Testing Electricity Meters

[Nicky Murtagh]

I have been asked by the owner of a caravan site to go round and check all the meters onsite to make sure they are working properly. Has anybody been asked to do this before? What is the best way to test them? I was thinking to plug something in which has a big load and watch the numbers going up?has anybody any other ideas?

Cheers

 

[Spoon]

I'm keeping an eye on this one as I'm interested to see how its done and if there is a special way of testing them.
I'd just plug in a heater at home for 10 mins and see what reading I get on the meter. Then I'd do the same in each caravan and see if I get a similar reading.... or is there more to it??

 

[Charlie_]

Calibrated ammeter and volt meter.
Plug in s fixer load, test the values, with out power and check it against the kWh meter

 

[Wilko]

Hi - I’m thinking heater load plus meter. Hopefully both go up the same amount
100A Single Phase Digital Check Meter | ElectricalDirect - https://www.electricaldirect.co.uk/product/100a-single-phase-digital-check-meter-436268?vat=1&shopping=true&gclsrc=aw.ds&&gclid=EAIaIQobChMI1ej-h9Kq4gIVyr_tCh1gyg2YEAQYASABEgLCSvD_BwE

 

[James]

When he says he wants them checked to make sure they are working properly, is this that he is concerned some aren’t working at all or is he after a calibration certificate for each so he can bill from the meters? You can rent load banks that have calibration certificates.

 

[Nicky Murtagh]

When he says he wants them checked to make sure they are working properly, is this that he is concerned some aren’t working at all or is he after a calibration certificate for each so he can bill from the meters? You can rent load banks that have calibration certificates.

I think he just suspects some of them aren't working correcctly, he doesnt need certs or anything.

 

[Nicky Murtagh]

Calibrated ammeter and volt meter.
Plug in s fixer load, test the values, with out power and check it against the kWh meter

What is 'S Fixer Load'??

 

[Nicky Murtagh]

Thanks for the replies, could you just use clapm meter and heater for a load, then calculate the kwh, from the ampage on clamp meter?

 

[Taylortwocities]

What is 'S Fixer Load'??

I expect it’s
A fixed load
When typed on a smart phone.

 

[PEG]

I would imagine,a proper test would include a range of loads,from smallest,to largest. This was common with meters of old.
The biggest error with mechanical meters,was their inaccuracy at lower loads,therefore not recording the majority of a days use.

I know of many properties,where you can stick on most of the downstairs lights,LED's,i know,but the meter wheel remains frozen

 

[Zerax]

Alot depends on how accurate you want to be with the test... it's very easy to check it within say 10%... harder within say 5%... and I would guess some very controlled bench testing to get it less than 1%

 

[PEG]

Just a quick calculation,shows a 1% error,as in 1A on 100A supply,is £250 over 365 days.

It would be this type of error,which accrued costs in either direction,not the short burst of kettle/shower use

 

[Wilko]

I thought I’d do a quick look up on what is considered accurate enough -

https://assets.publishing.service.g...lectricity_Determination_Report_2003-2014.pdf

Do read the report, but here’s an excerpt

 

[Zerax]

I thought I’d do a quick look up on what is considered accurate enough -

https://assets.publishing.service.g...lectricity_Determination_Report_2003-2014.pdf

Do read the report, but here’s an excerpt

View attachment 49476

Thanks... so not very accurate then...

 

[Wilko]

Thanks... so not very accurate then...

Trying to be glass half full - it might be that meters are in fact quite accurate and well within this range. Or not ...

 

[Lucien Nunes]

Testing a conventional induction meter requires a range of loads as specified by the manufacturer for a particular type. As mentioned above, calibration is often most important at low loads, as this is where the meter will often spend most of its time and clock up most of the total usage. You will spot gross errors with a simple test with a heater and another kWh meter, but to confirm that they are to spec is difficult to do without the proper kit. To check the calibration of a device, you need a device with an order of magnitude better accuracy.

Consider a simple test with a heater. You want the heater to be a constant load but it will vary with the square of the voltage. If the voltage fluctuates by 5% during the test, the load power will fluctuate by 10.25%. If you are just watching an ammeter and voltmeter and trying to take an average in your head, you're likely to be more in error with your 'test' instruments than the worst error permissible on the meter. If you compare to another known good kWh meter, that might itself be on the limits but shouldn't be beyond them. If the meter under test is twice as far out in the same direction you won't know about it, because it will still look just within cal.

Finally,

the ampage on clamp meter

Ampage... Clampage... Shmampage! Did you mean current?

 

[Nicky Murtagh]

Lol yes I meant current.

 

[Nicky Murtagh]

Thanks for all the replies guys.

I started the job yesterday, I just bought a meter and a heat gun. i made up a lead with a 16a caravan plug, then the meter then a single traling socket.

I turned the heat gun on, until my new meter went up by 0.05KWH and checked it against the parks meter, I found 3 faulty meters so far.

 

[Wilko]

Hi - can I ask what the difference in readings was?

 

[Nicky Murtagh]

most of them were within 0.01 kwh, but the 3 faulty ones were just not moving at all.

 

[Percyprod]

I used to have to do meter testing on disputed accounts in the days of Norweb
Used 2 is fire or consumer's cooker to give a load. Measure volts and current, then time disc for 5 minutes and multiply by 12 to give one hour equivalent. Later we had an electronic unit with ct's which did a lot of it. Not very scientific or accurate! Can't remember the accepted accuracy. Dear mestic meters were certified as accurate for 15 years I think, and had to be changed if ESMA seals were in sding (ones on the main case).

 

[static zap]

3 faulty ones were just not moving at all.

..also think possibly "Got at" ! ..