Electrical question

[Jay Radke]

I was at the big blue box last night getting a 30Amp 220V plug for my new Pflux and the corresponding outlet. As I was looking at the items I was asked if i needed any help by the friendly electrical dept guy. He asked what I was looking for etc. I told him and said I was looking carefully as sometimes items get put in the wrong box. In this was the first outlet I pulled out was a 50 Amp outlet. I said I only needed a 30 Amp. He replied who cares as long as you have a 30 Amp breaker i would be fine. I didn't quite like that answer so I wasn't going to ask him my other electrical questions. So instead I will ask them here.

I have a nice large garage that has plenty of room for my tools. The previous owner used the bay that I am going to be using for car work. There were already two 220V outlets in the garage one for a heater that was on the other side of the garage and one for a welder. The heater was on a 30 AMP breaker. I moved that outlet over to my bay as we won't be using the garage for social functions like the previous owner did. That was a simple task as the outlet matched my plug for my heater. The welder outlet is in the wall on a 50 AMP breaker. All other garage 120V outlets are on their own circuit on a 20AMP breaker. My heater and my new PFlux are the only things that I have right now that need 220V.

Here are the questions both revolve around the 50 AMP breaker.

1.) I was planning on replacing the 50 AMP outlet that was feeding the welder with my 30 AMP outlet for the PFlux. That should be fine, but can I use the same wires that are coming from the panel to attach the 30 AMP outlet?

2.) I have thought about adding a sub panel off the 50 AMP breaker as well. Not sure if this is really needed as I have confirmed that all the outlets are on their own independent circuit from anything else in the house or garage. And that the lights are alone on their own circuit, so that if somehow I tripped the outlet breaker the lights would still be on. But if I went the sub panel route, would I be able to use the existing wires feeding the 50 AMP outlet to install a new sub panel? I am thinking that for one thing the wires might not be long enough and that its probably not code to pigtail wires to feed a sub panel.

Thanks in advance.

Jay

[Alex Zeller]

Technically the guy was correct but may not be to code. If you have a 50 amp outlet on a 30 amp circuit you will be safe assuming what ever plugged into the outlet has the correct plug on it. The problem is that sooner or later someone may plug something into that outlet that needs more than 30 amps and the breaker trips. From a safety aspect you will be fine but annoying none the less. I personally like matching things up. If it's a 50 amp circuit then it has 50 amp outlets. So when I wired my house I used all 20 amp outlets because they are all on 20 amp circuit breakers. Code will allow the use of 15 amp outlets on a 20 amp circuit as long as there's more than one outlet (I'm not an electrician but I don't think the code specifies the voltage). So you could have 2 30 amp outlets on one 50 amp circuit.

If the person who did the wiring did it correctly they sized the wire based on the circuit breaker (maximum load). The problem you most likely will have is that the wire size could be too large to fit the 30 amp outlet. If possible a much simpler way to go would be to replace the plug on the PFlux to work with the 50 amp outlet.

What benefit do you think you would get if you installed a sub panel? To me it would be to add extra circuits. Unless you have a need to do so now I would cross that bridge if the need arises. How hard would it be to feed new wires from the main panel to this bay?

[Jim Becker]

Yes, you can re-terminate the wall receptacle to a 30 amp version to support your tool since the circuit is rated for at least that much. And as an alternative, yes you could install a sub-panel on that 50 amp circuit as long as it's a four wire circuit. If it's only a three wire circuit, you'll have to run new cable between the main panel and that location so you are supporting both "hot" legs, the ground and the neutral required for 120v circuits in a sub-panel. That's to keep things to code.

[Thomas Crawford]

For a dedicated outlet you'll want to reduce the breaker size. So even if you change the 50 amp outlet to a 30 amp style I would also downsize the breaker to 30 amps.

Jim is correct that you need 4 wires to the subpanel.

[Jay Radke]

Thanks for the replies. I think I will go the route of putting the correct 50 Amp plug on the PFlux. That will be the easiest as long as the experts here agree.

If changing to a 30 AMP outlet would require me to downsize to a 30 AMP breaker, then I would be better off going up to a 100 AMP breaker and putting in a sub panel. At least that is my thinking if I have to go inside the main panel might as well just do it once. But right now I do not think that I need that extra service yet. I can always go back and do that later.

[Jim Becker]

You are not required to reduce the breaker if you put a lower amperage capacity receptacle and matching machine plug ... but it's not a bad practice to do so for consistency. The breaker is to protect the wire, not the device plugged into it. What you can't do is put a 50 amp recepticle on a 30 amp circuit. That is dangerous.

[Bill Dufour]

Watch out for welder outlets. They can meet code with a 50 amp outlet and breaker but only use 40 amp wire to supply them. Verify the wire size before assuming you can run 50 amps to any machine that is not a stick welder. I would use the existing wire to supply an eye level subpanel. You can remove the outlet and wire nut a short run to the new subpanel. You can not daisy chain the outlet down to the panel.
Bill D.

[Jay Radke]

Bill, before reading your post I did some more investigation first to know what plug to get, the outlet said it was a NEMA 10-50. So I googled that and it said that is a 3 wire no ground. So that would work for my 3HP PFlux, it’s 3 wire bit with ground. So of course I went out and took the plate off to pull out to look at wires. Well it was wired with 3 wires, but with an uninsulated wire. Which I am assuming is ground to the ground. Now I will have to take the cover off the panel to check. At this point I am thinking it might just be best to go with sub panel after all. Now I just need to decide how much of it I would do on my own. I am quite comfortable with electrical work but have never worked inside a panel.

[Brian Behrens]

Jay, a subpanel is simple to add, but you need to brush up on it if you haven't done it in a while. Get yourself a main lug subpanel, they are less than $30. You have to understand this and make sure of it - if your garage is attached to the house, you must NOT, repeat DO NOT bond the neutral to ground in the subpanel. You've received good advice - you need to verify the wire size you are feeding the subpanel with. If you only have 2 hots and a ground you will need to run a neutral back to your main panel if you want 120v loads in your subpanel

Other than that, your 2 hots go to the lugs, your neutral to the neutral bar, ground to the ground bar. And again, make sure you remove the screw bonding the neutral bar to ground if it has one.
Then add your breakers and run wire to your additional outlets.

I'm concerned about your existing wire. Please look at it and tell us what size it is. I'm hoping at least #6 wire. This is a cheap and easy project and worth the effort for the flexibility it will give you in the future.

[Robert Engel]

If I'm understanding, you won't be using the heater? I that case I would use the existing 30A for the collector and supply a subpanel with the 50A

This will facilitate another 240V circuit plus 2 or 3 extra 120V circuits, which is desirable.

But my best advice to you is consult an electrician, not a forum

[Bill Dufour]

In house wiring the colors are simple. green or bare are ground. white is neutral, all other colors are hot.
But no promises that someone did not switch something around.
Bill D

[Bill Dufour]

If you buy another subpanel it might be a good idea to buy one that uses the same brand of breakers you already have. that way you can switch stuff around as desired assuming the wire. sizes can handle it.
Ignore this advice if you have Zinsco or federal pacific panels.
Bill

[Jim Becker]

In house wiring the colors are simple. green or bare are ground. white is neutral, all other colors are hot.
But no promises that someone did not switch something around.
Bill D

...except when whomever installed the 240v circuits didn't mark the white wire black to indicate it's hot...

[Bill Dufour]

...except when whomever installed the 240v circuits didn't mark the white wire black to indicate it's hot...

And switches and the boxes supplied by them.
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