220v wiring issue

[LandR]

All,

Long time lurking finally posting. I've searched the threads and can't exactly find an answer for my specific problem.

Issue : have a 4 prong 220v receptacle in garage of my new home. Bought a small new welder and compressor to plug into the wall (my big equipment is staying at the workshop).

Both compressor and welder are 3 wire. Compressor is 7.5A and welder is 20A.

I need to run an extension cord from wall to appliance.

Option 1:
Buy 4 wire sjoow cord with 4 prong male that plugs into wall receptacle and a 4prong female for the other end.
Rewire both new appliances for 4 wire.
Issue : don't know how to rewire the new appliances for 4 wire and the compressor only has 3 wires from pressure box to motor

Option 2:
Buy 4 wire sjoow cord with 4 prong male on one end and 3 prong female receptacle on other. Don't connect the white neutral on the 3 prong end. Use existing cords on welder and compressor.
Issue: is this safe?

Appreciate your help. I know very little about 240v and would prefer to not have to compromise the wiring in my garage by changing breakers etc.

Thanks in advance,
Sam

 

[jhelrey]

You could buy a 3 wire outlet and swap them out. One uses neutral, the other does not.

 

[Stuart in MN]

The four prong receptacle has two hots, a neutral and a ground. Your welder and air compressor use two hots and a ground, no neutral. The simplest thing will be to use a four prong plug, two wire w/ground wire, and no connection to the neutral prong.

 

[wyliesdiesels]

240v devices dont need a neutral. I would swap the 4 prong outlet to a 3 prong. What is the HP rating of your compressor and what outlet will u be using? Keep in mind outlets dont have a very high HP rating. For example, a 6-50R is only rated for 3HP...u may want to hard wire your compressor if the HP is too high!

 

[pattenp]

Just do option 2, but use 3 wire sjoow cord and and leave the neutral empty on the 4 prong plug. If the comp only uses 7.5A I wouldn't worry about the HP. I assume the comp and welder came with a cord and plug on them?

 

[LandR]

Thanks all for the responses and for the recommendation to go with option 2.

I am in the midst of building an adapter/extension from 4prong wall to 3prong receptacle.

The welder came with plug, the compressor came with 110v and i am putting a 220v on there and rewiring the motor(per manual).

Should be done in 30 minutes and will post pictures soon

 

[LandR]

Compressor is 2hp max and 1.7hp running.

Purchased from northern tool. It's the Morgan series but got mine for $70 less than list which was already a steal.

 

[zmaxmotorsports]

The four prong receptacle has two hots, a neutral and a ground. Your welder and air compressor use two hots and a ground, no neutral. The simplest thing will be to use a four prong plug, two wire w/ground wire, and no connection to the neutral prong.

That would be a simple way,not the smartest way from a liability stand point (speaking as a retired electrical contractor anyway)
Id just change the outlet in the wall to match the equipment youre plugging into it myself.

 

[pattenp]

Which may also require a breaker change (size reduction) in the main panel.

That would be a simple way,not the smartest way from a liability stand point (speaking as a retired electrical contractor anyway)
Id just change the outlet in the wall to match the equipment youre plugging into it myself.

 

[theoldwizard1]

Just do option 2, but use 3 wire sjoow cord and and leave the neutral empty on the 4 prong plug. If the comp only uses 7.5A I wouldn't worry about the HP. I assume the comp and welder came with a cord and plug on them?

What he said ^^^^ !

 

[Charles (in GA)]

That would be a simple way,not the smartest way from a liability stand point (speaking as a retired electrical contractor anyway)
Id just change the outlet in the wall to match the equipment youre plugging into it myself.

I'm missing something here. Why would not carrying the neutral to a three prong receptacle where it is not needed, create any more liability, than capping off the neutral in the wall and replacing the wall receptacle with a three prong and then making a the same three wire extension cord.

Just don't see the issue with leaving the neutral blade on the 4 prong plug not connected........

Charles

 

[zmaxmotorsports]

Which may also require a breaker change (size reduction) in the main panel.

Going from a 4 wire outlet to a 3 wire outlet of the same rating would have no affect on the size of circuit breaker feeding it,unless you know something Im not seeing here.
If he wants to down size the circuit breaker to match a certain piece of equipment thats totally unrelated to changing the outlet in the wall.

 

[zmaxmotorsports]

I'm missing something here. Why would not carrying the neutral to a three prong receptacle where it is not needed, create any more liability, than capping off the neutral in the wall and replacing the wall receptacle with a three prong and then making a the same three wire extension cord.

Just don't see the issue with leaving the neutral blade on the 4 prong plug not connected........

Charles

Well I suppose that it wouldnt make a differance doing it as a homeowner but if I was doing it as a contractor which I was for many years I would have to think of what would happen if an inspector saw it and wanted to know why I was mismatching equipment.
Or If it was on a machine at a plant someplace and some safety inspector saw it,or one of those fine folks from osha wisconsin saw my guys using it on a job site Id be willing to bet it would cost me lots of money.
Theres too many ambulance chasing lawyers out there looking to sue people,not to mention insurance companies wanting an excuse to deny a claim to take chances over an outlet you can buy for $8.00 at any box store.

 

[zmaxmotorsports]

http://search.yahoo.com/r/_ylt=A0oG...8614213_osha-rules-extension-cord-safety.html
Heres a little of what Im talking about

 

[LandR]

Thanks all. OSHA isn't coming around to my house hopefully. I want it safe and i want to sleep at night. It sounds like capping off the neutral wire or not using that pin is fine to do.

Naturally I get it all wired up and when I go to test - the guy at Home Depot handed me the wrong plug. So things don't match up. Off to fix it in the morning.

 

[pattenp]

I don't know what amp size outlet the OP has and what amp size plugs are on the comp and welder so that's why I said "which may"... The key word is "may". If the existing circuit is 50A with a 50A 4 prong outlet and the devices are corded with 30A 3 prong plugs then he can't put a 30A 3 prong outlet in it's place without reducing the breaker to a 30A breaker.

Edit: Well he can but he shouldn't.....

Going from a 4 wire outlet to a 3 wire outlet of the same rating would have no affect on the size of circuit breaker feeding it,unless you know something Im not seeing here.
If he wants to down size the circuit breaker to match a certain piece of equipment thats totally unrelated to changing the outlet in the wall.

 

[zmaxmotorsports]

Well if the existing outlet and breaker is 50a and the compressor needs a 30a breaker he should change the breaker anyway regardless of what outlet he has right?
But like you said we dont know the existing equipment to make that call.

 

[LandR]

Breaker is a 30 amp.

Wired everything up and tested it out and everything worked perfectly. I was surprised by the plugs that came on the welder nema 6-50p even though its only rated for 20a.

 

[wyliesdiesels]

Well if the existing outlet and breaker is 50a and the compressor needs a 30a breaker he should change the breaker anyway regardless of what outlet he has right?
But like you said we dont know the existing equipment to make that call.

No. Breaker can be rated higher than the equipment. The compressor should have its own overload protection.

BUT the outlet SHOULD be rated the same as the breaker or higher.