GMP
New member
- Location
- Clayton, NC , USA
I'm new to the forum, first post, have been a lurker for a lot of years getting answers to code questions from the brain trust that exists here. First off, thanks for all the information, opinions and interpretations of the NEC that i have used over the years. Here's the background and question(s)(please forgive me if this topic has been discussed before as i have not been able to find it);
In general, Article 110.14 of the NEC states that the temperature terminal rating of a device must be connected to a conductor(s) such that the temperature rating is not exceeded unless otherwise listed as such. For example, most if not all circuit breakers with mechanical lugs have a terminal temperature rating of 75 deg C. This means that the sizing of conductors for ampacity must adhere to the 75 deg C category of the ampacity tables of the NEC, correct? (first question)
Consider the following, the UL white book identifies the requirements for temperature terminal rating of breakers, switchboards, etc. to be based off of NEC table 310.15(B)(16) for ampacity to determine conformance to temperature terminal rating. So, all testing for temperature terminal rating that is done by the manufacturers of electrical equipment, which is UL listed, is done so according to the required conductors necessary at 75 deg C based on NEC table 310.15(B)(16) to achieve the rated ampacity. The manufacturers (i.e. GE, Sq D, Eaton, and Siemens) will not waiver from this interpretation based on UL requirements.
Here's the second question, when using cable tray, Article 392 permits the use of conductor sizing based on NEC 310.15(B)(17) as well as others based on certain conditions. So , if i employ the use of cable tray for conductors that are terminating in a mechanical lug of a large breaker that has a terminal temperature rating of 75 deg C based on table 310.15(B)(16) does it conform? I have been told that if the conductors are sized according to table (B)(17) it does not by the manufacturer, UL and a few engineers of record. They claim that the cable, installed in cable try, has to be sized in accordance with table 310.15(B)(16) and not 310.15(B)(17) and must not exceed the 75 deg C ampacity rating of table 310.15(B)(16) because of Article 110.14.
Is this correct?
In general, Article 110.14 of the NEC states that the temperature terminal rating of a device must be connected to a conductor(s) such that the temperature rating is not exceeded unless otherwise listed as such. For example, most if not all circuit breakers with mechanical lugs have a terminal temperature rating of 75 deg C. This means that the sizing of conductors for ampacity must adhere to the 75 deg C category of the ampacity tables of the NEC, correct? (first question)
Consider the following, the UL white book identifies the requirements for temperature terminal rating of breakers, switchboards, etc. to be based off of NEC table 310.15(B)(16) for ampacity to determine conformance to temperature terminal rating. So, all testing for temperature terminal rating that is done by the manufacturers of electrical equipment, which is UL listed, is done so according to the required conductors necessary at 75 deg C based on NEC table 310.15(B)(16) to achieve the rated ampacity. The manufacturers (i.e. GE, Sq D, Eaton, and Siemens) will not waiver from this interpretation based on UL requirements.
Here's the second question, when using cable tray, Article 392 permits the use of conductor sizing based on NEC 310.15(B)(17) as well as others based on certain conditions. So , if i employ the use of cable tray for conductors that are terminating in a mechanical lug of a large breaker that has a terminal temperature rating of 75 deg C based on table 310.15(B)(16) does it conform? I have been told that if the conductors are sized according to table (B)(17) it does not by the manufacturer, UL and a few engineers of record. They claim that the cable, installed in cable try, has to be sized in accordance with table 310.15(B)(16) and not 310.15(B)(17) and must not exceed the 75 deg C ampacity rating of table 310.15(B)(16) because of Article 110.14.
Is this correct?
