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# Normal Voltage Range?

#1
03-12-14, 02:52 PM
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Normal Voltage Range?

My house stays consistent around 122.

In my case, is that a normal reading?

Im confused because of all the book I have refer to 110-220, but then others refer to 120-240.

#2
03-12-14, 03:11 PM
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A lot of the writers of the books are writers not electricians. They researched before they wrote but didn't know enough to know what information was wrong or out of date. When George Westinghouse began introducing AC power he knew higher voltage would be better but set the voltage at 110 the same as the DC voltage being marketed by Edison to avoid confusion. Gradually over the decades the power companies raised the voltage. War of Currents - Wikipedia, the free encyclopedia

#3
03-12-14, 03:14 PM
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Last edited by AllanJ; 03-12-14 at 03:55 PM.
#4
03-12-14, 03:18 PM
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Lights and small appliance circuits are 110 to 120. The "official" term in the U.S. is 120.

Heating, dryer, water heater, most air conditioners, some tool, circuits are 220 to 240. The official term in the U.S. is 240.

Experts will vehemently dispute the exact numbers for normal in a victorian style library over tea and cookies.

To me 122 volts is a tad above normal. Most experts say 125 volts is above normal and 105 volts is below normal.

I want to say that 113 to 120 is the normal range.

Double all the numbers for the heating, etc. circuits.

Overvoltage shortens the life of electrical devices and equipment. Significant undervoltage also tends to shorten the life and also reduce efficiency (energy efficiency). Undervoltage for non-mechanical heaters and incandescent lights will result in longer life although also reduced efficiency.

There is another standard of "officially" 208 volts as normal for heating etc. circuits but the equipment must be designed for 208 volts or for the 208 to 240 volt range. If the "big" circuits are 208 then the "small" circuits are still 120. NOT 104!.

Last edited by AllanJ; 03-12-14 at 03:48 PM.
#5
03-12-14, 03:26 PM
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To me 122 volts is a tad above normal. Most experts say 125 volts is above normal and 105 volts is below normal.

Do you think I have an issue here? Something else I can check? Im assuming this is what the poco is giving me.

#6
03-12-14, 04:02 PM
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Voltage Range

Here is a link to utility voltage standards: NEMA (National Electrical Manufactures Association) recommends that all electreical appliances and motors should operate at plus or minus 10% (103-126.5V). Service Voltage Standard is plus or minus 5% (114-126V) which is within the range of your readings. If you are concerned I would call your utility company as they can record your voltage levels over time to see if any adjustment is needed to their correction equipment in your area.

http://4.bp.blogspot.com/-ifvy3HSFKT...tolerance2.jpg

#7
03-12-14, 04:06 PM
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122vac is a tad above the normal but is perfectly acceptable.
Check it again in the summer with all the A/C load on it.

#8
03-12-14, 06:36 PM
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Voltage is nominal and will vary depending on load and location. Standard nominal voltages listed in the NEC are: 120,208/240,277,(347),480,600 +/- 10% is considered normal.

#9
03-12-14, 06:50 PM
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Most utilities strive to provide their residential customers with 120/240 volts. What the individual customer actually receives is dependent upon several factors. First and foremost is the size (kVA rating) of the transformer serving the residence and how many other houses it serves. Second is the average load on each house and third the load on any particular house.

I have a 50 kVA transformer in my front yard (pad mount) and it serves four other houses in addition to mine. My nominal voltage right now is 124.2 to 124.4 as read from a Kill-A-Watt meter. My Fluke model 23 is reading 125.0 to 125.1 on a different circuit and the time is about 6:45 PM. I'll add that my total house load at the time I read those meters was quite low, probably in the neighborhood of 750 watts or less so those are probably the highest numbers I see.

At the hysterical museum where I volunteer the nominal "480 volt" supply from a 1,500 kVA transformer is 504 volts under minimum load.

#10
03-12-14, 07:05 PM
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The voltage in my house ranges anywhere from 110 to 130 volts depending on season, time of day, and what all I'm running. I'm fed off a 50KVA transformer up on the pole, which feeds 14 other houses. Voltage currently is 120.8 with about 9KW load. (electric heat and cleaning the fryer)

#11
03-13-14, 09:20 AM
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Utilities do not have to follow the same wire sizing rules (e.g. 30 amps max for 10 gauge) for overhead wires. The wires, hanging free in the air, won't overheat for somewhat larger currents. But voltage drop can be an issue. Particularly for homes farther from the pole transformer, there could be considerable voltage variation depending on current draw of other homes.

At least in the early 20'th century, if not persisting to this day, the pole transformer may be regulated to output over 130 volts so that during reasonable worst case loading, the homes at the far ends of the lines would get at least 100 volts. So called 130 volt (incandescent) lamps were manufactured in large quantities for use in such neighborhoods, primarily in rural ateas.

#12
03-13-14, 10:42 AM
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My house stays consistent around 122.
It's fine. .......................................

#13
03-13-14, 11:32 AM
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There is nothing to worry about. 122 is within the normal expected range.

#14
03-13-14, 11:54 AM
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As Tolyn said, the tolerance is 120v +/- 10%.. Which means anything from 108-132v is technically acceptable. Considering nearly everything these days contains a 'worldwide' power supply capable of running on anything from 100-250v anyway, 122v is not going to bother anything.

What is NOT acceptable however, is variations in the frequency. That tolerance is 60Hz +/- 0.01Hz. When the frequency goes above or below 60Hz bad things start happening to things with electronics in them. That is true 'dirty' power.

This is why if you ever consider a backup generator for your house, it's best to spend some money. because if you cheap out or undersize it, the frequency gets thrown off when it bogs down (the frequency is a product of the engine RPM). Many an electronic furnace controller and TV have been fried from the dirty power coming out of a cheap generator.

Electric clocks start to go out of whack when the frequency is off too, because their motors/crystals are keyed to exactly 60Hz.

#15
03-14-14, 02:15 AM
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Amazingly, there was a proposal a few years back that would have allowed the electric utilities to let the frequency vary several Hertz as a means to save fuel in the power plants. It was theorized at the time that there were very few clocks left that required precise frequency control and the same was true of other appliances. I think they, whoever "they" may have been, were absolutely wrong but other than the one mention, which I believe was a newspaper story, I never heard/saw/read anything more about it.

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