Electrical Code question from Jim

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j.hillstrom

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The MAXIUM current load, in amps, on a size #6 THHN copper conductor is permitted to be 65 amps where connected to a fusible disconnect
switch with terminals rated for 75 degrees c. Where did they get the number 65 amps for this question?
 
According to Section 310.15 (b)16

According to Section 310.15 (b)16

j.hillstrom said:
The MAXIUM current load, in amps, on a size #6 THHN copper conductor is permitted to be 65 amps where connected to a fusible disconnect
switch with terminals rated for 75 degrees c. Where did they get the number 65 amps for this question?
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The THHN conductor isn't a 75 degree celsius conductor, though the THHW & THWN is rated for both 75 degree celsius and 65 amps. The THHN #6 AWG is rated a 75amp 90 degree celsius Rated conductor.
DustinSparkmanthebulldog
 
Dustinsparkmanthebulldog said:
The THHN conductor isn't a 75 degree celsius conductor, though the THHW & THWN is rated for both 75 degree celsius and 65 amps. The THHN #6 AWG is rated a 75amp 90 degree celsius Rated conductor.
DustinSparkmanthebulldog
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Why do you say that thhn is not a 90C insulation. It is rated 90C for both dry and damp location
 
Dennis Alwon said:
Why do you say that thhn is not a 90C insulation. It is rated 90C for both dry and damp location
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Doesn't that require cross listing as THWN-2 for wet locations?
THHN on its own is not listed for wet at all.
Can you be sure that the damp environment in conduit is not really wet (i.e. outdoors)?
 
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GoldDigger said:
Doesn't that require cross listing as THWN-2 for wet locations?
THHN on its own is not listed for wet at all.
Can you be sure that the damp environment in conduit is not really wet (i.e. outdoors)?
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Aren't the differences between wet and damp locations clearly defined in the NEC?
 
GoldDigger said:
Doesn't that require cross listing as THWN-2 for wet locations?
THHN on its own is not listed for wet at all.
Can you be sure that the damp environment in conduit is not really wet (i.e. outdoors)?
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You are correct that THHN is not listed for wet locations, but Dennis said "damp" and THHN is listed as a 90C conductor for damp locations in T310.104(A).
 
Dennis specifically said dry or damp. The OP made no such limitation (unless you want to infer that from his not mentioning THWN cross listing, which given the setting of a test question is probably justified.)
 
I don't understand the confusion. Dustin stated that THHN is NOT a 90C conductor-- well it is the insulation not the conductor we are talking about here- and it absolutely is rated 90C. Why would we talk about wet location as thhn is not rated for wet location so I stand by what I said. THHN is rated 90C at least for de-rating purposes.
 
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