Learn me: Latent voltage in my house

My house was built in 1998, and isn't built particularly well. I've done lots of really important things to it and it's way better than it was, but there's an issue that I've always sort of just ignored.

In the whole house, at least everywhere that I've checked, when the switch is off, there's still something like 40 volts hanging around. The first time I tried to change a fixture by just flicking off the switch was pretty exciting.

Should I care? None of my appliances seem to care, am I wasting energy? I'm not really sure. What's the diagnostic tree look like?

I suspect a bad neutral. 

Sounds less than optimal.

Stampie said:

I suspect a bad neutral. 

In the main box? It's a really simple house, there's power into a box and everything comes from there through breakers.

I assume if it's a bad neutral, then it's a bad neutral into the house, since I have seen this on multiple circuits. Do I just call Duke? I'm not really sure how to test it other than that.

Ohm the neutral bus bar to ground with the main breaker off?

tuna55 said:

Stampie said:

I suspect a bad neutral. 

In the main box? It's a really simple house, there's power into a box and everything comes from there through breakers.

 

I assume if it's a bad neutral, then it's a bad neutral into the house, since I have seen this on multiple circuits. Do I just call Duke? I'm not really sure how to test it other than that.

I would definitely call the power company and tell them what you have told us. Switch off should = safe. Utility should send a trouble man out to probe the line and meter. After that (in my experience) they usually say "it sucks to be you" but it might help you get a free diagnosis. 

tuna55 said:

Stampie said:

I suspect a bad neutral. 

I assume if it's a bad neutral, then it's a bad neutral into the house, since I have seen this on multiple circuits. Do I just call Duke? 

Yo, homeboy, wassup?

Chances are what you're seeing is 'ghost voltage' and is nothing to worry about.  It happens with some digital multimeters.  https://www.diychatroom.com/threads/40-volts-occurs-when-switch-is-off.189851/

In reply to stuart in mn :

His comment about changing a fixture being exciting makes me think this is an actual issue. 

I have about zero experience with house wiring unfortunately so I have nothing more to add. 

In reply to pres589 (djronnebaum) :

Light fixtures and associated switches can be wired in many different ways, so I'm not sure if that's a guarantee something is a problem.

But it's definitely a reason to take a closer look when combined with the 40v residual reading. 

In reply to pres589 (djronnebaum) :

I suggested ghost voltage because of the 40V reading - it's a fairly common occurrence and the reading is always around 40 V.  The thing about changing a fixture could be some other unrelated issue, for instance if the fixture has the hot and neutral wires swapped.

stuart in mn said:

In reply to pres589 (djronnebaum) :

I suggested ghost voltage because of the 40V reading - it's a fairly common occurrence and the reading is always around 40 V.  The thing about changing a fixture could be some other unrelated issue, for instance if the fixture has the hot and neutral wires swapped.

The meter in multiple circuits reads something like 40V (it's been a long time).

I've been shocked by wires which should have been zero.

My hallway lights are -very- dim when they should be off.

Duke said:

tuna55 said:

Stampie said:

I suspect a bad neutral. 

I assume if it's a bad neutral, then it's a bad neutral into the house, since I have seen this on multiple circuits. Do I just call Duke? 

Yo, homeboy, wassup?

 

Hey come fix my electricity

It sounds like a floating neutral to me. 

If you aren't comfortable with electricity, call someone.

Electricity is invisible and it can kill you. No warning. No second chance. Just DRT. 

Is the neutral bus in your panel bonded to the ground bus? It probably is. If not, check the voltage between the neutral and ground buses. It should be zero. If the panel isn't bonded, I would want to take care of that first. A piece of #10 from the ground bus to the neutral bus will do the trick. Don't run it across the top of the panel. 

A bonded panel.

With the main breaker and all the other breakers turned off, check the voltage between both 120v busses and neutral and ground. It should be near zero. 

Then check the voltage between the 120v busses. It should also be zero. 

Any reading between the 120v buses suggests a breaker issue. Any reading between the neutral bus and any other bus suggests a neutral issue. It could be floating, as in not connected properly in the panel, meter base, or on the pole. 

Go through the panel and make sure everything is tight. Particularly at the ground and neutral buses.

If you aren't seeing anything obvious, call the power company and let them check their system. 

The last time I dealt with weird power issues it was a loose crimp at the weather head for the entrance cable. It was a major pain to track down. 

In reply to Toyman! :

That's super helpful, thanks. I am OK working around the stuff, but it does make me nervous in the box with the main power sitting there. I've done it before (adding a circuit for the compressor and also the car) and I'll do what you recommended soon. Duke is coming also to check the power at the pole.

Phantom voltage can also come from mixed ground and neutrals.  It can come from a swapped line and neutral as well.  Sometimes a DIY person might add an outlet and not pay attention to black and white since it's AC, then everything downstream of that swap is neutral-hot.  So even if you turn the switch off (breaking the black wire) you still have voltage coming through the white.

You can get a cheap tester that plugs into outlets that can identify a swapped neutral/line.

It also can't hurt to check all your neutrals on the affected circuit.  They go bad frequently.  A lot of people don't realize this because you can't hear it, but the electrons moving back and forth at 60hz buzzes the surface of the conductors.  After 25 years, it's understandable if one of the wire nuts in a junction box got a little loose.

Duke says everything on the outside is fine.

Time to go into the box.

In reply to tuna55 :

Keep in mind, that is what the power company always says. It took 3-4 phone calls to get SCE&G to do anything about my issue. It took threatening to sue them for damages to get them to put a recording voltmeter on the service before they actually sent a crew out to do any real troubleshooting. They always blame someone else.

In reply to tuna55 :

While you are in there check that the ground is bonded to the ground rod driven into the ground outside,unlikely it came loose but stranger things have happened.

Well that was fun, everything appeared normal, but when I power in the house back on only how half of the house came back on. Now I'm stuck with an angry family. I'm guessing some GFCI somewhere is not happy but I can't tell where. I've got at least eight circuits that aren't behaving despite everything looking fine.

As toyman said, floating neutral,put a good meter on the outlets then see if they are proper polarity, a good meter will show polarity (outlet wired backards) or get an outlet tester

The voodoo...

I turned off the house, checked everything with a meter, and everything is fine. 

I turn the house back on and half of the house doesn't come back. Random breakers are showing like 0.3vac. We go through and reset all of the GFCI outlets, try again. It's weird. 

Tunawife turns on the upstairs AC, suddenly half of the house lights up. It's dim and weird, but it's on. She turns on the downstairs AC and suddenly the house is back to normal. 100%. Everything is great. 

She commands the AC off, half of the house goes away and gets dim and weird. She turns it back on, it goes back to normal. I flick the AC breakers off and back on, then everything stays good. 

Now they kicker, the phantom voltage is nearly all gone. I checked everything with a meter. One circuit upstairs has 12 somehow though. The rest are zero. 

Neutral is finding ground through appliances, be very careful, something is very jacked up. If you cant move through it slowly and methodically call a pro