110.14(C)

[msi99]

When two solar systems are connected in a combiner panel with 2 breakers ( 40A and 20A ) the output of the combiner panel is 60A, so based on 75 degrees C and 90 degrees C, we should be able to use #6. Is there a reason why the AHJ would require you to upsize the wire to #4 so that the conductors satisfy 60 degrees C as well per 110.14 ( C).
Per my understanding, 110.14(C)(1)(a)(3) allows the conductors with higher temp ratings if the equipment is listed for use.
The 60A PV breaker ( after combining) and the output lugs in the combiner panel are rated for 60 degrees c or 75 degrees C so there's no requirement for the conductors to be sized for 60 degrees as well?

 

[ggunn]

When two solar systems are connected in a combiner panel with 2 breakers ( 40A and 20A ) the output of the combiner panel is 60A, so based on 75 degrees C and 90 degrees C, we should be able to use #6. Is there a reason why the AHJ would require you to upsize the wire to #4 so that the conductors satisfy 60 degrees C as well per 110.14 ( C).
Per my understanding, 110.14(C)(1)(a)(3) allows the conductors with higher temp ratings if the equipment is listed for use.
The 60A PV breaker ( after combining) and the output lugs in the combiner panel are rated for 60 degrees c or 75 degrees C so there's no requirement for the conductors to be sized for 60 degrees as well?

The AHJ is misinformed, but some battles are not worth fighting..

 

[jaggedben]

Yeah, the AHJ is wrong if your combiner sub has 75C rated terminals, which if it's new it almost certainly does.

Also they are wrong if your total namplate inverter output happens to be below 44A.

 

[Carultch]

When two solar systems are connected in a combiner panel with 2 breakers ( 40A and 20A ) the output of the combiner panel is 60A, so based on 75 degrees C and 90 degrees C, we should be able to use #6. Is there a reason why the AHJ would require you to upsize the wire to #4 so that the conductors satisfy 60 degrees C as well per 110.14 ( C).
Per my understanding, 110.14(C)(1)(a)(3) allows the conductors with higher temp ratings if the equipment is listed for use.
The 60A PV breaker ( after combining) and the output lugs in the combiner panel are rated for 60 degrees c or 75 degrees C so there's no requirement for the conductors to be sized for 60 degrees as well?

See if you can find documentation of the 75C listing for the equipment on both sides of this conductor. Most likely, you have 75C ratings, but 110.14(C) gives you an onus of proof to use it.

60C is the default, if equipment isn't specifically rated for 75C. This generally is more of an academic rule, rather than practical, since most equipment carries at least 75C ratings for 110.14(C). Older equipment may have a 60C rating, which might be the issue.

 

[ramsy]

Yeah, the AHJ is wrong if your combiner sub has 75C rated terminals

Not if inspector saw 60C rated wiring methods. What if installed by a Romex Jockey.

 

[ramsy]

2 breakers ( 40A and 20A ) the output of the combiner panel is 60A

If describe it to inspection as 60A output, inspector may hear 60A load, per 690.9(B).

Is there a reason why the AHJ would require you to upsize the wire to #4

60A x 125% = #4cu.

 

[Fred B]

Not if inspector saw 60C rated wiring methods. What if installed by a Romex Jockey.

Right, OP didn't indicate wiring method that will effect any proposed wiring, NM or AL wire both will effect that.
Don't know what the inspector saw.
Even though NM wire is rated as a 90 deg conductor code limits it's final size to 60 degree load value.
AL also would require up sizing to get to the 60A level.

 

[ramsy]

AL also would require up sizing to get to the 60A level.

Found some #4 CCA NM (55A @ 60c)

NM-B

Type NM-B CCA Building Wire. Copperweld NM-B Building Wire is a welcome value to every stakeholder in the residential building wire space. Drawn from a copper-clad aluminum rod, with the copper metallurgically bonded to an AA 8000 series aluminum core, where oxygen-free copper forms a minimum of...

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