Wire size to ductless mini split

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What minimum conductor ampacity is shown on the compressor nameplate? Then use the sixty degree ampacity column for #14 wire and for hermetically sealed refrigerant and ac motors you don't need to worry about the 15 amp restriction for #14 conductors. Compare the two numbers. If your wire is rated to carry the nameplate amps then you should be good to go for the portions located in dry locations. Conduit run in or on the exterior is not considered any longer to be a dry location, so the romex needs to be changed to an approved method if exterior conduit such as flexible non metallic conduit is used on the exterior portion between bullding and compressor , subjected to damp or wet area's.
 
macmikeman said:
What minimum conductor ampacity is shown on the compressor nameplate? Then use the sixty degree ampacity column for #14 wire and for hermetically sealed refrigerant and ac motors you don't need to worry about the 15 amp restriction for #14 conductors. Compare the two numbers. If your wire is rated to carry the nameplate amps then you should be good to go for the portions located in dry locations. Conduit run in or on the exterior is not considered any longer to be a dry location, so the romex needs to be changed to an approved method if exterior conduit such as flexible non metallic conduit is used on the exterior portion between bullding and compressor , subjected to damp or wet area's.
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This will be 14-2 from the panel to the disconnect outside, then 14 gauge THHN from there.


I was just a little confused from the last Mike Holt news letter about air conditioning and refrigeration equipment. In one part it says this...

Disconnecting means
For a hermetic refrigerant motor-compressor, the ampere rating must be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater [440.12(A)(1)].

I always thought all the calculations were done by the manufacture and you only need to go off of the nameplate.
 
crtemp said:
This will be 14-2 from the panel to the disconnect outside, then 14 gauge THHN from there.


I was just a little confused from the last Mike Holt news letter about air conditioning and refrigeration equipment. In one part it says this...

Disconnecting means
For a hermetic refrigerant motor-compressor, the ampere rating must be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater [440.12(A)(1)].

I always thought all the calculations were done by the manufacture and you only need to go off of the nameplate.
Click to expand...
First off 440.12 applies to the disconnecting means not the conductors.

What you are looking for is 440.4(B) which states multimotor and combination-load equipment needs to be provided with a nameplate .... MCA, MOCP.... are all covered in this section.

440.12(A) would be used if you were running an individual circuit to a compressor that was not a part of a multi-motor or combination load equipment that did not have such a nameplate. This scenario doesn't happen that much in residential and light commercial work.
 
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