Wiring outlets for two wall A/C units--questions

[Dick in Wisconsin]

I'm not an electrician, but I've read lots on the GJF and have done some light work.

One has a 20amp, 230 volt plug (25,000BTU) and the other has a 15 amp, 230 volt plug (18,500BTU).

Each A/C unit and hence the respective receptacles will be on separate circuits and breakers. I found 20amp, 250 volt receptacles at Home Depot.

I plan on using 12-2 wire and put black tape on the white wire since it will be hot. The green wire will be the neutral.

Is this correct?

What I find puzzling is that there is apparently no ground, just two hots and a neutral (green wire). I realize that there are lots of tools and appliances that don't have a three prong plug (just a two prong plug) and hence don't have a ground. If the units took more power, I could be going to a 50amp outlet which from what I've seen would have two hots, a neutral, and a ground.

 

[jkwilson]

No. Green is ground. Period. A 240 circuit doesn't need a neutral. Just the two hots and the ground. Only a circuit that has both 120 and 240 uses two hots, a neutral and a ground.

 

[theoldwizard1]

I plan on using 12-2 wire and put black tape on the white wire since it will be hot. The green wire will be the neutral.

Red tape is "more correct", but I would guess black would be acceptable.

12-2 Romex does not have a green wire. It does have a bare conductor. There is no neutral in most 240V circuit, but they do have a ground, just like 120V circuits.

 

[Dick in Wisconsin]

No. Green is ground. Period. A 240 circuit doesn't need a neutral. Just the two hots and the ground. Only a circuit that has both 120 and 240 uses two hots, a neutral and a ground.

Red tape is "more correct", but I would guess black would be acceptable.

12-2 Romex does not have a green wire. It does have a bare conductor. There is no neutral in most 240V circuit, but they do have a ground, just like 120V circuits.

Thanks!

 

[theoldwizard1]

What I find puzzling is that there is apparently no ground, just two hots and a neutral (green wire). I realize that there are lots of tools and appliances that don't have a three prong plug (just a two prong plug) and hence don't have a ground. If the units took more power, I could be going to a 50amp outlet which from what I've seen would have two hots, a neutral, and a ground.

Most 240V outlets are 3 prong, ground but no neutral.

NEMA Chart - You need a 6-15 and a 6-20.

 

[wyliesdiesels]

Red tape is "more correct", but I would guess black would be acceptable.

12-2 Romex does not have a green wire. It does have a bare conductor. There is no neutral in most 240V circuit, but they do have a ground, just like 120V circuits.

Red would make more sense but black is perfectly acceptable...

 

[Dick in Wisconsin]

NEMA Chart - You need a 6-15 and a 6-20.

Thanks Wizard!!!! That chart will be helpful. I'm going to print and laminate it.

Attached is a photo of the instructions for the A/C units with pictures of the plugs, I've X'd the two plugs on the two A/C units.

Attached is a photo of what I found at Home Depot. The woman who runs our local HD's electrical department and is extremely helpful (especially to a non-electrician) wasn't in the last couple of times I was there. Just a paint guy and a "mechanic" (that is what they told me when I asked for help as they walked through the electrical aisle) who were temporarily assigned to the electrical aisle; they were sincere in their desire to help me, but were completely ineffective.

Looks like what I found on my own, is a combination of at 6-15 and a 6-20. Package says its a 20amp/250 volt receptacle, so I presume I can use it in both a 15amp and 20amp application. I could not find either a separate 6-15 or 6-20 receptacle anywhere on the shelves.

The package indicates "Standard". Also on the selves were other receptacles and switches which were badged "Preferred" and "Professional". The higher grade receptacles and switches look more substantial than any of the "Standard" products.

I presume I can use these receptacles that I'll call 6-15/20 for my A/C units, please confirm.

Should I look for more substantial receptacles beyond the "Standard" ones that I found? I expect that the A/C units will run for extended periods of time and draw close to their rated amperage.

 

[offroadsteve]

Yes, that receptacle can be used for both of your A/C units, and both receptacles must be wired with 12 AWG and connected to a 20 amp breaker.

Regarding the "standard". "preferred" or "professional" products at HD, I usually like to use at least the "preferred", the minor extra cost only hurts once. Its probably not a big deal in your case as I've found you start to notice the difference in quality when the receptacle undergoes a lot of plug / unplug cycles. These will probably be plugged in once and never unplugged, so the extra cost of the "pro" receptacles isn't worth it.

 

[Stuart in MN]

Its probably not a big deal in your case as I've found you start to notice the difference in quality when the receptacle undergoes a lot of plug / unplug cycles. These will probably be plugged in once and never unplugged, so the extra cost of the "pro" receptacles isn't worth it.

I'd tend to agree with this - the biggest wear issue with receptacles is probably from plugging and unplugging devices, and air conditioners at most typically only get plugged and unplugged twice a year, in spring and fall.

 

[Dick in Wisconsin]

Yes, that receptacle can be used for both of your A/C units, and both receptacles must be wired with 12 AWG and connected to a 20 amp breaker.

Thanks!

One of the A/C units is 20amps, obviously use a 20 amp breaker. The other is a 15amp unit.

1. Would a 20amp breaker adequately protect a 15amp device?

2. Could I use a 15amp breaker on the circuit for the 15 amp A/C device?

 

[wyliesdiesels]

For single receptacles the breaker MUST match the receptacle rating. Single means a receptacle with ONLY one actual outlet/u can only plug in one device.

So if u use a single 6-15r, then the breaker needs to be 15a.

u could alternatively use a 6-20r for both as well as #12 NM-b(which u already plan on doing) and 20a breakers to simplify things. This will also make things more versatile.