Help Diagnose Another Electrical Question
 

Sometime recently I noticed that an outlet out on my deck lost power. There are no breakers thrown in the panel. I checked the outlet itself with a multimeter, and sure enough it was dead. I then tested the incoming wires to that outlet to see if was possibly just a bad outlet, but the wires too were dead. I then traced back the wiring to a junction box in the joists in the basement. In that junction box, I removed the wire nuts that joined the suspect wires to the source wiring.

This is where it gets puzzling. I am seeing approximately 158-160 volts AC at those wires! Now, that obviously means that there is power to that junction box, which seems to indicate a bad/exposed/shorted wire somewhere between that junction box and the outside outlet. Ok, that is about a 20 foot run, so it should be easy to test/replace.

My bigger question is around the voltage in that junction box. Why would it be 160 volts?? That is too much for 110 service, but not enough for 220 voltage. I'm no electrician, but that seems very odd to me. See pictures below. I tested both the hot (black) to neutral (white), as well as hot (black) to ground (bare copper). Results were the same.

Any thoughts on what is going on here, or if I am misunderstanding something?

Thanks,

JA

http://forums.pelicanparts.com/uploa...1346011393.jpg


http://forums.pelicanparts.com/uploa...1346011430.jpg

Probably a floating neutral. Check the hot wire to ground a post the voltage.

I did that. It is the second photo above. Same result.

JA

Do you have the meter set to AC volts not amps?

what else has lost power

If it was 159 Amps we'd be seeing smoke and sparks.

Check another outlet, do you get 115-120v?

Meter is set at 200 VAC. Nothing else has lost power.

Just checked two other outlets and they are both reading 160 VAC!! Thanks for asking me to check that dad!!

That means my meter is wacky?? Could a weak battery cause that, or is my meter shot? Odd that it is so consistent in converting 120 to 160!!

Thanks much!!!

JA

Just changed the battery and getting 124.9 VAC now in the other outlets. Is that ok, or still too high?

Thank you!!!!!

JA

I figured it was a wonky meter. No matter, no voltage at the other outlet means a break in the connection somehow. Loose wire, or there is a junction somewhere in between. Not supposed to do it, but I've seen splice connections behind sheetrock walls, so don't make assumptions when tracing the wires.

Its a shot in the dark but check your GFCI outlets to see if any of them have popped.

Another thought, test outlet while someone else switches all of the light switches in the area.... one might be wired wrong......

That was my first thought, as this is a "relatively" new home. But since I can visually see the wire that goes to this outlet over its entire length, I have verified that there is not a switch in the circuit. I think I am just down to replacing the 20' or so run of wire, which should be too bad. I do wonder where the break is, and why it appeared out of the blue. Replacement will require a bit of fishing, and then I can pull the old piece down and inspect it closely.

Thanks,

JA

Before the battery change I was going to ask if the meter was reading peak voltage instead of root-mean-square value. :)

Get one of these and run it along the cable. The light will go out as you pass the break. You'll likely find a screw or nail penetrated one of the wires and contact was eventually lost.

Look for a staple though the wire.

Breakers go bad....Might not be tripped, but not passing power.
Next, shut off the breaker and see what other outlets/switches it controls.....Might have a bad connection at an outlet/switch before it gets there?

If all else fails, disconnect the wires at the breaker box and check continuity........

Milt....THANKS for that suggestion!! I bought one tonight, and will try to trace to identify the break. Maybe unnecessary to actually find the fault since I will need to replace the wire anyway, but I like to know (and see) exactly what went wrong so I can make sure I got the root cause, and also avoid repeating!!

Thanks all for the feedback! Pelican to the rescue, again!

JA

Glad you got one. They come in handy for more than tracing an open. Someday you might go into a box that you thought you had killed all the breakers for and yet there is still a live wire in there. Non contact voltage testers will alert you.

Found the problem!! 2 minutes with the non-contact voltage detector that Milt suggested made short work of this diagnosis. Turns out that a genius cable tech drilled through the rim joist to route another cable line out to the satellite dish on the deck. When he did, the hole he drilled was about 1 inch away from where the power wire passed through the rim joist. He drilled at an extreme angle, and ran into the power wire (possibly a shocking experience from the looks of it!) Anyway, the power wire is clearly breached there, with torn insulation and a broken/exposed piece of copper! The break is literally in the middle of the hole, so it wasn't presenting any immediate danger.

Should be an easy fix. I need about 30' of exterior 110V house wire, and will have to re-fish it up through the hollow steel spindles on the deck, and up to the outlet. Re-staple it, and tear out the old wire. Probably no more than an hour or so work.

Thanks to all, especially dad911 for forcing me to validate my multi-meter, and to Milt for suggesting the quick working non-contact voltage detector! Money and time well spent!!

Thanks again,

JA

I'd have a chat with the satellite company. Blind drilling like that is BS.

Glad you found the problem.