Who is using my electricity - meter spinning no mcbs on

[dazzlerpalmer]

In an attempt to see if an unidntified circuit is consuming power I turned off all mcb's on the board except the one in question. The meter was spinning slowly. I then switched all mcbs on the main boad.
The meter was still moving very slowly.

How can this be? All circuits (both on rcd and non-rcd) are off. The only think switched on is the main double pole 100AMP switch.

Sh*t and I thought I had this leccy stuff licked

 

[BJS_Spark]

Faulty meter? Sounds old if it has a dial. Get your REC to replace it with a new modern digital one maybe.
What happens with the main switch off also?

 

[dazzlerpalmer]

as I was typing I thought - sh*t should have checked it with switch off.
All the washing machines etc are on now - do it tomorrow.

I am reluctant to get the board out since I have recently changed the board and we had to snip the main 100A FUSE security tab to get it out.
Still I suppose it is not the one to the actual meter.

 

[andy]

as I was typing I thought - sh*t should have checked it with switch off.
All the washing machines etc are on now - do it tomorrow.

I am reluctant to get the board out since I have recently changed the board and we had to snip the main 100A FUSE security tab to get it out.
Still I suppose it is not the one to the actual meter.

usually, if they see a new CU they dont ask about it

 

[plugwash]

if the main switch does cut it off then it means someone has wired something straight to the bussbars in your CU (very naughty but not unheared of)

otherwise its either a faulty meter or someone has tapped off power straight from the meter for some reason

 

[BJS_Spark]

I am reluctant to get the board out since I have recently changed the board and we had to snip the main 100A FUSE security tab to get it out.

Now we are getting more information! When you say you recently changed the board, I am assuming that you carried out all the necessary testing ie. loop impedance, R1+R2, Ze, Insulation, RCD times etc of each circuit as you went? How experienced are you as this is not normally a recommended DIY job and can you be sure you have carried it out correctly? A faulty meter is less likely than a fault introduced fitting a new CU without proper testing.

 

[Lectrician]

Umm - reverse polarity and small earth fault......

 

[mapj1]

Still needs something to be dissipating some power though. Either, one of the MCBs is effectively bypassed, either through reverse polarity as suggested, or even that it is stuck on internally, or there is an additional load you have ommited..
If the meter is spinning noticably, you will be dissipating 10s of watts at least - how does the meter speed compare to say , 1 60 watt light bulb on - it would have to be an earth fault that glows if its that sort of current (i.e. if the 60 watt bulbdoubles the rotation rate you are looking for a 60watt loss.)!
Check where live goes - it should only go to the inputs of MCBs.
(normal meters don't actually measure neutral current, the neutral terminal only loops through to supply voltage reading to the internals.)

 

[kai]

Shouldn't the circuit's red live cables all be connected to the OUTPUTS of the MCB's?

 

[mapj1]

yes v- I meant where the live feed from the meter goes, after the main switch. If the MCBS are off, that is where it should stop.

 

[Lectrician]

Reverse polarity from meter to CU is not un-heard of. A N to E fault in installation is then an L to E fault.

I have seen some earth faults drag 20-30 amps. TT supply with RCD gone squit, rod resistance high enough to restrict the surrent flow to about 20 odd amps on a cooker circuit (kitchen fitters hadn't use earth sleeve in the back box of the CCU, and shorted L to E).

A rod resistance or overal Zs as low as even 12ohm will drag only 20amp! This aint gonna glow

 

[mapj1]

True, but you'll get a heck of a step voltage shock if you stand by the rod with bare feet seperated by a foot or two, and when it rains that 4000watts mostly dissipated in the of earth nearest the rod may well cause it to steam and sizzle a bit
(always a fun party trick -please don't try this at home)

This is also why people who like to bring the rod earth into the RCD enclosure worry me a bit - a TT earth could easily be 20-100 ohms, and apart from a high bill, and tingles of the house metalwork, such a fault could go un-noticed for some time.
We need to know more about the installation, and checking he has live to the MCBs (not neutral) seems like a good first step, then the usual, 'Is your supply TT, TNS or PME(TNC-s)/PNB question.
I was a bit clumsy with my wording on what I wanted him to check.

 

[andy]

(always a fun party trick -please don't try this at home)

ok. will try it at work first thing on monday.

 

[mapj1]

better wear your horseriding boots to work then.
Oh, and don't pull the rod out with the power on unless you are wearing gloves.

If you have flat cloth cap you will find it can double as a high voltage glove or a fire extinguisher if you need, as you will be working at that level of safety.

- don't take my jibing at your comment in anything but fun, but I don't want anyone to get the idea that its even sensible to think about making an earth rod live deliberately, except, perhaps, except as part of a carefully controlled loop test of the earthing system.

As regards the earth itself sizzling, I've only seen it once, with a radio earth and equipment that had faulty power supply, but it was jolly un-nerving I can tell you.

 

[andy]

- don't take my jibing at your comment in anything but fun, but I don't want anyone to get the idea that its even sensible to think about making an earth rod live deliberately

you said dont try it at home, so i said i would try it at work

i didnt have any intention of doin it anyway (we need some better emoticons)

MOD

that do you andrew