HVAC wire sizing NEC

[electro7]

Was wondering if #10 thhn or thwn conductors are okay feeding this HVAC equipment? Im used to sizing the wire according to the max fuse size of 40A, and that is what is protecting this unit, but was wondering about NEC motor load requirements.

Thanks ahead of time for the help.

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[Dsg319]

MCA- conductor size.

Max fuse/ocpd device- OCPD size

The HVAC data plate does all the work for us.

No need to size conductors for 40amps

Number 10awg is perfectly acceptable

 

[electro7]

Awesome thanks. Whats the NEC code section for that for my reference.

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[Dsg319]

Awesome thanks. Whats the NEC code section for that for my reference.

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Some where in 440. Someone else will know exactly though

 

[augie47]

Awesome thanks. Whats the NEC code section for that for my reference.

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240.4(G) allows you to use ampacities not covered by other 240.4 stipulations,
440..22 and 440.35 guide you to follow the nameplate.

 

[electro7]

Thank you very much.

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[electro7]

Another question: so you dont need to multiply the MCA by 1.25 for continuous load?

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[augie47]

Another question: so you dont need to multiply the MCA by 1.25 for continuous load?

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No. The MCA has already taken that into account.

 

[infinity]

Another question: so you dont need to multiply the MCA by 1.25 for continuous load?

As Augie stated no. The MCA is typically calculated by the largest load the compressor *125% plus the fan load at 100 %.

 

[Ponchik]

Another question: so you dont need to multiply the MCA by 1.25 for continuous load?

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(14.6 x 1.25) + 7.1 + 1.3 = 26.775
MCA 27A

 

[electro7]

Got it thanks!

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[herding_cats]

On average, most all 14 SEER rooftop units use 1034 watts per ton. That metric can be used to get an idea of what to expect if you get a service call for a bid on power install for an RTU. Wire sizing, disconnect, etc.

This is a 5 ton unit, or possibly a 6 ton by manufacturer?