proper wire size?

Installing a 1.5 ton ductless ac unit requiring a 15 or 20 amp breaker, not sure on that yet, 65’ from the panel. What size wire do I want run? romex 12-2 or 10-2 awg.

Greetings Michael,

Not really the forum you should be asking that question. This is a Home Inspector Forum and you need an Electricians Forum. However, since some of us Electricians hang around here I will give you this advice.

Your HVAC unit specifications will tell you what size conductors you will need to install. In fact, most all of the ductless models have installation guides that provide the OCPD (Overcurrent Protective Device) and branch circuit conductor sizing…so we can give you an ampacity value based on NEC 310.15(B)(16) for the conductors you are planning to choose, and since they are Type NM-B Cables you are limited to the 60C column of 310.15(B)(16)…so 12 AWG = 20 Amps and 10 AWG = 30 Amps.

However, again I would consult your installation instructions to be sure you are in compliance with other factors that could affect your conductors ampacity as stated in NEC 334.80.

Note: sometimes the conductor sizes can be slightly smaller than the OCPD in accordance with 240.4(G) (per 440, Pt III and VI) but I honestly think you need to read your installation instructions first.

Michael - kinda sorry you asked now huh. :wink:
Paul is a great resource and unless you really understand electricity, he can feed you from a fire hose. We all greatly appreciate it when he chimes in.
Thanks Paul.

Whomever you are hiring to install this HVAC unit should be skilled enough to handle this issue.


Best answer. :slight_smile:

FACT- Even so it is always good to have the education to understand what others are doing so while the HVAC guy should know…as a consumer I want to know also so I can weed through the BS in the process.

Just Sayin!

I’m curious as to how he knows that it requires a 15 or 20 amp OCPD?

I was thinking the same thing. Which is it? 15 amps? Or 20 amps?

Maybe is says Maximum is 20 Amps…which would not eliminate him using a 15 Amp…or maybe just poor choice of words.:mrgreen: