Use 10-3 NM-B vs 10-2 NM-B for outdoor mini-split condenser

[ACI]

Per NEC is it acceptable to pull 10-3 NM-B when only a 10-2 NM-B cable is needed at this time? I understand that the 10-3 provides the "extra" hot (red) conductor, but what does NEC say about the "spare" wire in the cable that is not needed?

1. Cap the white conductor at both ends of the 10-3 NM-B cable?
2. Ground the white conductor at both ends, essential terminating it to the same location on both ends as the green ground wire?
3. Connect the white to the natural bar at the CKT Breaker Panel and cap in the field?

For this application the Black (hot) Red (hot) and Green (Ground) would be used.
Thank you

 

[JGinIndy]

It is but why would you want to? Black and Red will be the ungrounded line to line conductors, terminate the EGC bare to ground terminals and wire nut the white at both ends.

 

[augie47]

I see no problem with 1, 2 or 3. There well might be a problem using NM in general as it is not allowed in wet/damp locations including the interior of a raceway in a wet location which often applies to mini-splits.

 

[JGinIndy]

I assumed the OP was referring from panelboard to disconnect other wise I would have mentioned 300.9 and 334.12 good point glad you included that.

 

[infinity]

Use the Blk/Red/Bare and safe off each end of the white. I've seen guys do option #3 but landing the White in the panel is not necessary.

 

[ACI]

Thanks for the response everyone. We have access to 10-3 NM-B at less cost than 10-2 NM-B (I don't know why that is). I felt if the outdoor unit was to ever change and needed the natural then it would be available. Only concern was some NEC I was unaware of that would prevent this.

Indoors the cable is NM-B and runs from the panel board to the disconnect.
From the disconnect on the outside of the building to the min-split unit is a premade liquid-tight flexible conduit.

Thank you

 

[LarryFine]

I would do #3.

 

[Dennis Alwon]

Are you going to transition from 10/3 nm to some other method on the outside of the building?

 

[infinity]

He stated that he was using LFMC (or LFNC) for the transition: "From the disconnect on the outside of the building to the min-split unit is a pre-made liquid-tight flexible conduit.".

 

[ACI]

Yes, the contractor/installer is using a liquid-tight flexible pre-made "harness" from the disconnect to the mini-split.

 

[kwired]

Not too likely you ever need a neutral, but nothing prohibits running a method that has an unused conductor.

Not likely in a dwelling, but if this were a building with three phase, running a "three wire" cable would more likely allow switching to three phase unit before there ever would be a need for utilizing a neutral.

When running a circuit to wall ovens or cooktops and you don't know the model yet, it not a bad idea to run three wire just in case a neutral would be needed.

And as mentioned you don't have an extra red in case you need it. If the cable has enough "colors" for the needed ungrounded conductors you need to use those before you "repurpose" a white or gray.