air compressor

[Jr. Roby]

does anyone know how to wire an air compressor to 220?

 

[RayP(MI)]

Motor should have a diagram inside the cover plate... Needs a dual side pressure switch to switch on and off both sides of the 220v. Did that conversion on mine, years ago. Came factory wired for 110v, and was always a problem, blowing fuses, damaging pressure switch contacts. When wired for 220, no more problems. 2hp motor.

 

[Jr. Roby]

it came wired 110. if i use a double 30 and go to the switch will it work?

 

[Maxx]

First you have to change the wiring in the motor to 220.
The pressure switch has to have 4 contacts - 2 for motor, 2 for the line.

You legally need 4 wires from the breaker box. 2 are hot, 1 neutral and 1 ground.

The breaker value is lower when running 220.

Look at the info plate on the motor for the specs

What is the HP rating of the motor?

 

[Jr. Roby]

it is 3.7 running hp

 

[Jr. Roby]

do i need to ron 2 more wires from motor to switch? there are 2 there now

 

[Bob Huntress]

Roby, Maxx is striaght on. The only thing I would add is to verify that your motor was intended for either 110 or 220. Not all motors are able to be operated on either. Other than that, what Maxx said.

 

[Maxx]

Does the plate on the motor have ampere ratings for both 110 and 220?
If not it is just a 110 motor.

If it will run 220 a 20A double breaker will be fine.
You can get away with 12 gauge wire but I would recommend at least 10 gauge.

Edit: I forgot to add NEVER put a breaker in that is rated higher than the ampere rating of the wire.

14 gauge is good for 15A
12 gauge is good for 20A
10 gauge is good for 30A

 

[Earl Gray]

It doesn't sound to me like you should be attempting this, get someone that understands 110/220 to help you.

 

[Anonymous-0]

4 for 220???

 

[Jr. Roby]

a new compressor. it is a 240 volt. came from factory wired as 110. needs to b changed 2 220

 

[Maxx]

(quoted from post at 09:27:34 11/30/11) 4 for 220???

Yes,
By code you need 4 wires for service wiring.
Your 2 hots
a neutral
and a ground.

 

[Maxx]

Roby,

I'd suggest you look at the owners manual for info on wiring the motor for 220.
Or if you have a knowledgeable friend invite him or her over to give you a hand.

 

[Dusty MI]

Because of the way motors are being over rated in horse power I don't trust hp rating, you need to go by the amp rating at 220 volt. There no way to know what size wire is needed without know it's full load amps. Plus you need to know how far the compressor is from the panel.

I truly doubt you need a neutral wire. Just 2 hots and a ground.

Dusty

 

[fixerupper]

Like Dusty said, look at the amps, not the HP. I was duped that way on a Crapsman taable saw and I learned a lesson the hard way. Saw was advertised as 3HP but it really was 1.5HP and was underpowered. 3HP was some theoretical figure, not actual pulling power.When I finally looked at the plate on the motor a few years later I found out it listed the amperage of a 1.5 HP but I wasn't smart enough to look at it. It was wired at 110 and I used it that way for quite awhile so it could be portable but when I finally put it in a permanent place I changed it to 220. On this particular saw it was an easy job and it did give the little 1.5HP a small amount of more snap. Jim

 

[Maxx]

(quoted from post at 14:18:42 11/30/11) Because of the way motors are being over rated in horse power I don't trust hp rating, you need to go by the amp rating at 220 volt. There no way to know what size wire is needed without know it's full load amps. Plus you need to know how far the compressor is from the panel.

[color=red:3f212af076]I truly doubt you need a neutral wire. Just 2 hots and a ground.[/color:3f212af076]

Dusty

Dusty,
This is true, but if you noticed what I said it needs 4 to be legal by code.
I'm not going to tell someone to do it with 3 wires.
I also think he needs to get physical help as it seems he has no idea about doing this.


Maxx

 

[guido]

Hello Jr. Roby,
First of all, the voltages are 120V and 240V.
When you calculate amps you need to use these figures, not 110V nor 220V.
You asked if a 30 amp breaker would work for the 3.7 amp draw...........NO.
Here is an example. Say you have a motor that draws 10 amps, the breaker for that circuit would be 15 amps, or 50% above max draw.
So you see A 30 amp breaker on a 3.7 amp draw would be way too much.
Guido.

 

[buickanddeere]

no offence but you are in way over your head.Hiring a pro is cheaper than injury,death,fire or ruined compressor.

 

[Stephen Newell]

There should be a label on the motor giving instructions if and how it can be wired from 110v to 220v.

 

[rad]

Yes. They are L1, L2, neutral and ground.

220V is measured from L1 to L2.

L1 to Neutral is 110V as is L2 to Neutral.

 

[Dusty MI]

(quoted from post at 11:55:44 11/30/11)

(quoted from post at 14:18:42 11/30/11) Because of the way motors are being over rated in horse power I don't trust hp rating, you need to go by the amp rating at 220 volt. There no way to know what size wire is needed without know it's full load amps. Plus you need to know how far the compressor is from the panel.

[color=red:43f5c3eb75]I truly doubt you need a neutral wire. Just 2 hots and a ground.[/color:43f5c3eb75]

Dusty

Dusty,
This is true, but if you noticed what I said it needs 4 to be legal by code.
I'm not going to tell someone to do it with 3 wires.
I also think he needs to get physical help as it seems he has no idea about doing this.


Maxx

Maxx, I'm rusty on code, please refresh me. I've never known the code to require a neutral where it was not used.

In case of a duel voltage it always was if 120 volts 1 hot, and neutral and ground. if 240 volts 2 hots, and ground. Unless you are using 120 volt for control or maybe a 120 volt light.

Dusty

 

[Bus Driver]

Maxx, for motor loads, conductor sizes and overcurrent protection are determined by NEC Article 430. Very different from general purpose circuits. I can devise a theoretical scenario for a motor that would use #12 wire and 60 amp breaker and be fully compliant with the NEC. For the compressor, follow the manufacturers instructions. If those are not available, follow Article 430. It will take some time to digest Article 430.

 

[barnE]

Good to see 110 and 220. Somebody here is as old as me. Get electrician to hold your hand before something happens. Seriously. Dave

 

[barnE]

Good to see 110 and 220. Somebody here is as old as me. Get electrician to hold your hand before something happens. Seriously. Dave

 

[Bus Driver]

The pressure switch needs only one set of contacts, even for 240 volts. But having and using two sets is OK. For 240 volts, a neutral is not needed. A neutral is required for 120/240 volts, which is used by some items such as electric clothes dryers and electric ranges.

 

[Jr. Roby]

so all the wiring is done at the motor. right?

 

[dixon boy RL]

if you still at this get you electrician and be done with it. a guy can mess with alot of things and not really know what he doing but not when it comes to electricity. i wired mine 220 and i have a shutoff switch tied into the pressure switch so i can shut it off when leave shop or on phone etc if i have to. it bleads off also so no start up issues. good luck

 

[Jr. Roby]

gotter done....thanks

 

[buickanddeere]

I hope the money you saved was worth it. I'll bet a 24 of premium brew that the wiring is not up to spec.