Mysterious RCD tripping & mysterious readings for a boil

[Polly1]

Thanks

 

[Polly1]

Still no joy. The RCD is still tripping when a particular light is switched and occasionally when others are switched.

The occupiers have said today that they felt prior to the RCD being fitted that there was an excessive number of bulbs blowing mainly in the fitting that is the one causing the RCD tripping. But I know for a fact they've had the same bulb in (because it's yellow) for two months now since the job was first quoted.

Assuming they're correct and bulbs have tended to blow more often on that fitting, any tips on what might cause that and whether you feel that it's related to the RCD tripping?

I've checked for any continuity between the light ciruit and any of the cables on the RCD circuits and there is none.

 

[RF Lighting]

I'm running out of ideas. things I can think of at the moment are clutching at straws ideas. Is it possible that a lighting and socket cable have been crushed or nailed together? Have you tried insulation testing between the socket and lighting circuits? Try switching all the lights on with lamps in all of them (power off) then test for continuity between lighting live and sockets neutral to make certain there isn't a 'borrowed neutral' anywhere (if there is remove the lamps one by one to find the offending fitting) Can you disconnect part of the lighting circuitand leave it off for a day or so then slowly reconnect a bit at a time until the problem re-appears? (this is a mega pain and requires lots of visits back to site)

 

[Polly1]

Well I'm kind of coming to the end of the road on this one & tomorrow I'm shifting the sockets off the RCD & installing RCD sockets on the ground floor outlets close to doors (2 of them).

It's a bit of a cop out, but the occupiers are starting to blame me, when really it's their place, their problem.

It'll be disapointing walking away without knowing what the cause was, but it's a 5 bedroom needle in a haystack thing.

Thanks for the tips anyway.

 

[Polly1]

Well I'm kind of coming to the end of the road on this one & tomorrow I'm shifting the sockets off the RCD & installing RCD sockets on the ground floor outlets close to doors (2 of them).

It's a bit of a cop out, but the occupiers are starting to blame me, when really it's their place, their problem.

It'll be disapointing walking away without knowing what the cause was, but it's a 5 bedroom needle in a haystack thing.

Thanks for the tips anyway.

 

[securespark]

Well I'm kind of coming to the end of the road on this one & tomorrow I'm shifting the sockets off the RCD & installing RCD sockets on the ground floor outlets close to doors (2 of them).

That won't comply with 7671...

 

[Polly1]

Well I'm kind of coming to the end of the road on this one & tomorrow I'm shifting the sockets off the RCD & installing RCD sockets on the ground floor outlets close to doors (2 of them).

That won't comply with 7671...

Page 20 of the On Site Guide. RCD's required - (iii) on all socket-outlets that may reasonably be expected to supply portable equipment used outdoors.

The RCD sockets I've fitted are on the only outlets that would supply outdoor equipment.

No other point relevant to this property says that RCD protection is required.

 

[Polly1]

I think I found the problem today anyway. But I've left the ring main sockets off the CU RCD anyway as the occupiers no longer want to be guinea pigs. So I may never know if it was the real problem.

I took a voltage reading on the light fitting they complained was excessively blowing bulbs. I got the usual 240v reading when the light was on & a 12v reading when the light was off. It's a 2 gang light & when I alternated the switch positions, I got a 5v off reading.

I guess when off, the bulb was still receiving 12v which meant that it was constantly on even though not illuminated at all times.

I initially suspected that the light may have somehow been connected to a 12v transformer that is used in one of the bathrooms, but I took up the floorboards above the light & found 1 foot from the light fitting that the light cable was taped against 2 runs of the ring main.

I removed the tape & thought nothing of it as it wasn't taped hard & it was new wiring brown & blue. But later I checked the light voltage again & it was zero when off now including when I alternated the swicth positions.

What do you reckon? Could the magnetic field from 2 ring main leads cause a 12v charge on the light lead?

But I was happy that I at least had an explaination of why the bulbs have been blowing often. But I also reckon now that I the problem with that charge in the wire & taped against the ring main, I guess occasionally there would be feedback to the RCD unit & the RCD tripping was to be expected?

 

[jondiy]

Did the consumer unit have an rcd neutral bar and a non-rcd neutral bar and were they connected properly??

Have heard stories of them being mixed up thus causing non rcd circuits to trip the rcd due to imbalances on the neutral.

Easiest way would have been to check above , then replace ceiling rose , replace bulb , replace switch for a BRANDED one , then if still tripping, replace the switch cable, and at a last resort, find a new feed to the light, from a different rose - or even straight from the consumer , then test - test - test.

If that was the only part of the install that was causing the rcd to trip - then replacing the above would surely have cured the problem.

 

[securespark]

Page 20 of the On Site Guide. RCD's required - (iii) on all socket-outlets that may reasonably be expected to supply portable equipment used outdoors.

Which is interpreted by most sparks as being all those on the ground floor.

Even those which form part of a CCU...

The RCD sockets I've fitted are on the only outlets that would supply outdoor equipment.

How can you be so sure?

In the days before SL boards and RCBO's, a way to satisfy the then regs was to fit an RCD socket adjacent to the front and back doors. But that practice no longer complies.

No other point relevant to this property says that RCD protection is required.

The RCD sockets I've fitted are on the only outlets that would supply outdoor equipment.

This one is sufficient...

 

[Adam_151]

I took a voltage reading on the light fitting they complained was excessively blowing bulbs. I got the usual 240v reading when the light was on & a 12v reading when the light was off. It's a 2 gang light & when I alternated the switch positions, I got a 5v off reading.

Usually caused by capacitive coupling in the two way switch cable

I guess when off, the bulb was still receiving 12v which meant that it was constantly on even though not illuminated at all times.

You should find that the voltage drops off sharpish when the first hint of a loads thats not of neglidgeable impedance (like your digital volt meter) is applied

I initially suspected that the light may have somehow been connected to a 12v transformer that is used in one of the bathrooms

Pretty unlikely

but I took up the floorboards above the light & found 1 foot from the light fitting that the light cable was taped against 2 runs of the ring main.

I removed the tape & thought nothing of it as it wasn't taped hard & it was new wiring brown & blue. But later I checked the light voltage again & it was zero when off now including when I alternated the swicth positions.

What do you reckon? Could the magnetic field from 2 ring main leads cause a 12v charge on the light lead?

Could be capactivly cables to that one

But I was happy that I at least had an explaination of why the bulbs have been blowing often.

Not sure about that one, still looking for a bad connection IMHO

But I also reckon now that I the problem with that charge in the wire & taped against the ring main, I guess occasionally there would be feedback to the RCD unit & the RCD tripping was to be expected?

It certainly provides a patform on which a viable explanation involving capacative coulping can be involved in, a fleeting connection such as a bad connection or a lamp failing would cause this to leak more than normal (because of the higher frequencies)