Volt Reading Question


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Old 04-08-04, 11:13 PM
marcdm
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Volt Reading Question

When I put a voltmeter on any of my receptacles I get a reading of approximately 126 volts. Now Iíve recently installed a 50 Amp circuit for a kitchen stove that yielded a reading of approximately 256 volts. Should I be concerned, or is this kind of thing somewhat common. ThanksóMarc
 
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Old 04-08-04, 11:26 PM
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that is a little hi but normal.up here depending on what area you are in it is usually +/- 5v on a 120v cct.i think it has to do with power factor correctance.if you are in an industrial area it will vary more drastically because of all the inductive loads.....i think anyways
 
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Old 04-09-04, 05:53 AM
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It is high at my house as well. It goes down a volt or two when there is a large load running like my A/C. I asked a couple "experts" (engineers)about it at my work and they said the only downside is that your light bulbs might burn out faster. They said its well within the tolerance of major appliances and any electronics adapt the voltage anyway.

That was the answer I got anyay. I'm interested to hear anyone elses opinions.
 
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Old 04-09-04, 06:02 AM
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Overvoltage.

I checked with my POCO here in Fort Mohave, AZ and was told that a 5 or 6% voltage tolerance was normal.
 
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Old 04-09-04, 06:19 AM
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The power lines have devices on them to automatically regulate the voltage (strangely enough, they are called voltage regulators). The have circuitry in them to raise or lower the voltage acording to voltage and load.
Example; A regulator is looking at 5 miles of line and is set to maintain a volt level of 120 volts. At 3:00 AM when there is no load, there is very little voltage drop and the voltage is fairly uniform throughout the line.
But around 7:00 when everyone's cooking breakfast and showering, the load increases, as does the voltage drop in the line. Now, with the regulator set at 120 volts, the first house down the line still has 120 volts while the guy at the end may only have 110 volts.
To compensate for this, the regulators have load compensation in them that automatically raises or lowers the voltage depending on the current flowing through them.
So for this example, the regulator raises the voltage 5 volts to compensate for the line drop. Now the first guy next to the regulator has 125 volts, the one in the middle has 120, and the guy at the end is up to 115.
The trick here is to set the compensation so the the last customer has adequate voltage without burning up the equipment of the first guy. Most regulators have circuitry that limits how high they can go to protect against this.
At our Co-op, we set the regulators to try to get a maximum of 126 and a minimum of 118 volts at the meter. The high end limits are set to automatically run the voltage back down if other factors (say a capacitor bank switching on) causes a rise and it hits 128.
With most devices being designed to tolerate 120 volts plus or minus 10%, the extremes would be 108 to 132. I've seen some utilities set their high ends as high as 130, but I think that is extreme.
 
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Old 04-09-04, 06:37 AM
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Another possibility is that your voltmeter is a little off. Homeowner quality voltmeters aren't really high precision measuring devices. Does it have any calibration adjustments (i.e. can you zero it)?
 
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Old 04-09-04, 11:05 AM
blindrid
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To reinforce what WFO said...At the utility I worked at all the reg's filed with the state indicated voltages to be +/- 10%. There are so many conditions that influence the voltage it's impossible to go into here. Yours is OK.
 
 

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