Temperature limitations

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In addition to what don noted, the 60° ampacity of #8 is 40 amps. Art 110.14 (C) would require the #8 to be installed at that ampacity IF the terminations are rated at 60°.
In most case, breakers and devices are rated 75° so you are fine at that ampacity (50 amps) but you may find some devices rated 60° in which case the limit would be 40 amps.
 
Nitrovoltage001 said:
..trying to find what my boss is talking about but I think he's wrong
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Tell us if existing fuse box labels (not breakers) identify any temperature rating at all?

If not, the code default limit is given by Art 110.14 (C)(1)(a), as augie47 told us.
 
Are you talking rooftop installation? It used to be thought that a rooftop installation incurred much more heat from solar exposure and required de-rating. My understanding is there is consideration in the '23 code that will be addressed as UL testing has found that solar exposure even in the most extreme areas are not producing enough ambient temperature increase to warrent de-rating (according to a UL representative).
 
Nitrovoltage001 said:
110.14 c 1 a huh 60 degree only for 14 through 1 awg look at that thanks man
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110.14(C)(1)(a)(3) says conductors with a higher temperature rating if the equipment is listed and identified for use with such conductors.

So the ampacity of #8 THHN is 50, when the equipment is listed for use at 75C.
 
david luchini said:
110.14(C)(1)(a)(3) says conductors with a higher temperature rating if the equipment is listed and identified for use with such conductors.

So the ampacity of #8 THHN is 50, when the equipment is listed for use at 75C.
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I agree, for some reason people don't read that entire section.
 
david luchini said:
110.14(C)(1)(a)(3) says conductors with a higher temperature rating if the equipment is listed and identified for use with such conductors.

So the ampacity of #8 THHN is 50, when the equipment is listed for use at 75C.
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David, 60°C is required when the equipment is <=100A and temp. rating is unknown.

Existing residential fuse boxes --up to 100A-- rarely had temperature ratings on the labels, so the default is 60°
 
david luchini said:
110.14(C)(1)(a)(3) says conductors with a higher temperature rating if the equipment is listed and identified for use with such conductors.

So the ampacity of #8 THHN is 50, when the equipment is listed for use at 75C.
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If not told otherwise, I'm having visions of old panels <=100A, or Romex used in 60°C residential equipment, none of which permits 75°C Ampacity.
 
ramsy said:
David, 60°C is required when the equipment is <=100A and temp. rating is unknown.
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You are correct but David did state explictly that when the equipment is listed for 75° C then you can ignore the 60° C limitation of that code section. NM cable is something different because it is always limited to 60° C.
 
infinity said:
You are correct but David did state explictly that when the equipment is listed for 75° C then you can ignore the 60° C limitation of that code section. NM cable is something different because it is always limited to 60° C.
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I'm not sure David agrees in listing predominance over ampacity tables, such as Table 310.12
 
infinity said:
I'll wait for David to answer that.
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Combination inspectors may be trained to enforce listings, labels, nameplates & product instructions, at the expense of tables, and other code language, but engineers need not deal with inspectors when drafting plans.

The question for David is; if inspectors red tag an install, because engineered plans allow 75°C ampacity, in conflict with some equipment listing, how is that conflict resolved.

It may involve RFI's, and risk some delay, or crash the project schedule.
 
ramsy said:
Combination inspectors may be trained to enforce listings, labels, nameplates & product instructions, at the expense of tables, and other code language, but engineers need not deal with inspectors when drafting plans.

The question for David is; if inspectors red tag an install, because engineered plans allow 75°C ampacity, in conflict with some equipment listing, how is that conflict resolved.

It may involve RFI's, and risk some delay, or crash the project schedule.
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If it is a violation of an actual 110.3(B) listing and labeling instruction, the conflict must be resolved in favor of the inspector, as engineering plans cannot change code requirements.
 
Fred B said:
Are you talking rooftop installation? It used to be thought that a rooftop installation incurred much more heat from solar exposure and required de-rating. My understanding is there is consideration in the '23 code that will be addressed as UL testing has found that solar exposure even in the most extreme areas are not producing enough ambient temperature increase to warrent de-rating (according to a UL representative).
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The only change for 310.15(B)(2) for roof top ampacities that shows up in the second draft report for the 2023 code, is to change the spacing above the roof from 7/8" to 3/4". There were no other changes and you still have to add 60°F to the ambient for roof top ampacity correction where the raceway or cable is less than 3/4" above the roof surface.
 
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