Odd electrical Problem

[Chris]

Today, I had two rooms in my house lose power for no apparent reason. Both rooms are connected through the same circuit breaker, but this didn't trip. I know that there was power in my house earlier in the morning. After checking all the breakers, and reseting them three or four times, power hasn't come back into the two rooms. Using my DMM, I get a reading of 0.3 V at all connections on that circuit. I've checked the power going through the circuit breaker, and it's reading 120V.

Does anyone have any suggestions as to what could have happened to cause a lose of power? There doesn't appear to be a short in the circuit as the breaker hasn't tripped. Could it be that the breaker is bad, and needs to be replaced? All advice and suggestions are welcome, thanks.

[Jeff Wisnia]

If you've got 120V at the output terminal of the breaker (I assume you measured it relative to the neutral bus in the breaker panel) then you MUST have an open circuit somewhere, probably at a terminal screw on some device like a receptical, or a loose wirenut joining two or more wires.

It's what we used to call a "loose disconnection somewhere".

Because you weren't to clear about describing what you measured 0.3 Volts TO, the open circuit could be in either a hot (black) lead or a neutral (white) lead.

Start looking for an open connection, but don't electrocute yourself in the process.

HTH,

Jeff

[Joseph Meehan]

You did not say, but the usual cause is a GFI. Are all your bathroom, garage, outdoor and kitchen outlets working? If not start looking for the GFI's and reset them.

Other than that it means the first outlet that is not working or the last outlet that is working on that circuit has the problem. The likely problem is this case is a wire has come loose from one of the back stab connections at the outlet. You need to take a look to find it.

Note: that small voltage you are reading is meaningless, ignore it (pretend it is 0) On the other hand don't assume any of the outlets or other devices are safe to work on, there could be a powered wire in the box so be careful.

[Charlie Bress]

Along with the other suggestions (personally I vote for the back stabbed connection) be very sure that the breaker you are turning off is the right one for that branch.

Charlie

[kv888831393ster]

I just worked on a ladies house that had that exact thing happen only it was a shared backstabbed neutral that came loose. It blew the TV, DVD player and a Sony clock radio in the bedroom. The clock radio needed a fuse replaced in the xformer but the TV and DVD might be DOA. When you check the voltage, check it to ground or use an AC voltage probe. If the hot is gone trace it back toward the box you'll probably find a bad connection or popped back stabber in the circuit somewhere. Richard

[MoM]

We had a similar problem in our home. The power to our unit was underground and the freeze and thaw had caused the cable to first partially break and then completely break and we lost all power. The cable had to be replaced.

[Chris]

First thing, when I checked the voltage at each outlet, switch, and GFI, at the terminals where the wiring connects, the wiring itself, and into the outlet openings. I checked with both hot to neutral, and hot to ground, and got the same reading at all points (0.3, or basically zero.) I did this with my DMM set to AC voltages.

One of the first things I did was to check the GFI in the bathroom, as it is at the tail end of the circuit. It wasn't tripped, but I did test it, and reset it twice. All other outlets and lights work in the house, and the only GFI is in the bathroom (twenty year old house).

I've checked most of the wiring that I can get to, except that attached to the GFI in the bathroom. I didn't think that it was possible for the wiring to pull out of a recepticle, like it has been described here, but I'm going to start retracing everything tomorrow morning. It's really dark right now in that part of the house.

Thanks for the help.

[Jeff Wisnia]

Uh, Chris.... I presume that GFI is at the "tail end" of ANOTHER circuit, not the one that's dead, right?

It does very much sound like you've got an open in the hot lead, as it's unlikely BOTH the neutral and ground leads would developed open at the same time, though a ground lead could have opened years ago and not get noticed.

Good luck,

Jeff

[ChrisCoaster]

_______________________ I've got an amusing back-stab tale for you all..

I never liked back-stab(stick wire in no screw required) for as long as I've been on the other side of a common recept. I don't know why. Something about them just screamed "insecure!!".

15 years later: Present day. Last month, I had a hunch that the outlets in my apartment may not be totally up to snuff. So I check a few of them out and sure enough - backstabbers.

In total I converted 4 outlets to "side-wind"(wire around copper side posts) and rehabed an existing side-wind(snipped back the wires and re-torqued them.) The outlets were all part of the living-bedroom exept for one - a kitchen branch for small appliances.

Now I'm not kidding you - but both the living- and bedroom TV look better - sharper, more accurate colors, less "fuzz" or background interference. The sets both produce an awesome picture even with Contrast turned down to 40% of max. The surround system connected to that livingroom set sounds better, too.

I'm sure I'd get the same results with a "back-screw" wiring, but please - ANYTHING but a back-stab!

-ChrisCoaster

[Mark Lloyd]

Do you mean the ones where you put the wore in the hole, then tighten a screw? That sounds good.

[kv888831393ster]

Well as this poster says you must have an open somewhere. Since the hot and neutral both test 0 the open is probably in the hot also as this guy says.

Well if there's no power you couldn't test it. You can't reset it 'cause you can't test it. Look back toward the box. You might have to take the panel off. (don't do this if you're not comfortable with it) to see where the circuit leaves the box. Then you need to find where all the boxes where the connections are. Most codes require theses to be visable and available but I have seen them buried. Easiest behind drop ceilings, worst behind drywall. BTW non metalic sheath, conduit or BX? Richard

[lp13-30]

I have seen more than one backstabbed plug that looked perfect (not visibly loose or burned), but was not making contact internally, causing the plug and others down the line to be dead. Backstabbing should be illegal. Hell, it shoud be illegal to make a device that can be backsabbed.

[lp13-30]

Forgot to ask, do you by any chance have a window a/c in one of the rooms that went dead? Regardless of what the a/c sales people/ads tell you, window a/cs should be on their own separate circuit. If not, you are just begging for problems.

[Chris]

Actually, I did have a window a/c in the room before it lost power. As for the rest of the story, I've checked all the receptacles, switches, fixtures, anything that's part of that circuit. Nothing looks out of the ordinary. Since I've never trusted the backstabbed approach, I've taken the time to attach all the wires to the screw posts on the respective piece. But when I've checked the voltage on the bare wires, I still get nothing with the breaker on. I replaced the GFI in the bathroom, which is the start of the circuit it looks like, and took the other one and tried to test it on a good circuit in the house. It won't reset, and shows no power going into it (when properly wired) so I'm guessing that's bad. But the new GFI isn't getting power to it to allow me to reset it.

Can anyone tell me how to test the circuit breaker? I'm thinking that must be where this problem is lying. When I tested it, I checked to see if power was going from the hot bar, to the nuetral bar, with my DMM. I got 124V. Then I checked the screw where the wire attaches too, to the nuetral bar, and got 124V. I didn't turn off the breaker because I assumed power was flowing through it, becuase of the voltage reading.

Thanks for all the help, I'm going to still troubleshoot this until I save enough money to call an electrician.

[Chris]

Well, I finally found the cause to why I lost power in my house. My smoke detector, which is hard wired into the house, was shorting out and melted part of the wiring. Currently have that part of the circuit isolated with no power to prevent it from causing a fire. Now to call the electrician to fix that. Thanks for all the help.

[hallerb]

I would have such important loads put on a dedicated breaker, if for no other reason than a short could:(

Cause oiverheat

Start fire

trip breaker

Shutting off power to some detectors:(

NO ALARM WHEN YOU NEED IT THE MOST!

[Thomas D. Horne, FF EMT]

Many local codes require that the detectors be powered off of a main lighting circuit so that they can not be readily turned off. YMMV