Fratto
09-30-2025, 11:07 AM
My aux air compressor is powered by the general receptacle circuit in the basement bays. These receptacles are all protected by the GFCI that is first in line on that circuit. The other day the compressor quit working and the receptacle tester showed hot-ground reversed. Come to find out, if there is another load on the circuit, an open neutral will sometimes show up on the tester as a hot-ground reversed error. In my case, the 120 volt water pump (changed from the orginal 12 VDC pump at some point prior to me) was connected to this circuit. With that unplugged, sure enough the tester showed an open neutral. Using a volt meter on a down stream receptacle confirmed that there was no voltage between hot and neutral but there was between hot and ground.
Long story short, the only way to find that open neutral is to visually inspect each receptacle and the serving panel. After reviewing all of these and not finding anything wrong, I randomly tested the voltage on the incoming GFCI and it was normal. Testing the outgoing terminals on the GFCI showed a much lower voltage. So I replaced the GFCI and all is back to normal.
Note: the water pump still worked which was puzzling but it turned out to be wired to the incoming side of the GFCI. I changed that to the outgoing side so it would be protected since it is in the water bay.
Lessons learned:
1) Hot-ground reversed errors can be caused by an open neutral in some cases where there is a load on the circuit down stream of the neutral failure.
2) GFCI receptacles can fail internally with no visible signs.
3) 15 amp GFCI receptacles are actually rated for a full 20 amps of pass through. This is good since I was concerned that the aux air compressor and water pump would both be down stream of the GFCI.
Long story short, the only way to find that open neutral is to visually inspect each receptacle and the serving panel. After reviewing all of these and not finding anything wrong, I randomly tested the voltage on the incoming GFCI and it was normal. Testing the outgoing terminals on the GFCI showed a much lower voltage. So I replaced the GFCI and all is back to normal.
Note: the water pump still worked which was puzzling but it turned out to be wired to the incoming side of the GFCI. I changed that to the outgoing side so it would be protected since it is in the water bay.
Lessons learned:
1) Hot-ground reversed errors can be caused by an open neutral in some cases where there is a load on the circuit down stream of the neutral failure.
2) GFCI receptacles can fail internally with no visible signs.
3) 15 amp GFCI receptacles are actually rated for a full 20 amps of pass through. This is good since I was concerned that the aux air compressor and water pump would both be down stream of the GFCI.