Wire & Terminal Temp Rating
Wire & Terminal Temp Rating
(OP)
Hi All,
I'm working with NEC 310.16. Most wire terminals that I've encountered are rated for 75*C. I understand that that many people will use 90*C wire because then you apply derating factors for ambient temperature and number of wires in a single conduit without having to drastically increase the wire gauge. The way I understand the wire temperature ratings is this: 2 gauge copper conductor THHN wire carrying a load of 130 amps in a 30*C ambient environment will operate at 90*C. Further, if THHN wires are derated because of higher ambient temperature and used to the full derated spec then the conduction will still reach 90*C. My question is this: why is acceptable to hook a conductor operating at 90*C up to a terminal rated for 75*C? I assume I am misunderstanding something basic here...
Best,
Steris
I'm working with NEC 310.16. Most wire terminals that I've encountered are rated for 75*C. I understand that that many people will use 90*C wire because then you apply derating factors for ambient temperature and number of wires in a single conduit without having to drastically increase the wire gauge. The way I understand the wire temperature ratings is this: 2 gauge copper conductor THHN wire carrying a load of 130 amps in a 30*C ambient environment will operate at 90*C. Further, if THHN wires are derated because of higher ambient temperature and used to the full derated spec then the conduction will still reach 90*C. My question is this: why is acceptable to hook a conductor operating at 90*C up to a terminal rated for 75*C? I assume I am misunderstanding something basic here...
Best,
Steris





RE: Wire & Terminal Temp Rating
You can hook up any wire of any temperature rating to any terminal of any temperature rating. It's just a wire and a terminal.
You must use the lower of the temperature ratings for your derating factors. In your case, the derating (for both conductor and terminal) must be considered at 75°F. You will also have to consider the limit of 80 percent of conductor ampacity if your load is continuous.
Look at 310.15(B), 2nd paragraph. If your ambient is 30°C, you need 1/0 wire at 80 percent derating if your load is 130A..
Best to you,
Goober Dave
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RE: Wire & Terminal Temp Rating
Thanks for the reply. Can you please point me to the code section that requires 80% limit for continuous load? Thanks again!
RE: Wire & Terminal Temp Rating
210.19(A)(1)
Best to you,
Goober Dave
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RE: Wire & Terminal Temp Rating
RE: Wire & Terminal Temp Rating
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: Wire & Terminal Temp Rating