Understanding 120/240V Wiring Color Code | DoItYourself Understanding 120/240V Wiring Color Code By: connect it to an existing three-wire 240V circuit. There are still 240V appliances that only need two hot wires and a ground. An electric water heater and the outdoor condensing unit, or compressor, for central air conditioning, are two of those. Identifying House Electric Wiring ColorsAuthor: DIY Staff How to Wire a 240V AC Outlet - instructables How to Wire a 240V AC Outlet: We were given a welder that has a big 240 volt plug, but our home doesn't have any 240V outlets already wired. What to do? Wire your own! Turns out the plug we had is NEMA 6-50. You can probably figure out what yours is from a chart. If it's clo..