Voltage rise, not drop

[readydave8]

This was explained to me over the phone, not my job:

450' of #2 AL to a panel, gfci receptacle on one leg with nothing plugged in, 30 amp, 120 volt travel trailer on the other leg. The more that's turned on in camper, the higher the voltage in camper, going from 124 to 130 volts, seen on 2 meters, one a cheap digital, the other a greenlee true RMS.

Obviously the electrician has checked neutral connections, but what else could be causing this phenomonom?

 

[steve66]

Multiwire circuit shared with another camper? The higher the current on this camper, the more the voltage drop is canceling on the neutral.

 

[readydave8]

Multiwire circuit shared with another camper? The higher the current on this camper, the more the voltage drop is canceling on the neutral.

good thought but doesn't apply, what I'm saying is the only thing hooked to the other leg is a GFCI receptacle with nothing plugged in (no load on other leg of 240 v except whatever the GFCI receptacle itself uses).

 

[ptonsparky]

I believe you need to know exactly what is happening on the other half of that circuit even if it takes you to the POCO transformer. What is the volt reading at the unused gfci while the camper volt is going up?

 

[steve66]

I should of read a little more carefully.

Its hard to know exactly without more info. Is it possible that one of the camper loads is improving the Power Factor?

Is there a real problem, or are you just curious why this is happening?

To really get to the bottom of this, I think you would have to measure the current in both cases, and measure the voltage at the input end of the line, and the other end of the line.

We know increased current causes increased voltage drop, so there has to be something going on that you don't know about.

 

[readydave8]

I should of read a little more carefully.

Its hard to know exactly without more info. Is it possible that one of the camper loads is improving the Power Factor?

Is there a real problem, or are you just curious why this is happening?

To really get to the bottom of this, I think you would have to measure the current in both cases, and measure the voltage at the input end of the line, and the other end of the line.

No there is not a real problem, I was curious. Thought someone might have run into a similiar situation.

I told my friend that I didn't think anything was wrong but to try it with the breaker feeding the GFCI turned off, don't know if he will bother.

The way I understand what he said was that voltage stayed around 124 v at the input end, only changed at the camper end. But this is second hand, I might have it wrong.

I was suspicious that it might be false readings on meters.

Thanks for your help.
We know increased current causes increased voltage drop, so there has to be something going on that you don't know about.

1somehow my reply got intertwined with quote, I don't know how to fix it.

 

[jghrist]

If the neutral is shared, the voltage drop in the neutral will add to the voltage at the unloaded camper receptacle. For example, if you had a 10A load on one leg with a 1 ohm conductor and a 1 ohm neutral, the voltage will drop 10 volts across the conductor in one direction and 10 volts across the neutral the other direction. Voltage across the load would be 120-10-10=100. Voltage from the neutral at the receptacle to the other leg (which has no current and no voltage drop in the conductor) will be -10-120=-130.

          1 ohm
+-----------RRRR---------+
           + 10V -       |
 +     ---->10A          |  +
120V                  Load 100V
 -     <----10A          |  -
           - 10V +       |
+-----------RRRR---------+
          1 ohm          |
 +                       |  +
120V                      130V
 -                       |  -
                         |
+-----------RRRR---------+