Owl Monitor to Annex

[dazzawyc]

Hi All.

is it possible to use an Owl monitor to record how much electricity is being used just in a seperate annex?

my Mother is Law is happy to pay for her electric but would like to know monthly how much she is using.

so could I for instance, connect the owl sender to the wire from the main fuse box in my house to the annex and will I get a reading from it?

or if that would not work, is there a monitor that could be used for working out how much electric the annex uses?

the cable being used is connected to a RCD/trip box inside the annex and has been connected using armoured cable

many thanks in advance for any answers and advice given.

 

[Murdochcat]

If and I say IF your annexe has a separate CU, then you could have a meter fitted to cover the usage by a competent spark

 

[ericmark]

Not sure if an OWL monitor shows kWh or just kW, but yes you can measure how much power is being used, I have both plug in and clamp on monitors, however there accuracy is some times questionable. For 29 Apr 2024 British Gas App says 7.72 kWh my solar panel software says 8.8 kWh and neither can give my price, as power midnight to 5 am is different price to power 5 am to midnight.

This is what my solar software shows me, I also have a graph but although it gives one an idea what was used when, it can hardly be used to work out a bill.

My IHD (in home display) from my smart meter resets every day at midnight, it reading instructions or USB model instructions that they would both work, as long of course the batteries don't go flat, and the voltage is correct, what I would do is compare your meter reading and the OWL reading on whole supply first and see how much they vary from each other.

Our supply is 230 volt +10% - 6% so 216 to 253 volt, the clamp on only measures amps, where your meter measures both amps and volts so gives true watts, so they are close to correct value but not spot on, as long as you remember only approx then OK.

 

[JohnW2]

is it possible to use an Owl monitor to record how much electricity is being used just in a seperate annex?

Yes, BUT ....

so could I for instance, connect the owl sender to the wire from the main fuse box in my house to the annex and will I get a reading from it?

It would not work if you put the sensor around the whole of the cable going to the annexe - it would have to going around just the 'live' wire or the 'neutral' wire within that cable.

Kind Regards, John

 

[JohnW2]

Not sure if an OWL monitor shows kWh or just kW, ...

The OWL uses a clamp-on sensor to measure current roughly every 12 seconds. On the basis of those figures and programmed (fixed) values for voltage and PF, it calculates instantaneous kW and (together with time) kWh over periods.

.... however there accuracy is some times questionable.

Over the past ~5 years,and despite the inevitable approximation of the programmed fixed values for voltage and PF, my OWL has recorded a total kWh usage (over the entire ~5 years) closer than 0,.1% to the figure from the supplier';s meters.

 

[ebee]

Over the past ~5 years,and despite the inevitable approximation of the programmed fixed values for voltage and PF, my OWL has recorded a total kWh usage (over the entire ~5 years) closer than 0,.1% to the figure from the supplier';s meters.

Not bad at all for an "approximation". I wish my test gear was that accurate.

 

[JohnW2]

Not bad at all for an "approximation". I wish my test gear was that accurate.

You must remember that these are cumulative figures. If the voltage and PF variations remain essentially the same every day, such that vtheir average over a day (or week, or whatever) remains essentially constant, then cumulative calculations based on those average figures will be pretty accurate.

When I started using the system,it took me quite a long time fiddling with the voltage and PF used for calculation (different figures for day and night periods in my case) in order to get the calculated kWh figures to correspond with those from the supplier's meter.

The OWL itself cannot do all that. I download data based on 240V and PF=1.0 and then use my own software to adjust to the actual 'average figures' at my leisure.

Kind Regards, John

 

[ebee]

Yes but No but Yes but No but Yes but No .
It depends upon your eventual tweeks and how accurate it is.
So, cumulative is, example 10% over 10 years then each day, week, month, year might be further out but after ten years you`d get an idea how accurate it might be. I say might because you are comparing it to something else that may not be quite right but more likely to be nearer than anything you add to compare.
So a long (5 year) cumulative effect of 0.1% within that of something else seems pretty good to me, they might both be out by 6& or 3% or 1% or anything, yet it is an indication that your tweeks might have made it reasonably accurate (or thereabouts).

Like when I try different makes of multimeters and check different values with two or more of the group, I gain a little (but never absolute) confidence that readings are "within the parish" and therefore likely to be meaningful to a reasonable degree, but could all be wrong by similar amounts of wrongness too.

I use my mains electrics multifunction meter as useful but might contain some error on any or all functions.
So it is only as useful as ......................... a very good guide guess at best, but it is useful.
Actually I have two of the same make/model and I check them against my checkboxes and each other every month if low usage and twice a month if quite used or very rarely every week say ( also 3 or 4 times a year checked against two other alternative makes and models. Gives a reasonable expectation of confidence .

Actually I don`t now I`ve just about retired but I did for about 12 years as an addition to annual calibration,
Never had a problem with drift etc but if I had I would have been aware of it and the low number of tests that ought to be redone.

So john, your 0.1% figure does impress me.

 

[JohnW2]

Yes but No but Yes but No but Yes but No . ... It depends upon your eventual tweeks and how accurate it is.

Yes, of course. My point was that if the pattern of usage, and corresponding voltage and PF) are much the same every day (which they are), then calculations based on the average voltage and PF will result in pretty accurate figures over fairly long periods of time - but, as you say, dependent upon how correct those averages actually are.

The OWL could obviously be much less correct over short periods (say, an hour or three), since the assumed voltage and PF mightvthen be appreciably incorrect for that period.

I say might because you are comparing it to something else that may not be quite right but more likely to be nearer than anything you add to compare.
So a long (5 year) cumulative effect of 0.1% within that of something else seems pretty good to me, they might both be out by 6& or 3% or 1% or anything ...

Again, sure. Since one is simply comparing two (both imperfect) things, they could both be 'wrong' even if they were giving identical figures. However, it is ultimately primarily about 'money', and the OWL is being compared with the meter that determines my bills - so, even if both were 'wrong',they would still reflect what I have been charged..

So john, your 0.1% figure does impress me.

It impresses me, too. Having just looked, it's actually nearly 7 years, not just 5, and the actual figures for the entire period to date are:

DAY: OWL = 23,223.97 kWh meter = 23,233 kWh difference = 9.03 kWh (0.039%)
NIGHT: OWL = 21,380.90 kWh meter = 21,356 kWh difference = 24.9 kWh (0.117%)

I suspect that the somewhat greater 'error' at night is due to fluctuation in PF. Night-time usage is usually dominated by the immersion heater, hence PF very close to 1.0, but if the dryer, WM or DWM (with their motors) are used during the period (which they sometimes are),the PF will presumably fall a bit. The programmed 'average' PF for night is (as a result of experiment) is 0.980 (and 0.945 during day).

Kind Regards, John

 

[dazzawyc]

Thank you all for your answers, I have now added an Owl monitor by slipping the magnetic clip over the blue wire and it is all reading correctly.

Take care, and thanks again

 

[ebee]

Thank you all for your answers, I have now added an Owl monitor by slipping the magnetic clip over the blue wire and it is all reading correctly.

Take care, and thanks again

Any particular reason why the blue wire rather than the brown one?