Investigation on massive electricity bills

[a-z electrics]

At that monthly cost I would suggest buying an energy monitor for each of the three CUs.. they only about £30 each. And you /client can use them afterwards too.
I assume RCDs are fitted to each CU? This would trip if any earth leakage. If fitted, I would suspect faulty meter. Get elec company involved..

 

[a-z electrics]

To cut a long story short the voltage was about 2 milliamps finding it’s way through my clients house back to the supply, but the clamp meter does not care aboutvoltage just amps.

Do you mean millivolts?

 

[Pete999]

To cut a long story short the voltage was about 2 milliamps finding it’s way through my clients house back to the supply, but the clamp meter does not care aboutvoltage just amps.

Do you mean millivolts?

 

[Davisonp]

To cut a long story short the voltage was about 2 milliamps finding it’s way through my clients house back to the supply, but the clamp meter does not care aboutvoltage just amps.

Do you mean millivolts?

Yes, My mistake.

 

[davesparks]

Is the supply to the cottage undersized? If there's significant volt drop between DB and cottage then, V=IR, if volts go down amps must go up.

No, the current must reduce as the voltage is reduced, otherwise at zero volts the current would be infinite!

 

[Lucien Nunes]

Not necessarily true. Over the range of voltage at which they will operate correctly, some loads, mostly SMPSUs, have negative dynamic resistance, because they consume approximately constant power regardless of voltage. Current is therefore approximately inversely proportional to voltage. However, outside of the operational range, the current usually falls to zero as the device shuts down. There are other loads that behave like constant power loads integrated over a longer period of time, mainly thermostatically controlled heating. Increasing the voltage drop of a heating circuit, such that the heat dissipated by the cable causing the drop doesn't heat the target space, will require the heater to be on for a greater duty cycle to maintain the set temperature as its heat output will have decreased. But the consumption at the meter won't have decreased by the same amount, so the energy consumption to maintain the temperature will increase by the amount lost through voltage drop.

A moment's thought suggests that energy loss through voltage drop is not the culprit here though. We have been talking about 24/7 loads in the order of ten kilowatts in order to run up these bills, and it would be a surprise if there was that much capacity of SMPSU on the whole site. Then, to make the bill so much higher, the voltage drop would have to be a significant fraction of the supply voltage, for the wastage to have a significant efffect on the bill. There would be all sorts of other symptoms things randomly shutting down, filament lamps that glow dimly and almost go out when you turn the microwave on, which would take 2 hours to boil a cup of water.

Look elsewhere...

 

[DPG]

They haven't got an electrically powered cinema organ blower in the bungalow have they?

 

[davesparks]

Not necessarily true. Over the range of voltage at which they will operate correctly, some loads, mostly SMPSUs, have negative dynamic resistance, because they consume approximately constant power regardless of voltage. Current is therefore approximately inversely proportional to voltage. However, outside of the operational range, the current usually falls to zero as the device shuts down. There are other loads that behave like constant power loads integrated over a longer period of time, mainly thermostatically controlled heating. Increasing the voltage drop of a heating circuit, such that the heat dissipated by the cable causing the drop doesn't heat the target space, will require the heater to be on for a greater duty cycle to maintain the set temperature as its heat output will have decreased. But the consumption at the meter won't have decreased by the same amount, so the energy consumption to maintain the temperature will increase by the amount lost through voltage drop.

Yes it was a bit of a broad sweeping statement on my part, and I think in the context of the thread it was valid despite the exceptions.

Whilst the heater would behave as I find it was constant power, the current in the circuit would still be reduced in proportion to the reduction in voltage.

 

[davesparks]

On the job now. Reading a constant 7.6 amps in L3 incoming on main board. This L3 also had a constant 4.8 amps to main house. Any ideas

How are you measuring this, are the two readings averaged over a period of time or are they instantaneous readings?
If instantaneous then unless the two readings were taken at the same instant then they can't be related to each other.

 

[davesparks]

Just been in and the only circuit pulling any significant current is the cooker at 6.6 amps. Don't know why it kept spiking but it's only since they got home. L1 was pretty much inactive until try arrived then starts spiking at 36 amps at times.

Then clearly something has been switched on which draws that current.
What times does it spike at, are they regular intervals or apparently random, what is the duration of the spike?
Is the spike always of the same magnitude?

 

[buzzlightyear]

 

[buzzlightyear]

he can sing this song when he looking for it!

 

[DPG]

It's a mythtery!

 

[Squid]

With the amount of time the OP is spending on site he'll be singing this in the van on the way home,