Thread: Branch circuits

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110 to 120 volt range (and I don't mean stove/oven).
Also 220 - 240 volt range.
Some people shorten it to "110", some to "120", some probably to "115".

110 volt was a long, long, long time ago.

Most are now 120 volt - 125 volt.

Back when they were 110 volts, that created 220 volt circuits, remember that terminology?

Now, though, with 240 volt circuits, that makes the single pole circuits half that, or 120 volts.

More confusion.
The NEC uses 125v.
(A) Dwelling Units. All 125-volt, single-phase, 15- and
20-ampere receptacles installed in the locations specified in
(1) through (8) shall have ground-fault circuit-interrupter
protection for personnel.

I thought that the US standard is 117 volts. The odd value of 117 V is the RMS (root mean square) of a sine wave corresponding to 165 V peak, which is 330 V peak to peak. Wikipedia Mains electricity - Wikipedia, the free encyclopedia says that the standard is 120 V and that 110, 115 and 117 volts have been used in the past. So I guess it is 120 V.

- BOB

110 volt is an archaic designation.
Today the house service voltages are properly described as 120/240 on three wire services.
The NEC uses 125 volt, and certain equipment ratings will show 115 volt. The voltage from the utility co. does fluctuate -- "rolling brown outs" for instance. So if you actually measured the voltage on a two wire branch circuit you might get anywhere from 110 to 125 volts.

Evan Grugett

Evan Grugett Inspections
“Educating the Real Estate Consumer”

PO Box 188
Eastchester, NY 10709
914-723-5795
egrugett@optonline.net

Nearly all 120 receptacles that I check register 113-118 with an ampmeter.

I inspected a house last year, built in 2004, and the buyer didn't occupy for six months, then let her daughter move in.
Her daughter called me to complain about the electrical receptacles (blown tv, stereo, and computer). She just bought her third clothes dryer in six months. The appliance store said "this is the last one we will replace".
She called the electrical provider and the city inspector. They told her the ground wire is too small.??

I checked the inspection report, all in good order: 225 amp. service, #4 ground wire attached to the ground rod...

I went to the house checked the panel and ground wire/rod.

I then checked the breakers with an ampmeter.
120 amp read 140 amps
240 amp read 280 amps.
I checked the receptacles 140 amp reading. Dryer receptacle 280 amps.
I turned the oven on: Instant HOT!
I turned the cook top on: INSTANT VERY HOT!!!!

My conclusion was that the electrical transformer is not regulated and is overpowering the electrical to the house.

Randy, you identified the problem that only the power company can correct, I am sure your customer appreciates your extra effort. (you did let her know that this service was outside the scope of a home inspection, right?)

BTW, you might want to edit your post for volts and amps, as I am sure you are aware voltage and amperage are not interchangeable terms even though "Amprobe" brand meters will also measure voltage.
Jim

Refer to ANSI C84.1 2006 - National Standard for Electric Power Systems and Equipment - Voltage Ratings (60 Hertz).

"A standard specifying a steady-state voltage tolerance for the electric utility at the point of service to be within 5 percent of nominal for non-lighting loads. The standard also specifies steady-state voltage tolerances for acceptable performance of end use equipment of plus 6 percent to minus 13 percent."

There are two ranges (A and B) in the standard. Range A is plus or minus 5% on nominal. Range B is between +6% to -13% nominal. The nominal for Ranges A and B is 120V.

There's more about how the ranges are defined but basically for Range A the number of events outside the range should be few. When voltages outside of Range B occur, "on a sustained basis", the utility is to take corrective actions to bring the voltage back to within Range A.

Originally Posted by RANDY NICHOLAS

Nearly all 120 receptacles that I check register 113-118 with an ampmeter.

I inspected a house last year, built in 2004, and the buyer didn't occupy for six months, then let her daughter move in.
Her daughter called me to complain about the electrical receptacles (blown tv, stereo, and computer). She just bought her third clothes dryer in six months. The appliance store said "this is the last one we will replace".
She called the electrical provider and the city inspector. They told her the ground wire is too small.??

I checked the inspection report, all in good order: 225 amp. service, #4 ground wire attached to the ground rod...

I went to the house checked the panel and ground wire/rod.

I then checked the breakers with an ampmeter.
120 amp read 140 amps
240 amp read 280 amps.
I checked the receptacles 140 amp reading. Dryer receptacle 280 amps.
I turned the oven on: Instant HOT!
I turned the cook top on: INSTANT VERY HOT!!!!

My conclusion was that the electrical transformer is not regulated and is overpowering the electrical to the house.

Randy,

First, a minor correction ... you means "volts", not "amps", right?

With the 120 volt circuits you could read all kinds of voltages if there is a neutral problem (not a "ground" problem, but a neutral problem). If you leave turned 'on' whatever is 'on' and check voltages, you should get two different voltages on each phase, but both should add up to 240 volts (give or take a few volts), i.e., if one phase leg reads 60 volts, the other will read 180 volts (60 + 180 = 240).

If, however, you turn 120 volt lights, appliances, etc. on and off, the voltage will change as you do so, with no apparent reasoning behind it.

HOWEVER ... all 240 volt circuits will still read 240 volts, they will be unaffected by a bad neutral/bad neutral connection.

In converting you "amps" readings to "volts", the thing which stands out to me is this one "240 amp read 280 amps.", as that would be 280 volts, or 277 volts ... which would indicated an improperly connected 3-phase transformer somewhere, maybe feeding her house.

If that's the case (and there is no bad neutral), then the 120 volt circuits will be half that 277 volts, or 138.5 volts - which is eerily close to what you read at "120 amp read 140 amps", i.e., 140 volts.

First, DO NOT put that you used your ammeter and read amps, you used your voltmeter and read volts.

Second, DO NOT put "My conclusion was that the electrical transformer is not regulated and is overpowering the electrical to the house." as transformers are not "regulated".

I would even hesitate to state for sure that it was the power company based on your readings as you stated them (although they do work out nicely to 277 volts).

In a case like that, and if the house is not far from yours or not far out of the way, go back tomorrow and measure the voltage at the service equipment, i.e., the main disconnect. *IF* you are indeed measuring 277 volts at the two phase conductors coming in from the service, there is indeed a power company problem and they need to be called ASAP.

But, for the life of me, I can't figure out how they would have mis-wired that transformer to get 277 volts instead of 240 volts, but that would be the logical place to look first. Maybe they have voltage problems feeding into that transformer?

Jerry,
Your're correct, I meant "volts" not amps., in my post. I didn't use the phrase "amps" in my follow-up inspection.
I did probe each of the 240 breakers, the reading was 140 VOLTS at each = 280 volts.

Conclusion: The electrical provider changed the transformer, all is well.