[wlawless]

I have discovered that there is an open neutral condition in three of my home's rooms.

First, one of the bedrooms has an open neutral. I tested three receptacles on one side of the room. The end of the line is fine. The first two receptacles show the open neutral in the bottom outlet; the bottom outlets are on a wall switch. When I plug a lamp into one of the bottom outlets, the open neutral goes away. The multilester indicates 122 volts on the top outlet; about 29 volts on the bottom outlet when the wall switch is off.

Second, in another bedroom, again, open neutrals on two receptacles where the bottom outlet is controlled by a wall switch.

Third, in the living room, open neutrals on the bottom outlets of the receptacles where the bottom is controlled by a wall switch.

Based on what I have read, I have done some basic troubleshooting to look for loose neutral wires, etc. However, I am starting to believe there is a pattern here and the open neutrals in several rooms might indicate an overall problem with the house electrical versus a loose wire in one room.

Any information that you could provide will be appreciated.

Thanks,

Bill

[bhayne]

First, if the receptacles had an open neutral, they would not work.

Second, if you have a problem, tell us. I don't see any problem from what you have described.

[jgj6331]

What first made you decide to check your wiring? Are you testing (with your meter) with the switch on or off? With the wall switch off, you should get a "0" reading - not 29 volts. Are the switches the illuminated type - if so. It might be possible to get some bleed through voltage through the neon bulb used in them. This could also occur if you have any wired-in device like X-10 remote control switches or outlets. If you still have questions, your best bet would be to hire a professional to ferret out the problem (if there actually is one) for you.

[labman]

I know shared neutrals give flaky reading on an unpowered circuit. If a circuit shares a neutral with another circuit on the other hot leg, you will get a voltage reading on the other circuit with the breaker off. Perhaps the 2 halves of the outlets are doing the same. If you get good readings with the switch on, likely there isn't a problem.

I never worked with those testers, and am not sure how they work, and how the would react to your conditions.

I am not saying you have a shared neural, just getting a flaky reading like they would give.

[tkrussell]

First let's be clear, there can be an open neutral on a two wire circuit, which sounds like what you have, with the 29 volts. There can also be an open shared neutral, where one neutral wire is shared with two circuits.

A broken, or opened, shared neutral circuit, can cause one circuit to be much higher than 120 volts and the other to be much lower. If tested correctly, adding the two voltage readings can add close to 240 volts.

If you believe there is an open neutral, one troubleshooting method is to be sure nothing is ON or plugged into the circuit. This will prevent the possible "backfeed" or reading through a light bulb or appliance. This is what I believe is causing the 29 volt reading, which I assume is testing across the hot and neutral at that outlet. Testing across the hot and ground should result in 120 volts.

Before just testing and wondering what is going on and trying to figure out what to repair, you really should be sure what type of circuit you are dealing with. This entails opening the panel to check if the circuit or circuits are two wire or three wire.

Opening the panel and handling the wiring inside the panel requires extra caution and knowledge. Be sure to know your capabilities before opening a panel. If your not sure, best to hire a qualified electrician.

[labman]

Shared neutrals aren't common in residential construction. Perhaps you can check without opening the panel. Try turning the circuit breaker above and below the one for that circuit. Usually shared neutrals use adjacent breakers. If the 29 volts disappears, likely it is a shared neutral.

Before tkrussel educated me, I feared a poor little #12 shared neutral carrying 40 amps. It doesn't work that way. It is more like your stove where the controls for the burner can select either a hot wire and a neutral or 2 hot wires. The 2 circuits with a shared neutral are sort of like the 240 volt burner, the 120 volt loads in series with the neutral carrying the difference, not the total.

[ceilingfanrepair]

I don't know what's common and what's not, but my parents house, built in the 50s, every circuit shares a neutral with the one next to it. About 10 years ago or so they replaced the old Federal Pacific panel (perhaps TK and I can share a look on that one) with a new Siemens, and the wiring was left the way it was.

At one time there was an open neutral in the basement (my fault, I disturbed some wiring adding a new light fixture) and the result shorted out several fluorescent ballasts and a number of other things. So I learned a lesson about shared neutrals.

[omzig]

Shared neutrals aren't common in residential construction.

Not so sure about that. I have seen many houses with shared neutrals. I buy old houses, renovate them, and sell them for profit. Most of them either have knob and tube, or had knob and tube and were rewired at some point. I'd say that 3/4 of the rewires were done with shared neutrals.

[tkrussell]

Yes shared neutrals, using three wire circuits are very popular in homes, esp tract or subdivision homes, built to code but to save money and get the job done quickly. These work great until a loose connection happens and are notorious for causing problems such as wlawless is having.

Assuming he is correct about the 29 volts, which I need to take at face value, there is obviously a path, regardless if the switch is off. So the circuit needs to be completely looked at to understand what the circumstances are and to begin checking for the fault.

[wlawless]

Thanks to all for your valuable insights. When I get a chance I will isolate the circuit by shutting off breakers, and trying the suggestion(s) made above.

In the mean time, based on what all of you answered, I am sure that there are 29 volts with the switch off. This 29v shows up in the first recep of a 2-wire recep; 29v hot to neutral and 29v hot to ground. The wires then jump to the second recep that also shows 29v, then ends in a single wire recep that checks out fine.

I am using a little yellow tester made by A.W. Sperry. The open neutral is based on the Sperry tester. Given that 3 separate rooms have the open neutral indication, perhaps something unusual in the house wiring. I'm not a pro, but know enough to get around and do minor troubleshooting and repairs.

The house is 9 years old, so assuming code was met (or close) at that time.

Thanks again for all responses - they are appreciated.

[tkrussell]

OK I got to ask.. what is a "single wire" receptacle? Now you got everyone confused.

Do you mean that two of the duplez receptacles have a hot wire for the top outlet, and another wire for the bottom, to create a split receptacle? This is done to have a 24 hour hot outlet and a switced outlet in one duplex receptacle. If this si so, then there is a small metal jumper between the two brass screws that needs to be pried out to create a spilt receptacle with half switched.

Are these three outlets controlled by the one switch?

What meter are you using to read the 29 volts?

Seems you are paying attention to if there is two wire or three wire. However, you need to trace this and any circuit completely back to the panel to be sure if you are dealing with a true two wire or three wire circuit. A three wire circuit can go a distance , then split off one circuit in one direction and the other in another direction. You may be working at the end of a circuit , and not realize the feeder is a three wire with a shared neutal.

Since your getting 29 volts H-N & H-G to a wire that is switched, and that switch is off, I suspect a problem with the neutral/grounding, since they are common at one point in the distribution system.

If your using a multi-meter to read actual voltage, I would extend one test lead with a long wire to a known soild ground. And since there seems to be a problem that is spanning several circuits, I would not trust any nearby outlets and I would bring this wire back to the main water line or the panel. Then test the wires at these affected outlets.

I would hope the home was built to code at the time of construction. This is all that is required, as any older home never needs to meet any newer code, unless new work is done, then that new work needs to meet any newer code.

[abcdefgg]

Just had a similar problem, turned out that the white wire in the panel box was not fastened tightly and had the insulation partially into the terminal block causing the open neutral condition...