Some time back I had some folks who needed me to take a subfeed from a subpanel. That is to say, they had a 2-pole 50a breaker at the main house panel feeding a subpanel in the shop. From this subpanel they wanted me to take a 2-pole 30a to a second subpanel. The problem was that when I checked voltage at the subpanel in the shop, I found 120v on one phase to neutral but only ~46v to neutral on the second phase, giving me phase-to-phase voltage of ~166v. The best I could determine (i.e., guess) at the time was that one of the phases was grounded somewhere in the underground run between house and shop - only just not enough of a ground to trip a breaker.
Does anyone out there have any other ideas of what the problem could have been?
