fluctuating voltage


Old 02-06-17, 04:41 PM
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fluctuating voltage

I moved into a house that sat vacant for a while and have started remodeling. The house is all electric with a 200 amp service box. I noticed that a plug in fan would speed up then slow down, no obvious reason why. Traced a few circuits out and tightened up a few receptacle connections but no help.Before I found the cause, it stopped. A few days ago fans started speeding up and slowing down again. Turned the microwave on and it slowed to an almost stop before I cut it off. Got a multi-meter out and saw that when the microwave was turned on on one circuit, another circuit jumped from 115 volts to 139 volts. Today, I turned off every breaker, turned off the main breaker (measuring at the service cable coming into the service box) and the voltage on each leg was 123, steady. Across both legs it was 245, 246, 247, constantly changing.
I got two new receptacles and wired approx. 20" of #12 wire to each receptacle. I then wired one receptacle to the left leg through a breaker with nothing on it except this test receptacle. I wired the other test receptacle to the right leg with nothing on it except that test receptacle.
Each test receptacle had 123 volts steady. Measuring across the hots on both receptacles the voltage was 244, 245, 246, 247, 248, constantly changing.
I connected a 1500 watt space heater to the right test receptacle and turned it on. The left test receptacle went to 130 volts.
I connected the heater to the left test receptacle and when I turned it on the right test receptacle went to 130 volts.
I ran a #18 extension cord ( I know, not good to do, but I did not want the carry the microwave to the service box) from the microwave to the left test receptacle. When I turned the microwave on, the right test receptacle showed 148 volts. I switched the extension cord to the right test receptacle, turned on the microwave and the left test receptacle showed 144 volts.
The fans that speed up are doing so because the voltage is going to 130 volts. The fans that slow down show a circuit voltage of 99 volts.
From reading on this forum it seems (to me) I have an issue with an open neutral. Is there any other way I should check to make sure? I would like to be sure the problem is above the main breaker, not on my side of the main breaker. thanks, greg
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Old 02-06-17, 05:22 PM
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Call the electric companies emergency number now and tell them you thinik you have a bad neutral.
Old 02-06-17, 07:05 PM
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I would like to be sure the problem is above the main breaker, not on my side of the main breaker.
Then you would make your test measurements at the cable where it comes in from the meter and connects to the main panel.

However.... the problem is not going to be the main breaker.

Typically the neutral problem will be before the main panel. It will be at the service hook where the drop connects to the service cable or at the meter itself.
Old 02-06-17, 10:19 PM
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With an open neutral you would not have a return path for the current. You have a loose neutral.
Old 02-07-17, 07:59 AM
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Call the electric company as suggested. This is free in many locations. Tell the guy who comes out what the problem is, request that he "re-torque" your main lugs - electric meter wiring connections and main panel wiring connections.

High amperage electrical connections need to be torqued with a torque wrench to the proper tightness as specified by the panel manufacturer - should be on panel label or panel installation instructions. If these connections are not properly installed, they can heat up and work themselves loose!

So sort of like a plug in a loose outlet - you "jiggle" it, then the gizmo works for awhile. But replacing the outlet, so you then have a "tight" connection to the plug, will make things work properly.
Old 02-07-17, 08:25 AM
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Thank you for the quick replies. This reminds me of the old adage that it never acts up when you try to show it to someone........... I just checked and the microwave is doing fine. All breakers in the panel are back on and fridge and other items on. Measuring above the main breaker: With the microwave running, the left leg is 114 volts and the right leg is 126. With the microwave off, the left leg is 124 and the right leg is 119 (I don't know what appliances are running and which are not). Unless you say to wait, I will go ahead and call the power co to check and "re-torque" my main lugs as suggested. thanks, greg
Old 02-07-17, 09:05 AM
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Have them come out ASAP. This type of problem only gets worse over time. If you fix it fast you can prevent or reduce expensive damage.

The most common cause is probably wind causing wires to swing on the pole and working the connections a little loose. The power company can likely fix this in 10 minutes.
Old 02-07-17, 10:32 AM
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Just wanted to let you know, I called the power co. A crew was out in less than an hour and pulled the meter, tested then checked at the first service pole and found a squirrel had chewed the neutral up and they patched it and put in a service order to replace that line (after it stops raining!). So I think I am good to go. Thanks to everyone and your good advice. You guys are great!
Old 02-07-17, 05:03 PM
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Thanks for letting us know the outcome. It sounds like you are in good hands.

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