Unbalanced electrical load

[orezok]

I've been a licensed general contractor since 1979 and I've asked several of my electrical subs this question, but nobody seems to know the answer.

On a typical electrical main panel, the loads between the legs are usually "balanced". That is the labeled amperage of the breakers on leg A is roughly equal to the amperage on leg B (ignoring 2 pole breakers).

But what if the leg A breakers handle appliances in the kitchen, the furnace and other large draw items, but the breakers on leg B handle lesser (or no) draw items such as lighting or "unused" circuits.

The question is, does the electric meter measure the greater amperage draw of the 2 legs or an average of the 2?

 

[LD1]

I could be wrong but I thought they took the sum of the two legs based on 120v to ground. IE, 50 amps on one leg is 6kwh and 25A on the other is 3kwh so total would be 9kwh.

But if they are indeed averaged, there would be no difference. Because there are only two legs. so the average of 25 and 50 would be 37.5a on 240v would still be 9kwh.

But if they are indeed taking the larger leg, 50a, 6kwh, and doubling that.....that would be a ripoff @ 12kwh:confused2:

Either way, I'm not an electricial and I dont know. Just wanted to share what I "thought", and also subscribe because I might learn something.

If they do take the larger leg, it wouldnt take much to re-balance based on conditions (season, peoples preferences, etc) and save some $$$. But I dont see it being the case. I think you actually pay for what you use.

 

[hr3]

The simple answer is,,
The electric company charges you for watt-hours, not volts. To figure volts you use the fomula Volts x Amps = Watts. A device that runs on 240V will use half as many amps as an identical device that runs at 120V, so the wattage will be the same -- and so will the cost.
The kinds of appliances that use 240V tend to be energy hogs, like air conditioners and electric clothes dryers, so running those appliances will cost you. It's not because 240V costs more, it's because you're running energy-gobbling appliances.
Next will come several not so simple answers,,:laughing:

 

[orezok]

The simple answer is,,
The electric company charges you for watt-hours, not volts. To figure volts you use the fomula Volts x Amps = Watts. A device that runs on 240V will use half as many amps as an identical device that runs at 120V, so the wattage will be the same -- and so will the cost.
The kinds of appliances that use 240V tend to be energy hogs, like air conditioners and electric clothes dryers, so running those appliances will cost you. It's not because 240V costs more, it's because you're running energy-gobbling appliances.
Next will come several not so simple answers,,:laughing:

Yes that's a simple answer, but it doesn't address the question.

 

[ducks13]

It measure each leg separately and adds them together.

 

[grsthegreat]

There was another discussion here about that same thing, and even though i am an electrician i was always told that it only measured the highest leg.

I found out that that was wrong (even though i still get that told to me by power company employees and at code update classes.....i think everyone is unsure)....it measures both loads... so it doesnt matter if its balanced

We still try to balance our panels out the best we can, but its impossible to know what someone may plug in later on. The 240 loads are automatically balanced so they dont count.

Back in the good old days, i could unplug my meter and put it on upside down and spin the meter backwards well welding...cause i was a spoiled little brat those days.

The new electronic meters prevent that....too bad (cause im still a spoiled little brat at times).:mur::mur:

 

[crazyal]

There's a much bigger reason why you need to balance your load. Anyone ever wonder why the two 'hot' wires feeding the main breaker box are larger than the one neutral wire?

 

[grsthegreat]

There's a much bigger reason why you need to balance your load. Anyone ever wonder why the two 'hot' wires feeding the main breaker box are larger than the one neutral wire?

Cause alot of the larger loads in residential applications are 240 and dont require a neutral. In commercial applications the neutral and the hots are the same size.

 

[5030]

I'm so glad I always hire a certified electrician to hook things up.

I've considered unplugging the meter and jumping the lugs 'cause I'm cheap.

Just considered, I'd probably electrocute myself.

 

[BobRip]

They measure and charge for watt hours. Balancing is good as mentioned above, but it does not affect your bill.

 

[grsthegreat]

I'm so glad I always hire a certified electrician to hook things up.

I've considered unplugging the meter and jumping the lugs 'cause I'm cheap.

Just considered, I'd probably electrocute myself.

bACK IN THE GOOD OLD DAYS..YOUD GET A SLAP ON THE HAND AND SOMEONE SAYING "oH YOU KIDS". nOW DAYS ITS CONSIDERED THEFT OF A PUBLIC UTILITY AND WILL RESULT IN JAIL TIME. (OK. i officially hate my caps key. I'm going to pry that stupid thing out of the computer keyboard.)

SUCCESS. I just found out to disable the caps key on this stupid Microsoft cordless keypad. no more unintentional caps

 

[BobRip]

I'm so glad I always hire a certified electrician to hook things up.

Then the certified electrician sends his nephew, who could not get a job anywhere else.

 

[BeezFun]

The question is, does the electric meter measure the greater amperage draw of the 2 legs or an average of the 2?

Neither. It continuously measures the instantaneous voltage and the instantaneous current and uses them to display instantaneous power consumption. It does that by using induction to rotate a little wheel in the meter at a rate proportional to both voltage and current. There is a shunt circuit for voltage that exerts a force to rotate the wheel, and a series circuit for current that exerts a force to rotate the wheel. That little spinning wheel is what drives all those numbered disks you see spinning in the meter. Those numbered disks are counting how many times the little wheel spins. There only needs to be a single wheel for residential because it's only single phase. If you have 3 phases, the meter will have 3 spinning wheels.

So to answer your question, the meter doesn't know or care anything about whether you balanced the circuits in the service panel, it measures instantaneous power consumption.

 

[DaveOmak]

An electric meter is a simple device. It only measures the amperage on the highest leg and charges accordingly.
To prove this theory check which leg has the highest amperage flow and measure the dial rotation. Then plug a 1500 watt electric heater into an outlet on the leg that has the lowest amperage flow and measure the dial rotation. You might find the dial rotation has changed. Then plug the heater into the leg that has the highest amperage and check the dial rotation. You will find it has increased.
The reason for this is the meter is baxed on 220-240 volt equipment which is supposed to draw equally from each leg..

I moved into an older house which had been remodeled several times. My electric bill was very high. An industrial electrician friend of mine explained this theory to me and loaned me an ampmeter to check the electrical panel over several days and several times during the day. I found one leg to be 8 amps higher than the other. I checked individual circuits and found by moving the breakers to equal the load on the incoming legs I saved $45 a billing cycle.
Check it out before you call BS on this.. Buying an ampmeter and balancing your home electric panel load will pay for the meter.. This is "probably" only necessary on older homes or maybe on newer homes that the electrician didn't care...
I have done the balance on my panel and know it works.. Dave

 

[grsthegreat]

Neither. It continuously measures the instantaneous voltage and the instantaneous current and uses them to display instantaneous power consumption. It does that by using induction to rotate a little wheel in the meter at a rate proportional to both voltage and current. There is a shunt circuit for voltage that exerts a force to rotate the wheel, and a series circuit for current that exerts a force to rotate the wheel. That little spinning wheel is what drives all those numbered disks you see spinning in the meter. Those numbered disks are counting how many times the little wheel spins. There only needs to be a single wheel for residential because it's only single phase. If you have 3 phases, the meter will have 3 spinning wheels.

So to answer your question, the meter doesn't know or care anything about whether you balanced the circuits in the service panel, it measures instantaneous power consumption.

wheels...wheels... i don't need no stinking wheels. Mine is electronic now..... digital display also. Sends the readings to central center so no more meter readers also.

 

[slowzuki]

Here's another question to scratch your head on, what power factor is a residential meter calibrated for? Straight resistance or do they guess you'll have a bit of an inductive load?

 

[5030]

wheels...wheels... i don't need no stinking wheels. Mine is electronic now..... digital display also. Sends the readings to central center so no more meter readers also.

They (Detroit Edison) is contemplating that here, however, I don't want no stink'in digital transmitting meter. That meter can shut off your juice at the utilities whim. We ain't play'in that tune here.

I take it the meter inside is basically an induction motor?

 

[hr3]

Ok orezok let me try again then.. Inside your mechanical type electric meter there is an induction motor that spins the wheels..with me so far ?? There are 2 wires on it that come from your house.. Lets say you are drawing 500 watts on one leg and nothing on the other.. Then you are being charged for 500 watts.. Lets keep the 500 watts going on the first leg and add another 500 watts to the second leg now you are paying for 1000 watts,, Still with me,,, Now lets unbalance the load lets add another 500 watts to leg number 1 now you are drawing 1500 watts total and are paying for 1500 watts..
Did I do better this time ??