Phantom Current?

[baldy01]

OK here's an interesting thing that happened to me, I wonder what you think?

My electricity bills suddenly rocketed six months ago. After checking and double checking the meter figures, I decided to have a look at how much current we're pulling. I waited till the family was out so nothing apart from idle current should show, fridge, stuff on standby etc. Stuck a current clamp on the mains tail before the meter and hey presto got 8.5 amps. So I then tested after the meter so as to prove the meter at fault (gotcha!) except there it was - 8.5amps.

I then switched of upstairs lights, downstairs lights etc waiting for the current to drop. With all the breakers switched off except the main RCD/Breaker the current was 6amps. Switch off the main RCD/Breaker. Still 6amps. Huh?

Stuck the current clamp on a known load i.e. a kettle just to check it was reading correctly, and it was correct for a 3Kw kettle.

My conclusion - faulty RCD pulling 6amps? Question is why is it not hot? not even mildly warm? That makes no sense to me, 1.5Kw does not just disappear without cooking something.

Then the wierdest thing. I moved the tail circuits around in the box between where they exit the meter to where they go through the wall to the consumer unit. The 6 amps disappeared. With everything back on its running at 2.5 amps ish, which is where it should be.

Is it possible I've got some wierd breakdown in the insulation between the tails?

Any thoughts on what I should do next?

I don't like faults that go away on their own, cos they can just as easily come back on their own.

Cheers

Pete

 

[JohnD]

Do the tails go into a metal enclosure? (I'm thinking eddy currents)

 

[baldy01]

Nope. White plastic utility box in the outside wall, meter is screwed to a plywood board. Tails come out, there's a little slack which hangs in the utility box, then the tails go through the top of the plastic box into the wooden frame of the house for about 2 feet and exits the plasterboard just behind the consumer unit. So screw, nails and wall ties are the only metal in the vacinity.

 

[Lectrician]

Did you meter the live or the neutral? Could easily be circulating network currents via your main eq-bonding if on a PME supply.

 

[baldy01]

I metered the live as the neutral is earth bonded, which as I understand it means that it stays at 0v PD with reference to earth while the live swings between +-230. Well +-320v actually as 240v is the RMS value.

I guess there must still be current running through it, but I prefer to meter the Live.

I also made sure that there was a good six inches separation between Live and Neutral while doing this.

I'm not sure I understand what you mean by circulating network current though. Are you saying there could be current passing through my meter that isn't being drawn by any load in my house?

Thanks for the help btw chaps, its much appreciated.

Pete

 

[Spark123]

I doubt it would be network currents flowing through main equipotential bonding as the main earthing conductor from the MET should be to the DNO service head (which completely bypasses the meter.)

 

[baldy01]

The daft thing is that the bills are correct for a continuous draw of 8.5amps so it looks to me like that current is being drawn, I just can't understand where from.

Is it possible for an RCD to sink 1500watts without heating up? I'd find it difficult to beleive.

Is it possible that where the tail circuits are in contact as they pass through the wall the insulation could break down in such a way as to act as a 1.5kW load? I can't imagine you'd get a big enough contact area to dissipate all that heat.

I did say it was wierd.

P.S. I'm an electronics engineer not a sparky, so I understand the principles involved but not the jargon.

Thanks again.

 

[slippyr4]

Is it possible for an RCD to sink 1500watts without heating up? I'd find it difficult to beleive.

Is it possible that where the tail circuits are in contact as they pass through the wall the insulation could break down in such a way as to act as a 1.5kW load? I can't imagine you'd get a big enough contact area to dissipate all that heat.

The heat is going somewhere. Thats 1.5 bars of an electric fire. You can't throw away the energy.

 

[MattChan]

When you turn your main switch off does everything in the house / garage / garden etc etc go off?

Not got another CU tucked away for a huge pond pump or something thats making intermittent contact when you move the tails about?

Worth lifting the lid off the CU and having a look for wires on the incomming side of the switch?

 

[baldy01]

Hadn't thought of that. I haven't inspected the back of the RCD/Main breaker and I guess its possible that something is wired to it such that it stays on when the main breaker is off. Although what could be drawing that kind of power without me being aware of it is a mystery.

I'll take a look.

Thanks again.

Pete

 

[JohnD]

Neighbours drilled a hole through the wall and stealing your electricity?

Freezer not connected through the RCD to avoid nuisance tripping?