[Bob w]

I currently have a 220 volt compressor outlet that I want to convert to a 4 prong outlet to connect my generator. I have the new 4 prong outlet, a new 4 prong generator cord, and a circuit breaker panel interlock kit. Question is, the current 220 compressor outlet had 3 wires, but the new plug has 4 prongs. How or can I use safely the 3 wires with the new 4 wires outlets that for my generator cables and outlet? Thanks!

[hfcarson]

Sounds like the old cable was connected to two phase conductors and ground...
You cannot use the existing three conductor cable,
You need a (4) conductor cable for connection to the supply Neutral...

[Bob w]

Thanks for your response.

Actually the 220 line for the compressor was run, but never hooked up. It just has the box, but no outlet was ever installed.

There are 3 wires inside the box, hooked up to a 30 Amp double pole breaker in the panel. All I would have to do is install an outlet.

My question is, since the run is currently a 3 wire (2 hot and 1 ground), how can I either convert or use the current 3 wires for a generator 4 wire plug and cable outlet? What do I do with the neutral on the plug if there isn't a 4th wire?

Thanks again!

[hfcarson]

As you have indicated the generator was designed for a (4) wire connection...
To install this properly you will need to install a fourth conductor...

You cannot do this without the neutral...

[Bob w]

Thanks again!

How do I install a 4th? Can I run an 8 gauge wire through the conduit? And is so, where on the circuit breaker box do I connect the 4th? I would assume a neutral bar?

What if there is weren't a neutral bar, how else could this be done?

[hfcarson]

If the overcurrent device for this generator circuit is 30 ampere, #10 awg would be fine.

... the fourth wire is most likely a neutral, so yes on the neutral bar...

If there is no neutral you do not (will not) have any 120 volt outlets..

[Bob w]

Thanks much! Very helpful.