i have an air compressor with a 20 amp, 3 prong, 240 volt plug. my garage is wired for 240 volts, but it uses these giant 30 amp, 4 prong outlets. i don't want to have to completely rewire the wall (i'd have to run new smaller gage wire and everything) if i can help it. can i make an adapter cable of some kind? or perhaps just change the plug on the compressor?
Ray66V
Favorite Answer
Easiest way to do it is to change the wall receptacle, or the plug on the compressor. You can make an adapter cord, but it is going to cost over twice as much as the first 2 fixes would.
No reason to change the wire in the wall, or the breaker. Changing either, would be a waste of money. Breaker size is determined by the wire size used in the building. Having the wire over sized is a GOOD thing. Especially on a device that has very high start up draws like a compressor.
The motor on a compressor, will have its own factory set thermal overload protection. Which is more than enough to protect it, and probably if you check, likely to be UL approved. (That means throughly tested).
Thor
Yes as said, change the BREAKER and the outlet. It is fine if the wiring in the wall is oversized, just not undersized.
You can not find an adapter because it is illegal to use and foolish.
With a 30 amp breaker and a 20 amp appliance, if the compressor started to fail and drew like 25 amps, then your 20 amp wiring in the compressor could overheat, melt, and catch fire before the 30 amp breaker would trip.
That is why you can't do it without changing the breaker.
Irv S
Buy a plug to fit the outlets you have.
Put it on the cord for the compressor.
The trick will be to make the right connections.
You will need to connect to the two 'lines`
and either a neutral or a ground.
If your old 20A. plug is marked NEMA 6-20,
the third wire is a ground, if it's 10-20 the third
wire is the neutral.
On the 30 A receptacle (should be 14-30R),
the round pin is the ground, the one opposite
is the neutral.
tony h
It is ok to put a 30 amp plug top on a 20 amp machine. Going larger is fine (But you can't put a 20 amp plug top on a 30 amp machine) Circuit breakers are only there to protect the wiring, not the appliance.
normy in garden city
Making the adapter cable is fine but a 30 amp male and 20 amp female needed for the adapter would be quite expensive. Save money and put a 30 amp plug on the chord.