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Re: Balancing the Breaker Box

Discussion in 'Electrical Engineering' started by Bill, Nov 22, 2009.

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  1. Bill

    Bill Guest

    "RogerN" wrote in message

    When I hear people say nonsense like this, I like to challenge them. "Where
    did you get that information? Who told you that? Where does it say this?

    Furthermore it is pretty impossible to "balance" an electrical load in a
    home anymore than it already is. Larger loads are 240 volts and already
    balanced. This leaves 120 volt lights and 120 volt outlets to balance. Those
    mostly used would be kitchen and living room. That's about it!

    And just think about this for a moment. With all the technology in our
    world, wouldn't electric companies easily be able to design electric meters
    which record electric use of any type - balanced or unbalanced? Well they do
    and have done so for as long as I can remember. This is the way electric
    meters work!

    On electric meters...
  2. James Sweet

    James Sweet Guest

    If I had a dollar for every time someone started spouting a story like
    that in order to look like some sort of "expert"...

    It's complete BS, the power company does not charge based on Amps *
    Volts (apparent power), they charge by kilowatt-hours (true power), it's
    what it says on the bill, and if they were pulling some stunt to defraud
    customers there would be a massive lawsuit in no time flat. A kilowatt
    is a kilowatt whether it's drawn from one phase, the other, or both, period.

    As someone else pointed out, the big loads are 240V anyway so they
    already use both legs of the panel and are inherently balanced. The
    smaller loads vary so much based on what's being used at the time that
    you won't be able to optimize it much beyond what was done when the
    house was wired.
  3. Bill

    Bill Guest

    BTW - If you want to lower your electric bill, there is no "magic bullet".

    You need to learn the value of a penny and learn to add. (Pennies saved add
    up to dollars, and dollars saved all up to hundreds of dollars!)

    Do many things which are small savings on electricity and these combined
    will add up. Like replace regular light bulbs with compact fluorescent
    bulbs. Many electronic things always use electricity because they are always
    "on". Plug these into a power strip and turn the power strip off when not in

    An electric water heater can be 30% of an electric bill. Take fewer and
    shorter showers. Turn off the water when soaping up, then back on to rinse.
    Wash clothes in cold water. Basically use less hot water.

    Get new energy saving appliances which use less electricity or less hot

    More energy saving tips here...
  4. krw

    krw Guest

    How are you going to measure power factor directly (remember to
    include harmonics)?
    "Ather poster" is wrong, too. Power meters measure power directly.
    Why mess around with computation?
    Exactly. Somone is blowing smoke up your butt.
  5. daestrom

    daestrom Guest

    Not all meters are the same. In the UK they sense the current in one
    leg and that is enough because the current in the other leg must be
    equal to the first leg (they don't have a neutral over there, all of it
    is 240).

    Meters used in some 3-phase service also only have one current sensing
    coil. To measure all three phases it takes at least two meters,
    sometimes three.

    But the household meter used in the US has two current sensing coils,
    one in each hot leg. They don't sense neutral current because that is
    simply the difference between the two hot legs (not accounting for major
    ground faults)

    The torque developed on the wheel is the product of average current in
    the two legs and the voltage sensing coil that measures the 240V between
    the two hot legs and the phase angle between them. (this is the old
    induction style meter, but the modern digital ones do effectively the
    same thing, only in firmware).

    In single-leg meters, the current flows through two coils, one
    positioned on each side of the voltage sensing coil (one of the current
    coils is wound backwards from the other). These are positioned, one on
    each side of the potential coil. The interaction of the magnetic fields
    from the three coils is what turns the disk.

    In a residential meter for the center-tapped 120/240 service, one leg of
    the 240 is fed through one current coil and the other leg of the 240
    service is fed through the other current coil. The potential coil is
    fed from across the two hot legs. The neutral conductor passes straight
    through the meter box. So it 'senses' the average of both hot leg currents.

    Despite all the stories out there about "...a friend of mine did
    such-and-such and saved" or "the power company knows this but doesn't
    want to tell anyone...", it just isn't true. The metering schemes have
    been reviewed by state commissions for every public utility in the
    country. No way are they all 'in on it'. The simple fact is that the
    inventors of the modern kWh meter are smarter than that and tested just
    about every conceivable combination of imbalance/balance.

    I suppose there's a one-in-a-million chance that the power company
    installed the wrong type of meter and is only reading one current leg,
    but that isn't very likely. Or that some small mom-and-pop coop utility
    thought they would save money using the wrong type of meter, but that
    ain't likely either.

  6. Bill

    Bill Guest

    "RogerN" wrote in message
    Oh we have heard all sorts of nonsense like this!

    We just understand electricity and know these things are not true.
  7. James Sweet

    James Sweet Guest

    Sure, they could, just like they could have a little hamster in there
    running on a wheel to turn the dials, but they don't. Power meters have
    coils on both legs that act on a metal disk causing it to rotate in
    response to true power passing through either or both leg. Some newer
    meters are electronic and do measure the voltage as well as the current
    and power factor, again in both legs. There are some good application
    notes on Austria Microsystem's website that describe how their offerings
    work. The electronic meters also contain various tamper detection
    circuitry that will alert the electric company if suspicious
    circumstances are detected.

    Magical money saving methods to fool or otherwise alter the response of
    a residential power meter all fall into the same bucket as the mythical
    100 mpg carburetors, fuel magnets and other pseudoscience bullshit. The
    short answer is they don't work, but that doesn't stop countless people
    from trying every one of them, and failing, while others swear to have
    witnessed fantastic results.
  8. James Sweet

    James Sweet Guest

    Which many in here also understand. I have a couple of old KWH meters
    sitting around, I've played with them, they're simple devices, and they
    just plain don't work the way you seem to believe they do. Being
    mechanical, they don't calculate anything, they simply respond to true
    power, regulated by the laws of physics. Both sides of the meter act on
    the same disk so the result is additive. Draw through either leg and the
    meter turns. Draw through both legs at once and it turns faster. The
    disk is directly coupled through a gear set to the dials on the face
    which do nothing more than count the number of rotations the disk makes.
    Trust me, you can't fool it by shifting loads around. About the only
    thing that happens to the accuracy is dried up lubricant and/or aged
    mechanical parts which normally results in slowing the meter in the
    customer's favor.
  9. Guest

    Guest Guest

    They could "take.. other" but they don't - There will be two current coils
    for 120/240V 3 wire and a voltage coil (240V). so that (I1+I2)V is measured.
    The torque produced is proportional to the real power. It doesn't matter if
    all the load is on one leg, split between legs or all line to line - the
    real power will be read correctly independently of the power factor. The
    energy is measured by counting disc rotations. Accuracy requirements are

    Balancing the legs will not affect the meter except that there may be a
    marginal decrease in losses in the wiring and this gain will be lost as load
    balances change with activities.

    James Sweet has it right.
  10. krw

    krw Guest

    No, the meter measures *power*. As others have been trying to tell
    you, the torque (hence RPM) of the disk is proportional to the current
    times the voltage in the respective coils. No "calculating" at all
    and *certainly* there is no power factor calculated or measured.
    ....and reduces the neutral current, if that's important to anyone.
  11. James Sweet

    James Sweet Guest

    There only thing magical is the belief that you are somehow being
    charged for power that you are not using. The meters work, they are
    accurate, the response is not altered by balance. If it is already
    accurately measuring your consumption, then how do you propose to alter
    the reading without somehow fooling it into an inaccurate reading?

    Now it's starting to look like you're simply trolling here.
  12. krw

    krw Guest

    Does to me. Power companies aren't in the business of giving away
  13. krw

    krw Guest

    You have it backwards. Power factor is P/VA. Power factor is a "fudge
    factor" that describes the difference between apparent power and real
    power. PF is not a physical entity and is not measured directly.
    Right, as you were repeating here.
    Torque * RPM = HP The motor (meter disk) is doing work.
    Again, you have it backwards. PF is the conversion factor not what's
    being measured. POWER is being measured. Directly. No conversion
    Honestly, the only one here (ignoring Proteus) that doesn't understand
    this, is you.
    Wierd way of looking at it, but sure. That's the way the meter is
    The power company would be stealing from you. That's not allowed any
    more than you stealing from them. Laws are funny that way.
    It's NOT true, so saying "if it were" is a meaningless exercise.
    No wannabees here. Well, perhaps you wannabe.
    Of course it is. It's a promise that cannot be fulfilled. Hucksters
    sell this sort of magic pill all the time.
    Sorry you feel that way, but what you're posting (and continue to
    post) is crap. That's not the way things work, as you've been told
    here by *everyone*. Your electrician friends need to go back to
    school (and I am being kind).
  14. Dean Hoffman

    Dean Hoffman Guest

    Several of the guys who answered you are probably EEs. They
    don't generally say much about it. Once in a long while, one might
    mention something he did in college or something about their
    certification. They don't have to brag about it. They'll generally
    know by reading each other's writing. They'll know in an instant I'm
    not one if the subject is at all technical.
    I didn't see much that looked like wise assed remarks. There
    wasn't anything close to the flames I've seen other places. People
    are just stating facts.
    The public service commissions or possibly the states' attorney
    generals should be all over this if it was real.
    I know scales at farmer's coops are tested for accuracy by the
    state. Gas pumps have stickers on them assuring their accuracy. States
    have bureaus of weights and measures to make sure things are according
    to hoyle. Why would they ignore the utility companies?
    What about all the lawyers running around? Think of the money a
    lawyer could make from a class action lawsuit if he won against a major
    utility. Here's a list of some of the things lawyers have sued for:
    One example there is a lawsuit against the makers of Froot Loops
    because they don't contain fruit.


    Not an EE, and I don't play one on TV.
  15. James Sweet

    James Sweet Guest

    None of us are telling you that meters *could* not work that way, or
    that *if they did* work that way you would not be correct. What we are
    telling you is that meters *don't* work that way, so speculating what to
    do if they did is like speculating if the moon were made of cheese how
    best prepare it to eat. We know that it's not, so why worry about what
    to do if it is?

    Given the way meters *do* work (they accurately measure power used),
    getting them to read less (not accurate, false reading) is stealing
    power. If the meters were ever behaving in a manner that caused you to
    get billed for power you did not actually use, regardless of the load
    balance, that would be fraud on the part of the power company. Again,
    this is irrelevant outside of this imaginary situation because this is
    not how they actually work.

    I'm not sure what is so difficult about this concept. There is nothing
    to optimize, the rest of the discussion is a hypothetical (imaginary)
  16. krw

    krw Guest

    No, there is a difference between the physical quantities measured and
    the conversion factor between them. You can't measure power factor,
    only derive it from power and VA.
    Nothing limits RPM, other than the power measured. The whole idea is
    to measure the revolutions.
    You're talking nonsense again.
    I didn't say your calculation was wrong, just that you had the horse
    before the cart. You don't measure PF directly. It's the difference
    between watts and volt-amps.
    It *would* be stealing. In this case it would be the power company
    stealing form the consumer.
  17. The meter, is an electromeechanical integrator. It measures,integration
    calculus [from 0 to 2pi]tan (omega * t) dt where omega=2*pi*f (frequency in
    So, it's not to be fooled by trivial methods, like putting all loads to a
    high leg, etc. like some poster said, is like the elusive 100mpg carburetor,
    or fuel additives that increase mileage, etc.
  18. Guest

    Guest Guest

    What you heard from the" another electrician" was, purely and simply, BS.
    Balancing the load between legs is optimal with respect to losses but
    doesn't actually increase the KW capacity (not KWH) of the system. It just
    means that you can use the capacity slightly more efficiently.
    If you have a load of 15KW on one leg and 0 on the other, you will have more
    losses and poorer voltage regulation than if you have 7.5 KW on each leg.
    The meter simply measures what you actually use (+ losses on your side of
    the meter). Now the high leg metering X2 would be a cute but highly illegal
    trick that, along the way, would become apparent and the cost to the
    utility in class action suits would be prohibitive. Honesty in metering is
    something that is actually practiced.
    As to your torque without friction leading to infinite rpm- take a look at
    your meter- see those magnets which provide drag proportional to the speed
    of the disc? The result is that at any given torque, there will be a speed
    at which this torque is balanced by the drag. Adjustments to the meter does
    involve the positioning of these magnets.
  19. Guest

    Guest Guest

    I disagree with you regarding your interpretation of James Sweet's position.
    It was quite clear and correct.
    Otherwise I would have argued with him.
  20. James Sweet

    James Sweet Guest

    It isn't, that's not what he said. Think in terms of Watts, if you draw
    100A at 240V that is twice the wattage as drawing 100A from 120V because
    with a 240V 100A load it is drawing 100A from each side. If your loads
    are so badly balanced that you are drawing 100A from one side and 20A
    from the other and it is a 100A service, you cannot add any more 240V
    loads. The capacity is there, but you are already at the max of 100A on
    one side. If you can shift some of the load over to the under utilized
    side then you will have freed up capacity, but you will not affect the
    reading of the meter by doing so. The important part, which is beating a
    dead horse at this point is that there is a coil on each leg, and both
    coils create torque on the same disk so whether you draw 100A on one
    side and 0A on the other, 50A on each side, 10A on one side and 90A on
    the other, it doesn't matter, in any of these situations the disk will
    see the same torque and turn the same speed, the only thing changing is
    which of the two coils supplies more of the total amount of torque. It
    doesn't matter if one box of rocks weighs 500 lbs and the other box of
    rocks weighs 100 lbs, if both boxes of rocks each weigh 300 lbs, or if
    one box weighs 600 lbs and other other is empty, if you put them both on
    a scale, it will read 600 lbs either way. Balancing the panel is taking
    rocks from one box and placing them in the other, it is not changing the
    total number or weight of rocks and will not affect the reading on the

    Yes they do measure true power, and no, they do not measure VA * PF over
    time, they are different. I think what is happening here is the common
    failure to differentiate between *equal to* and *equivalent to*. Volts *
    Amps * PF is *equivalent* to Watts (true power) but it is not *equal*
    to, it is not the same thing. Power can be measured directly, if you
    then know any two of the three other variables, Volts, Amps, and PF, you
    can calculate the third, but any one can be measured on its own without
    knowing any of the others.

    Look at it this way, the speedometer in a car indicates vehicle speed in
    miles (or kilometers) per hour. This is equivalent to miles traveled
    divided by trip time, but it is not the same. Sure you could make a
    speedometer that recorded the distance traveled and time the vehicle was
    in motion and use that to calculate the speed in MPH and the answer
    would be right, but that isn't how real speedometers work. A mechanical
    speedometer, not to be confused with the odometer, has no concept of
    time or distance, rather it measures speed directly by magnetically
    coupled torque acting against a known friction, in this case a spring.
    In the same way, a mechanical power meter measures true power by energy
    passing through coils, causing a proportional amount of work to induce
    torque on the disk which rotates against a known amount of friction. In
    either case you have to have a known quantity of friction in order for
    the reading to have any meaning. Ignoring real world issues like
    insulation breakdown, a mechanical kWH meter doesn't know or care
    whether the voltage is 10V or 10,000V, rather it directly measures the
    amount of work being done by the power by acting on the disk with a
    proportional amount of work.

    As for motors, there are many different types of motors, each with their
    own characteristics, and the sort of motor in a power meter is unlike
    any you're likely to find anywhere else. The reason stepper motors need
    higher voltage to achieve higher speeds is that the windings are
    inductive and it takes time for the current, and hence the magnetic
    field to build up. The faster the motor is turning, the less time you
    have per step, so the higher the voltage needs to be in order to create
    a magnetic field of a given strength in the time available. Similar
    reasons dictate the need to vary the voltage with the frequency of
    induction motors.
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