Compressor to welder outlet?

[rartuin270]

I recently purchased my first home and want to hook up my compressor. The motor on it is 2hp and 230v. There is a welder hookup in the garage and I would like to run it off of that. The only issue is the plug on my compressor does not match the wall receptacle. Which wires go where? I have searched all over the internet and this forum looking for a solid answer and I keep getting mixed results. I've read that with my compressor being 3 wires I won't need to use one of the 4 prongs but which one?




This is the plug coming out of my compressor. It is 230v 2hp. It has 3 wires, white, green, and black.

This is the 50amp welder receptacle in my new to me garage.

This is the breaker.

This is the plug end I plan on putting on the compressor cord.

 

[pattenp]

Welders don't use 4 prong plugs. The 4 prong plug is a 125/250V plug that is used on things such as ovens and dryers that also need 125V. The center flat prong on the 4 prong plug you pictured is the neutral and is not used by a welder or by your compressor. The "U" shaped prong is the ground (green).

 

[Aceman]

For a 2HP 230v motor, the maximum breaker size you can legally use is 30 amp. Realistically, I'd probably have it on a 20.

 

[BillK]

For a 2HP 230v motor, the maximum breaker size you can legally use is 30 amp. Realistically, I'd probably have it on a 20.

Can you show me how you determined that ?

 

[Dugan]

If your not going to use the type of socket on the wall, change the breaker to a 30 and change the outlet cover to match the items you have.

 

[pepi]

For a 2HP 230v motor, the maximum breaker size you can legally use is 30 amp. Realistically, I'd probably have it on a 20.

REALY ?

That's bad and useless advice .......

 

[Norcal]

REALY ?

That's bad and useless advice .......

Have any proof it's bad advice?

 

[pattenp]

There is a good reason why the manufacturer put a 250V 20A plug on the compressor....... so you can't plug it into a 250V 50A outlet.

REALY ?

That's bad and useless advice .......

 

[ez-duzit]

Add a 20-amp outlet and separate breaker for the compressor.

 

[wyliesdiesels]

For a 2HP 230v motor, the maximum breaker size you can legally use is 30 amp. Realistically, I'd probably have it on a 20.

Exactly.A 2HP motor has an FLC of 12a. By code the breaker can be at a max of 250% of FLC. U should change the breaker to 30a max and put in the correct outlet.

Can you show me how you determined that ?

Based on NEC FLC tables. I posted the specifics above.

REALY ?

That's bad and useless advice .......

How do u figure? His comment is spot on code!! Do u have a code book handy??

 

[rartuin270]

So basically I have to replace the breaker no matter what?

 

[Radix2]

Exactly.A 2HP motor has an FLC of 12a. By code the breaker can be at a max of 250% of FLC. U should change the breaker to 30a max and put in the correct outlet.

30A breakers usually have a max wire size of 8ga - 50A circuits usually have 6ga copper or 4ga alu - so just slotting in a 30A breaker may not be possible.

 

[The mean fish]

So basically I have to replace the breaker no matter what?

Do you ever plan on using the welding outlet for a welding machine?

 

[ez-duzit]

So basically I have to replace the breaker no matter what?

No! You must ADD a breaker.

 

[j p smith]

Lot of good advise here on the correct breaker and receptacle. I think I would locate the compressor where it works best for you, install the correct outlet & breaker. Then run the appropiate size wire from your new breaker to the new outlet. Not sure but I think the recptacle in your picture is for 50 amps which uses 2 circut wires, 1 common & 1 ground wire. It is always in your best interest to match wire size, recetacles and plugs with whats recommended by manufactures. You can pick up a copy a code book and check the codes to be sure. Dewalt has a book with good info.

 

[Norcal]

Well I see Pepi has not returned to defend his comment.

 

[Radix2]

Exactly.A 2HP motor has an FLC of 12a. By code the breaker can be at a max of 250% of FLC. U should change the breaker to 30a max and put in the correct outlet.

Based on NEC FLC tables. I posted the specifics above.



How do u figure? His comment is spot on code!! Do u have a code book handy??

Is there more to this code than what you have referenced ? - for example a 1/2HP 230v motor on a drill press or something has a FLC of 4.9A... which gives a max breaker of 11.5A.... calling for a rather unusual 5 to 10A two pole breaker... the fractional hp fans and stuff wouldn't be allowed on a 15A circuit even at 110Vac if there is not some lower limit to this rule.

 

[wyliesdiesels]

Is there more to this code than what you have referenced ? - for example a 1/2HP 230v motor on a drill press or something has a FLC of 4.9A... which gives a max breaker of 11.5A.... calling for a rather unusual 5 to 10A two pole breaker... the fractional hp fans and stuff wouldn't be allowed on a 15A circuit even at 110Vac if there is not some lower limit to this rule.

Yes code allows u to go to the next standard size breaker.

 

[sberry]

I would say this is a poster case for adding a new circuit for the compressor. Space for it is super convenient and it doesn't get any better. The other one isn't a welder circuit either. Take the 4 wire off put on a 6-50 like it should be.

 

[sberry]

Yes code allows u to go to the next standard size breaker.

Yes and wire size has something to do with it as well as its own internal overcurrent protection and design. Even the cord it may come with in pre built machines limits the circuit it may be plugged to.

I can see from forum discussion many don't realize the amount of 12 wire in the world that had 50A overcurrent protection,,,, the amount of 14 that is on a 30 and 16 on a 20. Most of it isn't in structures or accessable for general use but designed as calculated load.

 

[Syberia]

To hook up the compressor to your 50A plug:

Green to the bottom u-shaped prong
The two other wires (I believe they're black and white in your photo, but the color is washed out by the flash) go to the two outside prongs.
The top center prong is neutral and is not used.

The screws on the plug will be color coded. Green wire to green screw, the other two to brass screws, silver screw will not be used.

It will not be "to code," but it will work. Don't worry about it. You're not going to get a permit/inspection for plugging a device into an existing outlet, so I fail to see the big issue.

 

[wyliesdiesels]

To hook up the compressor to your 50A plug:

Green to the bottom u-shaped prong
The two other wires (I believe they're black and white in your photo, but the color is washed out by the flash) go to the two outside prongs.
The top center prong is neutral and is not used.

The screws on the plug will be color coded. Green wire to green screw, the other two to brass screws, silver screw will not be used.

It will not be "to code," but it will work. Don't worry about it. You're not going to get a permit/inspection for plugging a device into an existing outlet, so I fail to see the big issue.

The big deal is fire protection, insurance companies and lawyers. A 50a breaker is the wrong size for that motor!

 

[Syberia]

I have a fan (motor) that draws less than 2A connected via 18/2 to a 20-amp circuit. Why is this allowed when the compressor example is not?

And if you say that one device is regulated by UL and the other by the NEC, that makes zero practical difference in terms of "safety."

 

[sberry]

Both places may apply,,, I believe the fan may be 16? The motor may be protected by other means.

 

[wyliesdiesels]

I have a fan (motor) that draws less than 2A connected via 18/2 to a 20-amp circuit. Why is this allowed when the compressor example is not?

And if you say that one device is regulated by UL and the other by the NEC, that makes zero practical difference in terms of "safety."

U have to realize that beakers in a motor circuit dont protect the motor or the wire from overcurrents. That is the job of the overload which for small motors is usually located on the motor...The breaker is only there to protect against shorts and ground faults.

 

[Syberia]

You seem to be supporting my position that being on a 50 amp circuit shouldn't matter, then. If the wire is sized appropriately for the 50 amp breaker then I don't see what the issue is, if the motor has its own protection.

 

[sberry]

There is a limit to it though and in some cases other parts of a machine may need limited breaker.

 

[madosta]

Ugh... you guys missed the mark... Don't tell his wife, but what he really needs to do is just buy a bigger air compressor with a bigger motor!!! Bahaha!!! more tools!!!

 

[Champanada]

There has been a lot of good (and not so good) advice given on this subject. But the BEST thing to do is actually run a separate circuit with a #10/2 with ground and install a 30 amp breaker in the service panel, and buy a receptacle that matches the plug that came with the compressor. Doing things RIGHT can (and sometimes WILL) save you some serious heartaches in the long run. As for the person that said that welders don't use 4 wires, I will have to agree and disagree; depending on the TYPE of welder, it could use either or; the only difference being is whether the particular welder utilizes 120v circuitry, in that case you would need a neutral, witch would be the 4th wire, to carry the unbalanced load.

 

[sberry]

But they don't use 120.

 

[pattenp]

If the plug pictured in the OP is original, it's a 6-20P. You are not to put a 6-20 receptacle on a 30 amp circuit.

There has been a lot of good (and not so good) advice given on this subject. But the BEST thing to do is actually run a separate circuit with a #10/2 with ground and install a 30 amp breaker in the service panel, and buy a receptacle that matches the plug that came with the compressor. Doing things RIGHT can (and sometimes WILL) save you some serious heartaches in the long run. As for the person that said that welders don't use 4 wires, I will have to agree and disagree; depending on the TYPE of welder, it could use either or; the only difference being is whether the particular welder utilizes 120v circuitry, in that case you would need a neutral, witch would be the 4th wire, to carry the unbalanced load.