Question about electrical problems in home

[sunfire]

I'm wondering if anyone knows if a good forum to ask questions about electrical problems in my home.

The gist of it is the power outlets in two rooms measure 55 volts AC. All other outlets in the house measure 118v. Went into the circuit breaker box and measured across all circuit breakers. They all measured 118v, including the one circuit breaker that regulates the two 55v rooms.

 

[pcoxe]

If it is a three-prong receptacle, take these measurements:

Small slot to big slot (hot to neutral):

Small slot to round (hot to ground):

Big slot to round (neutral to ground):

Hot to neutral should be 118v, hot to ground should be 118v, and neutral to ground should be 0v. I'm suspecting that you are missing a neutral connection. These voltage measurements will help to determine this.

 

[sunfire]

Your help is much appreciated...

Small slot to big slot (hot to neutral): 54v

Small slot to round (hot to ground): 0v

Big slot to round (neutral to ground): 0v

Everything was fine until I ran the window AC a straight week while I was at home. I took out one of the outlets that isn't working and there is no ground wire attached to bottom of the outlet.

 

[river_rat]

Looks like an open neutral.

 

[pcoxe]

Having no ground wire complicates things. You need to pull out both receptacles and check the wiring. They are supposed to be parallel wired. A black wire should be on the brass terminal and a white wire should be on the silver terminal. One receptacle should have two black wires and two white wires. The screw terminals should be tight. A loose terminal can cause low voltage as well as dangerous overheating. Another thought, there may be a third receptacle that feeds these two that has a wiring problem. Turn off the circuit breaker and see if you have another dead receptacle. That will probably be where the wiring problem is.

 

[sunfire]

Originally Posted By: pcoxe
Having no ground wire complicates things. You need to pull out both receptacles and check the wiring. They are supposed to be parallel wired. A black wire should be on the brass terminal and a white wire should be on the silver terminal. One receptacle should have two black wires and two white wires. The screw terminals should be tight. A loose terminal can cause low voltage as well as dangerous overheating. Another thought, there may be a third receptacle that feeds these two that has a wiring problem. Turn off the circuit breaker and see if you have another dead receptacle. That will probably be where the wiring problem is.

Originally Posted By: river_rat
Looks like an open neutral.

Your help is much appreciated. It's going to take some time to take apart those receptacles. I think may even go to HD and get brand new outlets. Even though the ones I have now are only a few years old.

 

[kasedian]

Check all your connections starting at the breaker panel. Try to follow the circuit, starting at the breaker panel going to the first outlet, and so on. Check your voltage at each outlet before, and after you tighten your connections. Have a helper at the panel to turn it on & off when you're at the outlets.

 

[Jiles]

I had an old electrician tell me once "If an electrical problem doesn't make sense---check ground. He was referring to 12V DC automotive but the same holds true for home electrical, except it could be neutral.
This has helped me many times!

 

[JHZR2]

are these low voltage circuits fed via a secondary power panel? If so, check neutral and ground on it. That was the issue a friend at work had, 55V due to incorretly wired secondary expansion panel.

 

[spackard]

You may also have wiring in your house called a multiwire branch circuit.

If you poke around enough you may find an outlet in another room with 166V measured from hot to ground.

There's a form of wiring, common in commercial but not that common in residential: a multiwire branch circuit, where 220V is used to feed two branch circuits. When the circuit gets an open neutral you can get a very high voltage on the branch that has the lowest draw and a low voltage on the branch that has the highest draw.

Your running the A/C for a week sounds like it was enough current to open it.

I had this symptom in an in-law's house, '50's construction, in So Cal. They had a refrigerator on one branch and a microwave oven on the other branch, and the microwave ovens kept burning out even though the only thing using electricity was the clock. On their third oven, they asked me to look at it.

I traced the branch back to where the multiwire branch began, in a box with a socket, to a wire nut with 4 conductors in it. They had separated enough to lift the neutral. Twisting the conductors back together and then fitting a new wire nut fixed it.

There was a nice powerpoint file I found back then illustrating the problem but Google isn't what it used to be. This is the best I could find:
http://code-elec.com/userimages/Lost Neutral.ppt

 

[sunfire]

Originally Posted By: kasedian
Check all your connections starting at the breaker panel. Try to follow the circuit, starting at the breaker panel going to the first outlet, and so on. Check your voltage at each outlet before, and after you tighten your connections. Have a helper at the panel to turn it on & off when you're at the outlets.


I started doing this but using an "AC Voltage Detector", one of those wands that beep in the presence of AC. Leaving the circuit breaker off, outlets that don't beep should be connected to the off circuit breaker. And surely there is an outlet in the living room (1st floor) that looks like its in very bad shape.

The outlet was burned and the faceplate had a crack in it. This outlet is very rarely used if ever. I think the answer machine was plugged into it 3 years ago for about a year. I'm hoping this is the culprit.

The circuit breaker is still off. I need to take care of a few errands first. Then get parts from HD to do the repair. I snapped a bunch of pictures which I will post later. Thank you all for your help.

 

[eljefino]

Originally Posted By: spackard
You may also have wiring in your house called a multiwire branch circuit.

If you poke around enough you may find an outlet in another room with 166V measured from hot to ground.

There's a form of wiring, common in commercial but not that common in residential: a multiwire branch circuit, where 220V is used to feed two branch circuits. When the circuit gets an open neutral you can get a very high voltage on the branch that has the lowest draw and a low voltage on the branch that has the highest draw.

Your running the A/C for a week sounds like it was enough current to open it.

I had this symptom in an in-law's house, '50's construction, in So Cal. They had a refrigerator on one branch and a microwave oven on the other branch, and the microwave ovens kept burning out even though the only thing using electricity was the clock. On their third oven, they asked me to look at it.

I traced the branch back to where the multiwire branch began, in a box with a socket, to a wire nut with 4 conductors in it. They had separated enough to lift the neutral. Twisting the conductors back together and then fitting a new wire nut fixed it.

There was a nice powerpoint file I found back then illustrating the problem but Google isn't what it used to be. This is the best I could find:
http://code-elec.com/userimages/Lost Neutral.ppt


^ I like this idea. I was thinking, before you mentioned it, "sounds like California".

Also note stuff like computers and home electronics get by on 100-240 volts, so you might have some normal working stuff elsewhere that's getting off-power.

 

[Stu_Rock]

Agree on the shared neutral. It's very common in California residential wiring from a few decades back.

 

[tom slick]

A shared neutral is allowed by the NEC and California adopts the NEC with few exceptions so it's not something particular to the state. In fact, the main coming into your house is a shared neutral.

 

[sunfire]

I found the culprit. This was one of the few outlets that wasn't replaced when I moved in. Only the faceplate was. The Old outlet was a bit burnt and faceplate cracked from the heat. A bit of the plastic around the outlet was melted.

A few camera phone pictures were overexposed. Sorry, but I didn't take any after photos.

All work was done with the circuit breaker off. Verified with AC detector and then multimeter. But everything is back in one piece. Air conditioner is working again. At some point I'll have to get an electrician to rerun some of those wires to the circuit breaker box. And put in a bigger electrical outlet box.

Once again thank you for your help.

Photobucket stinks, they won't allow me to change the size the of the thumbnails.

 

[dishdude]

wow you really got lucky on that one, looks like it could have been a disaster.

How old is the house? I have never seen wirenuts that looked that old.

 

[sunfire]

Built in the 1950s. Nobody has touched that outlet since. Something should have been done about that outlet when I moved in. I'm going to inspect all the outlets and light switches very soon so this doesn't happen again.

 

[Stu_Rock]

Originally Posted By: tom slick
A shared neutral is allowed by the NEC and California adopts the NEC with few exceptions so it's not something particular to the state. In fact, the main coming into your house is a shared neutral.
You won't see it as often in residential wiring east of the Rockies.

 

[tom slick]

East of the Rockies has other rules in addition to the NEC also, such as Chicago requiring all wiring to be in conduit, residential included.