HVAC wire size?

D

Daja7

Senior Member
Customer has an HVAC unit to be wired. Nameplate say 16.6 FLA with max OCP 25 Amp. HVAC installer says they want us to use #14 and stats it is listed as 20m amp rated. Yes? No? I would use #12 but he insist as it is less expensive.
 
You can't use #14NM but you could use #14 MC, etc unless the terminals are marked for 60 deg termination
 
Daja7 said:
Yes my mistake. compressor is 12.8 and motor is .6. MCA is listed as 16.6
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Then #14 is fine since it's rated at 20 amps for this application. It just cannot be NM or UF cable. What is the wiring method?
 
Daja7 said:
Customer has an HVAC unit to be wired. Nameplate say 16.6 FLA with max OCP 25 Amp. HVAC installer says they want us to use #14 and stats it is listed as 20m amp rated. Yes? No? I would use #12 but he insist as it is less expensive.
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Tell the HVAC guy that you'll handle the electrical and he can stick to the HVAC.
 
A lot of people are not aware of the Romex & Uf cable limitation (I wasn't). Romex and UF in #14 would have been allowed a few years ago.
If they make changes in the code that is fine but they should be consistent changes to keep the confusion down.

Not increase the confusion.
 
Ken_S said:
Tell the HVAC guy that you'll handle the electrical and he can stick to the HVAC.
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Agree, since when does the HVAC contractor dictate what size wire to use and why should he care if it's 14 or 12?
 
kec said:
Agree, since when does the HVAC contractor dictate what size wire to use and why should he care if it's 14 or 12?
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If the sparky is his sub-contractor then the cost for a #14 circuit vs. #12 is money in the hvac guys pocket. IMO not worth arguing about but some of these guys are really cheap and hey don't want to pay for anything above and beyond the minimum code requirement.
 
curt swartz said:
You would also need #12's if using a Liquid Tight whip to the unit.
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I don't agree. The operational load is 13.4 amps, not 16.6 amps, and that does not exceed the 60°C ampacity of 14 AWG. We do not need to use the MCA for this as that number includes a fictitious 25% increase to the compressor current.
 
don_resqcapt19 said:
I don't agree. The operational load is 13.4 amps, not 16.6 amps, and that does not exceed the 60°C ampacity of 14 AWG. We do not need to use the MCA for this as that number includes a fictitious 25% increase to the compressor current.
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In this case I do agree with you. My post was mainly to bring up that even with 75C conductors the 60C limit would still apply to the Liquidtight. I didn't take the lower MCA of the posted unit into account so even at 60C the #14 are adequate.
 
don_resqcapt19 said:
I don't agree. The operational load is 13.4 amps, not 16.6 amps, and that does not exceed the 60°C ampacity of 14 AWG. We do not need to use the MCA for this as that number includes a fictitious 25% increase to the compressor current.
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Seems to me that when the ampacity is required to be 16.6A, you need an installation that could carry 16.6A without violating any temperature limits. An LFNC installation in a wet location with #14 conductors would not meet that standard.

Cheers, Wayne
 
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