Air Compressor Electrical Outlet Questions

[biscuit141]

First off, I have a compressor that can be hooked up either 110 or 220. I have a 220 hook up in my garage where an old compressor used to be so I want to use 220 since it is less strain on the wire and maybe the motor? Plus it seems very simple to switch the wires in the motor fro 220v. Anyway, the outlet that is on the end of the line in the garage is what looks like a dryer plug or the like. It is a big *** 3 prong plug. My 220v line is on a 30 amp breaker and wire through a 10-2 w/ ground line, so I am assuming black and white would be hot and ground is ground.

My questions are these:
1) Can I use the standard power cord that came with the compressor when using 220v if I find a standard type of outlet that can support 30 amps? I figure if I can still use the same cord then I can easily switch it back to 110v if I ever need to. Or is there a special 220v cord I need to use?

Edit:I looked on the supplied power cord and it is 14-2 w/ ground

2) When looking around I have seen 220v, 230v and 240v used to describe this type of wiring configuration. Do these mean the same thing, much like people who use 110 and 120 volt to describe standard household power?

 

[Salem747]

Have a look at the outlet. From what you are describing it is a NEMA 50R. Like an oversized 3 prong outlet right? It should say on it somewhere.

If so, each of the slots will be connected to a hot on the breaker and then you will have the hole as a ground. Confirm this in your box to make sure everything is kosher. The white wire should be for Neutral. Whoever wired it should have used the red or blue and the black as hot wires and capped the white. In some cable the neutral can be a smaller gauge, not commonly in household cable, but it can happen.

Seems a little fishy that you can just plug your motor into 220V. Do you have the manual? Be extra careful in doing this, there must be something you have to do to the motor to make this work without frying things.

Your question about 220V vs 230V vs 240V is, like you mentioned, a localized thing. Depending on the power supplied to your house by your utility. The outlet I mentioned is rated for 250V for that reason, along with everything else: breakers, cable etc.

 

[rodnok1]

You need to reference the users manual, don't just plug the 110 cord into the 220 outlet unless you like buying new parts and seeing things spark. Usually a new cord is required as mentioned. Don't assume that plug is 220 volt without checking breaker box and testing the voltage.

 

[biscuit141]

If so, each of the slots will be connected to a hot on the breaker and then you will have the hole as a ground. Confirm this in your box to make sure everything is kosher. The white wire should be for Neutral. Whoever wired it should have used the red or blue and the black as hot wires and capped the white. In some cable the neutral can be a smaller gauge, not commonly in household cable, but it can happen.

Seems a little fishy that you can just plug your motor into 220V. Do you have the manual? Be extra careful in doing this, there must be something you have to do to the motor to make this work without frying things.

the breaker in the box is a double throw (?) breaker rated for 30 amps. The wire between the breaker and the outlet is 10-2 w/ ground, not 10-3, so white and black are used as hot wires and ground is ground, this should be ok right?

There are some wires in the motor that need to be switched in order for it to work on 220v. My question was/is if the supplied 14-3 power cord can be used as the power cord when using 220v, if I can find a standard socket outlet that supports 30 amps? Or do I need a new cord to support 220v, and what gauge and plug type should it be?

 

[Salem747]

OK. 14 gauge wire is only good for 15A. So you should be changing out your cord to 10ga. You might want to use 10-2 BX for your power cord, it is more expensive but since you only need a metre or so it won't matter too much. BX is armoured with aluminum so it won't be crushed as easily.

How many amps is it supposed to draw on 220V? The manual should tell you how many amps it will draw on 220V. But I guess if it was running on 110V with a 14-3 power cord it should be Ok for the current draw on 220V as long as the cable is rated for 250V.

 

[Brandon_K]

The amount of misinformation in this thread is astounding.

Your said your outlet is a 3 prong which means it's almost certainly a 6-30. It *could* be a 10-30, but I'm guessing not unless there was ever a dryer in that spot. You need to find this out for sure. Are the 2 hot blades horizontal with a round or "U" ground, or are they slanted with a "L" shaped ground? IE;

-- --
0

or

/ \
L

You're outlet needs to be a 6-30, this is wired as hot, hot, ground. There is NO neutral in this configuration as almost no 240v devices require a return. In a case where the neutral is required, it will never be a smaller gauge than the hot leg(s). The EGC (ground, bare copper) will be smaller, however.

It's not fishy, dual voltage motors are common in the 2-4HP range on good quality equipment, just don't expect to see them on something from Harbor Freight. It does require doing some internal modifications to the motor however, nothing major and the wiring diagram is almost always on the can.

If it were me, I would still double check in your panel, follow the wire and see where it goes to. The black and white (the white *should* have been taped red, but usually never is) should both go to the 2p breaker. The ground should go to the ground bus with the rest of the bare copper wires. If this is the case, great!

I'm surprised your cordset is only 14/3, that's pretty lightweight for compressor that apparently has come wired for 120v (I'm assuming it has a 120v 15A plug on it now?) Regardless, that question can't be answered until we know how many horsepower the motor is. There will be a nameplate on the motor that will show voltage, HP, current, RPM's, etc. Please post the voltage, HP and current (A) specs from the nameplate.

As far as the 2x0 thing, it's just how you were taught growing up. You're "240v" motor will operate just as well on 220v or 232v or 241v or anything in between. What you DO need to watch out for are straight 208v motors. Those are designed to be run off of 3 phase (typically Delta-Wye transformers) and will smoke on 240v. Some can be rewired for 208, 240, 480, etc, some cannot. It's very very rare to ever see 208v in a residential, however.

Hope this helps.

 

[biscuit141]

OK, i figured out the plug situation. I have a 20A 250V plug that I will use, it looks like this:
I -
o
if that makes sense. I will have the male version for the cord end, and use 14-3 wire for the cord, since it will only draw 7 or 8 amps at 220v. The wire to the outlet is 10/2 w/ ground and is wire as black and white are hot and ground is ground. This is hooked up to a 30A double pole breaker in the box.

My question is, do I need this to be on a 20A breaker? I know that outlets in a home are usually 15A, the most common, but are often on a 20 amp breaker, since most often 15 amps is never plugged in to a single outlet.

 

[Charles (in GA)]

Here is a NEMA pliug and receptacle chart for 20 amp. A NEMA 6-20 is a 250V 20A.

The breaker is protecting the circuit in the wall and the receptacle, not the plug and cord device. You could leave the breaker, but if this is all you plan on using this for, you might considering changing to a 20A breaker. If the compressor ran on this cord OK on 120V then it will work fine on the same cord on 240V after you change the plug and swap the jumpers in the motor as shown on the motor data plate.

Charles

The 2-20 is an obsolete 250V plug. The 5-20 is 125V and the 6-20 is 250V and the 7-20 is 277V and just ignore the last five plug and receptacle types.

This web page does a better job of showing the 125V and 250V plugs and receptacles in 15 and 20 amp, as they use pictures.

http://www.elect-spec.com/nema_plgsokt.htm

 

[biscuit141]

I just got back from Lowes and spent $20 on an additional six feet of 12/3 cord (it was thinner insulation than the thick 14/3 which was hard to work with, heavier gauge cant be bad right?) a 6-20 plug (already had a receptacle) and a 20 amp 2 pole breaker. I'm wondering if there is any benefit to running it on 220v, because this is costing me $20 and I already have everything I need for 110v.

 

[sberry]

I would rather run it on 240, just less drop on the line when starting, if the cord works for 120 its plenty sufficient at 240, no need to change it.