Acceptable voltage drop from Poco?

[MAD MAN]

I'm an electrician and have had trouble with my kitchen lights randomly flickering for a few years. New dimmer, new bulbs, had the wall open and everything was fine so I just pushed it off as interference with the LED bulbs as it randomly happens with no patten.

Was working in my panel the other day when they started flickering and decided to check voltage which I've done before but could never catch it at the right time. A phase was 117 volts and B was 121 with little load on my side and when I applied a 50 amp load to a phase my voltage dropped to 108. Looking down the street it appears to be a 50 kva transformer feeding a dozen houses.

Is this something worth calling the Poco about?

 

[infinity]

Sounds like voltage drop which increases with the amount of load. 108 volts is too low to me so I would call the POCO.

 

[LarryFine]

A phase was 117 volts and B was 121 with little load on my side and when I applied a 50 amp load to a phase my voltage dropped to 108.

Welcome to the forum.

Repeat the test and measure the opposite line's voltage to the neutral.

If that voltage rises significantly, you have a service neutral problem.

 

[nizak]

Welcome to the forum.

Repeat the test and measure the opposite line's voltage to the neutral.

If that voltage rises significantly, you have a service neutral problem.

Locally, the POCO is +/- 10%

 

[don_resqcapt19]

The maximum and minimum voltages are typically set by the state utility commission or what ever agency regulates the electric utilities in your state. This is what the Illinois Commerce Commission says about utility voltages in Illinois.

Section 410.300 Voltage Regulation
a) Standard voltage. Each entity supplying electrical energy for general use shall adopt a standard service voltage of 120 volts (when measured phase to neutral) and shall maintain the service voltage within the allowable variations from that value at all times.
b) Allowable voltage variations. For service rendered at the standard service voltage, voltage variations as measured at any customer's point of delivery shall not exceed a maximum of 127 volts nor fall below a minimum of 113 volts for periods longer than two minutes in each instance. For service rendered at voltages other than the standard voltage value, voltage variations as measured at any customer's point of delivery shall not exceed 10% above or below the service voltage for a longer period than two minutes in each instance.

 

[Eddie702]

108 is the brink of the low end. Anything lower than 110 is unacceptable IMHO.

Could be at weather head, POCO or meter socket. Maybe you could check voltage at a neighbors house.

 

[LarryFine]

Locally, the POCO is +/- 10%

I'm talking about diagnostic troubleshooting.

 

[MAD MAN]

Welcome to the forum. Repeat the test and measure the opposite line's voltage to the neutral. If that voltage rises significantly, you have a service neutral problem.

Welcome to the forum.

Repeat the test and measure the opposite line's voltage to the neutral.

If that voltage rises significantly, you have a service neutral problem.

Already tried that and only had a minor increase, less than a volt

 

[LarryFine]

Already tried that and only had a minor increase, less than a volt

That sounds perfectly normal.

Next I would try the same load test on the other line.

 

[herding_cats]

The issue is at the pinch crimps at the weather head. Have POCO replace them.

 

[Hv&Lv]

Depends on the A or B range of the variation.

Check both sides L to N with the 50 amp load. If one side goes down and the other side goes up it's a bad neutral. If one side stays at 121 and the other side drops significantly it's a bad connection somewhere.
If that XF has a dozen houses and none of them have the same problem it's in your house or the wire coming to your house.
Overhead or UG service?
Could be a bad UG cable

Going to require a little more diagnostics

 

[Hv&Lv]

The issue is at the pinch crimps at the weather head. Have POCO replace them.

Could be, but why jump to that conclusion without troubleshooting?

 

[ptonsparky]

Could be, but why jump to that conclusion without troubleshooting?

Calling the POCO always waited until we were sure.

 

[herding_cats]

Could be, but why jump to that conclusion without troubleshooting?

I'm not against troubleshooting by any means, but I see this 2-3 times per year. POCO pinches are junk or not done right or unprotected from weather. Or all of the above. POCOs don't use anti oxidant.

 

[ActionDave]

POCOs don't use anti oxidant.

Maybe where you are. The crimps that the POCO where I'm at are pre-loaded with anti-ox goo.

 

[herding_cats]

Here it depends. A lot of pinches are done dry aluminum ferrule. I'm in the KC area.

 

[Hv&Lv]

I'm not against troubleshooting by any means, but I see this 2-3 times per year. POCO pinches are junk or not done right or unprotected from weather. Or all of the above. POCOs don't use anti oxidant.

Believe it or not, I see some of ours fail, but I find a lot out there that are either in the meter base or breaker panel. Electrician should troubleshoot first always.

I’ve found a breaker panel at 2:00AM that had the copper jumper from ground to neutral loose. The electrician had been there twice already, and I had put a PQM on the house for a week and saw nothing.

 

[herding_cats]

Correct. I see very few issues in meter bases. Weirdly I see a lot of damaged neutrals in panels. Most of the failures I see are the pinch point of POCO and the building owner service entrance pre weather head. I found a NASTY one last year. On the side of a restaurant, totally smoked 208V 600A service. Again it was a cheap aluminum ferrule crimp. B phase was cooked. I was shocked it still worked and I had not seen any voltage irregularities in the building.