Wiring 220V compressor

[Volksfolks]

I recently purchased a 11/220V compressor and converted the motor to 220V.

My problem arises with the pig tail I need. My house is wired with a 4 prong 220V receptacle in the garage so I purchased a "dryer" cord with 4 prongs.

My compressor only has places for 3 wires. I was told by the "expert" at Home Depot to wire the green and white wires together and put them on the green spade.

That would leave me with the black wire on the black spade, the red wire on the white spade, and the green and white wires on the green spade.

Does this seem reasonable or am I about to ruin my compressor?

TIA.
Bill

 

[DavidJ]

The reason for the dryer to have 4 wires is that it needs a separate neutral because it uses 120 volt controls. Your compressor does not use 120 volts to control it, so it only requires the ground wire. The person at H. D. told you correctly. You could also leave the white wire disconnected and still be OK.

 

[uhmgawa]

</font><font color="blue" class="small">( The reason for the dryer to have 4 wires is that it needs a separate neutral because it uses 120 volt controls. Your compressor does not use 120 volts to control it, so it only requires the ground wire. The person at H. D. told you correctly. You could also leave the white wire disconnected and still be OK. )</font>

That's correct. Except the neutral in the 4-wire feed should never be
connected to the grounded conductor. In general doing so is only
allowable where the separate system ground/neutral originates in the
service entrance equipment.

 

[CTyler]

All you need is the two hots and a ground for the compressor, there is no nuetral wire.

If you take a voltmeter and measure from either hot to the nuetral it will read 120v. If you measure across the two hots it will read 220v, those are the ones you want to use. The ground connects to the to ground.

 

[boustany]

Using a dryer plug could be a hazardous route, if not for yourself then for the person you sell your house to, a kid, renter, or whatever.

A plug/socket is matched to the application/load. So if your compressor is rated for sub 15 amps at 220 (most likely if its convertabe to/from 110), then you should use a receptical for a 15 amp/220 volt circuit, which kind of looks like a regular 110 volt 15 amp receptical, except both prongs are turned 90 degrees. This should be connected to a 15 amp tandem (220 volt) breaker/fuse pair via a 14, or better yet 12, guage 2 conductor plus ground wire.

If you use a dryer recepticle, with is rated at something like 30 amps at 220, there is a risk you are essentailly saying 'its ok to plug a 30 amp/220 volt load like a dryer here. Lets say you strung a 30 amp circuit with proper (I think it 10 guage) wire and you fused it for 15 amps. Thats safe, but somebody could plug something in (like a dryer) and keep blowing fuses. Still safe, but a pain in the butt. If you don't hook up the neutal, you (or more likely the next occupant) could fry the dryer and maybe start a fire. Remember, somebidy sees a dryer receptical and they think its for plugging a dryer into.

Lets say you fuse your dryer receptical for 30 amps with 10 gage wire and your compressor starts seizing. This could cause a fire at the compressor.

There are all kinds of scenarios like this. (Wrong wire/breaker/plug combinations) which could kill somebody. So, use a dryer receptical/wire/breaker for dryer, not a compressor or anything else. The next guy who walks into that room may not know the story behind that receptical and somebody could die as a result.

The right thing to do is run a 20 gage 2 conductor plus ground with a tandem (poles tied together) 15 amp breaker. Get a 15 amp/220 plug/receptical (its written on the box). Join the copper wire to the ground terminal, black wire to one hot and red to the other (or white if there is no red).

If you see the Home Depot guy again, smack him and tell him his advice could have killed somebody.

Sorry for being a little sharp. Electricity done properly is safe to do and safe to use. Done wrong it can and does kill.

If you happen to be in Ontario, you can buy a little book called the 'Ontario Electrical Code Simplified' for, like $12 at Home Depot. Its a great book and put together for the DIYer.

 

[EastTexFrank]

This is interesting because I'm an electrical ignoramus. I have a 110/220 volt, full power recepticle on my generator but no rocker switch to move from one to the other. Are you telling me that whether I get 110 or 220 from the recepticle depends on how I wire up the plug???? If I use a 4-prong plug but a 3-wire cord connected to one hot spade, it'll put out 110 volts or if I connect up all 4-wires it'll put out 220 volts? This has always puzzled me because all my electrical piddling was done in the UK where everything is 220v and we never have this problem.

 

[higgy]

If the box is wired correctly and he hook the compressor with two hots and one ground on the compressor side of the box it should pose no theat to future use of the dryer plug. The only problem is the breaker may be to big for the compressor. I have made a pigtail that has a dryer plug and goes to 20 amp plug for mine. I use it when ever I am asked to work on sombodies house as most places do not have 20 amp 220 and I like my air tools. I have done this for years with no problem. Make sure that the ground is wired to the proper post on the plug.


Dane

 

[Junkman]

</font><font color="blue" class="small">( ..........
The right thing to do is run a 20 gage 2 conductor plus ground with a tandem (poles tied together) 15 amp breaker. Get a 15 amp/220 plug/receptical (its written on the box). Join the copper wire to the ground terminal, black wire to one hot and red to the other (or white if there is no red). )</font>

Did you mean to write 12 gauge and write 20 gauge by mistake /forums/images/graemlins/confused.gif?

 

[CTyler]

</font><font color="blue" class="small">( you telling me that whether I get 110 or 220 from the recepticle depends on how I wire up the plug???? )</font>

On the 220v dryer plug yes. On a standard two prong 110v outlet no. See my first post.




fyi...
Minimum sizes:
14 ga - 15 amps
12 ga - 20 amps
10 ga - 30 amps

 

[boustany]

Yes. 220 volts across both 'hots', 120 each across a hot and neutral.

As for the safety of using a dryer receptical, here is the acid test. Ask an electrical inspector or your utility if wiring a compressor into an dryer receptical/or non-standard wiring of a dryer receptical or hanging a dryer plug on a compressor meets code.

Then ask your insurance company if you are covered against doing your own wiring if you do commit a code violation.

I know some people make arc welder adaptors so they can temporarily power a buzz box (most houses don't have a 50 amp welder receptical handy). Thats a temporary solution, but ya takes yor chances.

I guess the question is, why do it wrong, when doing it right is safer, cheaper, and easier?

Better safe than sorry.

And, JUNKMAN, yes, I meant 12 gage. In fact I coulda sworn I corrected before I posted (but then again I RETYPED 20 gage again in this paragraph, so I must have my mind in the gutter again). Oooopps