1st floor lights

[Onz001]

Hi I'm new on here so hello and thanks for having me! I have a client who's r doing is tripping it's a 3 year old house with a split load 17th board the upstairs lighting circuit is split into two feeds one supplying half the rooms the other the 2 new half its on a 10 amp type b when I perform an IR test I get a dead short ( line + line to cpc) they mace a boarded loft with double insulation and full of stuff they also have about 40 gu10 halogen down lights when I just leave the radial feeds connected no fault occurs but as soon as I connect a switch line on either side the rcd trips even if I disconnect 1 at a time any ideas???? Thanks in advance

 

[Darkwood]

Welcome to the forum Onz001 .. you show some qualifications but also say your still a Trainee so if you are still on a course or about to start then please consider applying for access to the Trainee Forum which will better suit your learning curve, either way its good to welcome you.

 

[Richard Burns]

Welcome to the forum.

I am afraid your post is not quite clear, possibly some predictive text coming in.

Let me see if I have this correct:

You have an upstairs lighting circuit with GU10 halogen downlights, protected by a 10A MCB type B.
There are two supply cables from the MCB, one supply to one half of the upstairs and one supply to the other half of the upstairs.

The RCD? is tripping instantly on power up of the circuit?

If the circuit is disconnected from all switched lines then the RCD does not trip, any switched line being connected back in causes the RCD to trip.


If all of the above are correct then I would expect that the neutrals for the lighting are positioned on the wrong neutral bar in the consumer unit; someone has been messing about with the lighting and got it wrong.

 

[Onz001]

Hi sorry bloody predictive yes it is rcd and no the neutrals are on the right bar with the switch lines connected it fails the IR test that's with the twin and earths disconnected from the board so it's not that it just seems strange that both have dead shorts they are efictively two separate circuits until connected at the board??

 

[Richard Burns]

OK so there is a double fault on the circuit, as you say, not likely.
Has anything changed recently as someone could have linked the two circuits. It may be worth testing continuity line to line or neutral to neutral to see if they are linked somewhere upstairs.
You state originally that you tested IR line-line to earth I assume you mean line-neutral (or live-live) to earth.
If the reading is 0.00 MΩ (not a dead short), then you should then test low ohms continuity as the value may give you clue, if the low ohms reading is 0.0 -1 Ω or so then there is an incorrect connection to earth, either by a damaged cable or wiring crossover.
If you have say 1000Ω then a halogen bulb is wired to earth not neutral.