I recently got a ac current and power meter and something has become
apparent which makes me wonder if its significantly out of calibration... or
just the type of load.

It seems to measure pure resistive and most other loads accurately,
including those with SMPS like the TV / PC etc.

But try and measure a CFL or indeed any Fluorescent light and it is telling
me it is consuming about double the power it should be.

- The 60 watt circular kitchen lights each consume around 120 watts
- The dual 58 watt (116 watts) fluorescent lights takes approx 170 watts
- the 18 watt CFLs take approx 34 watts
In fact the Megaman 11 watt CFL has printed on it 96 mA
which is 230 x 0.096 = 22.08 watts

Can anyone explain ?

Is the power not going into the tube
not counted ? ( i.e what the ballast wastes not counted ?)

Thanks,

Nick

Nick wrote:
I recently got a ac current and power meter and something has become
apparent which makes me wonder if its significantly out of calibration... or
just the type of load.

It seems to measure pure resistive and most other loads accurately,
including those with SMPS like the TV / PC etc.

But try and measure a CFL or indeed any Fluorescent light and it is telling
me it is consuming about double the power it should be.

- The 60 watt circular kitchen lights each consume around 120 watts
- The dual 58 watt (116 watts) fluorescent lights takes approx 170 watts
- the 18 watt CFLs take approx 34 watts
In fact the Megaman 11 watt CFL has printed on it 96 mA
which is 230 x 0.096 = 22.08 watts

Can anyone explain ?

Is the power not going into the tube
not counted ? ( i.e what the ballast wastes not counted ?)

Thanks,

Nick

Its reading VA, not power. Google "power factor"


NT

"Nick" wrote in message
...
I recently got a ac current and power meter and something has become
apparent which makes me wonder if its significantly out of calibration...
or just the type of load.

It seems to measure pure resistive and most other loads accurately,
including those with SMPS like the TV / PC etc.

But try and measure a CFL or indeed any Fluorescent light and it is
telling me it is consuming about double the power it should be.

- The 60 watt circular kitchen lights each consume around 120 watts
- The dual 58 watt (116 watts) fluorescent lights takes approx 170 watts
- the 18 watt CFLs take approx 34 watts
In fact the Megaman 11 watt CFL has printed on it 96 mA
which is 230 x 0.096 = 22.08 watts

Can anyone explain ?

Is the power not going into the tube
not counted ? ( i.e what the ballast wastes not counted ?)

Thanks,

Nick

What's the model, have you looked at the spec regarding power factor.
Unfortunately fluorescents don't always have very good power factor, even if
they have a correcting capacitor. CFLs don't have the space.

Nick wrote:
I recently got a ac current and power meter and something has become
apparent which makes me wonder if its significantly out of calibration... or
just the type of load.

It seems to measure pure resistive and most other loads accurately,
including those with SMPS like the TV / PC etc.

But try and measure a CFL or indeed any Fluorescent light and it is telling
me it is consuming about double the power it should be.

- The 60 watt circular kitchen lights each consume around 120 watts
- The dual 58 watt (116 watts) fluorescent lights takes approx 170 watts
- the 18 watt CFLs take approx 34 watts
In fact the Megaman 11 watt CFL has printed on it 96 mA
which is 230 x 0.096 = 22.08 watts

Can anyone explain ?


'power factor'

On 12 Jan, 17:26, "Nick" wrote:
I recently got a ac current and power meter and something has become
apparent which makes me wonder if its significantly out of calibration... or
just the type of load.

It seems to measure pure resistive and most other loads accurately,
including those with SMPS like the TV / PC etc.

But try and measure a CFL or indeed any Fluorescent light and it is telling
me it is consuming about double the power it should be.

- The 60 watt circular kitchen lights each consume around 120 watts
- The dual 58 watt (116 watts) fluorescent lights takes approx 170 watts
- the 18 watt CFLs take approx 34 watts
* *In fact the Megaman 11 watt CFL has printed on it 96 mA
* * which is 230 x 0.096 = 22.08 watts

Can anyone explain ?

Is the power not going into the tube
not counted ? *( i.e what the ballast wastes not counted ?)

Thanks,

Nick

Any flourescent light has a power loss in the choke/control gear. If
you check in the OSG for a rule of thumb this is normally taken as not
less than 80% of the rated power of the lamp thus a 100 watt lamp
fitting will consume 180 watts of power or more. Your readings are
entirely ok
(For those with a copy of the 17th edition OSG its note 2 on page 96
dealing with assumed current demand)

On 12 Jan, 19:57, John Rumm wrote:
cynic wrote:
Any flourescent light has a power loss in the choke/control gear. If

This is true...

you check in the OSG for a rule of thumb this is normally taken as not
less than 80% of the rated power of the lamp thus a 100 watt lamp
fitting will consume 180 watts of power or more. Your readings are
entirely ok

You seem to be confusing the current demand, and power dissipated in the
load. The maximum circuit current may well be in excess of that expected
* by inspection of the lamp power alone, however not all of that
additional current flow corresponds to matching power dissipation (and
hence energy consumption) in the load.

I do know the difference and very much doubt the el-cheapo meter
readout is actual watts power. It is likely to be reading va and the
readings mentioned fit reasonably well with that. Maybe I should have
given a fuller description :-(

cynic wrote:
On 12 Jan, 19:57, John Rumm wrote:
cynic wrote:
Any flourescent light has a power loss in the choke/control gear. If
This is true...

you check in the OSG for a rule of thumb this is normally taken as not
less than 80% of the rated power of the lamp thus a 100 watt lamp
fitting will consume 180 watts of power or more. Your readings are
entirely ok
You seem to be confusing the current demand, and power dissipated in the
load. The maximum circuit current may well be in excess of that expected
by inspection of the lamp power alone, however not all of that
additional current flow corresponds to matching power dissipation (and
hence energy consumption) in the load.

I do know the difference and very much doubt the el-cheapo meter
readout is actual watts power. It is likely to be reading va and the
readings mentioned fit reasonably well with that. Maybe I should have
given a fuller description :-(

I have one of the plug in meters somewhere (the one Maplin flogged for a
while)... IIRC the one I have does make a stab at assessing power
factor, however it is probably not much good on things that have non
sinusoidal current waveforms like CFLs. It seems ok on basic reactive
loads with straightforward leads or lags though.

(spose I ought to dig it out and work out why this house is so much more
expensive than the last one for electricity use)

--
Cheers,

John.

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

"John Rumm" wrote in message
et...
cynic wrote:
..

(spose I ought to dig it out and work out why this house is so much more
expensive than the last one for electricity use)

--
Cheers,

John.

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

When my consumption jumped up I eventually, months later, discovered that
the control knob on the chest freezer was broken and although it indicated
the mid position the compressor was, in fact, running 24/7!!

Peter

cynic wrote:
On 12 Jan, 19:57, John Rumm wrote:
cynic wrote:

Any flourescent light has a power loss in the choke/control gear. If

This is true...

you check in the OSG for a rule of thumb this is normally taken as not
less than 80% of the rated power of the lamp thus a 100 watt lamp
fitting will consume 180 watts of power or more. Your readings are
entirely ok

You seem to be confusing the current demand, and power dissipated in the
load. The maximum circuit current may well be in excess of that expected
� by inspection of the lamp power alone, however not all of that
additional current flow corresponds to matching power dissipation (and
hence energy consumption) in the load.

I do know the difference and very much doubt the el-cheapo meter
readout is actual watts power. It is likely to be reading va and the
readings mentioned fit reasonably well with that. Maybe I should have
given a fuller description :-(


After a bit more thought I suspect the meter isnt reading VA after
all. The reason is that the high current for the CFL doesnt tally with
its wattage or VA rating. Since the current draw is in the high v
part of the mains cycle for a CFL, it wont draw excess mean current
compared to a resistive load. Rather it will draw higher peak
current.

I suspect instead that like many a cheap digital meter its measuring
peak current and doing a blind conversion to what will be power for
resistive loads, but will be simply a wrong answer for other stuff.


NT