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220V mini-split A/C wiring questions...

Posted by mikeinmayberry (My Page) on
Sun, Jun 20, 10 at 15:43

also posted on the wiring forum...

New here...I like what I've seen so far. I'm a jack of all trades, retired, working on a 2nd home I've recently purchased. This home, the money pit, is a 1-1/2 story with a full basement. The top room has a "mini-split" heat pump...darn thing wouldn't work. Upon further investigation I found the outside compressor was a 220V unit wired as a 110V. I called a local A/C outfit and they said I could remove the dedicated single 15A breaker, add a 15A 2 pole (30A) in its place. As the panel is 2 storys below in the basement, and all I have is 14/2 + bare grnd wiring, he suggested I hook the 2 pole breaker up with the black & white, and run the bare ground to the neutral bar. Now the A/C works (I do not need the heat pump to function). Everytime I leave this 2nd home, I shut the breaker off as I really have doughts this is correct. I haven't found a easy way to run a new 14/3 + grnd (or 14/4 if I want the heat pump to work) without tearing up a lot of sheetrock. An I over thinking this? I'd hate to burn the place down. Advice appriciated...Mike in Mayberry


Follow-Up Postings:

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RE: 220V mini-split A/C wiring questions...

Well, lets see: a heat pump IS an A/C that can run in both 'directions'. You don't need extra electrical wiring for that (the heat) to work.

It would be good to know if the unit requires both the neutral and the ground. It would also be nice to know how you connected it at the unit.

Scenario 1: It requires two hots, neutral and ground. You connected two hots and neutral but no ground. It runs happily. But it is not a safe installation since the unit is not grounded.

Scenario 2: It requires two hots, neutral and ground. You connected the two hots and ground but not the neutral. Then it would depend on whether the indoor unit uses a 120v blower. This probably would not work. but it might.

Scenario 3: It requires two hots, neutral and ground. You connected the two hots and neutral. There is an internal jumper between neutral and ground. This is similar to how older 220v appliances used to be connected. It runs happily. IIRC, new code does not allow this type of installation (for appliances).

The best long term solution will be to run the 14/3 from the box to the unit. Run it outside if necessary.


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RE: 220V mini-split A/C wiring questions...

The straight 240 V setup is missing in the above examples.

That would be two hots and ground.

This is commonly done using 2-conductor plus ground wire.

You only need the neutral if the unit is 120/240 V.

What is on the nameplate of the outside unit?


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RE: 220V mini-split A/C wiring questions...

You guys are wonderful...here's the nameplate:

Nordyne Model FT3BC-042K

Voltage: 208/230V
Phase: 1
Hertz: 60
Total Amps: 19.4
Compressor Amps: R.L.A. 17.9, L.R.A. 104
Outdoor Fan Amps: F.L.A. 1.5, HP 0.25
Minimun Circuitry Ampacity (Amps): 23.9


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RE: 220V mini-split A/C wiring NAMEPLATE

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RE: 220V mini-split A/C wiring questions...
Posted by mikeinmayberry (My Page) on Tue, Jun 22, 10 at 20:48

Let me try this again...I'm working off of pictures 140 miles away from the units...I fat fingered this the first time...pulled the info off of the wrong picture.
Ductless mini-split
Model S240HP-13K11-0
Cooling Cap: 12500 BTU
Heating Cap: 13000 BTU
Voltage: 208V/240V
1 PH/60 HZ
Total Input Current: 6.22A
Compressor RLA 5.7A, FLA 33A
Fan Motor Outside: 0.064 HP, .56A
Fan Motor Inside: 0.03HP, .16A

NCP (made in China...uck)


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RE: 220V mini-split A/C wiring questions...

"Voltage: 208V/240V "

The unit is a straight 240 V load and does not need a neutral.

It is common to run 2-conductor plus ground cable.

The white wire should be marked black at the unit to indicate it is NOT a neutral but a hot.

A wrap of black electrical tape is fine.
It should also be marked at the breaker (and any other boxes it passes through) but that is not as important.
Anyone working in the panel will instantly know it is a hot since it will be hooked to the breaker.
At the unit this is not as readily apparent.

If the panel is a main panel neutrals and grounds connect to the same bar.

In a sub panel neutrals and grounds are separate.


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