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Discussion Starter #1
Heres the problem. I borrowed a 110 plasma cutter to finish some of the sheetmetal work on the chassis. It will pop the braker (20amp) on the 110 outlets in the garage. The guy I got it from said this might happen. It power requirement is 110v and 24 amps.

I have a 220 outlet in the garage for my welder. It has two 50 amp brakers. Is their any way I could use one leg of this to power the plasma cutter temperarly????:confused:
Or something else???

Thanks, Dan
 

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It'd be better just to add the required single-phase breaker.

I know what you're thinking and my dad did it. Just had to pull one lead off the breaker and put it on a dead terminal to get it out of the way. Then jumpered the nuetral over. Then he put an existing 110v circuit on the output of the breaker.

Meanwhile, I was at a buddy's house picking up a 30 amp breaker, and when I got back I talked him into installing that. :rolleyes:

So anyway, I'm not sure it would work, we just ended up doing it the right way. Well, the wrong way since neither of us are electricians.
 

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Discussion Starter #3
Ok, could I replace the 20amp breaker with a 30amp just long enough to finish this project. Nothing else runs off this circuit.

Im not trying to be stupid about this. Just looking for options.

Dan
 

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Dan Dibble said:
Ok, could I replace the 20amp breaker with a 30amp just long enough to finish this project. Nothing else runs off this circuit.

Im not trying to be stupid about this. Just looking for options.

Dan
Yeah that's easy you can't miss because it's a replacement.

Why wouldn't you just leave it in there?
 

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Discussion Starter #6
Right, wire gauge. I relize this. The cutter only requires 24 amps not 30. It works well on the lower settings but when cutting 3/16" I have to max it out.

It looks like I have 12/2 on the recpticals. But I really would rather use the 220.

Thanks, Dan
 

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220 is just 110 on two legs.....

If your 220 plug is 3 prong, you can use one side and the ground to get 110 volt... If its 4 prong, you can use one leg and the neutral.....

People do this all the time on construction sites.... Most temporary power poles have a 50amp 220 plug and a 20amp 110 plug.... The 20 amp breaker just wont carry a compressor and several saws runnnng....
 

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Discussion Starter #8
tators said:
220 is just 110 on two legs.....

If your 220 plug is 3 prong, you can use one side and the ground to get 110 volt... If its 4 prong, you can use one leg and the neutral.....

People do this all the time on construction sites.... Most temporary power poles have a 50amp 220 plug and a 20amp 110 plug.... The 20 amp breaker just wont carry a compressor and several saws runnnng....
This is what I was thinking. But I would have no ground for the cutter. Is this ok?
 

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It should work, I actually planned on doing that when I build my welding cart. Have a single 220 line to the cart to run the welder, then branch off from one leg to neutral to mount a couple of 110 outlets on the cart.

Chad
 

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it's a borrowed tool right-?

and you're pondering using it out of it's scope-?

would you want a freind of yours that borrowed some tool

to use it for other than it was designed?


--Sherpa
 

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He is actually trying to use it in the correctly designed 30 amp circuit. It is actually doing it more damage by blowing the 20 amp breaker and killing the power to it during loaded operation. Change the breaker to 30 amp and be done with it. 12/2 is good to 30 amp.
 

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jeepinblackdog said:
He is actually trying to use it in the correctly designed 30 amp circuit. It is actually doing it more damage by blowing the 20 amp breaker and killing the power to it during loaded operation. Change the breaker to 30 amp and be done with it. 12/2 is good to 30 amp.
Check the NEC again... 12 gauge is only rated to 20 amps as he is using in this case. However, short periods of use drawing 24 amps probably won't hurt anything, but the potential is there to overload the wiring. You could get a short length of 10-2 w/ ground and run the hot off of one of the 50 amp breakers, run the nuetral to the nuetral buss bar and the run the grounding conductor to the grounding buss bar if in a subpanel or to the nuetral buss bar if in the main panel. Yes, you are technically feeding too small of a wire with the 50amp breaker, but as long as you are doing this for this one TEMPORARY KNOWN LOAD, you will be OK. The 10 gauge wire is rated at 30 amps and the known load is 24 amps.
 

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Just use your existing 220V outlet. If you want a ground prong, connect to the 110V ground (or if you have a 4-prong 220V plug you probably have a ground there) or just jumper it to the neutral on the 220V line. They are connected together in the breaker box anyway. All the 110V in your house is just one side of the 220V line anyway, so it's the same thing they allready did to give you 110V outlets in the first place. If you have an electric 220V clothes dryer, it probably does this internally. Many appliances do.
 

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Discussion Starter #14
SHERPA said:
it's a borrowed tool right-?

and you're pondering using it out of it's scope-?

would you want a freind of yours that borrowed some tool

to use it for other than it was designed?


--Sherpa
Sherpa, I understand your concern. The owner has been making these suggestions.
Dont assume people are not curtious. Oh ya and I own the house.:flipoff2: :flipoff2:

Dan

Did you read the part, where Im not trying to be stupid about this?? Im asking If it can be done.
 

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As others have pointed out, all 110V power in the US is derived from 1 leg of a 220V center tapped single phase system.

The only important distinction in using 1 leg of a 220V circuit has to do with the breaker set up. 220V circuits use a breaker on each of the two hot legs and these breakers are mechanically connected "ganged" so that they trip at the sime time. If you only run 1 leg, the "ganged" 220V breaker won't trip at its proper set point, so the smart thing would be to run it considerably under its 50A rating or temporarily remove the mechanical connector between the two poles.
 

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Discussion Starter #17
ttabbal said:
Just use your existing 220V outlet. If you want a ground prong, connect to the 110V ground (or if you have a 4-prong 220V plug you probably have a ground there) or just jumper it to the neutral on the 220V line. They are connected together in the breaker box anyway. All the 110V in your house is just one side of the 220V line anyway, so it's the same thing they allready did to give you 110V outlets in the first place. If you have an electric 220V clothes dryer, it probably does this internally. Many appliances do.
Thanks, This is what I was thinking. I bought a dryer plug assembly (30a) and a junction box for the 110 outlet. I will just cap the other 110 lead. And tie the neutral to the receptical ground in the box.

Thanks, Dan
 

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Pin Head said:
As others have pointed out, all 110V power in the US is derived from 1 leg of a 220V center tapped single phase system.

The only important distinction in using 1 leg of a 220V circuit has to do with the breaker set up. 220V circuits use a breaker on each of the two hot legs and these breakers are mechanically connected "ganged" so that they trip at the sime time. If you only run 1 leg, the "ganged" 220V breaker won't trip at its proper set point, so the smart thing would be to run it considerably under its 50A rating or temporarily remove the mechanical connector between the two poles.

Depends on how the breaker is ganged. I've seen many peanut breakers trip on just one leg when the amp rating was exceeded.
 

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the best advice you've been given in these posts is "do it the right way." why screw around? just set up a new circuit with the correct breaker and ampacity conductors. don't forget voltage drop. easy and inexpensive to do (since you're doing it yourself)and you are sure to use this circuit again. in addition, you could convert this new circuit back to 220-240 volts if you bought a piece of equipment requiring this voltage (like a shop compressor). pm me if you have a question on the conductor sizing for your length of run.
 

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An alternative with expansion

jdrocks said:
the best advice you've been given in these posts is "do it the right way." why screw around? just set up a new circuit with the correct breaker and ampacity conductors.

Good advice. The safest way to get what you want, a 30 amp plug outlet in the garage, is to install the correct plug.

How? How to get around homerunning #10 from the main breaker panel (a PITA)? Make it easy, but correct.

Go to the hardware store and purchase a small breaker panel (buy the same brand, or one that fits the same breakers, as the house main panel). Make sure you buy one with six or more breaker slots. These are cheap (go and price them).

Shut off the dual circuit 50A breakers in the main panel and replace that welder plug in the garage with the small breaker panel. Slave the plug off the new panel.

You might want to remove the 50A breakers from the main panel and install the maximum safe breaker size allowable for the existing wire that is installed between the main and the new small breaker panel (pick up a NEC book or ask at the store). This provides your garage panel the maximum amp capacity available with the installed wire, and it allows you to reuse the old 50A breakers in the new panel to feed the (reused) welder plug. You now know why you will remember to buy a panel that uses the same breakers (right).

You can feed the new breaker panel on the buss bars or through an input breaker (so you have a panel disconnect if desired).

You can also add breakers for isolated plug loads in the garage out of the new panel. This includes your 30A plug, and additional service plug circuits (including ground fault protection that is isolated from the house).

After completing this task you will never again have the angle grinder or other tool trip out the breaker (right when you squeeze under the vehicle) when the wife and kids fire up the toys and homeoffice coffee maker at the same time. They can trip the light off in the house and you will remain well lit in the garage (and the garage fridge will not trip, risking warm beer).

No long home-runs of wire to pull, expansion for future garage projects, and the safe way to get what you really want (permanent isolated power for the garage with the correct wire for each outlet).

Happy Trails!
 
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