Dual 220 plugs

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Old 11-06-16, 09:28 PM
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Dual 220 plugs

I suspect I already know the answer but looking for confirmation/options.

In my garage I have a 220v/40amp line used for my compressor. I recently acquired a dual voltage mig welder that is ratted the same but the plug is different.

That is the issue, different plugs.

I assume I can not tap into the existing plug, run a jumper to a new outlet and install the different plug, even though I would only have one item plugged in at a time.

I probably could make/buy an extension cord that would allow the welder to plug into the compressor outlet?

The ultimate answer I know would be to run a 2nd line.
 
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Old 11-06-16, 10:09 PM
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Nominal voltage is 240v not 220v. Is this an attached garage or a detached garage?

The receptacle use should be based on the line amperage. A 240v 40amp circuit should have a 50 amp NEMA 6-50 since 40 amp receptacles aren't standard. Is this what you have:
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If not what do you have? What is the full load amp rating of the compressor and the FLA of the welder?

My thoughts are the compressor may be on too large a breaker. A compressor large enough to need a 40 amp breaker would be far larger then the usual home air compressor. If this is a detached garage then there should be a subpanel and you need to run a correctly sized line for each piece of equipment.

If this is an attached garage then it may make sense to install a 240 subpanel on the 40 amp feed and install correctly sized breakers for each piece of equipment.
 
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Old 11-07-16, 05:01 AM
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240, typo

My compressor has a Nema 10 plug and the welder is the Nema 6 that you have shown.

Compressor load states 28 amps, the motor shows 21 amps

Welder load states 16 amps and they quote a 30 amp breaker

Attached garage, have two boxes in the basement.
 
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Old 11-07-16, 06:07 AM
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My compressor has a Nema 10 plug
Do you mean a Nema 10-30?
I assume I can not tap into the existing plug, run a jumper to a new outlet and install the different plug,
(Plug is male an outlet can be a receptacle or a light or a switch) Yes, you can have two receptacles. Just install a second receptacle that is correct for the welder. Just don't use both at the same time.
 
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Old 11-07-16, 07:45 AM
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Nema 10-50.

Follow up question:

The wire I ran was 6awg with ground, since the receptacle (got it this time) does not have a ground connection what do I do with that wire?
 
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Old 11-07-16, 08:08 AM
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the receptacle does not have a ground connection what do I do with that wire?
It does have a ground. That is the round hole. You have two hots and a ground. If you ran 2-conductor cable as you should have the white is recolored red (or any color but gray or green) and it and the black goes to the two flat prongs. The bare goes to the round ground.

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Note if you used 3-conductor cable the white is capped off with a wire nut and not used.
 
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Old 11-07-16, 02:02 PM
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If it's a 10-30 or 10-50 on the compressor it's the wrong plug/receptacle anyway. That style is for use only with pre-1996 electric ranges and cloths dryers. You can swap the receptacle on the existing circuit for a 6-50 and replace the plugs on both the compressor and the welder with matching 6-50s. There is no problem running both machines from the same circuit as long as you take care to only use one at a time.

You can extend the circuit to a second location or just use an adequate extension cord on the welder. I'd probably just use a longer cord on the welder and it is less hassle and gives you more flexibility on where you use the welder anyway. If the existing circuit was installed with aluminum wiring it will be more trouble than it's worth to extend it.

Can you post the exact electrical specs from the welder nameplate including rated duty cycle (or link to the information on the mfr website)? Welders can be very flexible in circuit sizing. I don't suspect the 40A breaker will be a problem, but we'd be happy to verify it for you.
 
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Old 11-07-16, 02:15 PM
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Compressor load states 28 amps, the motor shows 21 amps
Another issue is if the compressor motor is more than 3HP, then it should be hardwired because a standard 50A NEMA outlet and plug is not rated to be used as a disconnect for more than 3HP. What HP is listed on the compressor motor data plate?
 
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Old 11-08-16, 05:14 AM
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So the wiring scheme with the 10-50 plug/receptacle dates back to the original installation in 1988 so recommended installations may have changed.

The wiring used was 6agw 4-conductor (2 hots, neutral, and bare ground).

In the box, 2 hots come off the breaker, neutral and ground to their respective terminations, at the receptacle, the ground and neutral are connected together at the center neutral.

The compressor motor is 5hp, I do not recall ever hearing about not being able to use a plug.

As far as the welder goes, here is the link to the manual, section 5.03 top of page 15 is the amp

https://www.millerwelds.com/files/ow...65809B_MIL.pdf

This setup has been in service for 28 years with no issues, I certainly am not apposed to changing something that is blatantly incorrect.

After some thought yesterday I had concluded that just making a 40' extension cord would be easiest, no issues with having more than one item plugged in at a time. Just need to figure out going from the 10-50 to the 6-50.
 
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Old 11-08-16, 07:02 AM
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So the wiring scheme with the 10-50 plug/receptacle dates back to the original installation in 1988 so recommended installations may have changed.
No, it was never correct. It should alaways been a 6-50 as I posted in my first reply. A 10-50 as stated by others is a 120/240 receptacle with no ground. You should have had a 6-50 which is a 240v plug with ground. (The third hole on a 10-250 is neutral not ground.)
In the box, 2 hots come off the breaker, neutral and ground to their respective terminations, at the receptacle, the ground and neutral are connected together at the center neutral.
Which of course is wrong. That configuration is for 120/240 and you need 240.
Just need to figure out going from the 10-50 to the 6-50.
Neither. A NEMA 6-50 receptacle is only rated for 3HP (see chart Horsepower Ratings > L-300 Technical Information > Documents & Resources > Support from Leviton Web Site). Since the compressor is 5Hp it must be hard wired to a disconnect since the breaker isn't in sight.

However a better approach might be to install a 4 space main lug 60 amp (sub) panel. Your existing wiring if #6 should be adequate for that. Then install breakers for the two pieces of equipment. (25 amp for the welder and 50 amp for the compressor. Main panel breaker 50 amp.) As long as the compressor was in sight of the subpanel you wouldn't need a disconnect. You would hard wire the compressor to the sub panel.
 
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Old 11-08-16, 07:32 AM
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Does the compressor have a magnetic starter with or without fuses?
 
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Old 11-08-16, 12:57 PM
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Does the compressor have a magnetic starter with or without fuses?

No
 
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