I maintain when selecting the correct ampacity for circuits, article 110.14(C)(1)(a)(1)must be used and says anything under 100 amps needs to be taken from the 60 degree C column and you must use that column. My colleagues want to use the 75 degree C column. I work in a factory and am having a "discussion" on this with my fellow sparky's. Where do you come down on this? lbrown73.
Table 310.15(B)(16). Which column?
- Thread starter lbrown73
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texie
Senior Member
- Location
- Fort Collins, Colorado
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- Electrician, Contractor, Inspector
You are correct to a point. What you are missing is that 110.14(C)(1)(a)(3) says "conductors with higher temperature ratings if the equipment is listed and identifiedfor use with such conductors". The reality today is that almost all devices today are rated 75 degree.
Depends somewhat on what you are calculating.
For derating purposed, such as conduit fill, you can use the column based on your conductor insulation.
110.14 limits the termination temperature.
Note that in everyday situations, 110.14(C)(1)(a)(3) normally applies in that many devices with an ampacity 100 amps or less are listed for 75?
For derating purposed, such as conduit fill, you can use the column based on your conductor insulation.
110.14 limits the termination temperature.
Note that in everyday situations, 110.14(C)(1)(a)(3) normally applies in that many devices with an ampacity 100 amps or less are listed for 75?
- Location
- New Jersey
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- Journeyman Electrician
As stated most modern equipment has 75? C terminations meaning that you can use the 75? ampacity. The one caveat is if your using a cable that must be used at it's 60? C ampacity like NM cable.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Most conductors today are rated 90?c but we are limited to the terminal rating of the terminals they connect to so that the combination of the conductor and terminal can dissipate the heat that might develop as both the conductor and terminal must play a part in dissipating the heat like in a heat sink, so if the conductors are connected to a terminal with a 75?c rating then the 75?c column can be used, except as was mentioned cables such as NM that limit us to using the 60?c column.
And as Augie mentioned for derating purposes we can use the temperature rating of the conductors for derating purposes, as again most conductors today including NM has a 90?c rating so we can use the Ampacity in the 90? column to derate from.
Also keep in mind that the NEC limits small conductors in 240.4(D) so that a #14 can only be protected by a 15 amp breaker, 20 amps for a #12 and 30 amps for a #10 except when the conductors supply equipment listed in 240.4 (E) or (G) table 240.4(G) as protection for those conductors will be addressed in the sections listed in table 240(G)
And as Augie mentioned for derating purposes we can use the temperature rating of the conductors for derating purposes, as again most conductors today including NM has a 90?c rating so we can use the Ampacity in the 90? column to derate from.
Also keep in mind that the NEC limits small conductors in 240.4(D) so that a #14 can only be protected by a 15 amp breaker, 20 amps for a #12 and 30 amps for a #10 except when the conductors supply equipment listed in 240.4 (E) or (G) table 240.4(G) as protection for those conductors will be addressed in the sections listed in table 240(G)
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