I've been experimenting with a plug in power monitor. It reads out in
watts and also VA.

As I understand it VA and watts should read the same when it's a
straight resistance circuit, but differ when there's a capacitor or an
inductance in the circuit. I'm really only interested in how much
power comes in and I'm charged for through my external electricity
meter.

Is the VA reading of any practical use to me?

On Sat, 16 Feb 2008 09:18:43 -0800 (PST), andyv wrote:

I've been experimenting with a plug in power monitor. It reads out in
watts and also VA.

As I understand it VA and watts should read the same when it's a
straight resistance circuit, but differ when there's a capacitor or an
inductance in the circuit. I'm really only interested in how much
power comes in and I'm charged for through my external electricity
meter.

Domestic supplies are charged on kwh's, not kvah.

Is the VA reading of any practical use to me?

Haven't you answered your own question? (Rhetorical!)

--
the dot wanderer at tesco dot net

andyv wrote:

I've been experimenting with a plug in power monitor. It reads out in
watts and also VA.

The better ones do...

As I understand it VA and watts should read the same when it's a
straight resistance circuit, but differ when there's a capacitor or an
inductance in the circuit. I'm really only interested in how much
power comes in and I'm charged for through my external electricity
meter.

Yup

Is the VA reading of any practical use to me?

Only in that it lets you see when you have a reactive load.

(Depending on what other variables the meter can show you it may also be
useful to help you estimate the current carrying capacity required for a
given load).


--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 16 Feb, 20:56, John Rumm wrote:
andyv wrote:
I've been experimenting with a plug in power monitor. It reads out in
watts and also VA.

The better ones do...

As I understand it VA and watts should read the same when it's a
straight resistance circuit, but differ when there's a capacitor or an
inductance in the circuit. I'm really only interested in how much
power comes in and I'm charged for through my external electricity
meter.

Yup

Is the VA reading of any practical use to me?

Only in that it lets you see when you have a reactive load.

(Depending on what other variables the meter can show you it may also be
useful to help you estimate the current carrying capacity required for a
given load).

--
Cheers,

John.

/================================================== ===============\
| * * * * *Internode Ltd - *http://www.internode.co.uk* * * * * *|
|-----------------------------------------------------------------|
| * * * *John Rumm - john(at)internode(dot)co(dot)uk * * * * * * *|
\================================================= ================/

Thanks folks. I've been measuring individual circuits with the power
monitor and also the whole supply with a data logger attached to the
incoming meter. I've run this in lots of different ways with different
circuits on or off in an attempt to get an idea of electricity use.
Gradually I've found items of waste which I've been able to
eliminate.

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

andyv wrote:

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

There may well be - in that it will give you some clues as to type of
load you are looking for.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 17 Feb 2008 03:27:28 -0800 (PST)
andyv wrote:

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

Most likely: pumps (CH) and motors (fridge/freezer), both inductive.
Do come back and tell us when you do find out.

R.

In message
,
andyv writes
Thanks folks. I've been measuring individual circuits with the power
monitor and also the whole supply with a data logger attached to the
incoming meter. I've run this in lots of different ways with different
circuits on or off in an attempt to get an idea of electricity use.
Gradually I've found items of waste which I've been able to
eliminate.

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

So what's the stated accuracy of your new little toy then?

Are you losing watts or measurement errors ?



--
geoff

On 17 Feb, 17:01, geoff wrote:
In message
,
andyv writes

Thanks folks. I've been measuring individual circuits with the power
monitor and also the whole supply with a data logger attached to the
incoming meter. I've run this in lots of different ways with different
circuits on or off in an attempt to get an idea of electricity use.
Gradually I've found items of waste which I've been able to
eliminate.

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

So what's the stated accuracy of your new little toy then?

Are you losing watts or measurement errors ?

--
geoff

I have thought of that but the declared accuracy seems quite good -
see http://www.maplin.co.uk/module.aspx?...&doy=18m2#spec

Most of my readings come from the data logger though. This is separate
to the power monitor. I have a device which counts the red flashing
light pulses on the main meter. Each flash is 1 watt hour so I can
build up a picture of what passes through the meter over different
time periods. I'm particularly interested in what happens when
everything is idling in the middle of the night.

One potential item which I'm investigating is the frost thermostat on
the boiler.

In message
,
andyv writes
On 17 Feb, 17:01, geoff wrote:
In message
,
andyv writes

Thanks folks. I've been measuring individual circuits with the power
monitor and also the whole supply with a data logger attached to the
incoming meter. I've run this in lots of different ways with different
circuits on or off in an attempt to get an idea of electricity use.
Gradually I've found items of waste which I've been able to
eliminate.

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

So what's the stated accuracy of your new little toy then?

Are you losing watts or measurement errors ?

--
geoff

I have thought of that but the declared accuracy seems quite good -
see http://www.maplin.co.uk/module.aspx?...&doy=18m2#spec

Most of my readings come from the data logger though. This is separate
to the power monitor. I have a device which counts the red flashing
light pulses on the main meter. Each flash is 1 watt hour so I can
build up a picture of what passes through the meter over different
time periods. I'm particularly interested in what happens when
everything is idling in the middle of the night.

One potential item which I'm investigating is the frost thermostat on
the boiler.

I would expect something like that to be responsible for 3/5th of bugger
all (choose your own units)

--
geoff

On 18 Feb, 20:29, geoff wrote:
In message
,
andyv writes



On 17 Feb, 17:01, geoff wrote:
In message
,
andyv writes

Thanks folks. I've been measuring individual circuits with the power
monitor and also the whole supply with a data logger attached to the
incoming meter. I've run this in lots of different ways with different
circuits on or off in an attempt to get an idea of electricity use.
Gradually I've found items of waste which I've been able to
eliminate.

There's still 0.5 kwh going astray midnight to 6.00am and maybe all
day too, after I've accounted for everything I know about - fridge,
security lights, clocks, central heating and various other things like
garage door on standby. I wondered if there might be a clue in the VA
reading.

So what's the stated accuracy of your new little toy then?

Are you losing watts or measurement errors ?

--
geoff

I have thought of that but the declared accuracy seems quite good *-
seehttp://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=38343&doy=18m2...

Most of my readings come from the data logger though. This is separate
to the power monitor. I have a device which counts the red flashing
light pulses on the main meter. Each flash is 1 watt hour so I can
build up a picture of what passes through the meter over different
time periods. I'm particularly interested in what happens when
everything is idling in the middle of the night.

One potential item which I'm investigating is the frost thermostat on
the boiler.

I would expect something like that to be responsible for 3/5th of bugger
all (choose your own units)

--
geoff- Hide quoted text -

- Show quoted text -


You are probably right that it doesn't amount to much. My central
heating uses about 15 watts of electricity when it's off. I think
however that recent cold weather has been causing the frost thermostat
to trip and so run the full central heating in the middle of the
night. This then steps up to about 125 watts for the control gear and
pumps, and of course it uses gas and heats the whole house. The thing
is that the thermostat seems to be faulty and must be tripping in at
somewhat above the required 5º. I don't yet know if this is happening
regularly and is the only issue.

When you add up several small items like this it comes to a fair bit
of waste. Not massive but worth preventing, if you care about such
things.