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Faunsdale, AL | Sounds like there’s a place on the circuit you were hooking up (plug?) where it’s ground wire is connected to the building steel. I think the ground terminal on a receptacle is always tied into the metal mounting ears that would be touching the metal box fastened to the building steel.
That is true if it’s a type of 3 prong receptacle with a ground vs one with a neutral. I think the old crows foot 220 was intended for 2 lines and a neutral, so the ranges they were intended for had a neutral for 120 volt lights, clock etc. This is in contrast to some other types that were 220 only so the 3rd prong is only a ground and I would expect it to be tied to the metal mounting ears.
The other thing that made sense is that the current was coming from the neutral of the 120 volt lights and any other circuits that were active. Evidence for this is it decreased with fewer lights being on.
The whole thing points to a poor connection between the neutral bar in your panel and the transformer that’s supplying it. The ground bar and the neutral bar are supposedly bonded together only at the service entry/main panel. That’s where the two systems, the current carrying neutral and the safety ground that’s only supposed to carry current in an emergency are connected.
So, if there’s a high resistance connection on that service entry neutral running back out to the transformer, when you touched the ground from the circuit you were hooking up, it provided an alternate path through whatever building steel, concrete slab, reinforcing in concrete, earth, ground wire back up pole to transformer.
Signs that’s a serious problem with the neutral will be when some lights go bright or dim when you switch on a 120 volt load like a grinder or something that pulls a lot of current. This is because without a good neutral, the 240 volts supplied by the transformer splits between the two nominally 120 volt legs coming into your panel in inverse proportion to the load on each side. The higher loaded side will “see” a lower voltage while the lower loaded side will see higher voltage. This produces the brightening and dimming lights that are most noticeable.
Doesn’t sound like your neutral back to transformer is that bad yet, but it may get that way. Most likely the building steel is just a very good alternate neutral current return path to transformer that would not exist if the building were wood.
Edited by ccjersey 7/7/2025 11:10
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electrical question
