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NEMA 10 is obsolete and dangerous, as it does not have a ground wire, and the usual installation process ties neutral to ground, which is asking for trouble.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