Low Voltage at Receptacle

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Old 12-30-19, 02:00 PM
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Low Voltage at Receptacle

I'm trying to help out my father-in-law. Apparently he's been running his washing machine via an extension cord from another room for many years now. The original outlet in the 45-year-old house didn't work anymore, he said. I use an NCV tester to verify that there is indeed voltage on the circuit. I probed the receptacle and got around 95 volts. Now I would have thought that t a light bulb would at least light up dimly, but a shop light won't light up. Washer does nothing.

It's a 20-amp circuit and as far as I can tell it's dedicated to that receptacle. The wires go through finished space so I can't tell 100%, but it would make sense that it's dedicated and nothing else goes out when I shut the breaker off. And yes, when I shut the breaker off the 96 volts goes away.

So what gives? Can it be a bad breaker? He doesn't remember when or why it stopped working.
 
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Old 12-30-19, 02:04 PM
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I suggest u get a 40watt incandescent test lamp with a pigtailed socket. Try the breaker output first, if necessary work towards the inop recept.
 
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Old 12-30-19, 05:03 PM
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Try measuring the voltage when the light is plugged in and turned on. You will find it is not 95 volts.
Your problem is a loose connection somewhere. Could be in the bad receptacle or in the device feeding it. If any of your devices use the back stab push in connection move the wires to the screws. Back stabs are very common source of this issue.
 
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Old 12-30-19, 07:19 PM
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Thanks. The house is old an predates back stabbed outlets. I removed the outlet in question and the connections were secure. I really don't think there's anything else on that circuit - I think it's dedicated to that washer/dryer area.

Curious about plugging in the light and checking the voltage. It doesn't do anything when I plug it in. What am I looking for when I test for voltage with it plugged in? Further drop?

My next plan is to check the neutrals and grounds in the box as well as to check voltage right at the breaker.
 
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Old 12-30-19, 09:59 PM
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When you add a load(the light) you get a true voltage reading It will probably near zero.
 
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Old 12-31-19, 04:56 AM
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Non contact voltage sensors can be very misleading as they are way too sensitive.

FYI.
Below are a couple scenarios that will mislead using them.

Ghost voltage: When one AC wire runs beside another wire it induces a voltage in the second wire but there is no real power there.
This is basically how a transformer works but has many windings (wire length) so there is actual power.

Bad connection: A bad connection is often a high resistance. So with nothing attached to the line you will see voltage on both sides of that connection. But once you connect a load all the voltage is dropped across the bad connection and you get little or nothing across the load.
 
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Old 12-31-19, 09:28 AM
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Thanks all for the replies.

I'm only using the NCV to detect voltage on the wiring - he's got a bunch of spaghetti in that utility room so I wanted a quick way to see what shut off with what breakers. To measure the voltage I'm actually probing the outlet.

I checked the voltage at the breaker and it's 125V. So the issue is between the breaker and that receptacle. Again, I think it's a straight shot from the panel to the receptacle - I don't think there's any junctions or other receptacles on the circuit.

When probing the outlet, and seeing 96 volts, and then plugging in the shop light, the voltage does indeed drop to 0.

So I pulled the outlet out again. Now I would have sworn on a stack of Bibles that the outlet was not back stabbed. But it is and I'd bet that's the problem. I wiggled the wires a bit and reinstalled it, but I get the same 96 volts. I didn't have another outlet with me so I left. And for some reason I left without clipping out the outlet and checking the voltage on the wires. It didn't occur to me to do that until I had driven half way home.

Anyway, I bought a new outlet. I just need to find the time to run back over there and install it.
 
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Old 12-31-19, 11:37 AM
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Just move the wires to the screws on the old one until you can install the new one.
 
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Old 12-31-19, 03:50 PM
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It hadn't occurred to me to do that (move the wires to the side terminals) until after I left. It's no big deal - I can install the new outlet tomorrow. I'm hoping that's the issue.

Another part of the project was installing some LED lights (they look like 24" fluorescent lights) where a single, 60 watt bulb was. That went really well. I hardwired one fixture to the existing box (controlled by a wall switch) and daisy chained 2 others to it. My father in law was finding stuff he hadn't seen in decades in that previously barely-lit utility room!
 
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Old 12-31-19, 07:26 PM
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When I have found voltage low like you have found, I generally eventually found a bad neutral connection somewhere in the circuit.
 
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Old 01-04-20, 12:34 PM
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Well I replaced the outlet and it didn't fix it.

I don't know where to go with it now. He (my father in law) wants me to tap into another circuit for the washer outlet, which I'm okay with. But I don't know what to do with the existing (non-functioning) circuit. I think probably the safest thing to do is disconnect it at the breaker?
 
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Old 01-04-20, 05:21 PM
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There must a junction box between the breaker and the washer. It could be hidden behind a wall by a previous DIYer.
 
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Old 01-06-20, 11:56 AM
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Unless it's in the panel. But everything felt snug.

If someone were to put a nail through the neutral wire, or otherwise damage it, it could cause this right?
 
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Old 01-06-20, 04:54 PM
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If someone were to put a nail through the neutral wire, or otherwise damage it, it could cause this right?
Not necessarily. When I have found a nail to have penetrated a cable I generally have found it to be a short that was tripping a breaker. Just damaging or nicking the neutral shouldn't cause low voltage. The only condition that I could imagine would cause low voltage would be if the neutral was completely severed and the nail was completing the circuit. The loose contact between the conductor and nail could cause low voltage as well as heating up and causing a fire hazard, but I think this would be extremely rare.


Unless it's in the panel. But everything felt snug.
Did you actually use a screwdriver to check each neutral connection in the panel?
 
 

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