Post overlooked electrical issues here

I don’t know if there’s a thread like this already (search function almost always says “no results found”), so I figured it would be good for us to post important electrical issues that we suspect are often overlooked, such as taping wire nuts (tape can come loose and pull them apart) or insulation covering knob-and-tube wiring (wiring needs air space to cool). I didn’t know about those ones until I attended a NACHI seminar.

At the top of my chart is two or more circuits of the same polarity sharing a common neutral. Circuits sharing a common neutral is usually identifiable by the presence of colored hot wires (usually red) in the panel that are not on appliance circuits. I recently came across one panel in which this potentially disastrous situation was combined with oversized breakers: the #14 hot wires came off adjacent half-size 20A breakers that were on the same breaker space in the panel. Testing with a probe confirmed they were the same polarity, though it was obvious from the panel design. That means their #14 neutral could get up to 40A of current running through it.

When I find a major potential hazard such as this, I consider it imperative to make sure the seller finds out about it, and shut off one of the circuits if the house is vacant.

Try searching for “multiwire branch circuits” and Class CTL Cb’s.

I agree, the 3-wire circuit neutral will carry the total load.

Search for balancing the load evenly