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Old 02-27-2012, 11:28 AM   #1
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trouble shooting a bad nuetral in your house


Having diming lights sometimes extra bright, have unblanced load in outlet, belive I have bad nuetral connetion in the house. Power co. Hasbeen here 3 times cheking my service. Would like to know systematic way to find problem.

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Old 02-27-2012, 11:40 AM   #2
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trouble shooting a bad nuetral in your house


If this is in your whole house then the neutral wire somewhere is lose in the main panel or meter socket. What did the power company check when they were there?

If you are not comfortable or not capable of working in the main panel then it would be best to get an electrician that knows what he is doing to check it out.

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Old 02-27-2012, 05:22 PM   #3
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trouble shooting a bad nuetral in your house


What have you checked so far ?
What testing quipment do you have ?
What did the poco check ?
What type size main panel do you have ?
One hot in ? or two ?
Is there a pattern to the fluctuations ?
Are all circuits affected or just some ?
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Old 02-27-2012, 05:58 PM   #4
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trouble shooting a bad nuetral in your house


Take appropriate precautions while working inside the load center. The dangers are shock and arc flash.

Divide the problem into regions by first checking if the high resistance connection is in your panel or upstream of your panel .

Do this by finding a place where the fat neutral conductor is not covered by insulation at the point where it goes into the bolted connection. Call this point A.

Measure the voltage drop between the bare fat neutral conductor and the bolted connection in your panel while someone switches on and off a 120v, 10A or 15A load. If you see several volts change then this connection is your problem.

If not, measure between point A and a known good ground. If there is a voltage change now, the problem is upstream of point A.

If the problem is the neutral busbar in your panel the main problem is getting access to points on which to place the voltmeter probes.
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Old 02-27-2012, 06:45 PM   #5
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trouble shooting a bad nuetral in your house


Check all the screws and set screws in the panel to be quite tight, although do not use tremendous strength.

Measure voltage between the neutral bus bar (terminal strip with all the white wires) and different circuit breaker screws in turn, as someone upstairs turns on the hair dryer as described above. When the hair dryer is on, do all of the breaker screws give you one of two readings (high or low) or are some of the screws giving the normal 120 volts with others high or low (problem not upstream of the neutral bus bar)?
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Last edited by AllanJ; 02-27-2012 at 06:52 PM.
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Old 02-27-2012, 06:55 PM   #6
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trouble shooting a bad nuetral in your house


When testing in the main panel make sure you have a really good set of test leads not some cheap set. They should have a rating on them. You won't notice a voltage drop unless there is a load placed on the conductors being checked. Checking for resistance with the main off is a good way to check. Just don't test the resistance of any conductors going into your main breaker. Make sure everything is tight but again don't touch the two wires going into the main.
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Old 02-27-2012, 08:21 PM   #7
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trouble shooting a bad nuetral in your house


I had a similar situation and since a loose neutral is one of the most frequent sources of electrical fires I panicked while looking for the cause. I placed a logging voltage meter in different recepticals and was getting a consistent range of 80ish to 170ish volts. I had unplugged everything 120v other then lighting. After hours of searching and probing and snugging alot of connections in several panels I resorted to phoning my power co. and asked if they had reports of voltage fluctuations in my area. It was after midnite and within 15 mins. a lineman was out there checking the meter box. He said the voltage was correct so it had to be on my side.

I know... long story but in the end after a sleepless night and another long day I convinced them to put in a logging meter. Within an hour the voltage swing occurred and I phoned them to check it out. When they came back they plugged it in to a laptop and the guy immediately went up in his lift and re crimped the lugs to the line coming from the transformer to the meter. After that the problem never occurred again but they did leave the meter on and sent me the printout showing the range over the next week of 113-123volts.
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Old 02-27-2012, 08:45 PM   #8
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trouble shooting a bad nuetral in your house


Any trees in your yard that overhead lines pass through?
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Old 02-28-2012, 08:33 AM   #9
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trouble shooting a bad nuetral in your house


Quote:
Originally Posted by Daltex View Post
80ish to 170ish volts
the range over the next week of 113-123volts.
So the first line shows a variation due to normal line variation plus the neutral resistance x neutral current (which varies depending on what appliances are on and on what side of the neutral they are on.

If your normal line voltage is 118 +/- 5 v and you saw 80v that means 38 +/- 5v was lost in the neutral connection. With 10A in the neutral due to load unbalance this bad connection should have measured 3.8 ohms. The other side of the line should then have measured 118v + 38v at the same time.

Last edited by Yoyizit; 02-28-2012 at 11:18 AM.
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Old 02-28-2012, 10:17 AM   #10
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trouble shooting a bad nuetral in your house


As others have said if the problem affects multiple circuits in the house the problem is in your panel or upstream on the power company side. If this is only one circuit the problem is now an Easter egg hunt to find it. Start in the panel and work downstream.
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Old 03-02-2012, 07:09 PM   #11
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trouble shooting a bad nuetral in your house


The power meter case is supposed to be bonded to the neutral, and upstream of this point is PoCo's problem.

So, if your DVM is protected on the ohms range, with all CBs off measure the resistance between the meter case and your water pipes. Anything over 0.1 ohm is a problem.

The reason your meter should be protected is that there could be AC current (I've measured 50 mA AC in the grounding conductor and there might even be a DC component to this current) in the section of line that you are measuring. and while it won't screw up your ohms reading it may cause damage in your DVM unless it's protected.

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