DC voltage

[OscarO]

Hello everyone. I am wondering if anyone has ran into a similar problem to the one I am experiencing. About a week ago a friend called me and asked me if I could help him out. He said he lost power in the bathroom. When I showed up I check the voltage at the receptacle and got some weird readings. From hot to neutral I am getting from 109-111 volts ac but when I hook something up to it, it does not turn on. From the hot to the ground I am getting 137 volts ac. From the neutral to the ground I am getting 98-135 volts dc. I checked the voltage at the panel and I am getting 247 v ac between A and B, 137 v ac from A to the neutral, and 111 v ac from B to the neutral. I turned of the breaker that feeds the bathroom and I still get 10 v dc from the breaker to the neutral. Any ideas?

 

[jaggedben]

When I showed up I check the voltage at the receptacle and got some weird readings.

What kind of meter are you using? I think in a case like this we've got to know to what extent we can trust it.

From the neutral to the ground I am getting 98-135 volts dc.

That's a pretty large range. Is it constantly shifting within that range or is the voltage more or less stable at the time you take a given reading?

I checked the voltage at the panel and I am getting 247 v ac between A and B, 137 v ac from A to the neutral, and 111 v ac from B to the neutral. I turned of the breaker that feeds the bathroom and I still get 10 v dc from the breaker to the neutral. Any ideas?

Is the bathroom a multiwire branch circuit and/or does it also have lighting that was turned on when you measured?
What about other breakers when you turn them off? Or do you only get the DC reading on the bathroom circuit?

I don't really have a theory as to what's going on, but my main guesses would be either 1) the utility transformer is going bad or some other problem on the utility side, or 2) somehow a DC source of power is faulted to that bathroom circuit. I would probably turn off all the circuits in the house and re-measure what's coming from the utility as a way of narrowing it down.

If 137VAC is really the voltage at the service panel with all house circuits turned off then you should call the utility and have them check that out. That's out of the limits they are supposed to be within (max 12% over nominal voltage). And I've seen some unbalanced utility voltages, but that's extreme between the two legs. Anyone else in the neighborhood having problems?

 

[OscarO]

jaggedben, I am using a Fluke 233. The voltage will fluctuates every time I take the voltage. All the circuits coming into the panel are fed from a single romex which leads me to believe that there are no multiwire circuits. Thank you for your suggestion. I will turn off all the circuits and take voltage at the main lugs again.

 

[ActionDave]

I checked the voltage at the panel

What panel? Main panel or sub panel?

and I am getting 247 v ac between A and B, 137 v ac from A to the neutral, and 111 v ac from B to the neutral. I turned of the breaker that feeds the bathroom and I still get 10 v dc from the breaker to the neutral. Any ideas?

Ignore the 10V DC. There is a bad neutral somewhere. If you have not checked voltages at the service go there and check. If you get the same weird voltage readings turn off the main, call the utility and don't turn anything back on till they get there.

If it is only a problem at a sub panel then you have a bad feeder neutral.

 

[Sahib]

Hello everyone. I am wondering if anyone has ran into a similar problem to the one I am experiencing. About a week ago a friend called me and asked me if I could help him out. He said he lost power in the bathroom. When I showed up I check the voltage at the receptacle and got some weird readings. From hot to neutral I am getting from 109-111 volts ac but when I hook something up to it, it does not turn on. From the hot to the ground I am getting 137 volts ac. From the neutral to the ground I am getting 98-135 volts dc. I checked the voltage at the panel and I am getting 247 v ac between A and B, 137 v ac from A to the neutral, and 111 v ac from B to the neutral. I turned of the breaker that feeds the bathroom and I still get 10 v dc from the breaker to the neutral. Any ideas?

I guess problem on the POCO side. When all but one phase is lost on the POCO side, there would still be voltage on your side due to capacitive coupling but such voltage may not be able to do useful work such as experienced by you:

From hot to neutral I am getting from 109-111 volts ac but when I hook something up to it, it does not turn on.

 

[Besoeker]

I guess problem on the POCO side. When all but one phase is lost on the POCO side, there would still be voltage on your side due to capacitive coupling but such voltage may not be able to do useful work such as experienced by you:

The OP mentions a problem in just one room, the bathroom. Wouldn't a POCO problem affect all rooms?

 

[Sahib]

The OP mentions a problem in just one room, the bathroom. Wouldn't a POCO problem affect all rooms?

Wait for the feedback from the OP for this:

I will turn off all the circuits and take voltage at the main lugs again.

 

[kwired]

If you have a lost neutral, turning off all loads will result in seeing correct voltages, it takes unbalanced load to throw off voltage balance when there is a bad neutral.

I suggest not only testing voltage at no load but also to apply extra 120 volt load to each 120 volt ungrounded conductor at separate times - preferably something in the 1000 watt range and then testing voltages. If your 247 volts line to line remains fairly constant but line to neutral voltages vary with load changes - there is a bad neutral somewhere between your measuring point and the source.