# 4 prong 220v recep. to a 3 prong



## 300zx (May 24, 2009)

mopowers said:


> I have a 4 prong 220v outlet in my garage and would like to convert it to a 3 prong outlet for my welder and compressor.
> 
> Do I just put a wire nut on the neutral and tuck it back in the box? Then install the new 3 prong outlet using the two hots and ground?
> 
> Thanks.


Yes you can do that


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## mpoulton (Jul 23, 2009)

300zx said:


> Yes you can do that


Not necessarily. What, exactly, does the poster mean by "three prong" versus "four prong"? The original "four prong" installation contains two hots, a neutral, and a ground. Now, what does the new equipment require? If it is two hots and a ground, then he can do as you suggest. However, if it is two hots and a combined neutral/ground (an old-fashioned range or dryer connection) then your suggestion is not compliant - it would use the grounding conductor to carry current. He would need to keep the existing receptacle and swap cords on the equipment.

In any event, I would suggest changing plugs/cords instead of the receptacle. A four-wire receptacle is more useful and versatile than three-wire, and you can install a matching plug on any piece of equipment.


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## 300zx (May 24, 2009)

mpoulton said:


> Not necessarily. What, exactly, does the poster mean by "three prong" versus "four prong"? The original "four prong" installation contains two hots, a neutral, and a ground. Now, what does the new equipment require? If it is two hots and a ground, then he can do as you suggest. However, if it is two hots and a combined neutral/ground (an old-fashioned range or dryer connection) then your suggestion is not compliant - it would use the grounding conductor to carry current. He would need to keep the existing receptacle and swap cords on the equipment.
> 
> In any event, I would suggest changing plugs/cords instead of the receptacle. A four-wire receptacle is more useful and versatile than three-wire, and you can install a matching plug on any piece of equipment.


 A 3 wire comp 220 needs 2 hots and a ground same as welder.Swaping out cords where are you going to putNeutral Wire on the device? I dont know do whatever you want to do.:laughing:


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## Stubbie (Jan 7, 2007)

mpoulton said:


> Not necessarily. What, exactly, does the poster mean by "three prong" versus "four prong"? The original "four prong" installation contains two hots, a neutral, and a ground. Now, what does the new equipment require? If it is two hots and a ground, then he can do as you suggest. However, if it is two hots and a combined neutral/ground (an old-fashioned range or dryer connection) then your suggestion is not compliant - it would use the grounding conductor to carry current. He would need to keep the existing receptacle and swap cords on the equipment.
> 
> In any event, I would suggest changing plugs/cords instead of the receptacle. A four-wire receptacle is more useful and versatile than three-wire, and you can install a matching plug on any piece of equipment.


Maybe I missing your point.. the poster said what he is wanting to connect a 240 volt welder and a 240 volt compressor. why would you want to change the factory cords that are 3 wire to 4 wire cords.....

Simply cap the neutral and wire up the new receptacles that match the factory cords.

Only thing we should be concerned about after that is the correct ocpd and wire size in the branch circuit if he intends to change from one tool to the other. Connecting both to the same branch circuit may not work out but it might be fine just depends.


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## mopowers (Jul 20, 2009)

Stubbie said:


> Maybe I missing your point.. the poster said what he is wanting to connect a 240 volt welder and a 240 volt compressor. why would you want to change the factor cords that are 3 wire to 4 wire cords.....
> 
> Simply cap the neutral and wire up the new receptacles that match the factory cords.
> 
> Only thing we should be concerned about after that is the correct ocpd and wire size in the branch circuit if he intends to change from one tool to the other. Connecting both to the same branch circuit may not work out but it might be fine just depends.


I'm not sure if I understand all that 'ocpd talk.'

Maybe I should clarify my question a little.

When my house was built, I had them run a 220 circuit into my garage so I could use my welder and compressor (off the same outlet, but at different times). Instead of putting a 3 prong outlet, the electrician put a 50 amp circuit with a 4 prong outlet. He also used what looks like very large aluminum wire. I’m not sure what gauge. I think he must’ve thought I was going to have another oven/stove or something in my garage.

I just want to replace the 4 prong outlet with a 3 prong one so I can run my tools as I intended. In order to do so, I believe I can just cap the neutral and wire up the two hots and ground in the new 3-prong receptacle. Is this correct? Does it matter what side the two hots are in on the new receptacle??


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## 300zx (May 24, 2009)

Does it matter what side the two hots are in on the new receptacle?? No dosn't matter. very large aluminum wire sure its not coper wire Alum will be hard to conect also use some Nolox or similar and it wont corrode


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## mopowers (Jul 20, 2009)

300zx said:


> Does it matter what side the two hots are in on the new receptacle?? No dosn't matter. very large aluminum wire sure its not coper wire Alum will be hard to conect also use some Nolox or similar and it wont corrode


I'll take a picture tonight...

Thanks for your help!


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## Stubbie (Jan 7, 2007)

You have got the right solution...:thumbsup: No it doesn't matter which brass screw the hots connect to on the receptacle.

Sorry about the OCPD slang that's just an over-current protection device or circuit breaker.

As for using both from the same receptacle at different times you would need to give us the electrical specifications of the tools and what plug is on them. It appears the electrician ran a 50 amp circuit to that original 4 wire receptacle. So probably a 50 amp double pole breaker and #4 al cable maybe 6. 

The wire size is is fine but may be too large for the new receptacle to accept just have to see and make pigtails if necessary.

The tools are both 240 volt and cord and plug from the factory?? If so and both have the same plug on them then they can be ran from the same branch circuit at different times....that's probably obvious.....


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## wildblue09 (May 3, 2012)

*220V 3 vs 4 wires*

I have a similar situation needing clarification.

I have a single phase China built Two Value Capacitor Asynchronous Motor Type YL90- 2 driving a small hammer mill. 
I have a dryer 4 prong plug in my shop and want to connect a dryer cord to my hammer mill motor with a three wire cable. I have purchased a dryer plug and cable that fits the 220V receptacle and now I need to know which wires do I use to splice the four wire to the three wire?
Now moving down the cable to the motor connection there seems to be two options. Which option do I use? see attached diag.
Greatly appreciate your assistance.
Martin


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## Jim Port (Sep 21, 2007)

The connection diagram show the option to change from clockwise to counter-clockwise rotation.

Is your mill a straight 240 volt unit?


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## wildblue09 (May 3, 2012)

*220V 3 vs 4 wires*

Thank you for your prompt response.

Witch way is which looking at the motor? Do you determine cw or ccw looking at the shaft end of the motor?

I have single phase 2.2 kw 220V 50 hz 13A 2800 rpm 

See: http://www.mfrbee.com/product/1250084/YL_Asynchronous_Motor.html

Also the dryer plug cable has four conductors.... coloured Red Black White and Copper ground wire.

The hammer mill cable has three conductors ... coloured Green Black and White... 

I assume the black goes to black, white goes to white and green goes to copper... Whats up with red?

Thx

Martin


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## wildblue09 (May 3, 2012)

*hammermill termination block*

it looks like the jumper tabs are configured to run ccw. Now which coloured wire goes where?

Thx

martin


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