Did a panel replacement today and had a strange occurence which I am trying to understand. After reconnecting all the breakers and switching everything on, one 15 amp breaker would not hold. An ohmeter showed a tad over 8 ohms between this circuits hot wire and ground. Thinking there was a motor load or something I checked everything out and unplugged everything on the circuit. The 8 ohms remained. Then I happened to switch one of the 3 way switches for a stairway light. The 8 ohms went away. Switching the 3 way made it return. With the 3 way switched off, the breaker reset just fine. The stairway light works fine from both switching locations. It's a single, incandescent. Everything works fine now, but the breaker will not hold if you try to switch it on with the 3 way on. I should mention it is a multiwire circuit with the hots on opposing legs. Anyone have any idea whats up here?
I have seen switch legs brought into the panel and wirenutted into a branch circuit to control it. Panel basically being used as a J box. Had your same problem once with an oil burner emergency switch because of this. I assumed that the black& white was a branch circuit. Turn the switch on and the breaker tripped.
You should always be careful when taking the wiring apart in the old panel to note how everything is wired.
Hal, I do take a good note of everything before I take it apart and label if neccesary. I've seen switch legs brought to the panel, in fact I did a pool light this way once after the original switch leg went bad under a slab. There were no white wires anywhere but on the neutral/grd buss. Even the 240 loads were red and black. Take note where I said all works fine when hooked up, I just can't switch the breaker on with the 3 way on at the same time. Once the breaker is set, you can switch the 3 ways all day long with no problems. I'm baffled. I have another day to spend there, I will examine the 3 way wiring. Coastal, I am having a hard time picturing your scenario. And why everything works fine once the breaker is set.
[This message has been edited by BigB (edited 01-03-2005).]
BigB, This could be a loop fed circuit. I ran across this before. The original panel had a circuit fed from the panel on each end from two fuses. It was fed from the same side of the bus. When I changed the panel it was fed from opposite sides of the bus and tripped the breaker with no loads. Switch the offending breaked off and see if the terminal still has voltage. If it does then switch off the remaining breakers to see which circuit has the loop connection. Hope this helps.
Incandescent lamps have a very low resistance when cold, so draw a huge current at startup. The resistance rises as the filament warms up. But I'd have thought a breaker would cope with that anyway. Faulty breaker?