Help ! Lights tripping RCD after consumer unit change.

[sidekick]

Have done a consumer unit change and after finding and resolving all other faults I am now pulling my hair over this one.

Landing Lights when switched on trip the RCD.
Originally placed light circuits on different RCD's and tripped,
put all light circuits on same RCD and still tripped,
have now put every circuit on same RCD and stiil trips.

Have checked all accessible accesories and connections but unable to get into any ceiling or under any floor, can find nothing wrong. How do I find the fault (taken three days to do this job and no idea how to find the fault now) Could I have got a wire wrong on the consumer ghange. The rewireable fuse and now MCB has two lines, two neutrals and two earths.

 

[tony mc]

You did put the lines and neutrals of the lights on the same RCD not just the neutrals (Just a thought)

 

[sidekick]

You did put the lines and neutrals of the lights on the same RCD not just the neutrals (Just a thought)

Yep all lines and neutrals on same rcd. Thats why so baffled. Was hoping borrowed neutral.

 

[tony mc]

With light circuit removed all RCD trip times on rings etc now ok. Also ok when light circuit connected as long as landing light not switched.

When you tested the final rings etc without the lights connected did you put loads on the cct and switch them to make sure the RCD held just incase there is another borrowed neutral it has been known.

I know how you feel especially when your starting to go around in circles.

Keep at it and you will find the fault.

Good luck!!!

 

[sidekick]

When you tested the final rings etc without the lights connected did you put loads on the cct and switch them to make sure the RCD held just incase there is another borrowed neutral it has been known.

I know how you feel especially when your starting to go around in circles.

Keep at it and you will find the fault.

Good luck!!!

Do you mean load on the sockets etc. If so yes as customer been using all as norm for three days with no landing lights.
Cheers

 

[sidekick]

When you tested the final rings etc without the lights connected did you put loads on the cct and switch them to make sure the RCD held just incase there is another borrowed neutral it has been known.

I know how you feel especially when your starting to go around in circles.

Keep at it and you will find the fault.

Good luck!!!

Do you mean a borrowed neutral on one of rings?

 

[telectrix]

no the fault has to be the landing light. it's a remote possibility that some idiot has taken a L or a N from the socket circuit. to the lighting.

 

[sidekick]

no the fault has to be the landing light. it's a remote possibility that some idiot has taken a L or a N from the socket circuit. to the lighting.

I did the IR test accross both neutral bars when one bar only had two rings on it and I got a low reading which made me think that was a possability

 

[tony mc]

no the fault has to be the landing light. it's a remote possibility that some idiot has taken a L or a N from the socket circuit. to the lighting.

I think you have to look at that just in case you never know where idiots operate !!!

 

[sidekick]

Thanks to everybody so far. Going to have to bail out for the night to rest my brain.
Need to sort it though quickly so if any one can put down a check list I can work to it would help a great deal as i don't think I can think logically on this one anymore. ttfn

 

[robsparky1975]

disconnect offending lighting circuit/s,divide the lighting up,from ccu to say landing,if you have to take out a downlight than it has to be done,find main junction box with feeds/switch wires,IR test,then you might be able to define is the fault from the ccu to say that first point or is it further in the circuit,keep dividing the circuit up,unlikely but you may have more than one fault,how old is the wiring?,this is why checking n-e pre change is about the best advice advice ive ever received on here,saves problems later,you will find it,ive been stumped before and found a nail touching between n-e.dont panick,process of elimination.

 

[BlueToBits]

Unless I've missed something, I suggest eliminating some of the possibilities

Link out live - neutral in the landing light and establish the LN pair at the CU to eliminate everything else.

If you would like it step by step, this is how I would do it:

1. Total power off. Switch off and unplug everything. Remove fuses, switch off breakers, split any grouped lines from MCBs.
2. Link N-L in the landing light and ensure the landing light switch is in the ON position
3. Continuity test between each Line the neutral bar in CU.
4. If you get around 1 ohm, identify, mark, disconnect and seperate the neutrals from the CU to find which one. There may be more than one.
5. Be thorough. Check end-end continuity for ring circuits as you go. Suspect anything that does not 'feel' right and note for for later investigation.
6. If there are none, test again for L-E continuity. If still none, re-check the switch is on and start over again.
7. Disconnect link in landing light and confirm continuity test on LN/LE pair is now greater (may not be open circuit if other lamps are connected.)

You should now know where the landing light gets it's power from.

IR everything else and, if it makes sense to, reconnect if OK. You may have more than one neutral. The L&N may be different sizes. If you have no continuity reading, the landing light may be fed L-E, live to water pipe in the loft, or even L- next door's neutral, Keep an open mind and trace back the neutral.
Don't make any assumptions. Go only on what you can prove. Take everything one step at a time.
Tell your customer that you won't have any information for them until 5.00pm, or whenever, to keep them off your back whilst you work.
Good luck.

 

[sidekick]

Unless I've missed something, I suggest eliminating some of the possibilities

Link out live - neutral in the landing light and establish the LN pair at the CU to eliminate everything else.

If you would like it step by step, this is how I would do it:

1. Total power off. Switch off and unplug everything. Remove fuses, switch off breakers, split any grouped lines from MCBs.
2. Link N-L in the landing light and ensure the landing light switch is in the ON position
3. Continuity test between each Line the neutral bar in CU.
4. If you get around 1 ohm, identify, mark, disconnect and seperate the neutrals from the CU to find which one. There may be more than one.
5. Be thorough. Check end-end continuity for ring circuits as you go. Suspect anything that does not 'feel' right and note for for later investigation.
6. If there are none, test again for L-E continuity. If still none, re-check the switch is on and start over again.
7. Disconnect link in landing light and confirm continuity test on LN/LE pair is now greater (may not be open circuit if other lamps are connected.)

You should now know where the landing light gets it's power from.

IR everything else and, if it makes sense to, reconnect if OK. You may have more than one neutral. The L&N may be different sizes. If you have no continuity reading, the landing light may be fed L-E, live to water pipe in the loft, or even L- next door's neutral, Keep an open mind and trace back the neutral.
Don't make any assumptions. Go only on what you can prove. Take everything one step at a time.
Tell your customer that you won't have any information for them until 5.00pm, or whenever, to keep them off your back whilst you work.
Good luck.

Thanks for this very useful check info. This is exactly what I will do.
I am a little worried that all I will come up with is the same L-N-E I already have and not resolve the tripping. What then? Sorry to be a pain, but trying to cover all events as I want to get this done Thursday and not have to go back.

 

[Lioned]

First off it sounds like you had two circuits coming off your old fuse.Guess you may have had an old wylex fuse box or something like that,par for the course as people add things and have nowhere to put them.
Each circuit should have its own fuse/mcb/rcbo,so in a new box you should definitely split them up.
If IR test shows low resistance on one circuit and you have loop round your lights,disconnect lights from first light on circuit and so on until it trips,then at least you'll find the section which is faulty.