Meter puzzle

[diynotpaulm]

Our electricity usage seemed high - 4860 kWh per year for a 3 bedroom semi-detached house - so I started looking more closely at my meter. It's a Sangamo Weston S200.16. It has 5 white digits whose value is submitted as a reading, and two red digits to the right of these. The red digits might be expected to record tenths and hundreths of a unit, but they do not. The rightmost red digit records tenths of a unit, and the left hand red digit records units. The white units digit is in sync with the left hand red digit - for the most part. Both change slowly so that when a half unit is recorded, two digits can be seen - e.g. both 6 and 7 are in the window when 6.5 units have been consumed since zero.

When the red digits show 08, and the white units digit fully shows 9 (that is, 9 units have been consumed since it showed 0) , the white units digit jumps to 0. In other words, the white digits counts nine whole units from 0, then skips to 0. That is, the white digits count as follows,

xxx00, xxx01, xxx02 ..., xxx08, xxx10.

So for every 9 units consumed the meter adds an extra unit to the counter. We have had this meter unaltered for 17 years, and it must have been doing this all that time.

I have some ideas of what has happened, but I'd like your suggestions and thoughts,

1. Is there any way this meter could be recording usage correctly? The wheel revolution rate and tenths readings correctly reflect load wattage.
2. What is causing this behaviour?
3. Is it (a very peculiar) fault condition or has there been a modification. If so when and why would the modification have been made?

 

[securespark]

Surely if the meter starts at 00 and skips 09, that's still 10? Or am I misunderstanding something?

 

[diynotpaulm]

Good question.

Say the meter starts at xxx00. That right hand units digit gradually moves until it shows a 1 fully in the display - that is one unit consumed. Similarly xxx02 fully shown means two units consumed ... and xxx08 is fully shown when eight units have been consumed, and xxx09 is shown when nine units have been consumed. The issue is that when nine units have been consumed, and a nine is fully shown in the display, the meter skips to xxx10. So for nine units consumed, ten units are recorded.

What makes this confusing is that the units digit rotates gradually, (when it is not jumping from 9 to 0). (The 10s and 100s digits don't do this - they move in steps.) So,

xxx00 - xxx01 - part of one unit consumed
xxx01 - xxx02 - one to two units consumed
...
xxx07 - xxx08 - seven to eight units consumed
xxx08 - xxx09 - eight to nine units consumed
xxx09 - xxx10 - does not appear (skipped over)

When nine units have been consumed, xxx10 is shown. So if I submit the first reading as for example 77700 and the final reading as 77710 (both numbers fully shown), I will be charged for ten units while having used only nine.

 

[ericmark]

Our electricity usage seemed high - 4860 kWh per year for a 3 bedroom semi-detached house

So I looked at my house, 5270 kWh per year for a 5 bedroom detached three-story house, but size of house with oil central heating is really immaterial, there are two of us using the electric, for freezers, fridges, dishwashers, washing machines, tumble drier etc.

I expect it to be a little on the high side, as we have three freezers running, we live out in the country, so tend to have a high stock, and also we are not that careful on how much we use when the sun is shining, as we got 5036 kWh from solar, of which 2431 kWh was lost as exported with no payment.

But since we have a split tariff, most of what we buy is at off-peak rate.

However, looking at that, what you are using is about normal.

 

[diynotpaulm]

Yes, usage will depend very much on the appliances, and we have an electric shower and cooker. So 4860 kWh is not outlandish when I monitor usage, but there is still a gap. That will be partly explained by the "restaurant receipt" effect where the total always seems to be more than the sum of the parts. I still need to check if the meter is taking a tip, though.

 

[ericmark]

I have basic three meters, the smart meter, an export meter, and the solar panel software. The solar panel software always shows I have used more than the smart meter does, but near impossible without having solar to see if something has gone wrong.

Yes, you can get CT coils to measure usage, like this which with a hub connect to your PC. I have the 13 amp socket type, and this

does show how much my freezers used. But it is not as accurate as the meter, so it is only any good if the results are wildly different.

Scottish power use to use meters that clamped around the meter tails before smart meters came out, and would use the readings for the bill, then correct once a year, with actually meter reading, and to be fair within £5 to £10 each year, but the problem was, if batteries went flat (2 x D cells) the whole system failed, so now we have smart meter which are claimed to do the same, however my app shows we have over paid by just short of £1000, so it seems they don't work as well as the simple system they replaced.

 

[Mister Banks]

Our electricity usage seemed high - 4860 kWh per year for a 3 bedroom semi-detached house - so I started looking more closely at my meter. It's a Sangamo Weston S200.16. It has 5 white digits whose value is submitted as a reading, and two red digits to the right of these. The red digits might be expected to record tenths and hundreths of a unit, but they do not. The rightmost red digit records tenths of a unit, and the left hand red digit records units. The white units digit is in sync with the left hand red digit - for the most part. Both change slowly so that when a half unit is recorded, two digits can be seen - e.g. both 6 and 7 are in the window when 6.5 units have been consumed since zero.

When the red digits show 08, and the white units digit fully shows 9 (that is, 9 units have been consumed since it showed 0) , the white units digit jumps to 0. In other words, the white digits counts nine whole units from 0, then skips to 0. That is, the white digits count as follows,

xxx00, xxx01, xxx02 ..., xxx08, xxx10.

So for every 9 units consumed the meter adds an extra unit to the counter. We have had this meter unaltered for 17 years, and it must have been doing this all that time.

I have some ideas of what has happened, but I'd like your suggestions and thoughts,

1. Is there any way this meter could be recording usage correctly? The wheel revolution rate and tenths readings correctly reflect load wattage.
2. What is causing this behaviour?
3. Is it (a very peculiar) fault condition or has there been a modification. If so when and why would the modification have been made?

The meter is correct. You count 00 to 09 and then start again.

 

[diynotpaulm]

It does display digits 0 to 9 fully, but there is a twist. Transitions (0 to 1), (1 to 2), ..., (8 to 9) occur gradually with use, transition (9 to 0) is a jump immediately after 9 units are used. So it measures the use of 9 units, immediately displays 10 and keeps going. Then it goes (10 to 11), ... and so on.

 

[Murdochcat]

Consumption of about 5000 units per year - how many people ? How do you heat the property? The water? Do you have an electric cooker? Tumble dryer?

 

[diynotpaulm]

We do have high electricity usage - gas central heating, but electric cooker and shower. But that's not the whole story - we use less than 2 units a day on the shower. The high usage made me look closely at the meter, and wonder if it was recording correctly.

 

[Murdochcat]

What makes you think your consumption is high?

I note you didn’t answer all my questions

Prior to us fitting PV our annual usage was about the same as yours with 4 adults, gas heating / water and a tumble dryer. The PV dropped our usage by about 40%


And 5000 units per year is less than 14 per day, take away 2 for showers, then about 5 per day for back ground usage

 

[ericmark]

Prior to us fitting PV our annual usage was about the same as yours with 4 adults, gas heating / water and a tumble dryer. The PV dropped our usage by about 40%

As said use wise, I am also above @diynotpaulm it is only the solar and batteries which mean now £1 or £1.55 with standing charge per day, or 9.20 kWh most of that off-peak. Average of 10.87p per kWh. (Off-peak 8.95p and peak 31.31p) Hard to say how much due to solar, and how much the battery, but bill is halved, if not a third of bill before solar panels.

 

[Murdochcat]

And old fridges and freezers consume far more electricity than people realise

 

[Rodders53]

That picture is not very clear or out of focus so I can't see the red digits at all.

Maybe you need an in focus time-lapse video of it counting up the digits consumed to demonstrate what you observe, as I'm confused by it all.

Your meter was last calibrated in 1987 and has a 25 year certificate. So that expired in 2012 and it is well overdue for replacement.

NB That exact model of meter is the subject of a You Tube video showing only one red digit which is moving the white digit from 2 to 3. See THIS
But then the same model number is used for the clock dial meter by the same maker so who knows how many variants exist

 

[flameport]

It does display digits 0 to 9 fully, but there is a twist. Transitions (0 to 1), (1 to 2), ..., (8 to 9) occur gradually with use, transition (9 to 0) is a jump immediately after 9 units are used.

That is how that meter was designed. It's not defective, or reading incorrectly.
Explanation for a similar movement: