I have a small commercial building with a 3-phase, 120/212 400 amp
service.

The billing meter is in a locked cabinet (for which the local utility
has a key) and out of this cabinet run 4 large cables (each about 1 or
1.25 inches in diameter) that run to their own insulator or terminal
blocks where smaller cables (3/8" diameter) connect to them and run to
separate panels and switch boxes.

All of these large cables are black, and one of them is (I believe) a
neutral or ground (it has a white stripe running down it's length).

A voltage reading from this neutral wire to each of the other 3 terminal
blocks is 120 vac, and voltage readings between the 3 terminal blocks is
about 212 vac.

I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looks
exactly like this:

http://www.tequipment.net/ProductIma...ke/33_ap_w.jpg

I don't know exactly how old this meter is, but I believe it's at least
10 years old and quite possibly 15 years old.

The electrical devices in the building are typical for an office with
some very light manufacturing. About 15 desktop computers, many with
small UPS backup, telephone system, some networking switches and
routers, a few printers, flourescent lighting, a few soldering irons,
microwave, coffee maker, fridge, water cooler / distiller. At this time
or year neither the building's furnace (forced air natural gas) or AC
unit is running (the breaker powering the outdoor AC unit is off).

When I put the meter clamp around each of the 4 large cables, I read
anywhere from 10 to 20 amps on them during normal day-time electrical
usage inside the building. During a test when all computers, monitors,
printers and lights are turned off (but all UPS's are still turned on) I
read a total sum of about 4 or 5 amps across all 4 power cables.

So my questions a

1) when coming up with a total current measurement, do I include the
current flowing on the neutral line? Should I indeed measure any
current on that line at all - or should the current on the neutral be
equal to the sum of the currents on the other 3 lines?

2) I am not computing the instantaneous power as a product of the
instantaneous voltage and current because I don't know the phase
relationship between the current I'm measuring with the clamp-on meter
and the AC line voltage. But if I take the meter's RMS amp reading (or
the sum of the 3 or 4 readings for each cable) and multiply that by 120,
will I get a power or wattage measurement that is AT WORST the highest
possible energy consumption number I can have (ie - equivalent to if all
the loads were resistive and not inductive) ?

3) There are (on average) 30.4 days in a month, and therefore 730 hours
in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I should get
a quantity energy measurement (KWh) that should match (or approximate)
my bill from the local utility - assuming that the load in use at the
time of the readings are representative of daily or continuous use. If
this method of obtaining a representative monthly KWh measurement is not
correct (or needs more refinement) then please state what, why or how.

"Home Guy" wrote in message ...
I have a small commercial building with a 3-phase, 120/212 400 amp
service.

The billing meter is in a locked cabinet (for which the local utility
has a key) and out of this cabinet run 4 large cables (each about 1 or
1.25 inches in diameter) that run to their own insulator or terminal
blocks where smaller cables (3/8" diameter) connect to them and run to
separate panels and switch boxes.

All of these large cables are black, and one of them is (I believe) a
neutral or ground (it has a white stripe running down it's length).

A voltage reading from this neutral wire to each of the other 3 terminal
blocks is 120 vac, and voltage readings between the 3 terminal blocks is
about 212 vac.

I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looks
exactly like this:

http://www.tequipment.net/ProductIma...ke/33_ap_w.jpg

I don't know exactly how old this meter is, but I believe it's at least
10 years old and quite possibly 15 years old.

The electrical devices in the building are typical for an office with
some very light manufacturing. About 15 desktop computers, many with
small UPS backup, telephone system, some networking switches and
routers, a few printers, flourescent lighting, a few soldering irons,
microwave, coffee maker, fridge, water cooler / distiller. At this time
or year neither the building's furnace (forced air natural gas) or AC
unit is running (the breaker powering the outdoor AC unit is off).

When I put the meter clamp around each of the 4 large cables, I read
anywhere from 10 to 20 amps on them during normal day-time electrical
usage inside the building. During a test when all computers, monitors,
printers and lights are turned off (but all UPS's are still turned on) I
read a total sum of about 4 or 5 amps across all 4 power cables.

So my questions a

1) when coming up with a total current measurement, do I include the
current flowing on the neutral line? Should I indeed measure any
current on that line at all - or should the current on the neutral be
equal to the sum of the currents on the other 3 lines?

2) I am not computing the instantaneous power as a product of the
instantaneous voltage and current because I don't know the phase
relationship between the current I'm measuring with the clamp-on meter
and the AC line voltage. But if I take the meter's RMS amp reading (or
the sum of the 3 or 4 readings for each cable) and multiply that by 120,
will I get a power or wattage measurement that is AT WORST the highest
possible energy consumption number I can have (ie - equivalent to if all
the loads were resistive and not inductive) ?

3) There are (on average) 30.4 days in a month, and therefore 730 hours
in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I should get
a quantity energy measurement (KWh) that should match (or approximate)
my bill from the local utility - assuming that the load in use at the
time of the readings are representative of daily or continuous use. If
this method of obtaining a representative monthly KWh measurement is not
correct (or needs more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate that
way. There is no reason that you shouldn't be able to look at the electric
meter. If you really need to self meter the service get an "emon demon" for
3 phase 4 wire 208 volts

RBM used improper usenet message composition style by full-quoting:

3) There are (on average) 30.4 days in a month, and therefore 730
hours in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I
should get a quantity energy measurement (KWh) that should match
(or approximate) my bill from the local utility - assuming that
the load in use at the time of the readings are representative of
daily or continuous use. If this method of obtaining a
representative monthly KWh measurement is not correct (or needs
more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate
that way.

I want to establish several use-case situations, primarily a
"worst-case" KWh monthly usage by assuming that all the devices that are
normally on during a week-day 9-am to 5-pm work day and turned off at
all other times are instead left on continuously 24/7.

I can also get current readings for other use-case situations (evenings
and week-ends) that should give me a more closer-to-reality current
reading and factor in their time-of use over the course of a month.

This is a small office - not a home. There are fewer variable involved.

There is no reason that you shouldn't be able to look at the
electric meter.

The meter is in a locked cabinet. The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

On May 27, 8:47*pm, Home Guy wrote:
RBM used improper usenet message composition style by full-quoting:

3) There are (on average) 30.4 days in a month, and therefore 730
hours in a month. *If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I
should get a quantity energy measurement (KWh) that should match
(or approximate) my bill from the local utility - assuming that
the load in use at the time of the readings are representative of
daily or continuous use. *If this method of obtaining a
representative monthly KWh measurement is not correct (or needs
more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate
that way.

I want to establish several use-case situations, primarily a
"worst-case" KWh monthly usage by assuming that all the devices that are
normally on during a week-day 9-am to 5-pm work day and turned off at
all other times are instead left on continuously 24/7.

I can also get current readings for other use-case situations (evenings
and week-ends) that should give me a more closer-to-reality current
reading and factor in their time-of use over the course of a month.

This is a small office - not a home. *There are fewer variable involved..

There is no reason that you shouldn't be able to look at the
electric meter.

The meter is in a locked cabinet. *The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? *Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

yes you are correct you can get a rough reading this way..
you need to measure and sum only the 3 black cables, do not include
the white striped cable in the sum.

Add up the 3 currents and multiply by 120 and this is your VAs and the
actual Watts will be equal to or less then the VAs.

Multiply by hours and you have Watt Hours.

Divide by 1000 and you have kWh which is how you are billed.

Mark

On May 27, 8:06*pm, Mark wrote:
On May 27, 8:47*pm, Home Guy wrote:





RBM used improper usenet message composition style by full-quoting:

3) There are (on average) 30.4 days in a month, and therefore 730
hours in a month. *If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I
should get a quantity energy measurement (KWh) that should match
(or approximate) my bill from the local utility - assuming that
the load in use at the time of the readings are representative of
daily or continuous use. *If this method of obtaining a
representative monthly KWh measurement is not correct (or needs
more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate
that way.

I want to establish several use-case situations, primarily a
"worst-case" KWh monthly usage by assuming that all the devices that are
normally on during a week-day 9-am to 5-pm work day and turned off at
all other times are instead left on continuously 24/7.

I can also get current readings for other use-case situations (evenings
and week-ends) that should give me a more closer-to-reality current
reading and factor in their time-of use over the course of a month.

This is a small office - not a home. *There are fewer variable involved.

There is no reason that you shouldn't be able to look at the
electric meter.

The meter is in a locked cabinet. *The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? *Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

yes you are correct you can get a rough reading this way..
you need to measure and sum only the 3 black cables, do not include
the white striped cable in the sum.

Add up the 3 currents and multiply by 120 and this is your VAs and the
actual Watts will be equal to or less then the VAs.

Multiply by hours and you have Watt Hours.

Divide by 1000 and you have kWh which is how you are billed.

Mark- Hide quoted text -

- Show quoted text -

You may be lucky and only have an error of 10 - 20%, but I wouldn't
be surprised if your error was as much as 25%.

"Mark" wrote in message
...
On May 27, 8:47 pm, Home Guy wrote:
RBM used improper usenet message composition style by full-quoting:

3) There are (on average) 30.4 days in a month, and therefore 730
hours in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I
should get a quantity energy measurement (KWh) that should match
(or approximate) my bill from the local utility - assuming that
the load in use at the time of the readings are representative of
daily or continuous use. If this method of obtaining a
representative monthly KWh measurement is not correct (or needs
more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate
that way.

I want to establish several use-case situations, primarily a
"worst-case" KWh monthly usage by assuming that all the devices that are
normally on during a week-day 9-am to 5-pm work day and turned off at
all other times are instead left on continuously 24/7.

I can also get current readings for other use-case situations (evenings
and week-ends) that should give me a more closer-to-reality current
reading and factor in their time-of use over the course of a month.

This is a small office - not a home. There are fewer variable involved.

There is no reason that you shouldn't be able to look at the
electric meter.

The meter is in a locked cabinet. The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

yes you are correct you can get a rough reading this way..
you need to measure and sum only the 3 black cables, do not include
the white striped cable in the sum.

Add up the 3 currents and multiply by 120 and this is your VAs and the
actual Watts will be equal to or less then the VAs.

Multiply by hours and you have Watt Hours.

Divide by 1000 and you have kWh which is how you are billed.

Mark


This is a commercial service and metering equipment. How is he going to
guestimate demand?

"Home Guy" wrote in message ...
RBM used improper usenet message composition style by full-quoting:

3) There are (on average) 30.4 days in a month, and therefore 730
hours in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I
should get a quantity energy measurement (KWh) that should match
(or approximate) my bill from the local utility - assuming that
the load in use at the time of the readings are representative of
daily or continuous use. If this method of obtaining a
representative monthly KWh measurement is not correct (or needs
more refinement) then please state what, why or how.

**You're not going to be the least bit accurate trying to calculate
that way.

I want to establish several use-case situations, primarily a
"worst-case" KWh monthly usage by assuming that all the devices that are
normally on during a week-day 9-am to 5-pm work day and turned off at
all other times are instead left on continuously 24/7.

I can also get current readings for other use-case situations (evenings
and week-ends) that should give me a more closer-to-reality current
reading and factor in their time-of use over the course of a month.

This is a small office - not a home. There are fewer variable involved.

There is no reason that you shouldn't be able to look at the
electric meter.

The meter is in a locked cabinet. The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

**You need to put 3 clamp on meters on the wires and monitor them
continuously over the desired period of time, which still won't be accurate
because they won't give you the peak demand. If you have some reason to
believe that the utility company equipment is faulty, you can request that
the utility company hang a testing meter to verify the accuracy

"hr(bob) " used improper usenet message composition style
by full-quoting:

You may be lucky and only have an error of 10 - 20%, but
I wouldn't be surprised if your error was as much as 25%.

When you speak of this error, do you mean

a) an error between (what the billing meter is reading in terms of KWh
for some arbitrarily short time span) AND (what my amp-meter derived
watt-measurement would give for the same arbitrarily short time span)

or

b) an error between (the monthly power use of the office derived from
several different measurements with various devices and appliances
turned on or off as per time-of day and day-of-week) AND (the actual or
real pattern of device usage over the course of a real month).

What is the error you speak of?

"Home Guy" wrote

..
The meter is in a locked cabinet. The only time I get to see it is when
the meter-reader guy comes around once a month to read it.

I suspect the meter is in a locked cabinet to prevent tampering / bypass
(the meter is inside the utility / furnace room of the building and is
not accessible from the outside).

And besides, having the ability to lay my eyes on the meter won't tell
me anything about the accuracy of the meter, or the real-time current
consumption.

All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive
with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

There is no special math, but I'd wonder just how accurate your number is
going to be. Don't for get about seasonal changes too, more lighting in
winter, AC in summer, etc. At work, I take readings on some of our
utilities daily, others, monthly, and can spot a trend when correlated with
material used on a given day, etc. This will often tip you off as to
problem areas and waste when you see aberrations from the norm.

Have you talked to the utility company? Some will do the work for you and
put a recording meter on the line for a week or two to get you want you
want. Your approach, of course, is in the interest of energy conservation.
They are big on selling you less these days.

Reading the meter on a daily basis would be a help to determine trends also.
Perhaps they will allow a window to the meter so you can take readings.

RBM used improper if not deplorable usenet message composition style by
full-quoting:

This is a commercial service and metering equipment. How is he
going to guestimate demand?

Demand (or load) doesn't have to be guestimated.

There are a fixed set of lights, appliances and devices in this office,
as well as a relatively fixed schedule of use for them. We have a basic
week-day and week-end pattern, and for the week-days we have diurnal
(day - night) pattern of usage. Since the average month has 730 hours,
comprised of 4.34 weeks, we know that there will be 209 "week-end" hours
and 521 "week-day" hours. The week-day hours can be further decomposed
as 217 "day-time, week-day" hours and 304 "night-time, week-day" hours.

So we have 3 different loading conditions where the energy consumption
during each condition is assumed to be constant: Week-day day-time,
week-day night-time, and week-ends. If a current measurment is
performed once for each of the 3 conditions, and then extrapolated over
their projected duration over the course of a month (217, 304 and 209
hours respectively) then if the three total are summed the result should
approximate what the billing meter should measure if that same exact
device and appliance usage pattern is replicated during a typical month.

The exact hours of each loading condition can be exactly specified to
match a given utility bill if the meter-reading dates are known for the
bill in question (that will tell us how many week-end and week-days
actually occurred during the billing month of interest).

Based on 5 years of previous bills, about 75% of the monthly meter
readings are between 1750 and 2250 kwh. Very few go higher than 3000,
and only 2 have ever gone above 4000.

On Fri, 27 May 2011 23:09:46 -0400, "RBM" wrote:

**You need to put 3 clamp on meters on the wires and monitor them
continuously over the desired period of time, which still won't be accurate
because they won't give you the peak demand. If you have some reason to
believe that the utility company equipment is faulty, you can request that
the utility company hang a testing meter to verify the accuracy

They make clamp on amp meters that graph usage over time. I have no
idea how much they cost to buy or rent.

We took amp measurements on a parallel run of 3-500. I was amazed
that supposedly equal lengths of copper varied as much as 25 amps on
the same phase.

Ed Pawlowski wrote:

Have you talked to the utility company?

Yes, I have contacted the "front-line" customer service people and
expect to hear more from someone more technical or in more authority (or
at least someone more "male") next week.

Our last bill was for 5,160 kwh, with a billing period from april 5 to
May 4.
The previous month (March 5 - April 4) was 1915 kwh.

Infact, looking at the last 12 bills I see some very suspicious things:

5162.41 April
1915.26 March
1582.17 Feb (meter changed end of Feb)
1998.53 Jan 2011
1915.26 Dec
2081.8 Nov
2664.7 Oct
1498.9 Sept
3414.15 Aug
3913.78 July
1998.53 June
2248.34 May
1915.26 April
1915.26 March
5162.86 Feb
3247.61 Jan 2010
2331.62 Dec 2009

Our meter is always read on the first business day of each month. The
meter was changed at the end of February. The old meter was electronic
(it had a digital LCD readout). The new meter *I believe* is different
in that it can do time-of-use measuring and it can do RF (wireless) data
transmission. Time-of-use billing is not yet being performed in our
area, and at least for our new meter a person is still coming around to
read it.

I note that I see 1915.26 show up suspiciously 4 times during the past
year (what are the odds that we'd use the exact same amount of
electricity for any 2 months, let alone 4?).

It was the large jump from 1915 to 5162 that tweaked me on this and I
had an assistant enter all previous numbers from other bills in a
spreadsheet. The large spike back in Feb 2010 to almost exactly the
same number of 5162 is also suspicious.

I would have expected our electricity use to decline from March to April
given a reduced furnace on-time in April vs March.

I have no idea what remedy or proceedure my utility company follows in
disputes of this nature. I have the vague idea that they circle the
wagons and defend their meters to the last drop of their blood, and that
the laws or service contracts may favor them and not the customer. We
shall see.

In article , Home Guy wrote:

I have a small commercial building with a 3-phase, 120/212 400 amp
service.

The billing meter is in a locked cabinet (for which the local utility
has a key) and out of this cabinet run 4 large cables (each about 1 or
1.25 inches in diameter) that run to their own insulator or terminal
blocks where smaller cables (3/8" diameter) connect to them and run to
separate panels and switch boxes.

All of these large cables are black, and one of them is (I believe) a
neutral or ground (it has a white stripe running down it's length).

A voltage reading from this neutral wire to each of the other 3 terminal
blocks is 120 vac, and voltage readings between the 3 terminal blocks is
about 212 vac.

I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looks
exactly like this:

http://www.tequipment.net/ProductIma...ke/33_ap_w.jpg

I don't know exactly how old this meter is, but I believe it's at least
10 years old and quite possibly 15 years old.

The electrical devices in the building are typical for an office with
some very light manufacturing. About 15 desktop computers, many with
small UPS backup, telephone system, some networking switches and
routers, a few printers, flourescent lighting, a few soldering irons,
microwave, coffee maker, fridge, water cooler / distiller. At this time
or year neither the building's furnace (forced air natural gas) or AC
unit is running (the breaker powering the outdoor AC unit is off).

When I put the meter clamp around each of the 4 large cables, I read
anywhere from 10 to 20 amps on them during normal day-time electrical
usage inside the building. During a test when all computers, monitors,
printers and lights are turned off (but all UPS's are still turned on) I
read a total sum of about 4 or 5 amps across all 4 power cables.

So my questions a

1) when coming up with a total current measurement, do I include the
current flowing on the neutral line? Should I indeed measure any
current on that line at all - or should the current on the neutral be
equal to the sum of the currents on the other 3 lines?

2) I am not computing the instantaneous power as a product of the
instantaneous voltage and current because I don't know the phase
relationship between the current I'm measuring with the clamp-on meter
and the AC line voltage. But if I take the meter's RMS amp reading (or
the sum of the 3 or 4 readings for each cable) and multiply that by 120,
will I get a power or wattage measurement that is AT WORST the highest
possible energy consumption number I can have (ie - equivalent to if all
the loads were resistive and not inductive) ?

3) There are (on average) 30.4 days in a month, and therefore 730 hours
in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I should get
a quantity energy measurement (KWh) that should match (or approximate)
my bill from the local utility - assuming that the load in use at the
time of the readings are representative of daily or continuous use. If
this method of obtaining a representative monthly KWh measurement is not
correct (or needs more refinement) then please state what, why or how.

Why do you want to do this?

"Home Guy" wrote

Our last bill was for 5,160 kwh, with a billing period from april 5 to
May 4.
The previous month (March 5 - April 4) was 1915 kwh.

Infact, looking at the last 12 bills I see some very suspicious things:

5162.41 April
1915.26 March
1582.17 Feb (meter changed end of Feb)
1998.53 Jan 2011
1915.26 Dec
2081.8 Nov
2664.7 Oct
1498.9 Sept
3414.15 Aug
3913.78 July
1998.53 June
2248.34 May
1915.26 April
1915.26 March
5162.86 Feb
3247.61 Jan 2010
2331.62 Dec 2009

Our meter is always read on the first business day of each month. The
meter was changed at the end of February.
I note that I see 1915.26 show up suspiciously 4 times during the past
year (what are the odds that we'd use the exact same amount of
electricity for any 2 months, let alone 4?).

It was the large jump from 1915 to 5162 that tweaked me on this

I have no idea what remedy or proceedure my utility company follows in
disputes of this nature. I have the vague idea that they circle the
wagons and defend their meters to the last drop of their blood, and that
the laws or service contracts may favor them and not the customer. We
shall see.

You are correct in being suspicious. My findings from tracking electric,
July and August are the highest, January is second highest. There will be a
curve on the months between. Winter is high because of running heat and more
lighting, then it comes down as you approach spring, then goes up again as
the AC use kicks in. Then in September, it comes down then back up for
winter use.

I can understand with the old meter that you'd possibly get 4 identical
readings if the meter was not read and the bill was estimated. Actual
readings, I'd say "no way" you'd have that situation at that use. We do have
one tenant that uses very little electric and the meter was originally
installed for some machines. It has a multiplier Most bills are the same,
in increments of $18. A few a year are $36. Another has bills in the $400
to $800 range and follows the curves a I outlined.

A couple of possibilities I can think of. The meter is incorrect. (yes, it
really does happen) A tenant is carelessly leaving on a space heater. a
tenant is running both heat and AC out of stupidity, not a maintenance
problem. You have some other pump or device that is running all the time.

Good luck and please keep us posted on what happens.

On Fri, 27 May 2011 23:17:30 -0400, Home Guy wrote:

"hr(bob) " used improper usenet message composition style
by full-quoting:

You may be lucky and only have an error of 10 - 20%, but
I wouldn't be surprised if your error was as much as 25%.

When you speak of this error, do you mean

a) an error between (what the billing meter is reading in terms of KWh
for some arbitrarily short time span) AND (what my amp-meter derived
watt-measurement would give for the same arbitrarily short time span)

An amp meter measures amps, not watts. Even if you assume 120V, you're still
calculating volt-amps, not watts.

or

b) an error between (the monthly power use of the office derived from
several different measurements with various devices and appliances
turned on or off as per time-of day and day-of-week) AND (the actual or
real pattern of device usage over the course of a real month).

What is the error you speak of?

c) The error between Volt-Ampere-hours and Watt-hours.

The errors you mention above will likely be even bigger, though. Surprisingly,
a watt-hour meter (it's already there) is the real way to measure watt-hours.
;-)

Home Guy wrote:
I have a small commercial building with a 3-phase, 120/212 400 amp
service.

The billing meter is in a locked cabinet (for which the local utility
has a key) and out of this cabinet run 4 large cables (each about 1 or
1.25 inches in diameter) that run to their own insulator or terminal
blocks where smaller cables (3/8" diameter) connect to them and run to
separate panels and switch boxes.

All of these large cables are black, and one of them is (I believe) a
neutral or ground (it has a white stripe running down it's length).

A voltage reading from this neutral wire to each of the other 3 terminal
blocks is 120 vac, and voltage readings between the 3 terminal blocks is
about 212 vac.

I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looks
exactly like this:

http://www.tequipment.net/ProductIma...ke/33_ap_w.jpg

I don't know exactly how old this meter is, but I believe it's at least
10 years old and quite possibly 15 years old.

The electrical devices in the building are typical for an office with
some very light manufacturing. About 15 desktop computers, many with
small UPS backup, telephone system, some networking switches and
routers, a few printers, flourescent lighting, a few soldering irons,
microwave, coffee maker, fridge, water cooler / distiller. At this time
or year neither the building's furnace (forced air natural gas) or AC
unit is running (the breaker powering the outdoor AC unit is off).

When I put the meter clamp around each of the 4 large cables, I read
anywhere from 10 to 20 amps on them during normal day-time electrical
usage inside the building. During a test when all computers, monitors,
printers and lights are turned off (but all UPS's are still turned on) I
read a total sum of about 4 or 5 amps across all 4 power cables.

So my questions a

1) when coming up with a total current measurement, do I include the
current flowing on the neutral line? Should I indeed measure any
current on that line at all - or should the current on the neutral be
equal to the sum of the currents on the other 3 lines?

2) I am not computing the instantaneous power as a product of the
instantaneous voltage and current because I don't know the phase
relationship between the current I'm measuring with the clamp-on meter
and the AC line voltage. But if I take the meter's RMS amp reading (or
the sum of the 3 or 4 readings for each cable) and multiply that by 120,
will I get a power or wattage measurement that is AT WORST the highest
possible energy consumption number I can have (ie - equivalent to if all
the loads were resistive and not inductive) ?

3) There are (on average) 30.4 days in a month, and therefore 730 hours
in a month. If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I should get
a quantity energy measurement (KWh) that should match (or approximate)
my bill from the local utility - assuming that the load in use at the
time of the readings are representative of daily or continuous use. If
this method of obtaining a representative monthly KWh measurement is not
correct (or needs more refinement) then please state what, why or how.
Hi,
I am wondering why you are trying to do this? First what is the power
factor in this circuit? If your goal is to increase efficiency to result
in savings, look into that. If you suspect meter is inaccurate you can
request for a replacement. Newer digital meters are more dependable and
accurate. Even my cabin located in the boondogs have digital power,
natural gas meters. You already know typical power consumption pattern.
So what is the purpose?

In article ,
"Ed Pawlowski" wrote:



A couple of possibilities I can think of. The meter is incorrect. (yes, it
really does happen) A tenant is carelessly leaving on a space heater. a
tenant is running both heat and AC out of stupidity, not a maintenance
problem. You have some other pump or device that is running all the time.

Good luck and please keep us posted on what happens.

Something seems a tad fishy, but I don't think sampling some current
readings is going to help sort it out. 400 amps of 3-phase is a lot of
juice to run a few computers, lights, and soldering irons. I know the
type of usage that leads to $5000 electric bills, and that ain't it.

OP needs to spend less time fantasizing about how many hours are in a
month and more time inventorying the equipment in the building, talking
to its occupants, and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark.

On May 28, 1:17*am, Home Guy wrote:
I have a small commercial building with a 3-phase, 120/212 400 amp
service.

The billing meter is in a locked cabinet (for which the local utility
has a key) and out of this cabinet run 4 large cables (each about 1 or
1.25 inches in diameter) that run to their own insulator or terminal
blocks where smaller cables (3/8" diameter) connect to them and run to
separate panels and switch boxes.

All of these large cables are black, and one of them is (I believe) a
neutral or ground (it has a white stripe running down it's length).

A voltage reading from this neutral wire to each of the other 3 terminal
blocks is 120 vac, and voltage readings between the 3 terminal blocks is
about 212 vac.

I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looks
exactly like this:

http://www.tequipment.net/ProductIma...ke/33_ap_w.jpg

I don't know exactly how old this meter is, but I believe it's at least
10 years old and quite possibly 15 years old.

The electrical devices in the building are typical for an office with
some very light manufacturing. *About 15 desktop computers, many with
small UPS backup, telephone system, some networking switches and
routers, a few printers, flourescent lighting, a few soldering irons,
microwave, coffee maker, fridge, water cooler / distiller. *At this time
or year neither the building's furnace (forced air natural gas) or AC
unit is running (the breaker powering the outdoor AC unit is off).

When I put the meter clamp around each of the 4 large cables, I read
anywhere from 10 to 20 amps on them during normal day-time electrical
usage inside the building. *During a test when all computers, monitors,
printers and lights are turned off (but all UPS's are still turned on) I
read a total sum of about 4 or 5 amps across all 4 power cables.

So my questions a

1) when coming up with a total current measurement, do I include the
current flowing on the neutral line? *Should I indeed measure any
current on that line at all - or should the current on the neutral be
equal to the sum of the currents on the other 3 lines?

2) I am not computing the instantaneous power as a product of the
instantaneous voltage and current because I don't know the phase
relationship between the current I'm measuring with the clamp-on meter
and the AC line voltage. *But if I take the meter's RMS amp reading (or
the sum of the 3 or 4 readings for each cable) and multiply that by 120,
will I get a power or wattage measurement that is AT WORST the highest
possible energy consumption number I can have (ie - equivalent to if all
the loads were resistive and not inductive) ?

3) There are (on average) 30.4 days in a month, and therefore 730 hours
in a month. *If I take the above wattage calculation (120 x
total_current) and multiply it by 730, then divide by 1000, I should get
a quantity energy measurement (KWh) that should match (or approximate)
my bill from the local utility - assuming that the load in use at the
time of the readings are representative of daily or continuous use. *If
this method of obtaining a representative monthly KWh measurement is not
correct (or needs more refinement) then please state what, why or how.

Yes you can determine the power being consumed but only at the isntant
you have taken a reading. The meters monitor the power constantly.
The three large cables are the phases.
The neutral is smaller because it only carries the "out of balance
current". You can ignore this cable for your purposes.

Multiply the current by the voltage (120 in your case) for each of
the three cables and then add them together & divde by 1000
This actually gives Kva. If there is only heating/incandescent
lighting in the building, this is the same as Kilowatts.
If there are electric motors or uncorrected fluorescent lights, the
Kva needs to be multiplied by the "power factor" to get Kw which you
don't know. In practice it could be anywhere between 1 (unity) or
0.7. For office premises, you could assume 0.9

So there you have it. Current in each phase X 120 X 0.9
Add the three together.

"Metspitzer" wrote in message
...
On Fri, 27 May 2011 23:09:46 -0400, "RBM" wrote:

**You need to put 3 clamp on meters on the wires and monitor them
continuously over the desired period of time, which still won't be
accurate
because they won't give you the peak demand. If you have some reason to
believe that the utility company equipment is faulty, you can request that
the utility company hang a testing meter to verify the accuracy

They make clamp on amp meters that graph usage over time. I have no
idea how much they cost to buy or rent.

We took amp measurements on a parallel run of 3-500. I was amazed
that supposedly equal lengths of copper varied as much as 25 amps on
the same phase.

** That's the sort of meter that the utility company hangs on the service to
test the accuracy of their equipment

"Smitty Two" wrote in message
news
In article ,
"Ed Pawlowski" wrote:



A couple of possibilities I can think of. The meter is incorrect. (yes,
it
really does happen) A tenant is carelessly leaving on a space heater. a
tenant is running both heat and AC out of stupidity, not a maintenance
problem. You have some other pump or device that is running all the
time.

Good luck and please keep us posted on what happens.

Something seems a tad fishy, but I don't think sampling some current
readings is going to help sort it out. 400 amps of 3-phase is a lot of
juice to run a few computers, lights, and soldering irons. I know the
type of usage that leads to $5000 electric bills, and that ain't it.

OP needs to spend less time fantasizing about how many hours are in a
month and more time inventorying the equipment in the building, talking
to its occupants, and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark.

I can visualize someone having a hobby that requires an induction furnace of
some sort. You take all sorts of readings, day and night, and this guy
fires up the furnace on Sunday mornings while you take the family to church
and breakfast..

On May 28, 12:08*am, Home Guy wrote:
Ed Pawlowski wrote:
Have you talked to the utility company?

Yes, I have contacted the "front-line" customer service people and
expect to hear more from someone more technical or in more authority (or
at least someone more "male") next week.

Our last bill was for 5,160 kwh, with a billing period from april 5 to
May 4.
The previous month (March 5 - April 4) was 1915 kwh. *

Infact, looking at the last 12 bills I see some very suspicious things:

5162.41 April
1915.26 March
1582.17 Feb (meter changed end of Feb)
1998.53 Jan 2011
1915.26 Dec
2081.8 *Nov
2664.7 *Oct
1498.9 *Sept
3414.15 Aug
3913.78 July
1998.53 June
2248.34 May
1915.26 April
1915.26 March
5162.86 Feb
3247.61 Jan 2010
2331.62 Dec 2009

Our meter is always read on the first business day of each month. *The
meter was changed at the end of February. *The old meter was electronic
(it had a digital LCD readout). *The new meter *I believe* is different
in that it can do time-of-use measuring and it can do RF (wireless) data
transmission. *Time-of-use billing is not yet being performed in our
area, and at least for our new meter a person is still coming around to
read it.

I note that I see 1915.26 show up suspiciously 4 times during the past
year (what are the odds that we'd use the exact same amount of
electricity for any 2 months, let alone 4?).

It was the large jump from 1915 to 5162 that tweaked me on this and I
had an assistant enter all previous numbers from other bills in a
spreadsheet. *The large spike back in Feb 2010 to almost exactly the
same number of 5162 is also suspicious.

I would have expected our electricity use to decline from March to April
given a reduced furnace on-time in April vs March.

I have no idea what remedy or proceedure my utility company follows in
disputes of this nature. *I have the vague idea that they circle the
wagons and defend their meters to the last drop of their blood, and that
the laws or service contracts may favor them and not the customer. *We
shall see.

My first guess would be that the logical explanation for 1915.26
showing
up 4 times would be that it is some form of an ESTMATED reading
used when they didn't take an actual reading. The odds of that number
showing up 4 times from a true reading would be very low. And if it
has, I'd suggest using it to play the lottery.

Smitty Two wrote:
In articlew_idnbd2hIRTHH3QnZ2dnUVZ_uydnZ2d@giganews. com,
"Ed wrote:



A couple of possibilities I can think of. The meter is incorrect. (yes, it
really does happen) A tenant is carelessly leaving on a space heater. a
tenant is running both heat and AC out of stupidity, not a maintenance
problem. You have some other pump or device that is running all the time.

Good luck and please keep us posted on what happens.

Something seems a tad fishy, but I don't think sampling some current
readings is going to help sort it out. 400 amps of 3-phase is a lot of
juice to run a few computers, lights, and soldering irons. I know the
type of usage that leads to $5000 electric bills, and that ain't it.

OP needs to spend less time fantasizing about how many hours are in a
month and more time inventorying the equipment in the building, talking
to its occupants, and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark

Hmmm,
Oh, no! Grow op?, LOL

Smitty Two wrote:

Something seems a tad fishy, but I don't think sampling some
current readings is going to help sort it out.

It's a start.

400 amps of 3-phase is a lot of juice to run a few computers,
lights, and soldering irons.

The main disconnect switch before the meter is name-plate rated at 400
amps. It doesn't mean we're going to ever draw that much.

OP needs to spend less time fantasizing about how many hours are
in a month and more time inventorying the equipment in the building

I know exactly what equipment is in the building - I work there.

talking to its occupants

I talk to them every day.

and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark.

What-ever.

Another example of a usenet post that starts with a question, and
devolves into "why are you asking?".

I have to waste more time explaining why I want to do something or why I
want certain information about measurement techniques, and instead I get
a bunch of arm-chair blow-hardts that think they know better.

harry wrote:

Yes you can determine the power being consumed but only at the
instant you have taken a reading.

So I shouldn't assume that, say, a bank or three of florescent lights
won't necessarily draw a constant amount of current?

Or a dozen PC's?

The three large cables are the phases.
The neutral is smaller because it only carries the "out of balance
current".

The neutral is not smaller (physically) than the other 3 cables. It's
the same size.

Most charts I see only go as large as AWG guage size OOOO (almost 1/2
inch diameter). In my case, the cables running from the meter to the
distribution blocks (a run of about 7 or 8 feet) are at least 1 inch
diameter (OD). The conductor diameter is at least 7/8".

Multiply the current by the voltage (120 in your case) for each of
the three cables and then add them together & divde by 1000
This actually gives Kva. If there is only heating/incandescent
lighting in the building, this is the same as Kilowatts.
If there are electric motors or uncorrected fluorescent lights,
the Kva needs to be multiplied by the "power factor" to get Kw
which you don't know. In practice it could be anywhere between
1 (unity) or 0.7. For office premises, you could assume 0.9

So if I don't multiply my VA number by the power factor, then I'm
OVER-ESTIMATING my KWh calculation by 5 or 10%.

Tangent:

Why does my utility apply (add) a 5% "correction factor" to the KWh
measurement that comes from the meter?

On 5/28/2011 9:03 AM, Home Guy wrote:
Smitty Two wrote:

Something seems a tad fishy, but I don't think sampling some
current readings is going to help sort it out.

It's a start.

400 amps of 3-phase is a lot of juice to run a few computers,
lights, and soldering irons.

The main disconnect switch before the meter is name-plate rated at 400
amps. It doesn't mean we're going to ever draw that much.

OP needs to spend less time fantasizing about how many hours are
in a month and more time inventorying the equipment in the building

I know exactly what equipment is in the building - I work there.

talking to its occupants

I talk to them every day.

and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark.

What-ever.

Another example of a usenet post that starts with a question, and
devolves into "why are you asking?".

I have to waste more time explaining why I want to do something or why I
want certain information about measurement techniques, and instead I get
a bunch of arm-chair blow-hardts that think they know better.

Poor you and that incredible amount of time you wasted reading three
posts after you clearly described you already know and presented
everything anyone needs to know and everyone didn't catch on that no
questions are allowed and no opinions are wanted..

" wrote:

My first guess would be that the logical explanation for 1915.26
showing up 4 times would be that it is some form of an ESTMATED
reading used when they didn't take an actual reading.

A meter reader always pays a visit to the building either on the first
or second work-day of the month. He reads both the electric and water
meter (both are inside the building and can't be read from the
outside). I know that because we have to escort the reader to the
utility room, and I'm the one that does it about 1/2 the time, and when
someone else does it they tell me they did it.

There is never a month that goes by without someone coming to read the
meter.

" wrote:

An amp meter measures amps, not watts. Even if you assume 120V,
you're still calculating volt-amps, not watts.

A volt-amp is a watt, when the load is resistive.

If I perform high-speed sampling of both the voltage and current, and if
I multiply each reading together to get VA for each sample, and if
integrate those VA samples over time, I will get the actual watts or KWh
that I should be billed for. That would correctly take into account
reative / inductive loads (like motors, light ballasts, computer power
supplies, etc).

If I simply calculate watts as equal to VA based on the current
measurement from a clamp-on meter, then I'm over-estimating what the
billing meter is "seeing" because I'd be assuming that all my loads are
resistive. In other words, my calculation of watts = VA can't help but
assume that current and voltage are in phase with each other.

The billing meter knows how to calculate wattage correctly when the
current and voltage is out of phase.

I guess a clamp-on amp meter that also had a couple of voltage probes so
that it could simultaneously measure the voltage could measure true
wattage would be needed.

The errors you mention above will likely be even bigger, though
Surprisingly, a watt-hour meter (it's already there) is the real
way to measure watt-hours. ;-)

As long as the watt-hour meter is working correctly.

Which seems highly suspect given all the info I've been posting here.

George wrote:

I have to waste more time explaining why I want to do something or
why I want certain information about measurement techniques, and
instead I get a bunch of arm-chair blow-hardts that think they
know better.

Poor you

No. Poor usenet.

Poor every future poster to any newsgroup that asks a simple technical
question and gets told by the peanut gallery that it's important to know
all the ancilliary circumstances surrounding the question when in
reality in the end those circumstances have no bearing on the question
or it's answer.

On 5/28/2011 8:40 AM, Home Guy wrote:
" wrote:

....

The errors you mention above will likely be even bigger, though
Surprisingly, a watt-hour meter (it's already there) is the real
way to measure watt-hours. ;-)

As long as the watt-hour meter is working correctly.

Which seems highly suspect given all the info I've been posting here.

Far too little real data to infer that (at least yet)...

I'd figure it's likely a combination of estimated or leveled billing w/
a catchup period annually and some tenant or group of tenants w/ loads
you're unaware of.

Not that there aren't errors both in manual reading and that the meter
can fault but generally those get caught in routine maintenance checks
and if the meter were, as you say, replaced recently it's not a high
probability.

--

Home Guy wrote:
harry wrote:

Yes you can determine the power being consumed but only at the
instant you have taken a reading.

So I shouldn't assume that, say, a bank or three of florescent lights
won't necessarily draw a constant amount of current?

Or a dozen PC's?

The three large cables are the phases.
The neutral is smaller because it only carries the "out of balance
current".

The neutral is not smaller (physically) than the other 3 cables. It's
the same size.

Most charts I see only go as large as AWG guage size OOOO (almost 1/2
inch diameter). In my case, the cables running from the meter to the
distribution blocks (a run of about 7 or 8 feet) are at least 1 inch
diameter (OD). The conductor diameter is at least 7/8".

Multiply the current by the voltage (120 in your case) for each of
the three cables and then add them together& divde by 1000
This actually gives Kva. If there is only heating/incandescent
lighting in the building, this is the same as Kilowatts.
If there are electric motors or uncorrected fluorescent lights,
the Kva needs to be multiplied by the "power factor" to get Kw
which you don't know. In practice it could be anywhere between
1 (unity) or 0.7. For office premises, you could assume 0.9

So if I don't multiply my VA number by the power factor, then I'm
OVER-ESTIMATING my KWh calculation by 5 or 10%.

Tangent:

Why does my utility apply (add) a 5% "correction factor" to the KWh
measurement that comes from the meter?
Hmmm,
You know what? You ought to monitor frequency. Usually it is not 60Hz,
the lower it shows power factor is getting worse. Ideally load should be
pure resistive which does not exist in real world. They are mostly
inductive load. There is such a thing called Pf correcting device to
improve efficiency. My SIL owns/operates mechanical moulding business
based on CAD/CAM. His average monthly bill is pretty constant. The
amount of monthly bill is pretty predictable. Other source of energy his
plant use is NG, mainly for heating.

On May 27, 10:17*pm, Home Guy wrote:
"hr(bob) " used improper usenet message composition style
by full-quoting:

You may be lucky and only have an error of 10 - *20%, but
I wouldn't be surprised if your error was as much as 25%.

When you speak of this error, do you mean

a) an error between (what the billing meter is reading in terms of KWh
for some arbitrarily short time span) AND (what my amp-meter derived
watt-measurement would give for the same arbitrarily short time span)

or

b) an error between (the monthly power use of the office derived from
several different measurements with various devices and appliances
turned on or off as per time-of day and day-of-week) AND (the actual or
real pattern of device usage over the course of a real month).

What is the error you speak of?

BOTH

On May 27, 11:08*pm, Home Guy wrote:
Ed Pawlowski wrote:
Have you talked to the utility company?

Yes, I have contacted the "front-line" customer service people and
expect to hear more from someone more technical or in more authority (or
at least someone more "male") next week.

Our last bill was for 5,160 kwh, with a billing period from april 5 to
May 4.
The previous month (March 5 - April 4) was 1915 kwh. *

Infact, looking at the last 12 bills I see some very suspicious things:

5162.41 April
1915.26 March
1582.17 Feb (meter changed end of Feb)
1998.53 Jan 2011
1915.26 Dec
2081.8 *Nov
2664.7 *Oct
1498.9 *Sept
3414.15 Aug
3913.78 July
1998.53 June
2248.34 May
1915.26 April
1915.26 March
5162.86 Feb
3247.61 Jan 2010
2331.62 Dec 2009

Our meter is always read on the first business day of each month. *The
meter was changed at the end of February. *The old meter was electronic
(it had a digital LCD readout). *The new meter *I believe* is different
in that it can do time-of-use measuring and it can do RF (wireless) data
transmission. *Time-of-use billing is not yet being performed in our
area, and at least for our new meter a person is still coming around to
read it.

I note that I see 1915.26 show up suspiciously 4 times during the past
year (what are the odds that we'd use the exact same amount of
electricity for any 2 months, let alone 4?).

It was the large jump from 1915 to 5162 that tweaked me on this and I
had an assistant enter all previous numbers from other bills in a
spreadsheet. *The large spike back in Feb 2010 to almost exactly the
same number of 5162 is also suspicious.

I would have expected our electricity use to decline from March to April
given a reduced furnace on-time in April vs March.

I have no idea what remedy or proceedure my utility company follows in
disputes of this nature. *I have the vague idea that they circle the
wagons and defend their meters to the last drop of their blood, and that
the laws or service contracts may favor them and not the customer. *We
shall see.

I agree the billing usage numbers look very suspicious.. I would
contact the power company, bypassing the regular customer service, by
calling the chairman's office and working from there. You can usually
get that sort of information from the investor information section of
the stock listing for the company.

Home Guy wrote:
harry wrote:

Yes you can determine the power being consumed but only at the
instant you have taken a reading.

So I shouldn't assume that, say, a bank or three of florescent lights
won't necessarily draw a constant amount of current?

Or a dozen PC's?

The three large cables are the phases.
The neutral is smaller because it only carries the "out of balance
current".

The neutral is not smaller (physically) than the other 3 cables. It's
the same size.

Most charts I see only go as large as AWG guage size OOOO (almost 1/2
inch diameter). In my case, the cables running from the meter to the
distribution blocks (a run of about 7 or 8 feet) are at least 1 inch
diameter (OD). The conductor diameter is at least 7/8".

Multiply the current by the voltage (120 in your case) for each of
the three cables and then add them together & divde by 1000
This actually gives Kva. If there is only heating/incandescent
lighting in the building, this is the same as Kilowatts.
If there are electric motors or uncorrected fluorescent lights,
the Kva needs to be multiplied by the "power factor" to get Kw
which you don't know. In practice it could be anywhere between
1 (unity) or 0.7. For office premises, you could assume 0.9

So if I don't multiply my VA number by the power factor, then I'm
OVER-ESTIMATING my KWh calculation by 5 or 10%.

Tangent:

Why does my utility apply (add) a 5% "correction factor" to the KWh
measurement that comes from the meter?

You're pushing a very big rock up a hill to nowhere.
Your meter will give you little useful information.
You need to KNOW the phase.
Sticking your finger in your favorite orifice and pulling out a power
factor number is just that...a useless number. You don't
even want to think about the orifices you find here.

Why do you care?
A decision tree is often helpful.
If you think the equipment is faulty, you should enlist the power company.
I've found 'em to be very knowledgeable and helpful. They have the
equipment to determine whether your meter is faulty. A friendly
conversation with customer service should get you a call from
a real engineer. If it turns out to be faulty, make sure you
get calibration numbers off the old system so you can negotiate
a refund.

If you think they're intentionally screwing you, you need to hire
an electrician with the equipment to measure WATTS. That's what you
pay for. Measuring VA is an exercise in futility. Your "finger"
ain't gonna hold up in court anyway.

You might be able to get some advice from the local electrical
inspector.

If you think one of the tenants is charging their electric car
when you're not looking, your amp meter can point you in the right
direction.

I've used current clamps into a computer to log AMPS. Useful
for determining relative consumption from the same load...in
my case it was a water heater.
RMS amps is better than peak or average amps, but still not
a short path to WATTS...well, in the case of a water heater,
it is, but that's a special case of resistive load.

Depending on how the power meter's made, you can get cheap wireless
monitors that you might get the utility to let you clamp
on the meter...but that will have the same systematic
errors that the meter has. But it might help you find
any clandestine loads at odd hours.

Newer digital readout meters have an infrared light that blinks in concert
with the load. Mine is one blink per watt-hour. I programmed
a pda to read out and log consumption in real time. Again, for
my relative use. It has same systematic errors as the meter.
But you still gotta be able to "see" the meter...or put a fiber
optic cable to the outside.

You can buy clamp-on current transformers that also hook to the volts
and measure REAL power accurately. But it's much easier to pick up
the phone and have the power company help you.

The question about the 5% adder is one for customer service.

Did I mention...rock..hill...futility?

"hr(bob) " wrote:

You may be lucky and only have an error of 10 - 20%, but
I wouldn't be surprised if your error was as much as 25%.

When you speak of this error, do you mean

BOTH

a) an error between (what the billing meter is reading in terms of
KWh for some arbitrarily short time span) AND (what my amp-meter
derived watt-measurement would give for the same arbitrarily short
time span)

That error should be no higher than 10%. The billing meter is measuring
power (watts) that is phase-corrected. My method (of just measuring
current) is not phase corrected. So my calculation of watts will always
be higher by 5 or 10%. If all the loads in the building were purely
resistive, then my method should exactly match the billing meter.

b) an error between (the monthly power use of the office derived
from several different measurements with various devices and
appliances turned on or off as per time-of day and day-of-week)
AND (the actual or real pattern of device usage over the course
of a real month).

The variability or error in actual device or appliance usage is (I would
think) quite low, given that this is an office environment where the
duty cycle (ie the on/off power cycle pattern) of all of the 15 or so
computers is very regular and known, as are the lights.

The lights and computers probably account for 50 to 75% of the
electricity usage, the rest being fixed electronic infrastructure
(networking routers / switches / DSL modem, multi-function printer-fax,
multi-line phone system) a few low-power exit lights, a couple out-door
75 watt out-door mercury vapor lights (on a mechanical timer), an 18 CF
refrigerator, small microwave, a small capacity water distiller /
chiller (instead of bottled water), a toaster, a couple of small
bathroom ventillation fans wired to the bathroom light switches, the
furnace fan (granted it's a large motor, 220 VAC and probably 1 hp) but
it's not running all the time, a couple of radios.

In article , Home Guy wrote:

George wrote:

I have to waste more time explaining why I want to do something or
why I want certain information about measurement techniques, and
instead I get a bunch of arm-chair blow-hardts that think they
know better.

Poor you

No. Poor usenet.

Poor every future poster to any newsgroup that asks a simple technical
question and gets told by the peanut gallery that it's important to know
all the ancilliary circumstances surrounding the question when in
reality in the end those circumstances have no bearing on the question
or it's answer.

No bearing on the question or its answer? If there ever was an answer
(how much current is running through a wire at a given moment in time)
that has no bearing on the question (why does my electric bill
occasionally come in at 3x normal), you certainly postulated it. Some of
us are trying to steer you towards relevancy, and you keep on chasing
nonsensical "tests" that could hardly be less informative.

On May 28, 9:27*am, Home Guy wrote:
" wrote:
My first guess would be that the logical explanation for 1915.26
showing up 4 times would be that it is some form of an ESTMATED
reading used when they didn't take an actual reading.

A meter reader always pays a visit to the building either on the first
or second work-day of the month. *He reads both the electric and water
meter (both are inside the building and can't be read from the
outside). *I know that because we have to escort the reader to the
utility room, and I'm the one that does it about 1/2 the time, and when
someone else does it they tell me they did it.

There is never a month that goes by without someone coming to read the
meter.

Then I'd have a conversation with the electric company and
ask them to explain how 4 months in a year can have
the exact same usage, down to the hundreth of a kwh. And how
there are two other month pairs where the usage is exactly
the same down to less than 1 kwh. It's possible but the
probablities are clearly very low. Even if you had a truly fixed
load that never varied, you'd expect more variation than
that due to some months having more days.
possible and we could calcu

mike used improper usenet message composition style by unnecessarily
full-quoting:

You're pushing a very big rock up a hill to nowhere.

I should not see a huge spike in monthly usage during a month when our
hvac usage is practically zero. Investigating the reasons for this
spike is not path to nowhere.

Your meter will give you little useful information.

An unnecessarily dramatic statement.

To say that a clamp-on amp meter can't give useful information is
hyperbole.

You need to KNOW the phase.

To the extent that my aggregate power factor is less than .95 or .9,
yes, then I need to know the phase.

Are you suggesting that my effective power factor is likely to be less
than .9?

What is the power factor of 10 to 20 year-old florescent lamp ballasts?
Or a 1 hp, 220 VAC fan motor? Or a 10 year old refridgerator? Or a
typical desktop PC power supply?

Those are the largest (and probably only) non-resistive loads in
question here.

Why do you care?

Because I pay the bills. What a stupid ass question that was.

If you think the equipment is faulty, you should enlist the power
company.

I've already stated that I've contacted them, and that I expect to
encounter difficulty in having them ever admit that their metering
equipment could be faulty or even undertake a process to evaluate the
meter, but I will pursue every course of action and give them every
chance to determine that.

I've found 'em to be very knowledgeable and helpful.

In the pages and pages of materials and contracts that exist for this
utility, describing all manner of service obligation and liability,
billing, etc, I find nothing in print that defines a process whereby a
billing meter is tested or what is done if a meter is found to be
defective.

There is absolutely nothing I can find in writing even contemplating the
possibility of a meter that does not measure correctly.

I believe that issue is a political "hot potatoe" for all municipal
electricity suppliers, something they'd rather not have to deal with and
hence they largely remain silent about it.

If you think they're intentionally screwing you,

I believe that they never "intentionally" screw anyone, but that instead
they put up a front that their meters are always correct, all the time,
and reinforce that by not mentioning the possibility of erroneous meter
operation anywhere in any printed material they make available, let
alone define in writing a process or methods to test a meter that the
client believes is suspect.

Measuring VA is an exercise in futility.

The worst I can do by measuring VA is to OVER-ESTIMATE my watts used by
5 or 10% - unless you think it's likely that my aggregate power factor
is less than 90%.

Your "finger" ain't gonna hold up in court anyway.

Making my own measurements would be a first-step. I never said I'd use
those measurement in court (that is your hyperbole again).

If indeed it got that far, then I would investigate my options have
having an acredited third-party measurement performed, and that would
only happen if my local utility did not perform their own tests that I
was satisfied was unbiased and accurate.

On Fri, 27 May 2011 20:47:53 -0400, Home Guy wrote:



All I want to know is - should the current readings from a clamp-on
meter (when extrapolated across the 730 hours of a typical month) jive

Jibe.

I know I sound pedantic, but I want you to look your best when
complaining to the electric company, should it come to that point.


with the accumulated KWh reading as measured by a typical billing
meter? Do I have to do any "special" math to the wattage I calculate
with the meter to arrive at what the billing meter is measuring?

On Sat, 28 May 2011 09:03:36 -0400, Home Guy wrote:

Smitty Two wrote:

Something seems a tad fishy, but I don't think sampling some
current readings is going to help sort it out.

It's a start.

400 amps of 3-phase is a lot of juice to run a few computers,
lights, and soldering irons.

The main disconnect switch before the meter is name-plate rated at 400
amps. It doesn't mean we're going to ever draw that much.

OP needs to spend less time fantasizing about how many hours are
in a month and more time inventorying the equipment in the building

I know exactly what equipment is in the building - I work there.

talking to its occupants

I talk to them every day.

and looking for wires running off across the parking
lot to a secret garage lab that glows in the dark.

What-ever.

Another example of a usenet post that starts with a question, and
devolves into "why are you asking?".

I have to waste more time explaining why I want to do something or why I
want certain information about measurement techniques, and instead I get
a bunch of arm-chair blow-hardts that think they know better.

You should ask for a refund

Just for the heck of it go after hours and turn off your main breaker
with friends watching building.

I had a customewr at a local shopping mall they had electrical
troubles and found a connection from their meter powering public
spaces in the mall, seemingly left over from the malls construction in
the 60s. Tenants on that meter had been paying a big chunk of the
malls electric bill..

This was identified one night when the customer had a fire. The fire
department pulled the meter blacking out a big piece of the mall.

The mall claimed no knowledge I believe there was a lawsuit,,,,,,