Mini Split Wire Size

[goldbergma8]

We are installing a 115volt minisplit heat pump in our building and our quote from an electrician does not seem right. Our electrical panel is 250 feet away from where the mini split will be installed but the electrician only stated he will use 3 (hot,neutral, and ground) 10AWG THHN wire in conduit. From my calculations, that will end up having 7.8% voltage drop. Is this ok? I figured we would need 6AWG to keep the voltage drop at a reasonable amount. Its a long wire run so I dont want the electrician to do the job then have the system fail or have the wiring start a fire. The minisplit specs are: 115volt, 60Hz, 1 phase, .7Amps (fan motor), 9.5 amps(compressor), 15amp min circuit ampacity, and 20Amp Max fuse.

 

[Dennis Alwon]

You are correct that the vd is alot but generally motors can handle it. If the unit rated 115V? If so, then 112V is not so bad

Why are you not using 240v mini split. I have installed on 120v mini split in my life and we have wired many of them

 

[JFletcher]

The voltage drop calculator I used gave a 5 volt drop using 10.2 amps at 250 feet, 120 volt voltage, on number 10 copper wire. A little over 4% VD.

Welcome to The Forum

 

[curt swartz]

Are you sure these units are 120 volt? I have never seen a 120 Mini.

 

[JFletcher]

I missed the edit time... He could actually run number 14 out there, so number 10 is already upsized wire. And if you go with a 240 volt unit, the voltage drop will be practically nil with the same wire and distance.

Not sure if a 240-volt mini-split needs a neutral, however if they do, I would have him run an extra wire out there to give you the option of swapping straight to 240 volts.

 

[Dennis Alwon]

I missed the edit time... He could actually run number 14 out there, so number 10 is already upsized wire. And if you go with a 240 volt unit, the voltage drop will be practically nil with the same wire and distance.

Not sure if a 240-volt mini-split needs a neutral, however if they do, I would have him run an extra wire out there to give you the option of swapping straight to 240 volts.

240 v units do not need a neutral usually-- a least I had not seen one that did.

 

[kwired]

If 240 volt unit does need neutral the proper labeling/specs should say 120/240 volts.

Most I believe are foreign made and to standards that work here as well as in other countries where 120 volts isn't typically found.

 

[Andy Delle]

Are you sure these units are 120 volt? I have never seen a 120 Mini.

The 9000btu and below are often available in 120v.

 

[Dennis Alwon]

The 9000btu and below are often available in 120v.

Years ago we found this out the hard way... Nuf said-- never expected the voltage to not be 240V

 

[kwired]

Years ago we found this out the hard way... Nuf said-- never expected the voltage to not be 240V

Does it really change much of what you will bring other then if a long run and you decide 10 AWG might be good for voltage drop?

NM or MC cable you just reidentify the white if not a grounded conductor.

If you need more then 10 AWG as base ampacity you kind of took the "mini" out of "mini-split" there are 3.5-4 ton units that can be supplied with 10 AWG.

 

[Dennis Alwon]

Most all of them can be wired with a 12/2 nm. The problem was we hooked up the unit 240V-- we checked the max overcurrent protective device but never thought to check the voltage rating since every one we ever did, to that point, were 240V. Easy fix-- the unit actually work for 6 months even though we ran the 120V unit on 240V for 10 minutes or so. We did volunteer to take care of the cost of a replacement.

 

[ActionDave]

Years ago we found this out the hard way... Nuf said-- never expected the voltage to not be 240V

I blew up a mini split under the same circumstances. Wasn't the worst day I ever had, but it was a bad one.

 

[Dennis Alwon]

I usually like to blame it on my guys (I tell them that's why I hired them) but I'll have to own up to this one..