A person at work was telling about someone that cut their electric bill
approximately in half by balancing their breaker box. If I understand this
correctly, the power company charges for power based on the current draw of
the highest leg. If you are using 100A on L1 and 50A on L2 then you would
pay based on 100A instead of the average 75A.
If this is the case, since loads change constantly based on what is ON and
what is OFF, would a person save money by installing an isolation
transformer, wired for 240V in and 240/120 out?
Thanks!
RogerN
No. There's one way to get free electricity, and that's illegal;to hook a
load before the meter. Balancing only helps you distribute electricity more
efficiently. Here, in EU, we have single phase service, for residence, 1 X
40 A, and then three phase. We use special bus bars that connect one of
every three breakers to onle leg, the second to the second, the third to the
third... for all breakers, but that only to not overload one leg. One of the
largest residential services I've seen is my sister's house, with 3 X 50 A,
3 X 25 mm^2 (# 6).
--
Tzortzakakis Dimitrios
major in electrical engineering
Of course the technology is their for the power company to bill for actual
usage, but if they can get away with charging for the high leg amps X volts,
they may choose to do so.
An electrician at work said he knows some people that balanced their breaker
box and their electric bill went down. The power company sent their workers
out to inspect 3 different times. The third time, they asked why the guys
are inspecting their service for the third time. They said it was because
the usage went down so much. The homeowner said that he had the breaker box
load balanced. The power company worker said "Oh, you know about that.".
The homeowner said Yeah. The power company was satisfied and didn't order
any more inspections.
This was supposed to be a true story with actual people known by the person
telling it. This didn't involve anyone selling any kind of product or
service for "free electricity" or anything like that. The person I heard
this from has a brother and cousin that I used to work with and now works at
an Ameren power plant, along with many of the other techs that I used to
work with.
So, I don't know, but it wouldn't cost me much time to ampprobe the lines
and move a couple of breakers if needed to better balance the load, but
maybe (hopefully) it's just BS anyway.
RogerN
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.
<snip>
They could take volts X amps X power factor, and the amps could be taken
from the higher leg or they could average the current for each leg. From
the power meter description link from another poster, they read volts from
one leg and amps on the other, if that's the case then they would have to
measure at both legs and average.
In my own situation, I have a 240V stove that is off the majority of the
time, an electric dryer that is off the majority of the time, my constant
240V draw would be the water heater. My heat comes from propane and is
supplemented by electric heaters (120V), my AC is 120V, fridge is 120V. So
the big loads are 240V but they are not drawing most of the time. The 120V
loads are present constantly. I know many have 240V heat and air, probably
their major draw. I've never had a problem with any mains kicking out and
if it doesn't save any money their would be no reason to balance unless I
wanted to check when adding a circuit.
RogerN
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.
daestrom
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.
Duh! Nobody was talking about magical money saving methods. Only using the
power you are being charged for OR not being charged for power you are not
using. Does that appear as magical to you?
RogerN
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
stringent.
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.
Good answer Don Kelly, I remember you from other posts, you seem to have a
great foundation on these electrical things. At least you could give an
informative answer that most others could not. James Sweet has the idea
right but seems to think it is magical to use the power you are being
charged for.
RogerN
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.
From the very start this post was based on hearing that the meters run based
on the power drawn from the high leg. Quote you "If it is already
accurately measuring your consumption", if the meter recorded KWH of the
high leg then it wouldn't be accurately measuring your consumption. If it
were measuring high leg consumption X 2 then you could balance the load and
use the power it was measuring, no magic involved. I'm not disagreeing that
the meters are accurate, I heard they measured based on the high leg, hadn't
heard this before, so I posted here. Many here gave good replies, others
gave replies showing they didn't understand the question acting like I was
looking for free power or something magical. So a meter doesn't read KWH
based on the high leg, that's what I was trying to find out. However if a
meter did work based on the high leg then balancing the load would let the
consumer use more of the power they were paying for. Nothing free, just
using what you're paying for. Some of these replies are on the line of
claiming repairing a hole in your fuel tank is like stealing gasoline.
RogerN
My total propane bill for the entire last year was $380 and my electric for
the past 2 months has been $100 per month, that is with electric hot water
and their are 3 living here. I'm happy enough with my utility bill but if I
could save a little by moving a breaker or two then it would be worth doing.
If what I heard was true I don't think I'd save much. I figured if it were
true the folks on here would have heard about it, apparently it's not, found
out what I wanted to know.
I guess an easy experiment would be to run a 120V 1500W heater from each
leg, turn other breakers off, the meter speed would change if either heater
were turned off/on if the balance info was incorrect.
Thanks!
RogerN
Understanding electricity has absolutely nothing to do with it,
understanding how the KWH meter works has everything to do with it. Power
for an AC circuit is Volts X Amps X power factor, in that equation you could
use amps from either leg or average the amps from each leg. Of course the
correct way would be to use the current from each leg X the voltage from
each leg X the power factor from each leg. Like I said, it has nothing to
do with understanding electricity but everything to do with how the KWH
meter measures it.
RogerN
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.
First, I don't have any specific belief on how KWH meters work, I heard that
they run based on the high leg but evidently that is not the case. However
if that was the case it wouldn't have anything to do with fooling the meter,
it would have to do only with using all the power you are paying for.
Digital electronics is not the only way to calculate, it's just what we are
used to in these times. You can also calculate with analog electronics,
pneumatics, hydraulics, fluidics, and even mechanical. A KWH meter converts
power to torque (or speed?) and counts the revolutions, the result is volts
X amps X power factor X time, a mechanical calculator.
Thanks for explaining the operation of the meter, sounds like balancing the
load would only help with the overall KWH capacity of the circuit.
RogerN
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