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I built a garage and electrician installed what a plug that won't receive my 250 volt appliances. The hardware store tells me it is a dryer plug and can't understand why it was installed in a garage. It is a NEMA 30 AMP (14-30R) 125/250 volt receptacle, with 4 holes. So, I have 4 wires (red, black, white and bare ground) and need to set it up with the 3 prong plug they provided me. It is a 30 AMP 250 Volt receptacle with 3 prongs holes. One of which is labeled ground.

How do I set this up - if I can? Do both the 2 live wired go in one connection?enter image description here

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  • What are the "250 volt appliances" you want to connect? Just get a cord which will plug into the NEMA 14-30R receptacle. This is now the standard, and it would be a code violation to replace it with the older three-wire one.
    – Jim Stewart
    Oct 11, 2017 at 21:50
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    "Do both the 2 live wired go in one connection?" - No!
    – RedGrittyBrick
    Oct 11, 2017 at 21:52
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    Can you provide a photo of the plug on the appliance that shows the ends of the prongs clearly?
    – ThreePhaseEel
    Oct 11, 2017 at 22:36

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The NEMA 14 series connectors are the correct, legal, safe and state-of-the-art connectors. It is absolutely correct for the electrician to install NEMA 14 unless you specified NEMA 6.

NEMA 10 is obsolete and dangerous, as it does not have a ground wire, and the usual installation process ties neutral to ground, which is asking for trouble.

You say your plug does have a ground wire, which makes it a NEMA 6. It is fairly trivial to convert a NEMA 14 receptacle to NEMA 6, since all the needed wires are present. Or you can change the plug/cord on the appliance, the neutral in NEMA 14 is simply not used.

You will need to change the breaker to whatever size of NEMA 6 you fit.

  • One NEMA 6-15 socket -- 15A breaker
  • More than one NEMA 6-15 socket -- 15A or 20A breaker
  • Any number of NEMA 6-20 receptacles -- 20A breaker
  • NEMA 6-30 receptacle -- 30A breaker
  • NEMA 6-50 receptacle -- not allowed on 10 AWG wire
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  • Seems replacing the plug on the appliance is a solution. This is what I originally intended, The Hardware store did not have the plug needed (did not stock), and suggested I switch out the hardware. I will leave the receptacle alone and change the plugs - starting with electric heater
    – Derek
    Oct 12, 2017 at 8:36
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    @Derek, the hardware store didn't have a 4-prong dryer cord? That's a pretty common item. And it's just labeled as a "dryer cord" in the store because that's what most people buy them for, but can be used for other appliances that have the same electrical requirements.
    – JPhi1618
    Oct 12, 2017 at 21:01

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