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Confused about cord plug on my "new" compressor...

mm08822

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No kidding, that why I reminded him that if he swaps the receptacle to a 20A the CB needs to be changed....
No I wasn't! I'm of the opinion, leave it alone as is (after rotating the existing recept.) It will be fine as I'm sure the motor has internal o/l protection.

My compressor has has been plugged into 30A welding recept for 40 years. Same situation....it's fine.
 
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mm08822

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Not to totally derail the post but why does the breaker need to be changed? We all have 20amp circuits in our house with 15amp outlets on them with stuff plugged in that pulls less than 15amps. How is that different than a 30amp circuit with a 20amp outlet and a device that pulls less than 20amps? Just trying to understand how this situation is different than the other? (I am not an electrician, nor do I stay at the holiday inn).
The internals of 15a duplex recepts are rated for 20a pass-through. Not the case with other amp sized rated recepts. The duplex 15s are where neither single receptacle on the duplex could pull 20a alone. Larger recepts are singles.
 

PCustoms

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No I wasn't! I'm of the opinion, leave it alone as is (after rotating the existing recept.) It will be fine as I'm sure the motor has internal o/l protection.

My compressor has has been plugged into 30A welding recept for 40 years. Same situation....it's fine.

If he leaves a 30A outlet, leave the breaker as 30A.

If he swaps to a 20A outlet, he should put a 20A breaker.

That's all.
 
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sparky 1971

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My compressor has has been plugged into 30A welding recept for 40 years. Same situation....it's fine.
Oh yeah? Mine is on a 30 amp breaker, I think it has #10 wire from the panel to a 30 amp DP switch, but from there to the compressor is a 6' piece of 16/3 SJ cord. I didn't have any 12/3 and 10/3 wouldn't fit in the pressure switch hole. It's a "temporary" solution.
 

mm08822

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Oh yeah? Mine is on a 30 amp breaker, I think it has #10 wire from the panel to a 30 amp DP switch, but from there to the compressor is a 6' piece of 16/3 SJ cord. I didn't have any 12/3 and 10/3 wouldn't fit in the pressure switch hole. It's a "temporary" solution.
Only you can shame yourself for how long" temporary" is. Until it becomes an "OOPs/Oh ****" , you're ok.
 
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lyonkster

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Thanks for all the comments, it's a done deal and the compressor is in full operation. I decided to just rotate the outlet and use the 14-30 to 6-20 adapter cable. That preserves the 30A circuit in case I need it in the future, and was the easiest thing to do:

20251013_082203.jpg

To answer some other points (I'm sure the electrical pros did it better):

- It is in fact a 20A 240V compressor plug (NEMA 6-20); the 20A 120V (NEMA 5-20) is a mirror image:

1760373998405.png

- Code has a provision that allows a 15A receptacle on a 20A circuit, but not for higher amperage circuits;

- The circuit breaker is intended to protect the "built in" elements from overload, i.e. the wiring and the receptacles. It does not protect whatever I plug into the receptacle; that's the job of the device itself, in this case the motor's overload device. It's no different than if I plug a delicate 1A device into a 15A receptacle - the device will burn up way before the circuit breaker trips if there is no internal protection in the device.
 
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lyonkster

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A side note about the "idiot" electrician... In addition to the upside down outlet on the 30A circuit for the compressor, I asked for a 50A circuit in the garage for a welder. It was shown in the electrical plan, and being OCD, I drew its location on the wall and wrote "50A" next to it:

1760377467489.png

They came in and roughed everything in, and I didn't give it a second thought until they came back weeks later when drywall was up to do finish electrical. I noticed that they put in a 40A breaker, and said that I wanted a 50A circuit. Well, the tech (different from the original tech) said that the previous tech roughed in 8 AWG wire, not 6 AWG. So much for the 50A circuit. That's what I get for not doing things myself (or checking others' work closely).
 

dave*99

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A side note about the "idiot" electrician... In addition to the upside outlet on the 30A circuit for the compressor, I asked for a 50A circuit in the garage for a welder. It was shown in the electrical plan, and being OCD, I drew its location on the wall and wrote "50A" next to it:

1760377467489.png

They came in and roughed everything in, and I didn't give it a second thought until they came back weeks later when drywall was up to do finish electrical. I noticed that they put in a 40A breaker, and said that I wanted a 50A circuit. Well, the tech (different from the original tech) said that the previous tech roughed in 8 AWG wire, not 6 AWG. So much for the 50A circuit. That's what I get for not doing things myself (or checking others' work closely).
If it's for a welder, you are likely OK. What welder do you have?
 

PCustoms

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Welder circuits are rated differently, without checking the table that should be fine on a 50A as long as it's marked "welder only"
 

PCustoms

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mike93lx

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It's the PrimeWeld MIG180, which can run even on 120V, so I'm sure it's fine. But it's the principle of it that pisses me off :(.
To be fair, wiring a welder receptacle with wire rated for 50a is a waste of money. He should have asked for clarification, but you'll be fine. Besides that the wire is sufficient for a 50a welder circuit, I bet your welder will never pop a 40a breaker.
 

wyliesdiesels

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A side note about the "idiot" electrician... In addition to the upside down outlet on the 30A circuit for the compressor, I asked for a 50A circuit in the garage for a welder. It was shown in the electrical plan, and being OCD, I drew its location on the wall and wrote "50A" next to it:

1760377467489.png

They came in and roughed everything in, and I didn't give it a second thought until they came back weeks later when drywall was up to do finish electrical. I noticed that they put in a 40A breaker, and said that I wanted a 50A circuit. Well, the tech (different from the original tech) said that the previous tech roughed in 8 AWG wire, not 6 AWG. So much for the 50A circuit. That's what I get for not doing things myself (or checking others' work closely).
if they quoted you for a 50a circuit, either they need to refund you or make it right... i wouldnt let them walk away from that screw up
 
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lyonkster

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To be fair, wiring a welder receptacle with wire rated for 50a is a waste of money. He should have asked for clarification, but you'll be fine. Besides that the wire is sufficient for a 50a welder circuit, I bet your welder will never pop a 40a breaker.

Good to know, and you're right, I'll probably never need the 50A circuit for this welder. Like I said, it's the principle if it that annoys me - it's shown as 50A on the plan, it says 50A on the wall, and I'm pretty sure I verbally mentioned it when he was here.
 
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lyonkster

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if they quoted you for a 50a circuit, either they need to refund you or make it right... i wouldnt let them walk away from that screw up

I got them to credit me the difference in cost between 40A and 50A, which was minimal. They charged $700 for the "50A" circuit (about 25 ft from the subpanel), which I thought a bit high, but it stinks to pay that much and end up with a 40A.
 

mm08822

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I got them to credit me the difference in cost between 40A and 50A, which was minimal. They charged $700 for the "50A" circuit (about 25 ft from the subpanel), which I thought a bit high, but it stinks to pay that much and end up with a 40A.
They should have comp'd more b/c they didn't follow plan.

What if you said rip it out and I expect an expert drywall repair and painting so it likes it never happened? They would have really been in the hole.
 

kbuhagiar

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if they quoted you for a 50a circuit, either they need to refund you or make it right... i wouldnt let them walk away from that screw up
^^^This right here.

Gald to hear you were refunded the difference, no matter how small.
It's the principle, and your way of acknowledging his screwup (fraud?).
 

no704

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I’d go ahead and delete this. Save myself reading the 12 rebuttals coming in. 3,2,1…
Ya, I don’t know my plug configurations as well as some. When I need something specific I will look it it up. Although incorrectly I suggested it was a 120v20a that was pretty close. Obviously would not work. But geese!
 

dave*99

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Ya, I don’t know my plug configurations as well as some. When I need something specific I will look it it up. Although incorrectly I suggested it was a 120v20a that was pretty close. Obviously would not work. But geese!
This is GJ. Close only counts in horseshoes and hand grenades.
 
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