Difference in amperage though household meter question

[Cheshire man]

Hi,
I have just joined as I have a non urgent but nagging question...hope you guys can give me peace of mind!
Thank in advance.
I have just checked the amperage coming in on the meter tails prior to the meter (Between the main fuse and the old style dial meter) this is 0.85 amps. However the measured amperage in the tails between the meter and the consumer unit (actually between the meter and an old 50mA RCD that then goes onto the consumer unit) this is 0.97 amps. Why the discrepancy?
Any thoughts/revelation or 'that should be bleeding obvious mate' answers?

 

[Pete999]

Hi,
I have just joined as I have a non urgent but nagging question...hope you guys can give me peace of mind!
Thank in advance.
I have just checked the amperage coming in on the meter tails prior to the meter (Between the main fuse and the old style dial meter) this is 0.85 amps. However the measured amperage in the tails between the meter and the consumer unit (actually between the meter and an old 50mA RCD that then goes onto the consumer unit) this is 0.97 amps. Why the discrepancy?
Any thoughts/revelation or 'that should be bleeding obvious mate' answers?

What sort of test equipment was used to check the current

 

[R-fur]

Assuming you are using a clip on ammeter, these are not all that accurate. Depending where the conductor is in the jaws can affect the reading.
In theory the current going into the meter should be slightly higher than that coming out as it will include the current for the voltage coil. The voltage coil is connected before the current coil so you don't pay for the current it uses. The current for the voltage coil will be very inductive so that may also affect the reading.

 

[Nelder]

I noticed once on a job that even though the tails out of the meter to the CU were disconnected, the meter was still spinning. I only noticed it because i heard it spinning

 

[Cheshire man]

Assuming you are using a clip on ammeter, these are not all that accurate. Depending where the conductor is in the jaws can affect the reading.
In theory the current going into the meter should be slightly higher than that coming out as it will include the current for the voltage coil. The voltage coil is connected before the current coil so you don't pay for the current it uses. The current for the voltage coil will be very inductive so that may also affect the reading.

Hi, thank you for your response.
Your right, I am using a clip on meter, but I have checked multiple times and I get the same readings every time, so its very repeatable. I would have expected the supply side to show the higher reading as you say the meter must use a fraction of power. I was just surprised to see the higher current on the 'wrong' side and its quite a large percentage higher.
Serves me right for messing around in the house with meters when I should be gardening

 

[static zap]

What earthing arrangement. (TNC ?)

 

[alasdairp]

I suspect that the missing 0.12 amps is going down the Earth bonding conductor. This is very common in PME areas. Measure that. Also check the Neutral-Earth voltage (ideally it should be zero - but I bet it is not). It does not sound like a worrisome problem.

I once found over 300 amps returning down the Earth route (in a commercial premises - and only 20 amps down the Neutral main feed conductor). That was worrisome! Turned out to be due to a corroded u/g main untility feed XLPE cable.

 

[Cheshire man]

What earthing arrangement. (TNC ?)

Hi,

Its a TT system but it does not have a dedicated earth rod. Its earthed via the old copper going into lead mains water pipe. I am the only person on my estate still on lead and I have it all to myself and I have a long drive so there is plenty underground.

 

[Cheshire man]

I suspect that the missing 0.12 amps is going down the Earth bonding conductor. This is very common in PME areas. Measure that. Also check the Neutral-Earth voltage (ideally it should be zero - but I bet it is not). It does not sound like a worrisome problem.

I once found over 300 amps returning down the Earth route (in a commercial premises - and only 20 amps down the Neutral main feed conductor). That was worrisome! Turned out to be due to a corroded u/g main untility feed XLPE cable.

I will check the N-E voltage later and let you know...thanks again.

 

[shaun1]

If it's a TT system then the current returning via earth should be almost zero as there should be no connection between earth and the live conductors (other than filtering caps etc that can cause a small leakage.)