Below normal voltage on each phase

[oscaro5]

Hi everyone. Just wondering if anyone could give me some insight on what’s possibly going on. I’m thinking this is just undersupplied voltage from the utility company?

So here’s the setup. Residential single phase 120/240 system. Meter main is surface mounted outside with a single 200a distribution breaker. Nothing in the meter main was touched other than to pull out the old wires and refeed in new. The old were too short to reach the lugs. Panel was fed with 3x 2/0 and a #4 ground.

The 200a fed an old meter main that had been converted to a sub panel. This old meter main got demo’d and a new 200a sub got installed in its place but semi flush into the garage. Exterior pipe work was adjusted a bit.

Unfortunately no one checked voltage before disconnecting the old feeders… but now we have between 103-109v A or B to neutral and ground, 205-220v phase to phase. Lighting is flickering or won’t turn on throughout the house.

I’ve never came across equally low voltage on each phase. Voltages have been checked in the new sub panel as well as the meter main and are the same in both locations. Is this just a situation of weird coincidence and the client has been supplied with low voltage for some time now or could there be an issue I’m missing.

Thanks

 

[infinity]

I would check the voltage at the meter with no load. If it's too low then that's an issue for the poco to solve.

 

[letgomywago]

Voltage with no load or a couple lights should be hardly any voltage drop. Make sure almost everything is off and check again.

 

[oscaro5]

I didn’t have time today but will swing by tomorrow to run some tests with all loads off. Say it isn’t a service provider issue. I’m having a hard time thinking of what it could be. A loose neutral would give me a higher and lower voltage phase not an equal voltage. At this point just brainstorming before running more tests

 

[letgomywago]

They could have tapped the transformer low instead of high. I think they have 10% leeway or something like that.

 

[infinity]

I didn’t have time today but will swing by tomorrow to run some tests with all loads off. Say it isn’t a service provider issue. I’m having a hard time thinking of what it could be. A loose neutral would give me a higher and lower voltage phase not an equal voltage. At this point just brainstorming before running more tests

It sounds like a supply voltage issue. Before wasting any more time on it you'll need to determine if your voltages are good at the source which in this case is at the metering equipment. I agree with you if it isn't the supply finding the answer may be tricky.

 

[ptonsparky]

We've had failure of both hots on underground before, but pretty rare. Usually the neutral is failing also.

 

[gar]

230519-0919 EDT

oscaro5:

You have received good comments.

I wii assume the first place you can make measurements is in your main panel. Turn off all breakers, and open any fuses in the main panel. This puts no current load on the source. Measure the voltage directly on the conductors into the main panel. This means each line to neutral, line to line, and neutral to earth. This provides you with the source voltage no load voltage at the earliest possible point.

Next measure one hot line input in the same way, and load that phase somewhere with a 1500 W 120 V space heater. In my home that reading will drop about 1 V. Then move the meter to the other phase, and again do the load test. This opposite phase should rise about 1/2 V in my case.

If these results for you are about the same, then it is likely a transformer tapping problem.

Much greater changes likely means wimpy supply wires or impedance in the supply to or thru the meter.

You can also do the same test on the other phase.

Depending on your results you determine whether or not to call the power company.

..

 

[gar]

230519-1201 EDT

oscaro5:

An additional point.

If your voltage is jumping around from 103 to 109 V over a short time, and you have no load changes during this period, then I would be concerned with what might be the cause. Further, if this change is on the input wires to the main panel, then I would assume an external cause.

.

.

 

[hillbilly1]

If the main is plug on, could be a burnt buss, may have been aggravated by changing the load wire on the breaker. Easy test is FOP. (Fall of potential) with the loads on, measure voltage on each leg from line to load, you should get close to zero volts. If you get several volts, the connection is bad.

 

[Joethemechanic]

A handheld hairdryer with some good alligator clips makes a nice little portable load bank

Don't steal your wife's though, you'll never hear the end of it.

 

[jaggedben]

A handheld hairdryer with some good alligator clips makes a nice little portable load bank

Don't steal your wife's though, you'll never hear the end of it.

Heat gun. It's not a hair dryer. It's a heat gun.

 

[ptonsparky]

OP... we're ready for an update.

 

[LarryFine]

I would add fall-of-potential testing, with an extension wire in one lead if needed.

 

[oscaro5]

Thanks everyone for the suggestions. Was able to take measurements on line side of meter the following day, readings were consistent across meter and main disconnect. Called poco and was told ongoing work was being done in the area. Voltage issues resolved the following day.