Consumer unit change

[stilllearning]

Recently changed a consumer unit and had a problem with the upstairs lighting as it kept tripping rcd removed all lamps and checked all fittings , circuit tested out fine when insulation resistance r1+r2 and Zs but still kept tripping rcd so put circuit on non rcd side of consumer unit would I have to note this as deviation on the test sheet ? And add it in to the 'comments on existing installation ' section any ideas please ?

 

[snowhead]

What about finding the fault?

 

[Leesparkykent]

Recently changed a consumer unit and had a problem with the upstairs lighting as it kept tripping rcd removed all lamps and checked all fittings , circuit tested out fine when insulation resistance r1+r2 and Zs but still kept tripping rcd so put circuit on non rcd side of consumer unit would I have to note this as deviation on the test sheet ? And add it in to the 'comments on existing installation ' section any ideas please ?

No you should find and rectify the fault. Upstairs lights and downstairs lights on separate RCDs by any chance?

 

[stilllearning]

It was tripping the rcd when the 2way switching was operated ? Downstairs and upstairs lighting on separate Rcds any ideas on fault posibbility ?

 

[Leesparkykent]

It was tripping the rcd when the 2way switching was operated ? Downstairs and upstairs lighting on separate Rcds any ideas on fault posibbility ?

shared neutral, one of the most common faults you will come across!

 

[stilllearning]

How would you rectify that fault then as I can't see how too ?

 

[telectrix]

try a forum search on borrowed neutral. this is a classic case. landing light fed with L from downstairs cct.and N from upstairs cct.

 

[stilllearning]

Iam unable to rectify the fault as the property has been decorated and customer is unwilling to have fault rectified the circuit will have to stay on a Mcb now what are my options do I note it as a departure from bs7671 ?

 

[telectrix]

what you have to do is put both lighting circuits onto the same RCD. preferably also on the same MCB.

 

[davesparks]

Iam unable to rectify the fault as the property has been decorated and customer is unwilling to have fault rectified the circuit will have to stay on a Mcb now what are my options do I note it as a departure from bs7671 ?

You carry out testing for this before you start the job, not after you have finished it, and agree the fault finding and repair with the customer before starting. If they refuse to have it done then you walk away from the job.

If you leave the lighting circuit without RCD protection then the work you have done does not comply with the regulations, and makes a mockery of the point of installing a new CU. You have identified a potentially dangerous fault which could place the life of anyone working on the installation at risk, you now need to do something about this to make it safe.

If you have not made the customer aware of the possibility of finding such faults and the need to rectify them before starting then you may well have to carry out the repairs at your own cost.

 

[kenai36]

I come across this one quite a lot. It's not ideal but if the customer really doesn't want the circuits segregated and you've already changed the board I'd put them both on one RCD and MCB as telectrix said. Not ideal but better than having one circuit not protected by an RCD.

 

[davesparks]

I come across this one quite a lot. It's not ideal but if the customer really doesn't want the circuits segregated and you've already changed the board I'd put them both on one RCD and MCB as telectrix said. Not ideal but better than having one circuit not protected by an RCD.

Then it is your fault for changing the board without testing the installation properly beforehand, and you should be fixing it at your own expense.

 

[kenai36]

I worded that badly. I always test mine was advising the first guy.

 

[newtothis]

I have this situation in my house.
Whoever installed experienced the same issues with tripping.
He did what Telectrix suggested.

I think I have a non destructive solution, can someone please critique ?
Put both circuits on the RCD side in separate MCBS

At the landing switch, wire it as a one way switch terminate cables.
Same with the hall swicth
Then fit a discreet flush mounted pir to operate the landing light. ?

 

[gnselectricals]

I would definitely put them on the same mcb as you would have risk of shock due to the borrowed neutral.