Folks-

I am building a special project box and can't figure out why my breaker keeps tripping...


I have a 240v 2 pole GFI breaker 30 amps supplying power to the box via 4 wire 10/3 feed. Inside the box, on the back side of the outlet power comes in on, I'm tapped/bridged off one of the hots and the neutral and take it over to a small computer device (also within the box, which is about 12" square and 8" deep). The other hot goes through a relay, and then to a heating element (which is NOT hooked up for testing).

The computer only pulls about 1amp, so I'm sure that's not it. For testing, I disconnected everything from the feed and wired a 40 watt desk lamp in, and as soon as I turn it on that side of the breaker trips.

Arff? How come? And can this be rectified? (no pun intended)

Is the neutral wired to the 240V GFCI breaker like it should be or directly to the neutral bar? If your breaker does not have a place to wire the neutral then the breaker will not work for this application. To wire your GFCI properly take the neutral to the proper lug on GFCI and the pigtail on the GFCI to the neutral bar.

A straight 240V GFCI compares the current on each of the two hot legs and trips if they are not the same. A 120/240V GFCI also measures neutral current and figures it in.