The Public Service Commission with jurisdiction in the particular areas sets the allowable voltage range. (I worked in the utility industry and at a manufacturer of meters and meter reading systems for electric utilities.)
Excellent article. In my area, St. Louis County. Missouri, the allowable voltage at the electric meter (the entrance for the electrical service) is 120.0 VAC +/- 5%. which equates to 114.0 VAC to 126.0 VAC. I worked in the utility industry. Many years ago, prior to the advent of sophisticated remote monitoring equipment, the manner in which the electric utility would become aware of overly high voltage was complaints from customers that their (incandescent) light bulbs were wearing out too quickly.
When I worked in the industry we would set our taps depending on the load at the time and would have to adjust as needed depending on how much equipment was on line. They probably had the taps set high so if they had a lot of RV's plugged in it wouldn't be a bad low voltage issue. Not good and bad safety practice!
At home, I once plugged in my progressive industries surge protector and it would not let me connect the motorhome. The voltage was 135. I thought the surge protector was faulty so I removed it and sent it to the factory for repair. They checked it and told me it was fine. I re-installed it with the same result. I called the power company and told them of the high voltage. To my surprise, the sent a crew out that day.
About 6 pm they called and told me they found the problem at a substation about 7 miles away!
I believe the rule of thumb for a building is 5% overall, 3% at the service drop and 2% at the furthest outlet. My Surge Guard has saved me 2 times that I know of, once in Canada when at every night at Sox 7PM the voltage went to 132 on one leg of the 50amp, luckily the 30 amp was not on that leg. Once in New Hampshire the voltage dropped down to around 100 volts when load was applied, camp ground owner knew he had issues and was upgrading system, he moved us to new service however he did rent the spot to the next person that had no protection.
IRRC, the NEC doesn’t actually list a minimum service voltage except to supply dedicated water pumps for fire suppression. But they do have recommended voltage drop percentages for feeder and branch circuits as you note.
Hi - I had the same "over voltage" issue at a New Mexico State Park last Fall. Grrrr..... PI EMS was reading 1 volt over their cut-off... Unfortunately needed the power, so ended up putting my 35' extension cord in line between the pedastal and the EMS, created enough resistance to lower the voltage enough to let power pass. As more folks returned later in the day the demand increased enough to lower the voltage a bit.
As an electrician in New Jersey from the 80's, I can't remember an inspector putting a voltmeter on a service in a strip mall or anywhere a transformer was installed. We checked the voltage and worked with the power company to get acceptable voltage output. Sometimes changes to or upgrades to the grid, maybe to increased loads or needs above my pay grade happen, attention needs to be paid downstream. Not all unfavorable conditions are caused by owner deception or cheating. If appliances are rated at 110, 115 or 120 on the name plate, shouldn't the low be around 108 and the above around 125? I've witnessed 123 from the utilities a lot.
The Public Service Commission with jurisdiction in the particular areas sets the allowable voltage range. (I worked in the utility industry and at a manufacturer of meters and meter reading systems for electric utilities.)
The voltage governed by the PSC is the voltage at the service entrance/the electric meter..
Excellent article. In my area, St. Louis County. Missouri, the allowable voltage at the electric meter (the entrance for the electrical service) is 120.0 VAC +/- 5%. which equates to 114.0 VAC to 126.0 VAC. I worked in the utility industry. Many years ago, prior to the advent of sophisticated remote monitoring equipment, the manner in which the electric utility would become aware of overly high voltage was complaints from customers that their (incandescent) light bulbs were wearing out too quickly.
When I worked in the industry we would set our taps depending on the load at the time and would have to adjust as needed depending on how much equipment was on line. They probably had the taps set high so if they had a lot of RV's plugged in it wouldn't be a bad low voltage issue. Not good and bad safety practice!
At home, I once plugged in my progressive industries surge protector and it would not let me connect the motorhome. The voltage was 135. I thought the surge protector was faulty so I removed it and sent it to the factory for repair. They checked it and told me it was fine. I re-installed it with the same result. I called the power company and told them of the high voltage. To my surprise, the sent a crew out that day.
About 6 pm they called and told me they found the problem at a substation about 7 miles away!
That’s why it’s good to have a separate multimeter to double-check voltages.
I believe the rule of thumb for a building is 5% overall, 3% at the service drop and 2% at the furthest outlet. My Surge Guard has saved me 2 times that I know of, once in Canada when at every night at Sox 7PM the voltage went to 132 on one leg of the 50amp, luckily the 30 amp was not on that leg. Once in New Hampshire the voltage dropped down to around 100 volts when load was applied, camp ground owner knew he had issues and was upgrading system, he moved us to new service however he did rent the spot to the next person that had no protection.
IRRC, the NEC doesn’t actually list a minimum service voltage except to supply dedicated water pumps for fire suppression. But they do have recommended voltage drop percentages for feeder and branch circuits as you note.
I worked at a major utility in California for 35+ years, allowable voltage was 114 to 126 volts at the meter.
Clearly something is wrong at the POCO transformer.
Hi - I had the same "over voltage" issue at a New Mexico State Park last Fall. Grrrr..... PI EMS was reading 1 volt over their cut-off... Unfortunately needed the power, so ended up putting my 35' extension cord in line between the pedastal and the EMS, created enough resistance to lower the voltage enough to let power pass. As more folks returned later in the day the demand increased enough to lower the voltage a bit.
As an electrician in New Jersey from the 80's, I can't remember an inspector putting a voltmeter on a service in a strip mall or anywhere a transformer was installed. We checked the voltage and worked with the power company to get acceptable voltage output. Sometimes changes to or upgrades to the grid, maybe to increased loads or needs above my pay grade happen, attention needs to be paid downstream. Not all unfavorable conditions are caused by owner deception or cheating. If appliances are rated at 110, 115 or 120 on the name plate, shouldn't the low be around 108 and the above around 125? I've witnessed 123 from the utilities a lot.