Neutral readings looked strange in a remodel job today

[ChaseGo]

I was working a remodel job here in Florida today and got neutral readings that did not look normal. Load was light, everything was wired the way it should be, but the numbers on the neutral kept drifting a bit instead of settling down. It was not anything dangerous, just off enough to make me pause and double check everything.

This place is an older home so I am wondering if I am dealing with shared neutrals that were never documented or maybe a hidden connection from an old repair. Before I start opening walls I wanted to hear from others who work in Florida a lot. Have you seen neutral readings act a little strange in older remodels and what did you usually find behind it?

 

[Alan]

Yeah, older Florida homes can get a little weird with neutrals. Sometimes the house looks tidy upfront but the wiring behind it tells a different story. A drifting reading usually means something is tied together where it should not be. Did you notice anything else odd on the hot leg or was it only the neutral acting jumpy?

 

[PGB1]

I'm not in Florida, but if someone used a ground for a neutral, your neutral reading can wobble all over the place.
Prime Suspect: Dimmer for LED. People buy the ones requiring a neutral & do the big cheat because there was no neutral in the switch box.

Electronics with Switch Mode Power Supplies can also make a neutral dizzy. Routers, televisions, chargers, desktop computer power supplies are common places to find SMPS.

Suspect #3: Inverters. A UPS device can send tilt-a-whirl neutral readings on the line side.

Finally, if the utility neutral connection in the load center, the meter socket or at the transformer is loose, corroded or simply came off; neutral readings can go goofy. All the electrons are trying to get down the grounding electrode(s) which isn't always a good path. The neutral readings will bounce. (Aluminum service entrance cable? Check the connections for hidden corrosion or a loose terminal.)

 

[electroshak3]

Don't open the walls yet! check the panel bus bar first. in older FL homes, those screws can loosen up over decades of thermal expansion
a loose neutral at the bar will cause that exact floating drift
if the panel is an old Zinsco or Federal Pacific, the connection might be failing internally
pop the dead front and check for any signs of arcing or heat

 

[PGB1]

if the panel is an old Zinsco or Federal Pacific, the connection might be failing internally
pop the dead front and check for any signs of arcing or heat

If the load center is Federal Pacific Stab-Lok, be certain to stand to the side and face away from the cover when removing it. (And, ideally, arc flash goggles). Stab Lok circuit breakers in the aluminum bus panels have a habit of falling off of the bus when the dead front is removed. Some bright arcs can result as can the automatic reflex to try to catch the circuit breakers.