What might cause this? Diff voltages between H,G, N


Old 02-27-15, 04:44 PM
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What might cause this? Diff voltages between H,G, N

Replacing some smokes and just verifying what was hot (Yeah, I know, but not a single breaker is labeled and it would have taken me an hour just to find the right one. I undid and reconnected one wire at a time with the wires well separated out of the box.), but the readings kinda confused me. Hot to ground...97.4V. I thought, that can't be right. Different meter, same. Hot to neutral...120.3V, just fine.

What would cause that? Any other time I've measured hot to ground anywhere, it was the same as hot to neutral.

If you remember a prior post, where I said the place was wired by monkeys? I gave them too much credit. House wiring was stripped probably 1 1/4" in all the wirenutted connections. Smoke mounting plates held on with sheetrock screws to the box. Sheetrock screws!!!
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Old 02-27-15, 05:12 PM
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The quality of the contact with the wire can influence the voltage readings. Try to take a reading at a receptacle while moving the probes.
Old 02-27-15, 05:29 PM
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Vic.....are those three wire smokes (black,white,red).... they communicate to each other ?

If yes.... it sounds like they are using the ground as the signaling line.

Sheetrock screws actually work pretty good in a plastic box.
Old 02-27-15, 05:54 PM
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Nope, there's a red for communication and the ground is just pushed up in the box.

PC, my probes won't go in deep enough in the slots, even though they are pretty small. I probably have an old junk three prong power cord so I may fab a widow maker out of one to see whats up. And the bare ground was clean and free of paint or joint compound. It was a good solid reading at the 2 smokes I checked. No fluctuation at all. It had a small loop at the end, so it was solid.

If outlets read the same, what would be something to check? In the panel maybe?

I mean, it's a rental, but if it's as simple as cleaning and tightening something, I can do that. I know the company would never end someone based on this info. Heck, they wouldn't pay to replace the 15+ y/o smokes and I'm still waiting for something about the non-functional dishwasher and the missing screens. Man I hate having to go back to renting after owning for 30 yrs.
Old 02-28-15, 06:31 AM
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Since you said such a specific voltage it sounds like you are using a digital meter. For home work I prefer an old fashioned analog needle type meter. They are not as susceptible to phantom current that can give wacky readings on a digital meter. And in general with an anolog meter you're just looking for the needle to swing over to about there so you don't sweat minor issues.

The detectors in my house have black, white and red wires. The ground is not used and the black and white power the detector and red is for communication between detectors. I'd just just wire up the detectors and test and not sweat minor voltage readings unless you're snowed in for the day and want a project.
Old 02-28-15, 06:42 AM
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" The ground is not used "

In the OP's case the ground wires might also not have been connected to anything*, and any voltage reading between that ground wire and something else is meaningless.

* Or, so as to be more confusing, ground wires might have been wire nutted together in some boxes but not others, thus still not having correct grounding.
Old 02-28-15, 08:05 PM
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Sheetrock screws actually work pretty good in a plastic box.
With a stripped thread on a plastic box or an older zip box I always liked a 1" X #8 panhead.

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