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ianmac 05-27-2010 09:08 AM

Neutral Problem
 
Yesterday I lost power to all the outlets in our master bedroom. The outlets in one other bedroom are on the same ciurcut and appear to be fine.

The cuircuit in the master bedroom has 7 outlets, 2 of which are controled by a 3 way switch (One switch by the door, and one by the bed).

All the outlets are testing like this:

Hot to Ground: 121.5 volts
Neutral to Ground: 22.5 volts
Hot to Neutral: 98.5 volts


A friend of mine suggested that there must be a problem with the Neutral in one of the outlets.

I'm in the process of replacing the outlets, in hopes that one of them is causing the problem. I have replaced 3 out of the 7 so far, and the problem remains.

Am I going about this the right way?

AllanJ 05-27-2010 09:56 AM

Quote:

Originally Posted by ianmac (Post 447531)
Yesterday I lost power to all the outlets in our master bedroom.

Hot to Neutral: 97 volts

As I understand it, the Hot to Neutral should be around 118.5 in this situation. (am I correct?)?

Yes the hot to neutral should be around 118.5 volts, except that, as you said, it is not working.

With one batch of outlets dead and another batch live on the same circuit, it is possible that the bad connection is at one of the live outlets, specifically where the wires continue on to the dead group.

I am guessing that the neutral is broken somewhere and you are measuring phantom voltage of 97 volts. Phantom voltage is a phenomenon that is very lengthy to explain and it is more likely to be measured with modern digital voltmeters. Phantom voltage is measured in a dead line that runs within a cable juxtaposed with another line including a ground wire that could have completed the circuit.

Example: Hot wire is intact supplying 120 volts. Ground wire is intact. Voltmeter probes touched to hot and neutral. Neutral is dead but miniscule amount of current can leak between it and the ground wire, through insulation and all. A circuit is indeed complete although only a few microamperes can make the jump from neutral to ground, but enough that the meter's internal circuitry rates it as 97 volts. Next, measure neutral to ground. Hot wire in the same cable leaks a miniscule amount of current into the dead neutral running alongside, the voltmeter picks it up and through the voltmeter circuitry to ground, the current happens to cause a readout of 1.5 volts on the meter. Different brands of meters will read out different numbers.

A test that electricians often do to avoid confusion with phantom voltage is to use a small incandescent light, say 25 watts, with the terminals or leads acrross the supposedly 120 volt circuit. When phantom voltage is involved, it will not light up the bulb and will be seen to drop to zero when both the light and the voltmeter are put across the circuit.

Yoyizit 05-27-2010 11:13 AM

Quote:

Originally Posted by ianmac (Post 447531)
I'm in the process of replacing the outlets, in hopes that one of them is causing the problem. I have replaced 3 out of the 7 so far, and the problem remains.

Keep those outlets unless they do not grip plugs tightly.

ianmac 05-27-2010 11:14 AM

Sorry Guys.. I'm an idiot.

I messed up when I first posted the question. I said that the neutral to ground was reading 1.5, when in fact it was reading 22.5 volts. (1.5 is what the neutral to ground reads when the breaker is off.. which I think is irrelevant.)

So... Any idea why I'd be having this problem? FYI.. I have now replaced 6 out of the 7 outlets with no effective change. I'll run off to Home Depot today to get one more outlet, and two three way switches so I can try swapping them out too.

By the way, the one outlet that I have not changed is the only one with just one hot, and one neutral line. Am I right in guessing that it is the last outlet on the circuit?

ianmac 05-27-2010 11:19 AM

After reading Allen J's response, I guess my next step will be to check the connections at the live outlets in the other room. Should I continue with the outlet replacement regime, or do you think I'll be able to identify the bad outlet / bad connection some other way?

brric 05-27-2010 11:22 AM

Bad connection could be in a switch box not necessarily in a recep box. Is everything else in the home operating normally? Had any bad storms or high wind lately?


BTW in a normal circuit hot to neutral should be the same as hot to ground.

Yoyizit 05-27-2010 11:27 AM

Quote:

Originally Posted by ianmac (Post 447585)
Am I right in guessing that it is the last outlet on the circuit?

An outlet downstream or upstream of another?

Always start with your meter on the highest range.

With everything unplugged on that branch circuit put a 10A load on outlet A. Measure between the empty H slot of this duplex outlet and the empty H slot of outlet B.

If you read 'zero' volts there is no current flowing in the hot lead and so outlet A is upstream of outlet B.

If you have 10' of #14 copper between outlets and if outlet B is upstream of outlet A you should read 0.26 vac between the empty H slots of these duplex outlets.

ianmac 05-27-2010 11:40 AM

Quote:

Originally Posted by brric (Post 447591)
Bad connection could be in a switch box not necessarily in a recep box.

I figured that too.. that's why I'm going to go to Home Depot to grab a couple of new switches.

Quote:

Originally Posted by brric (Post 447591)
Is everything else in the home operating normally?

Yup

Quote:

Originally Posted by brric (Post 447591)
Had any bad storms or high wind lately?

A fair bit of wind.. but that is normal around here... curious why that would be an issue?

Quote:

Originally Posted by brric (Post 447591)
BTW in a normal circuit hot to neutral should be the same as hot to ground.

I tested some working outlets, and came up with that conclusion on my own.. I'm a newbie with this stuff.. so I'm happy to have my assumptions confirmed.

Now to figure out why the neutral to ground is reading 22.5 volts.. I imagine that accounts for the drop in the hot to neutral reading.. The neutral line is "bleeding" 22.5 volts off somewhere?

ianmac 05-27-2010 11:52 AM

Quote:

Originally Posted by Yoyizit (Post 447584)
Keep those outlets unless they do not grip plugs tightly.

Will do... Thanks

Quote:

Originally Posted by Yoyizit (Post 447595)
An outlet downstream or upstream of another?

Always start with your meter on the highest range.

With everything unplugged on that branch circuit put a 10A load on outlet A. Measure between the empty H slot of this duplex outlet and the empty H slot of outlet B.

If you read 'zero' volts there is no current flowing in the hot lead and so outlet A is upstream of outlet B.

If you have 10' of #14 copper between outlets and if outlet B is upstream of outlet A you should read 0.26 vac between the empty H slots of these duplex outlets.

Sorry.. I'm a real newbie at this.
  • Any suggestions for a good 10A load?
  • What's an H slot?

brric 05-27-2010 12:30 PM

It's not the swithces. Swithches only switch the hot conductor. There may be a loose neutral in a switch box however.

The wind issue comes into play if other parts of the house are acting up-showint strange voltages. A loose service neutral would be suspected.

Yoyizit 05-27-2010 01:17 PM

Quote:

Originally Posted by ianmac (Post 447606)
[*]Any suggestions for a good 10A load?
[*]What's an H slot?

A toaster or hair dryer will pull 10A to 15A or so.

H = hot, the short slot on a correctly wired outlet.
N = neutral, the long slot
G = ground, the round hole

The voltage drop along the single conductor will be different for copper vs. alum wire, other distances and whether it's #14 or #12, but it can be calculated.

joed 05-27-2010 01:53 PM

You definitely have an open neutral. If you know or can guess the route the cabling takes around the room then the problem is inthe first not working or the last working device on the circuit. The problem could be in a a switch or light also if the power goes through them to the receptacles.

Most common cause of this problem is back stab connections on recpetacles. Use the screws for making connections.

ianmac 05-27-2010 01:59 PM

Quote:

Originally Posted by joed (Post 447671)
Most common cause of this problem is back stab connections on recpetacles. Use the screws for making connections.

If I try to pull the back stab connection and the wire breaks off inside, is the receptical garbage now, or can I safely use the screws instead?

AllanJ 05-27-2010 02:31 PM

Quote:

Originally Posted by brric (Post 447572)
Can you give us some documentation about how current leaks through insulation? I'd love to know about it. I'd also like to know about currents between neutral and ground in a properly installed circuit.

Phantom currents "leaking through insulation" are due to capacitance. When AC voltage is present (relative to something such as ground) on one metal object and another nearby metal object is bonded to the same something (ground) then a flow of current is induced. In the situation, the two metal objects are lengths of wire in the same Romex cable.

The material (plastic, air, glass, waxed paper etc.) separating the two metal object influences how much current will flow, as well as other things such as voltage, AC frequency, distance between the metal objects, surface area of the metal objects, etc.

Quote:

Originally Posted by ianmac (Post 447678)
If I try to pull the back stab connection and the wire breaks off inside, is the receptical garbage now, or can I safely use the screws instead?

Probably not. If something inside the switch or receptacle got deformed during your efforts to yank the wire out, it's not safe to use any more. Also, the loose piece of wire could migrate within the switch or receptacle and cause a short circuit.

joed 05-28-2010 05:03 PM

And what has all this got to do with the power loss the OP is experiencing. NOTHING.


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