110v from public utility?


Old 10-05-15, 12:32 PM
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110v from public utility?

A month ago, during a heat wave, I measured 110v at a box next to my panel, with nothing in the house turned on. I suppose everybody had their AC running, but isn't the utility obligated to give me 114v?

On the cooler days we have been having recently, or even at night last month, the voltage is 119-121v.

This morning I was talking to a guy servicing my generator. He said he had another customer in the neighborhood with the same problem; the utility told him to live with it.
I realize the utility is unlikely to increase the capacity of the power line for a problem that probably only comes up a few days a year; but they could increase MY voltage a bit; so that I fluctuate from 125v-114v instead of 121v-110v.
Would that be an improvement?
Am I likely to get anywhere with them?
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Old 10-05-15, 12:43 PM
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It's +/- 5% of 120. So that would be 114v-126v for a normal service.

However.... under certain conditions they are allowed to droop based on system demand.

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Call them and see if there's anything they can do. Most likely not.

Last edited by PJmax; 10-05-15 at 05:35 PM. Reason: corrected figure
Old 10-05-15, 12:45 PM
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No, you're not likely to get anywhere with that request. One, the transformer probably has fixed taps, two you probably exceed 125V in the middle of the night so tapping it up any higher would be out of spec the other direction.

They're more obligated to make an honest attempt to provide you 120V nominal, with the understanding that they are at the mercy of mother nature and it isn't always possible. Unless you're willing to drop serious investment on equipment (e.g. a hospital or datacenter) for the extra guarantee of stability, you have to accept some dips out of spec a few times a year.

Realistically their solution if the voltage got low enough would just be to loadshed you and/or your neighbors on the hot days (a.k.a. rolling blackout) as the few hours of lost revenue from you is significantly less than the cost of upgrading the infrastructure that will only be used a few hours a year.
Old 10-05-15, 03:20 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
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If 120 volts is nominal then +/- 10% would be a low of 108 and a high of 132. A tolerance of +/- 5% would be 115 to 126. Total range with a tolerance of +/- 5%, from 115 to 126 is 10% of the nominal voltage from the low to the high.

Most distribution transformers will sag with an increasing load so the utility tends to set the taps at the high end of the allowable voltage range on minimal load.

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