Bizarre household electical problem.

[Steve]

Hi folks.

I went by my mother's house for dinner and she asked me to check out a florescent closet light that wasn't working. She already installed a new bulb and that didn't solve the problem.

I removed the cover at the fixture and connected my VOM and found 120v. When I shut off the light switch, I had 2 volts.

Finding this somewhat unusual, I turned the switch back on and we cycled through a couple of breakers. With the breaker in the off position, I still had a couple of volts.

Mom's house is 20 years old and has two electrical panels (and 4 heating/cooling zones, but that's an entirely different story). One panel is in the first floor laundry room, and the other panel is in the basement.

Every circuit on the basement panel I tested had somewhere between .5v and

5v with the breaker off. The main panel circuits had 0v.

I'm no expert on household electricals. I'm really curious where this volt or two could be coming from. I'm not sure if it's normal either - I would assume not. I also wouldn't be surprised to learn the demise of the florescent fixture had something to do with it getting 2 volts pretty much all the time.

For grins, I decided to air gap the switch - I removed it entirely and capped off the hots. I was still seeing 2v at the closet light, which makes even less sense now that the only things connected (at least, as far as I could tell) were ground and neutral, and I was measuring that silly

2v between neutral and hot.

Any takers?

-Steve

[Robert A. Barr]

You're using a meter with a really high input impedance. This means that you are measuring a voltage generated in the wiring, via a number of ways -- most usually induction from proximity to another (live) conductor.

You could probably use the same meter to measure a voltage at a TV aerial connected to nothing. It's a predictable source of puzzlement for people uninitiated to this phenomenon.

Years ago, a typical low-dollar meter would have such low input impedance that the meter itself would dampen out any such stray induced voltages.

[m Ransley]

It may be nothing But I would get a clamp on amp meter that reads to

01 amp You will have to order one at a supply house, Greenlee has one for apx 35$ Check your ground wire for a short. And ck circuts with the meter

[Joseph Meehan]

Robert explained why you got 2V, not at all unusual BTW.

As for the light, I will make a few suggestions.

First make sure the fixture is grounded.

Next check the lamps. If they are dark on one or both ends, they likely need to be replaced

Is it cold? Fluorescents don't do will in the cold.

Cheap ballast or lamps often have problems. Good electronic ballast and good lamps fix a lot of problems.

Try just removing and replacing the same lamps in the fixture. Many times moisture has caused a film of oxidation to form on the contacts and the removal and replacement will clean it off.

Good Luck

[Steve]

Hi Joseph. I've confirmed the fixture itself is dead - I replaced the bulb ... no success. The light uses an electronic ballast. I'll either replace the ballast or just trash the fixture and start over, depending on how much price difference there is.

The fixture is grounded.

I did notice the fluorescent lighting in mom's garage was dim and flickering. I kind of figured it had something to do with the fact that the door was open for several hours and it was 20 degrees outside..:-) I don't own any fluorescent lighting - I personally can't stand it.

Thanks for the help!

-Steve

[Steve]

Hi Robert.

You're right. I seem to remember someone mentioning that to me at some point. I've got an old Simpson 260 in the closet... I'll bring it when I go to replace the ballast in that darn light!

Thanks for your help.

-Steve

[M.Burns]

I'm absolutely no electrician, but I did run across a situation once in a house where I threw a circuit breaker to "Off" and there was still some trace voltage at a light fixture. I found that the switch was wired to interrupt the neutral (instead of the hot) wire. As soon as I corrected it, the voltmeter read "0". M.B.

[Stormin Mormonn]

Assuming it did have two volts (and not that your meter was off) it was likely cause the lamp has a ballast. Which was near a charged wire. Picking up magnetic energy off the charged wire.

A transformer is two coils of wire which aren't electrically connected. But which are close enough to pick up magnetic energy. It's possible that your ballast was picking up energy.

Best guess. Worth what you paid for it.....

[j j]

electromagnetic fields induce voltages in wires wires also have a finite conductivity meaning that the ground in your panel is never zero under heavy loads

[EL]

Inductive coupling. If all breakers are turned off, or all loads or all circuits are disconnected (no current possible in other wiring) there should be no coupling.

Boden

Steve wrote: