Very Low Voltage

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Old 02-18-12, 08:21 AM
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Question Very Low Voltage

I have a small outbuilding that I use as a pottery studio. The electricity has worked well since the studio was built a couple of years ago. Then yesterday morning I experienced a problem with very low voltage on one circuit in the building. All the other outlets and lights work fine. When I plug in a 3 prong tester it indicates that the circuit is good but it doesn't have enough energy to light a 60 watt light bulb.
I took a hand mixer from my kitchen and tested it on the line, the motor turns but very, very slowly --really hardly at all.
I have replaced the circuit breaker, that did not help.
I isolated and replaced the first outlet, that did not help.
I ran a cable directly from the circuit panel to an outlet, still low power.
I connected a GFCI outlet to the circuit panel via this direct cable but it will not reset.
All the connections in the circuit panel are tight.
I'm now completely stumped. I would really appreciate any help I can get on this problem.
Thank you,
 
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Old 02-18-12, 08:50 AM
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Low Voltage

Tell us more about the circuit to the building. Is it above ground or buried? Is the circuit to the building 120 volt or 240 volt?
 
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Old 02-18-12, 09:15 AM
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Beyond what Wirepuller posted, an electrical meter would be very helpful. You need to measure between both hots (if you have 240v available) and between each hot and neutral.

There is no way to have low voltage, unless you have an open neutral on a multiwie circuit, which would put a load in series with the circuit you are having problems with. (likely burning up the other device)
 
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Old 02-18-12, 01:26 PM
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Thanks for the replies.
The power is run underground and I believe it's 240 but the area in question is standard 110. The 240 is only used for the kiln. I don't have the testing equipment that you speak about and I'm not sure if it would tell me anything that I would understand.
I keep on reading "open or bad neutral" but I'm not clear how I would fix that.
Everything else that works off of the same circuit panel works perfectly. Is it possible that the panel box has gone bad? How would I test that?
If it were a bad neutral coming from the box wouldn't it effect the entire building?
I've taken every outlet out of the circuit and even eliminated the wiring inside the walls to the outlets.
Again, I appreciate the help.
 
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Old 02-18-12, 01:53 PM
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area in question is standard 110.
Standard voltage is 120v. What you have is a 120v/240v subpanel. For 240v equipment a neutral is not used. For 120v applications it is.

I keep on reading "open or bad neutral" but I'm not clear how I would fix that.
Usually it is a loose connection that you would tighten.

Everything else that works off of the same circuit panel works perfectly. Is it possible that the panel box has gone bad? How would I test that?
It is unlikely the panel is bad but you need to turn off the breaker to the subpanel and test all the neutral screws for tightness. If not the problem then each 120v receptacle, switch, and light junction boxes must be checked including any wire nuts. All screws tested for tightness, any back stabs moved to the screws. To check the wire nuts remove, look inside for corrosion, then redo or just replace with new wire nuts.

I've taken every outlet out of the circuit and even eliminated the wiring inside the walls to the outlets.
Please explain how you did that.
 
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Old 02-18-12, 03:00 PM
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It is unlikely the panel is bad but you need to turn off the breaker to the subpanel and test all the neutral screws for tightness. If not the problem then each 120v receptacle, switch, and light junction boxes must be checked including any wire nuts. All screws tested for tightness, any back stabs moved to the screws. To check the wire nuts remove, look inside for corrosion, then redo or just replace with new wire nuts.
I did this, everything is tight.
I've taken every outlet out of the circuit and even eliminated the wiring inside the walls to the outlets.
Please explain how you did that.
I ran a cable directly from the circuit panel to an outlet, still low power.
 
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Old 02-18-12, 03:32 PM
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I ran a cable directly from the circuit panel to an outlet, still low power.
In the subpanel using a multimeter you need to measure the voltage between each hot and neutral bar. Also in the subpanel measure from hot to hot and each hot to ground.
 
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Old 02-18-12, 03:39 PM
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3 prong tester it indicates that the circuit is good
I keep on reading "open or bad neutral"
Which is it? I agree with the others. Until you get a multimeter and test the actual voltage, you won't know any more to tell us, except the experiments you are performing. You can get an inexpensive multimeter from one of the box stores cheap. Take readings across both hots and from hot to neutral. Let us know what you have.
 
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Old 02-18-12, 03:56 PM
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Buy the cheapest analog (one with a needle) meter you can find. If you can't find one of those then a digital will work in a pinch. They are only about $10

How to use the multimeter: (This must be done with the panel hot so use caution!)
Set meter to at least the voltage you will be reading, so at least 240 volts. "V"
Take one prob and connect it to one hot, take the other probe to the other hot. You should get around 240V
Take one probe to one hot and the other to neutral. You should get about 120V
Do the same above from the other hot to neutral. You should also get about 120V
Please post your results here.
 
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Old 02-18-12, 04:05 PM
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The OP says all other circuits are functioning correctly?

It does need to be tested with an multimeter but minus such, I would have tested that circuit on a different breaker or installed into a different slot. It really doesn't make sense but maybe there is an issue with the panel tab for that particular circuit breaker?

Good luck
 
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Old 02-18-12, 04:31 PM
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Thanks, I guess I'll be buying a multimeter this weekend. I appreciate the advice about how to use it. That's helpful and makes it less of a mystery.

I will also try connecting to another circuit in the panel. Since I've eliminated so much else and nothing is making sense that really could be the issue.

I'll report back.
Thanks for all your help
 
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Old 02-18-12, 04:39 PM
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It's a circuit that reads good on the 3 prong tester that only gives me low voltage which people think is an open or bad neutral. It's weird, it's frustrating, it makes no sense.
 
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Old 02-18-12, 05:09 PM
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It's a circuit that reads good on the 3 prong tester that only gives me low voltage which people think is an open or bad neutral. It's weird, it's frustrating, it makes no sense.

The 3 prong tester is giving a false reading. People think there's an open neutral because that's the only likely scenario.
 
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Old 02-19-12, 12:08 PM
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What I can't understand is how I would have an open neutral on one circuit in the panel but not on any of the others. Remember, I ran a cable directly from the box to 2 different outlets (they were not connected together) just sitting on a shelf 6" away from the circuit panel.
 
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Old 02-19-12, 01:09 PM
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What I can't understand is how I would have an open neutral on one circuit in the panel but not on any of the others.
Each circuit has its own neutral. Until we get readings with a multimeter, preferably analog, we won't have reliable data to work with.
 
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Old 02-19-12, 05:57 PM
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Take one prob and connect it to one hot, take the other probe to the other hot. You should get around 240V Got that.

Take one probe to one hot and the other to neutral. You should get about 120V I got 20v

Do the same above from the other hot to neutral. You should also get about 120V I got about 20v

What does that mean?

Thanks
 
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Old 02-19-12, 06:25 PM
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It means your neutral is open.
 
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Old 02-19-12, 06:36 PM
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Originally Posted by lorib01 View Post
Take one prob and connect it to one hot, take the other probe to the other hot. You should get around 240V Got that.

Take one probe to one hot and the other to neutral. You should get about 120V I got 20v

Do the same above from the other hot to neutral. You should also get about 120V I got about 20v

What does that mean?

Thanks
I'd bet if you did that test again and checked each hot wire to ground you would get 120 volts on each hot wire.
 
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Old 02-20-12, 05:30 AM
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Some of the signs of a bad neutral:

1. Neutral to ground measures voltage that gets higher as you increaset he load such as turn the mixer from low to medium to hign.

2. Incandescent lights on some other circuit get brighter than they should be.

When you are using a multimeter for the first time, be very sure it is set to AC volts before touching live wires or terminals. Power must be shut off before doing continuity (ohms; resistance) measurements.
 
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Old 02-20-12, 06:08 AM
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Ok, so I have an open neutral. What does that mean?
I'm testing at new wires coming out of a new circuit breaker in an 18 month old panel. Everything had been working, nothing had changed, no nails driven into the wall, nothing. It worked at 5pm on Thursday but not at 10am on Friday, it did not rain between uses. So what might cause this open neutral?
 
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Old 02-20-12, 07:46 AM
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Open neutral is a bad connection or bad wire.

it did not rain between uses.
Rain would not likely cause it. Temperature change, vibration, or gnawing animals could. You need to check the neutral connections both at the subpanel and main panel. You need to see if you can tighten them and look for corrosion. If not the connections it could be the cable to the outbuilding.
 
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Old 02-20-12, 09:24 AM
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Yup, I have voltage at the main and all along the route until it goes underground. When it comes out of the ground one leg has power, the other doesn't.
 
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Old 02-20-12, 09:47 AM
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Yup, I have voltage at the main and all along the route until it goes underground. When it comes out of the ground one leg has power, the other doesn't.
May be time to start digging if it is cable not conduit.
 
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Old 02-20-12, 05:25 PM
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This can be very bad! With an open neutral you can get 240 volt across a circuit which will can burn up whatever is plugged in to that circuit.

Your readings might be a little off since you say both hots to neutral is only reading 20 volts (or is that just a typo?) I would expect one hot to neutral to be 120 volts due to you saying that your other lights and outlets work fine. Please recheck your readings (or your post for typos).

Could you also post readings off your breaker in your house that is feeding this outbuilding?
Hot1 to Hot2 =
Hot1 to Neutral =
Hot2 to Neutral =
Also, what size is this breaker and wires?
 
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