240v from two 120v outlets?

Question

I'm thinking about getting a smaller 240v tig welder. It draws 24 amps at maximum, and I won't go to 130 amps for most of my work. I don't have a 240 outlet that is near my garage, and I thought I could create a cord to hook up two 120v outlets into a 240v outlet. I could take two extension cords, cut off the ends, get a 240v plug and wire the hot from one cord to the hot on the outlet and the hot from the second cord to the other hot on the outlet. I could check which outlets are out of phase in the breaker box, or just guess a few and check the voltage. I tested it with my multimeter and it worked.

Update : also, could you explain why its a bad idea if you say it is?

Update 2: I'm wanting to not have to rewire anything, so 240 at 20 amps is twice as much as 120 at 20 amps

Answer 1

Completely Illegal and electrically dangerous, also not sufficient ampacity on that wiring. Amps is still amps whether it is 120 or 240 volt so you still need minimum # 10 wire gauge for that welder (you have to derate by 20% and size it to the maximum draw.) NOt only do the two legs have to be out of phase with each other , they MUST be running parallel in the same cable or raceway. To do what you are planning will induce currents on the neutrals in the separate cables and cause a serious hazard.

Source:

I;'ve been a licensed electrician and BOCA certified electrical inspector for over 30 years

Asker's rating & comment

Thank you for this information. I'm alittle confused on how this will induce current on the neutral. The word induce implies induction, so how does this happen. As for as I know there is know magnetic affet from this.

Answer 2

Not only is what you are thinking of doing stupid, it is very dangerous.

Edit: As for explaining why it is a bad idea, there are multiple reasons.
First of all, it is illegal. Since it is illegal, any property damage or injury caused by your setup would not be covered by insurance.
On to the next question you would surely ask: Why is it illegal?
You are attempting to wire up a device that, by design, would overload any normal receptacle. The receptacles (and the circuits associated with them) would have a maximum ampacity of 20 amps. Drawing more current through a device than is allowed by design could cause the catastrophic failure of that device. Also, the configuration you describe would not guarantee that the circuit breakers would trip before serious injury or damage occurs. While one circuit might trip on overload, the other circuit may stay energized long enough to pose a fire and safety hazard.

You obviously know enough to be a danger to yourself and others. Heed some advice and refrain from doing any electrical work in the future.

Source(s):

Master Electrician

Answer 3

It is a bad idea because it is more than likely someone will end up dead or in hospital...... if you are going to get the 240v tig welder get yourself a step up transformer too. It wont make any differance to your electricity costs as 120v @ 100 A would be the same as 240v@50A. You cant cheat the electric company. AC electricity is not like DC electricity putting 2 supplys together will not give you twice the voltage but it will give you is twice the trip out rate which at best will probably as i said earlier kill you, your family or burn your house down :)

Answer 4

It is easy to do what you are proposeing. However, it is illegal and if anyone gets hurt you could spend time in prison.