After a high electricity bill I've been trying to find out why. I've been
checking my meter readings each day and so far (after 3 days) the usage is
around 23kwh / day peak rate and 8kwh / day low rate (Economy 7). This seems
very high to me.
My house is a 3 bed semi, heated by gas (water also). Washing machine &
dishwasher are always run at night in the E7 period. The only form of
electrical heating is a 500w "frost watcher" in the [insulated] garage - I
will fit my plug-in power watt / usage meter on this tonight to see how much
it's on, but seems very little this time of year.
No immersion heater. Most lights are compact flourescents, apart from ones
which are on dimmers and a few low voltage fittings. (CFL's are in all the
regulally used lights left on for long periods though). No electric shower
or cooker. Oven *is* electric but used rarely, and only about 2kw IIRC.

There are 3 computers running 24/7, when I last checked the power used by
these was about 60w each - will re-check. Will reduce this to 2 computers
soon.
Other stuff on 24/7 is a fish tank, again when I last checked total wattage
was pretty low, and the heater doesn't come on much due to being in a warm
room etc. Lights on for about 6 hours/day (fluroescents and Metal Halides).
Will fit watt meter here after it's stint in the garage.

My equipment / power usuage hasn't really changed in the last few years, but
looking at an electricity bill from 2001 the used units were way below what
it is now.

I have an ammeter connected to a current transformer on the incomming mains
supply, and even on a typical evening with lights on etc it reads about 4
amps, and during the day the meter is usually resting on it's end stop
(0-80A scale).

So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?
I will have a better idea in about a week of power usage of equipment but to
me I just can't see where a total of around 31 kwh per day is going!

Thanks in advance,

Alan.

On Fri, 19 Nov 2004 11:16:55 GMT, Alan wrote:

snip

So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?
I will have a better idea in about a week of power usage of equipment but to
me I just can't see where a total of around 31 kwh per day is going!

You don't say - is it a solid-state meter, or an old-style with a
rotating disc? If it's disc type, they are moderately easy to check with
a bit of simple arithmetic, the name plate will have a figure for the
number of revolutions per kwh.

Switch *everything* off at each individual appliance - not just flipping
off the consumer unit - and see if the disc is still revolving. If it
is, then either there's something still on that you've forgotten about,
or the meter is faulty.

If the meter stops with everything switched off then switch on one
single appliance with a bit of load, like a 3kw fire for a few minutes,
and take an *accurate* timing for, say, twenty revolutions of the disc.
You should then be able to work out by simple arithmetic whether the
meter is running fast or not.

Say the name plate gives 80 revs per kwh. You have 3kw of load, so in 60
minutes you'd expect 240 revs. Simple ratio will tell you how many kwh's
your 20 revs represents.

If it's a modern solid-state meter, sorry, but you've got to rely on the
company testing it.

--
the dot wanderer at tesco dot net

Alan wrote:
So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?

Turn off the power at the CU, and see if the meter records any usage.
Turn on the CU and turn off all circuits, and check that the meter still
isn't recording usage. Turn on one circuit at a time. Etc - you get
the idea.

Ben

You don't say - is it a solid-state meter, or an old-style with a
rotating disc? If it's disc type, they are moderately easy to check with
a bit of simple arithmetic, the name plate will have a figure for the
number of revolutions per kwh.

Sorry, modern solid-state meter :-(

So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?

It certainly sounds buggered. Alternatively the chavs next door are stealing
it, or there is something plugged in that you don't know about or forgot
about, like a fan heater in the loft or something.

Christian.

Alan wrote:
After a high electricity bill I've been trying to find out why. I've been
checking my meter readings each day and so far (after 3 days) the usage is
around 23kwh / day peak rate and 8kwh / day low rate (Economy 7). This seems
very high to me.

There are 3 computers running 24/7, when I last checked the power used by
these was about 60w each - will re-check. Will reduce this to 2 computers
soon.
Other stuff on 24/7 is a fish tank, again when I last checked total wattage
was pretty low, and the heater doesn't come on much due to being in a warm
room etc. Lights on for about 6 hours/day (fluroescents and Metal Halides).
Will fit watt meter here after it's stint in the garage.

I'd recheck the PCs, unless they are old/low powered models, my guess
would be that they are using a lot more than 60W each
My desktop uses between 150 and 300W depending on what it's doing.
Whereas the laptop I use mostly now, is between 40 and 90W depending on
whether I'm playing 3d games or not.

Also when my BiL had a 6ft marine tank it was costing him nearly
UKP10/wk, lots and lots of low wattage stuff soon adds up when it comes
to fish tanks - although the lights are usually the biggest load

You can roughly check the electronic meters by switching on a known load
and counting the led flashes over a timed period.

Lee
--
Email address is valid, but is unlikely to be read.

Lee wrote:

You can roughly check the electronic meters by switching on a known load
and counting the led flashes over a timed period.

Oops, missed a "just" there, but you know what I meant

Lee
--
Email address is valid, but is unlikely to be read.

In article , Alan alz_deane@nosp
am.ntlworld.com writes
You don't say - is it a solid-state meter, or an old-style with a
rotating disc? If it's disc type, they are moderately easy to check with
a bit of simple arithmetic, the name plate will have a figure for the
number of revolutions per kwh.

Sorry, modern solid-state meter :-(

The principle is exactly the same, measure the exact time between 2
readings ie. start when the smallest digit clicks over & then stop again
when the smallest digit ticks over some (much higher) reading later.

My electronic meter has a 0.01kWhr resolution, so the worst
measurement reading error you can have if measuring over ~1kWhr is 1%
and if you start & stop exactly when the dials (or lcd) clicks over then it will
be better than that.

The load you are using (1kw fire or 3kw fan heater) will certainly not be an
accurate load, just measured one here (1kW) and it was 1088W so 8.8%
error. That will be the limiting factor of your accuracy.

So you should be able to check accuracy within about 10% quite easily
which may suit you as it appears you are looking for gross errors rather
than the last 0.1%.
--
fred

Also when my BiL had a 6ft marine tank it was costing him nearly
UKP10/wk, lots and lots of low wattage stuff soon adds up when it comes
to fish tanks - although the lights are usually the biggest load

It is a 6' marine tank, but it's been running 5 years and it's only recently
my electricity bill has gone up. Most pumps on the tank are about 5w each,
and only 4 of them in total. I'll check load though but don't expect it to
be much.

"Christian McArdle" wrote in message
. net...
So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?

It certainly sounds buggered. Alternatively the chavs next door are
stealing
it, or there is something plugged in that you don't know about or forgot
about, like a fan heater in the loft or something.

Christian.


I see a weekend of testing coming up. Just found my power meter, blew the
dust off and replaced the batteries. Ready for business now!

On Fri, 19 Nov 2004 11:16:55 GMT, "Alan" wrote:

After a high electricity bill I've been trying to find out why. I've been
checking my meter readings each day and so far (after 3 days) the usage is
around 23kwh / day peak rate and 8kwh / day low rate (Economy 7). This seems
very high to me.
My house is a 3 bed semi, heated by gas (water also). Washing machine &
dishwasher are always run at night in the E7 period. The only form of
electrical heating is a 500w "frost watcher" in the [insulated] garage - I
will fit my plug-in power watt / usage meter on this tonight to see how much
it's on, but seems very little this time of year.
No immersion heater. Most lights are compact flourescents, apart from ones
which are on dimmers and a few low voltage fittings. (CFL's are in all the
regulally used lights left on for long periods though). No electric shower
or cooker. Oven *is* electric but used rarely, and only about 2kw IIRC.

There are 3 computers running 24/7, when I last checked the power used by
these was about 60w each - will re-check. Will reduce this to 2 computers
soon.
Other stuff on 24/7 is a fish tank, again when I last checked total wattage
was pretty low, and the heater doesn't come on much due to being in a warm
room etc. Lights on for about 6 hours/day (fluroescents and Metal Halides).
Will fit watt meter here after it's stint in the garage.

My equipment / power usuage hasn't really changed in the last few years, but
looking at an electricity bill from 2001 the used units were way below what
it is now.

I have an ammeter connected to a current transformer on the incomming mains
supply, and even on a typical evening with lights on etc it reads about 4
amps, and during the day the meter is usually resting on it's end stop
(0-80A scale).

So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?
I will have a better idea in about a week of power usage of equipment but to
me I just can't see where a total of around 31 kwh per day is going!

Thanks in advance,

Alan.


Fridge? Freezer..?

Alan wrote:
Also when my BiL had a 6ft marine tank it was costing him nearly
UKP10/wk, lots and lots of low wattage stuff soon adds up when it comes
to fish tanks - although the lights are usually the biggest load


It is a 6' marine tank, but it's been running 5 years and it's only recently
my electricity bill has gone up. Most pumps on the tank are about 5w each,
and only 4 of them in total. I'll check load though but don't expect it to
be much.

Ok, if you setup has stayed stable then you can obviously discount it
Of course what happened in the case I mentioned was him was adding a UV
sterilizer one month, then a couple of metal halide lights etc.

Lee
--
Email address is valid, but is unlikely to be read.

"Alan" wrote
| After a high electricity bill I've been trying to find out why.
| I've been checking my meter readings each day and so far (after
| 3 days) the usage is around 23kwh / day peak rate and 8kwh /
| day low rate (Economy 7). This seems very high to me.

If you were using electric storage heating, my first suspicion would be the
timeswitch was erroenously putting the heavy off-peak load on in peak hours.
Even though you are using plug-in timers for the washing m/c etc, it is
still possible the timeswitch is switching your meter over to cheap rate at
the incorrect times.

With that ratio of day:night units I wonder if E7 is the right tariff for
you. Its daytime rates cost more.

A 500 W "frost watcher" will use 12 kWh per day unless its thermostat
reduces down, which it may not in this weather, compare that to your 30 kWh
a day and you can see it isn't much.

| I have an ammeter connected to a current transformer on the incomming
| mains supply, and even on a typical evening with lights on etc it
| reads about 4 amps, and during the day the meter is usually resting
| on it's end stop (0-80A scale).

Switch off everything on your consumer unit and see if the current drops to
nil.

Switch everything in the house off, and then put the circuits back on at the
CU one by one, and watch for any increase in load.

Owain

Alan wrote:

"Christian McArdle" wrote in message
. net...
So, I'm wondering of the accuracy of the electricity meter which was
replaced about a year ago. Any tests I can do to confirm?

It certainly sounds buggered. Alternatively the chavs next door are
stealing
it, or there is something plugged in that you don't know about or forgot
about, like a fan heater in the loft or something.

I see a weekend of testing coming up. Just found my power meter, blew the
dust off and replaced the batteries. Ready for business now!

Some models can be significantly inaccurate.
I've measured 250% inaccuracy on some models of plug-in power meter for
some loads.

Lee wrote:
Alan wrote:
After a high electricity bill I've been trying to find out why. I've been
checking my meter readings each day and so far (after 3 days) the usage is
around 23kwh / day peak rate and 8kwh / day low rate (Economy 7). This seems
very high to me.

There are 3 computers running 24/7, when I last checked the power used by
these was about 60w each - will re-check. Will reduce this to 2 computers
soon.
Other stuff on 24/7 is a fish tank, again when I last checked total wattage
was pretty low, and the heater doesn't come on much due to being in a warm
room etc. Lights on for about 6 hours/day (fluroescents and Metal Halides).
Will fit watt meter here after it's stint in the garage.

I'd recheck the PCs, unless they are old/low powered models, my guess
would be that they are using a lot more than 60W each
My desktop uses between 150 and 300W depending on what it's doing.
Whereas the laptop I use mostly now, is between 40 and 90W depending on
whether I'm playing 3d games or not.

This may be inaccurate.
How are you measuring the 150-300W?
My PC also read 150W+ on a plug-in power meter, but a proper power
reading (using a scope) revealed that the plug-in power meter was
overreading by a factor of 2.

300W is very, very unlikely, unless you have a multiprocessor PC
with terabytes of storage, or you use a projector for your monitor.

"Ian Stirling" wrote in message
...
....
This may be inaccurate.
How are you measuring the 150-300W?
My PC also read 150W+ on a plug-in power meter, but a proper power
reading (using a scope) revealed that the plug-in power meter was
overreading by a factor of 2.

300W is very, very unlikely, unless you have a multiprocessor PC
with terabytes of storage, or you use a projector for your monitor.

Custom PC recently ran an article on power supplies. They estimated a fairly
modest desktop machine as needing 280W without reserves, 295W with headroom.
Admittedly, you probably would not often need to use the DVD drive (25.5W)
and the CD-RW drive (19.88W) simultaneously when also running everything
else at full chat. However, they were the only significant power users that
you might not want to use together. My CPU, graphics card and memory would
need about 60W more than the ones they used in the example, so it is not
that hard to top 300W on a home machine working flat out.

Colin Bignell

On Fri, 19 Nov 2004 11:16:55 GMT, "Alan"
wrote:

My house is a 3 bed semi, heated by gas (water also). Washing machine &
dishwasher are always run at night in the E7 period. The only form of
electrical heating is a 500w "frost watcher" in the [insulated] garage - I
will fit my plug-in power watt / usage meter on this tonight to see how much
it's on, but seems very little this time of year.

Hi,

What is the frost watcher used for specifically?

cheers,
Pete.

Ian Stirling wrote:
This may be inaccurate.
How are you measuring the 150-300W?
My PC also read 150W+ on a plug-in power meter, but a proper power
reading (using a scope) revealed that the plug-in power meter was
overreading by a factor of 2.

300W is very, very unlikely, unless you have a multiprocessor PC
with terabytes of storage, or you use a projector for your monitor.

Err, yes that may be a bit misleading since it includes the monitor,
Sorry about that.
I measured the voltage across a shunt resistor with a true-RMS Fluke
DMM. I *think* I did the maths properly.
Hmm...maybe I should measure it again.

For the laptop I just measured the DC input current - can't get that
wrong

Lee
--
Email address is valid, but is unlikely to be read.

tony sayer wrote:

Remind me which way that is(.....

Eh, what what is?

--
Andy

Andy Wade wrote:
tony sayer wrote:

Remind me which way that is(.....

Eh, what what is?

I think Tony means to deteriorate in accuracy up or down.

Maybe it is the leccy co's timeswitch that is out and you are using
your appliances at night, and getting the cheap rate in the day. Not a
likely issue if it's a radio teleswitch. But have you actually checked
the meter to see when the cheap rate is kicking in? and do your timers
coincide?

--
Richard
"Pete C" wrote in message
news
On Fri, 19 Nov 2004 11:16:55 GMT, "Alan"
wrote:

My house is a 3 bed semi, heated by gas (water also). Washing
machine &
dishwasher are always run at night in the E7 period. The only form
of
electrical heating is a 500w "frost watcher" in the [insulated]
garage - I
will fit my plug-in power watt / usage meter on this tonight to see
how much
it's on, but seems very little this time of year.

Hi,

What is the frost watcher used for specifically?

cheers,
Pete.

In article , Andy Wade
writes
tony sayer wrote:

Remind me which way that is(.....

Eh, what what is?


Accuracy.. over;( or under reading
--
Tony Sayer

On Fri, 19 Nov 2004 11:16:55 GMT, Alan wrote:

the usage is around 23kwh / day peak rate and 8kwh / day low rate
(Economy 7). This seems very high to me.

And me, we cook by electric (spit) and only use about 23kwh/day total.

My house is a 3 bed semi, heated by gas (water also). Washing
machine & dishwasher are always run at night in the E7 period.

If you are not space heating by electicity it might be better to drop
the E7. You need to use roughly 20% of your power in the night period
to break even on the increased standing charge(*) and day unit rate.

Check that your E7 timeswitch and those used to control your other
appliances agree about when the E7 period is. Ours is currently most
of the afternoon...

Lots of small loads add up surprisingly quickly. Your computers are
using over 4/units per day, the 500W heater on for four hours (just
10min each hour) 2 more, 6hrs of tank light at 250W 1.5 units. 8 units
without really trying...

(*) Even if you have a "standing charge free" tarrif, on these the
first X units per quarter at Y more expensive, it is odd that X * Y =
standing charge...

--
Cheers
Dave. pam is missing e-mail

tony sayer wrote:

Accuracy.. over;( or under reading

OIC what you mean: do they read high or low? I don't know really.
You'd expect a rotating-disc meter to under-read at low power levels due
to the friction in the bearings, but they have some sort of compensation
for that, I think, with various tweaky-screws inside the meter. In
principle power factor shouldn't make a difference because the
accelerating torque on the disc at any moment is proportional to the
instantaneous v*i product. If that's so then over a whole number of
cycles the disc's movement will be proportional to the net energy flow -
IOW the meter should respond to the true mean power. Errors, I guess,
could then be in either direction. There are doubtless particular
trends for actual practical meter designs, but I wouldn't like to
speculate on that. Are there any meter specialists reading?

As to the electronic ones I have _absolutely_ no idea. How do they
work? Do they sample and digitise v and i first and then compute energy
flow in the digital domain - in which case accuracy will be down to the
performance of the CT and VT and the ADCs - or do they use an analogue
front-end with a 4-quadrant multiplier and integrator? - in which case
the scope for errors would be rather greater...

--
Andy

Andy Wade wrote:


How do they
work? Do they sample and digitise v and i first and then compute energy
flow in the digital domain.

The last one's I worked on were operating AIRI, by using resistive
current sampling, with an integrated amplifier and a/d convertor + a
direct sample of V which was digitised. All the amplification and
sampling took place in the same instrumentation, error corrected IC,
with an external resistor for current and an external potential divider
network for volts. The accuracy was very good, provided the current
connections were sound. IIRC some units were trying out Hall effect
current sensors, but the 10e5 current level variations could cause a
few problems. The current input was of necessity integrated before
amplifying and sampling, in order to cope with the problem of high speed
transients from power factor corrected PSU's. The known problems were
current resistor and semiconductor drift. The potential dividers were
generally trouble free. Todays technology should undoubtedly be better
than 15 years ago.

Regards
Capitol

Capitol wrote:

stuff about electronic elctricity meters

Interesting - thanks for that. Having mentioned CT and VT I realised,
after posting, that that would be too expensive and that simple
resistive coupling could be used, there being no need for isolation from
the mains.

The current input was of necessity integrated before amplifying and
sampling, in order to cope with the problem of high speed transients
from power factor corrected PSU's.

Which, presumably, just amounts to the anti-alias filtering you'd need
in any A to D system. What sampling rate was used? - thinking about it
if you're only trying to measure kWh (as opposed to kVARh) you're not
interested in anything above the 50Hz fundamental - so the sampling rate
could be very pedestrian...

--
Andy

Andy Wade wrote:
What sampling rate was used?

100KHZ at the time. See http://www.metering.com/archive/031/42_1.htm

for some present practice.

Regards
Capitol