in the UL-Green Book.
[ March 21, 2003, 11:50 PM: Message edited by: grant ]
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
Re: CB data
Grant
The way I understand this is as long as the panel is rated for 75C conductors you can use the 75C rating listed on the breaker.
From the UL Green Book:
Circuit breakers rated 125 amps or less and marked suitable for use with 75C rated conductors are intended for field use with 75C rated conductors at full ampacity only when the circuit breaker is installed in a circuit breaker enclosure or individually mounted in an industrial control panel with not other components next to it. Unless the end use equipment (panelboard, switchboard, service equipment, power outlet, etc.) is also marked suitable for use with conductors rated 75C.
Grant
The way I understand this is as long as the panel is rated for 75C conductors you can use the 75C rating listed on the breaker.
From the UL Green Book:
Circuit breakers rated 125 amps or less and marked suitable for use with 75C rated conductors are intended for field use with 75C rated conductors at full ampacity only when the circuit breaker is installed in a circuit breaker enclosure or individually mounted in an industrial control panel with not other components next to it. Unless the end use equipment (panelboard, switchboard, service equipment, power outlet, etc.) is also marked suitable for use with conductors rated 75C.
BAHTAH
Senior Member
- Location
- United States
Re: CB data
Curt,
Thanks for looking up the information. For others it is found in the UL-Green Book under Circuit Breakers(DHJR on page-22 and is stated as Curt has shown. What I was pointing out is, unless the panel states the branch breakers can be terminated using the 75-deg rating, you must use the 60-deg rating. If the breaker is in its own enclosure or in an industrial panel with nothing mounted next to it, you can use the 75-deg c rating for terminations. Not all panelboards state the branch breakers can be terminated using the 75-deg c rating, they may show the main lugs as 75-deg c, but that does not automatically include the branch breakers. I guess the bottom line is, read the label of the panelboard to be sure. It is one of those grey areas that one may not think about if only going buy the requirement for terminations based on the ampacity of breakers and not where the breakers are installed.
Curt,
Thanks for looking up the information. For others it is found in the UL-Green Book under Circuit Breakers(DHJR on page-22 and is stated as Curt has shown. What I was pointing out is, unless the panel states the branch breakers can be terminated using the 75-deg rating, you must use the 60-deg rating. If the breaker is in its own enclosure or in an industrial panel with nothing mounted next to it, you can use the 75-deg c rating for terminations. Not all panelboards state the branch breakers can be terminated using the 75-deg c rating, they may show the main lugs as 75-deg c, but that does not automatically include the branch breakers. I guess the bottom line is, read the label of the panelboard to be sure. It is one of those grey areas that one may not think about if only going buy the requirement for terminations based on the ampacity of breakers and not where the breakers are installed.
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