I just bought a house and am changing around some outlets in the garage, and I want to make sure the electricity is wired properly. There are 6 wires in a conduit going to the garage, three hot (red, purple, and blue) 2 neutrals (white), and one ground (green). Each of the hot wires has their own circuit breaker. Red and blue were wired to share a common neutral, and purple had it's own neutral. When I used a voltmeter and put one lead on red and one on blue it reads roughly 0 volts, when I do the same for blue and purple it reads roughly 240 and purple and red also 240.
Should red and blue share a common neutral? My guess is that I should rewire it so that red and purple or purple and blue share a neutral, but I want to confirm.
Thanks a lot!
Best Answer
You're correct that red and blue need to be on different neutrals
You are correct that the original wiring was wrong; having red and blue share a neutral would subject that neutral wire to the sum of the currents from the red and blue wires as they're on the same leg of the service. Which wire you pick to go with the purple wire depends on the position of the corresponding breakers in your panel; ideally, either red's or blue's breaker would be next to purple's breaker, so you could whack the appropriate $2 handle-tie for your panel on the two breaker handles to provide a common maintenance shutoff for both circuits on that neutral. However, if neither red's breaker nor blue's breaker is next to purple's breaker, then you may need to rearrange your panel to accommodate the common-shutoff requirement. (If you plan to put red and blue on the same yoke, by the way, you'll need a three-pole handle-tie as different circuits on the same yoke need common maintenance shutoff as well.)