Often times when inspecting an electric panel we find double tap wiring. Double tap wiring is two wires in the same breaker. But how bad is double tap wiring?
First of all, let's make two things clear. First, just because we find it a lot does not make it right. But just because it is not right does not make it a huge issue. Double taps happen because, most of the time, it is just easier than putting in a new breaker or because the panel is out of breaker slots and it is cheaper than putting in a whole new panel. In fact, brands like Square-D make their standard breakers to be double tapped.
But if the breaker is not made to be double tapped, then arching and other issues can occur and it can be a concern. Most of the time these are a maintenance issue. The fix is usually simple to - either get a breaker made to be double tapped, or just give each wire its own breaker if there is room in the panel.
Mike McFadden, Certified Master Home Inspector in Orlando, FL