How does an electric meter work?

I did not check this out on snopes but have heard that the eletric meters on our houses always read the higher of the two lines coming in to determine the amount of juice used. The rumor goes on that you should *balance* your panel so that the same number of constant users are on either side of your panel. An example might be that your fridge should be on one side and your furnace on the other, or electric range on one side and electric dryer on the other.
Is there any truth to this or is it one of those tall tales based on some obscure Tesla theory?
Would this gadget really save me money on my electric bill?
http://www.renaissance-pacific.net/ElektraBand_Product_Info.pdf
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the only thing this does is bring more money to the merchant.
Yes both sides of the power line should be balanced, but BOTH items must be on at the same time. So the neutral doesnt carry current.
SAVE YOUR MONEY!
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Wow.
I actually read that whole PDF just now. It's kind of interesting. Other than not explaining in technical terms, looking silly, and having a lame brochure, it actually doesn't make any wild claims like I would have expected.
It makes a claim of 3-5% reduction. It specifically says it doesn't work for digital meters, and it is not a magnet, and it won't cause inductive heating problems. It mentions a handfull of other caveats too even. Since when does a scam make such modest claims and have so many caveats? What is the world coming to? Will I start getting "Enlarge your ***** by 3%!", or "Lose 1 to 3 lbs and keep it off as long as you keep exercising and maintaining a healthy diet!" emails?
So can anyone answer the op's original question? Does a mechanical meter overestimate when the load is imbalanced? And if so, can anyone think of a plausible scenario, in any possible situation, real or imaginary, that would let the device in the PDF picture (I can't tell what it is -- just some kind of metal C-shaped thing I guess) do anything that could even have a remotely possible chance of having even a miniscule, undetectable, insignificant but still non-zero effect on the meter? I.e., is this just a not-very-useful and very poorly marketed invention, or a not very useful and poorly hyped scam?
-Kevin
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Urban legend. To start with the stove and dryer heating elements are on both sides of the line anyway as is anything that is 240v. The meters do a pretty good job of accurately measuring the power used but there is some saving to be had by balancing your panel because the voltage loss (heat) in the neutral wire is eliminated. It will not be a big number tho.
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I would look into power factor correction first.
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On 24 Apr 2006 09:58:46 -0700, snipped-for-privacy@gmail.com wrote:

dubious claim from some website that this is "legal"?
The Power Companies take theft of service very seriously and rest assured that if you device does what it claims to do, you could set yourself up for serious problems. At the very least, they can afford better lawyers then you.
BTW, most of the mechanical electric meters that I have seen don't even have a connection to the neutral.
Beachcomber
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wrote:

Power correction factor is different. It can be done inside, after the meter and is perfectly legal. I don't know if it is a viable option for residential, but for industrial use, there are savings to be had.
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I have wondered why certain appliances (espically washers and dryers) didn't already have power factor correction already built in.
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wrote:

Residential Meters do not measure for lagging or leading power factor. I've never heard of a utility charging a residence for low power factor. If this is true, there is no economic justification for making corrections to the power factor. Hence... I do not understand why you made the statement above:
"I would look into power factor correction first"
Beachcomber
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On Mon, 24 Apr 2006 17:49:56 GMT, snipped-for-privacy@notreal.none (Beachcomber) wrote:

I've been good at recognizing BS at least since the age of 5, and this product smells like it. Also, I think a meter designed to recognize and use the line with the HIGHEST current would be a lot more complicated than one that responded to the total.
A claim of ONLY 3% savings is good enough if people still buy the thing and would attract those who wouldn't believe 50%.
--
Mark Lloyd
http://notstupid.laughingsquid.com
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My understanding is that large, commercial, installations such as factories, supermarkets, refrigerated warehouses etc. use capacitor banks to adjust the power factor of their motors. In fact, power companies also have capacitor banks installed alongside the street, beside switches, to adjust the "average" power factor of loads to neighborhoods. On the individual scale, where a commercial consumer has a meter that measures amperes against time, that can be a benefit to both the consumer and the power company.
The average homeowner has a meter that's called a VAR meter- Volt Amp Reactive. The cumulative power factor of the home's A/C, fan motor, refrigerator etc. are not measured by the meter and even a professionally calibrated and installed capacitor bank would make no difference in the 'Kilowatt Hours" consumed each month. To take advantage of this, the consumer would have to install a meter such as found in commercial installations. On some home-type of installations, such as an A/C compressor, pump, air compressor or possibly a refrigerator, a run capacitor to correct the power factor of the individual motor might benefit from a longer life or cooler operation, but it would be minimal and not seen on the electric bill.
I'm sure that there are some engineers out there who can correct what I've written or expand on it. I'd sure like to learn more about this.
Mark
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snipped-for-privacy@gmail.com wrote:

There are companies marketing power factor correcting boxes to homeowners. They are just boxes with a bunch of capacitors in them and instructions on how to connect up the "right" number of capacitors to your incoming power conductors to try and bring your home's average power factor closer to unity. I think the guys promoting them are just "Sharp cookies selling Girl Scouts." <G>
AFAIK none of those boxes do an automatic correction when the overall power factor of the loads being used changes as different appliances get turned on and off.
Also, the big joke is that very few utilities install meters which can measure power factor at peoples homes so nearly all the residential meters in use now measure only the "real power" consumed anyway.
So, using one of those power factor correction boxes won't do much to directly reduce your electric bill. It will however help reduce the power company's losses on THEIR lines, which in a perfect world could allow them to pass those savings back to their customers about the same time as pigs start flying.
Installing power factor correction capacitors directly at the larger AC motors used home appliances would reduce by a tiny amount the power "wasted" in heating wiring within your house, but I wouldn't expect the resultant savings to be worth the effort.
A bit more effective is the addition of capacitors arcoss the starting winding switches on induction motors to make them work in a "capacitor run" mode. That was shown by some US Navy researcher back in the 70s (IIRC) to improve the efficiency of those kind of motors by about 10%. AFAIK nothing much ever came of that, but maybe the skyrocketing cost of fuels will bring that idea to the fore again.
Jeff
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snipped-for-privacy@gmail.com wrote in

Why? Household meters read true power usage, and happily ignore any power factor adjustments (or misadjustments).
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Try doing so. That claim doesn't make sense.

240V appliances are always on both sides. They have 2 hot wires, 1 connected to each side.

Sounds like BS.
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wrote:

Not only that, there is no explanation as to how this thing works that conforms to the known laws of physics.
Any little piece of material that you wrap around your service entrance conductors is going to have little if any effect on "equalizing" the load between the hot wires. It is the current flowing that creates the magnetic field.
Beachcomber
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snipped-for-privacy@gmail.com (kevin) writes:
| So can anyone answer the op's original question? Does a mechanical | meter overestimate when the load is imbalanced?
Yes, in the sense that the typical 4-terminal (1.5 element) meter most often used in residential split-phase service charges the customer for 150% of the losses in the neutral on the utility's side of the meter. (That's the simple case of one service drop from transformer to customer. For multiple connections the analysis gets more complicated.) This seems to surprise many people. Google for Blondel's theorem before trying to come up with an argument that the meter does not make this error. :)
N.B. This has nothing to do with the meter's being mechanical. You can build a 5-terminal (2 element) mechanical meter that does not have the error. You can build a 4-terminal (1.5 element) electronic meter that does have the error.
| And if so, can anyone | think of a plausible scenario, in any possible situation, real or | imaginary, that would let the device in the PDF picture (I can't tell | what it is -- just some kind of metal C-shaped thing I guess) do | anything that could even have a remotely possible chance of having even | a miniscule, undetectable, insignificant but still non-zero effect on | the meter?
I certainly can't.
                Dan Lanciani                 ddl@danlan.*com
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Thanks for answering (partially) my question. This thread is interesting -- it seems to be filled with more BS and hype than the original link even was.
I don't entirely understand your answer, though. I wasn't aware that there was a "neutral on the utility's side of the meter". And if there were, and I had a perfectly balanced load, then the neutral would have no current, right? Which means... no losses, and hence no cost? Obviously wrong... can you explain a little more?
And moreover, there was a lot of BS in this thread about balancing the panel to begin with. To say that 240V devices are on both legs is irrelevant to the question of whether balancing a panel makes economic sense for the homeowner. Does a homeowner with a horribly imbalanced panel get charged more than the same homeowner if they just rearranged the breakers on the panel?
-Kevin
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Edwin Pawlowski ( snipped-for-privacy@snet.net) said...

It is not a viable issue for residential customers as they are charged for actual power used (kWh).
Industrial users tend to have heavy motor loads that create a lagging power factor. With a power factor of 1, kVA is equal to kW, so the facilities needed to deliver 1000 kWh only has to be able to carry 1000 kVAh, and the losses due to heating that equipment is at its minimum.
If the customer's power factor was 0.5, then the equiment need to deliver that same 1000 kWh needs to support 2000 kVAh! This means twice the current for the same power. Since heat losses are proportional to the SQUARE of the current, you lose FOUR times the power just heating the infrastructure.
Industrial customers are charged for kVAh if they exceed a certain threshold, so it is in their interest to keep the power factor close to 1. They maintian large capacitor banks to do so.
Residential customers do not generally run at a lagging power factor. In fact, it is likely they have a slightly LEADING power factor resulting from the combined capacitance of all the wiring in the home. I know this from when I used to work as a watchman in a plastics moulding plant. During the weekends when the plant was shut down, it was not unusual for the power factor to be about 0.9 on the leadinig side (there was a PF meter at the service entrance).
As the plant was started up and various motorized equipment was started, the power factor would shift towards the lagging side and capacitor banks would be switched in.
--
Calvin Henry-Cotnam
"I really think Canada should get over to Iraq as quickly as possible"
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