240v, 30a to 15a Adapter

Git

I have my garage wired for a 240v, 30a circuit for my welder which uses a 3 prong plug. I also have a 240v planer which uses a much smaller, 15a, 3 prong plug. I could add another outlet for the planer, but I have a very nice ($$) extension cord for the welder that I would like to be able to use with the planer.

I made up this adapter using a plastic weatherproof box that is connected to a new plug with a piece of 1/2" pvc. I then wired in a new outlet.

Is there any problems with using this? The wire is some extra 12 guage THHN that I had

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Stubbie

It always amazes me the contraptions resourceful people come up with....

What you have is not acceptable but just how unacceptable it is will depend on a lot of things.

1.) What amperage circuit breaker is protecting the branch circuit?
2.) What size wire was used for the branch circuit?
3.) What are the electrical specifications of the equipment.ie..what does the manufacturer say is required for the branch circuit supplying the equipment?

The first thing that comes to mind is you have a 20 amp nema 6-20P connected or tapped, if you will, to a 30 amp cord and plug branch circuit. For cord and plug equipment this is not allowed.

If the welder came with a nema 6-30P it needs 10 awg branch circuit conductors on a thirty amp breaker. The planer is a nema 6-20P most likely. You cannot mix them if they are cord and plug.

Git

Yes, the welder circuit is a 10 awg circuit with a 30 amp breaker

Welder
Millermatic 175
230v, 19.5 A

Planer
Delta 62-175
2hp
230v, 12A

Stubbie

These are the specs. from Miller for the Millermatic 175 230 vlot 60Hz model.

Unfortunately or fortunately () I have got to get ready to leave town for a fishing trip...so I'll have to let the other guys on the site finish. Hopefully this information from Miller Welders will help get your ship going straight as to the required branch circuit for the welder. Whether or not you can use both planer and welder on the same circuit will depend on if you can install a single 6-20R receptacle in the wall that both units can use. Off hand I would say you can do that and you can just through the contraption away.
I would also mention 210.21 B(1)exp.2 of the 2005 NEC this might help but I believe it only allows the receptacle under the conditions listed to be used exclusively by a welder. The thing that will probably cause the most confusion is the welder comes with a 6-50P power cord. Your specifications are correct about the 19.5 input amps at rated output they have just rounded up in the chart.

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