Head scratcher and a half

[ImpededLoop]

the only thing I can think is the kitchen sockets feed boiler / heating system and there is a lot of zone valves etc, There all housed in a airing cupboard upstairs. I'm wondering if there is a possibility that there is an interconnection which due to the stats, and possibility not showeing up as its dead IR test.

That's where I'd be looking now. As it's now summer, have they got an immersion heater for the hot water? If you can't see anything wrong with the valve wiring, you could isolate the boiler for a few days to see if the fault occurs or not.

 

[onions1066]

Is there supplementary bonding from the upstairs lighting to circuits on the other rcd.

Sent from my GT-I9505 using Tapatalk 4

 

[UKMeterman]

Also try IR L board 1 to N board 2 and the same reversed. Try finding out why you only have 20 Mohms N to E

 

[happysteve]

Did you fettle it?

 

[Farmelectrics]

fettle ???????????????

 

[Farmelectrics]

dave what was the outcome

 

[marconi]

Re: Head scratcher and a half - key clues as how to proceed

Right here goes, I have a large domestic house in Yorkshire which I've attended due to tripping RCD. Originally a dual RCD and I'm the third spark to look at this. Previous spark is a guy I work with and I know it's had a lot of time spent on it.

The side that was originally tripping had been swapped to individual RCBOS and the circuit that trips is upstairs lights however will only trip when a large current is pulled (kettle, toaster) on the kitchen sockets and this circuit is on the other side of the split loads board covered by the one RCD.

the tripping does not continue when the CPC is removed from the earth bar (upstairs lights) all class 2 fittings.

test results - IR global for DB (N-CPC ) 10.6 meg CPC - Live 15.7 meg L-N 21meg

IR between two n bars 999meg

IR between lives all 999 meg

RCD tests fine and been replaced along with RCBO

I'm due to go back but the contractor I work for is suggesting we just rewire the circuits we are having problems with as the cost of testing and time it's costing the company money not having the install working as it should. I Hate being beat.

By Marconi When I have pondered this problem the key information which provide clues on how to proceed are when you say the tripping stops when the upstairs lighting CPC is disconnected at the DB and the discrepancy between the N-CPC and L-CPC global IR readings, the former being much less than the latter. These individually and together hint at some N-CPC conductance path.

To investigate I would methodically disconnect all the CPCs at each ceiling rose or fitting, one by one, having first identified the incomer cable and the outgoer cable(s): A study of the loop in and neutral bars enables this to be done. I would then power up and operate the kettle/toaster to discover if the tripping occurred. If not then the branch with the connected CPC is satisfactory but the branch with its disconnected CPC is faulty. Measure the global N-CPC and L-CPC IR readings and note down readings before CPCs disconnected and re-connected in turn.

For this faulty branch disconnect the line in this CPC's cable, power up, and take note of which ceiling roses or luminaires do not illuminate when switched on. This set of lamps are on the faulty branch. Reconnect the line and CPC for this branch and move on to one of the lamps in the set just identified; proceed for this set as in the previous paragraph. Eventually one will home in on the defective circuit (lamp or set of lamps) which can then by investigated, again by disconnecting the CPC(s) to the switch runs or other light fittings and taking the global N-CPC and L-CPC IR readings.


I have used this approach to discover a nail through a switch run in a boarded loft.

It does of course require meticulous power off and proving dead before touching any live conductors.

I suspect some N-CPC fault at a ceiling rose (often behind it) or in a luminaire.

 

[sandford55]

Had a similar problem to this - found to be a neutral touching earth in a socket fitted by the householder - no grommet in the backbox and bare neutral touching backbox - fine until any load plugged in.

 

[happysteve]

fettle ???????????????

Summat my dad would ask me if I was trying to fix, or understand, a problem. "Did yer fettle it, lad?" Not sure if it's a Lancashire or Yorkshire thing. Both, 'appen?

 

[PEG]

View attachment 29322

Summat my dad would ask me if I was trying to fix, or understand, a problem. "Did yer fettle it, lad?" Not sure if it's a Lancashire or Yorkshire thing. Both, 'appen?

A lovely Lancashire word,used,as in a lot of instances,for extended meanings. It was once actually a job title,for those at a foundry or casting works,who cleaned off the 'broke' mold castings,using,on occasion,large electric or pneumatic axial die grinders,suspender on gravity pendants.

Not all our wonderful words are in every edition of the "Oxford",and some of our regional words and phrases,corrupted or not,are treasures that need keeping alive and passing on.

The Gypsies have done it with Romanes,and we should too...