RCBO Tripping on Sockets circuit when Down stairs lights are switched on

[ionelec1967]

Hi hope somebody out there can help me on this one ,

Problem


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Recently i installed 3 downstairs rooms with downlights, not had any problems when installed.



When the downstairs lights are switched on the socket RCBO ois tripped at the fusebox , the lights stay on plus the RCBO for the downstairs light stays on dosen't trip and you can turn them on and off at the switches.
Tried disconecting room by room but dosent stop the sockets from tripping there is only one ring circuit for the house.
any ideas ....

 

[Sintra]

So you say you've tried disconnecting room by room but what actual testing have you done.

 

[Jay Sparks]

Something borrowed, something blue, something old, something new????

 

[trev]

When did the problem manifest itself? Before you installed the downlights or after?
What tests did you perform when you did your bit and what were the results?

Have you tried an IR test between the RFC and the lighting circuit?

 

[cotty]

Shared neutral? By any chance??

 

[trev]

Shared neutral? By any chance??

The only possible explanation I'd say

 

[ionelec1967]

Tested for continuity between each room on the live neutral feed to the lights ok
Tested insulation resistance on downstairs lights circuit Live Neutral Earth >299 M ohms
Tested insulation resistance on sockets Live Neutral Earth >299 M ohms
Tested between downstairs lights LNE & Sockets >299 M ohms

Visual checked each cable going to every lamp
Tried every switch trips the sockets RCBo on each one but lights stay on

 

[Darkwood]

Insulation test your lighting cables and socket cables then do it between them ..its possible you have a trapped/crushed cable that is fine off load but manifests itself as soon as load is added.

 

[ionelec1967]

Thought about that one but if shared from the sockets when it trips the RCBO for the sockets the lights still work, the neutral would be took out

 

[ionelec1967]

Good point, just cant figure why the socket RCBO trips not the Lighting RCBO

 

[ionelec1967]

Could be bud but if the Sockets are tripping when lights are switched on the neutral feed would be disabled from the lights but thew lights are working

 

[GLENNSPARK]

whats the earthing arrangements?

TN-C-S?

 

[Darkwood]

Ive been called out twice to the set up I have suggested .. an unrelated circuit tripping a RCD or RCBO on another circuit but only when loaded and both times it was crushed cables that only leaked down when loaded ... sometimes the conductor is crushed and weakened to a point that when energised they are ok but under load they generate heat which increases resistance at the crush point and derates the dielectric strength of the insulation value ... ive seen sockets circuits rcd trip when a upstairs lighting circuit was turned on. Conceptually this is a beast of a fault to realise if you have never experienced it and all you need to do is remove each circuit fully and load the circuits up until you isolate the issue.

 

[ionelec1967]

The problem started about a week ago a month after i intalled the lights the house is empty at the moment need to nail it this week upstairs lights working fine just downstairs tripping socket rcbo never come across a fault like it

 

[SirKit Breaker]

Start with the basics, and work from there. But first off, check the RCBO is operating properly with the outgoing side disconnected, than at least you know that the RCBO is good (or not).

Run through the proper testing sequence, this should highlight all but the nastiest of problems, such as the one mentioned by dark wood. Until you adopt a methodical testing procedure, you will keep going round in circles with this one.

Cheers…………Howard