Two way trip

[Nicktric]

Hi, recently done a Cu change and tests were all fine, put up lights on one RCD down on the other rcd switched on fine. Switched on the two way in the hall and tripped. I thought I had mixed the neutrals as it's wired in singles but checked and all fine. If I move both circuits to one rcd and same neutral bar as previous board then no probs.
I am sure this must be quite common fault from 16th board to 17th but haven't come across it and can't see quickly where the fault lies but presume it is a neutral missing to one of the lamps if the neutrals have split at the board? Any ideas?
Cheers

 

[Robinson]

Shared neutral somewhere within circuits?

 

[Ponty Massive]

Shared neutral being used on the landing light. (Actually it's a shared live). Either need to put both circuits on the same on the MCB or run a new switch wire in from downstairs 2-way to upstairs light.

 

[telectrix]

definitelyas ^^^^. landing light has L from downstairs and N from upstairs'

 

[Robinson]

Shared neutral somewhere within circuits?

Yep Of coarse...that makes a whole lot more sense

 

[Superspark23]

Shared neutral being used on the landing light. (Actually it's a shared live). Either need to put both circuits on the same on the MCB or run a new switch wire in from downstairs 2-way to upstairs light.

You need to have 2 seperated circuits for downstairs an upstairs under the 17th

 

[Ponty Massive]

You need to have 2 seperated circuits for downstairs an upstairs under the 17th

He's changing the CU, not rewiring.

 

[brightspark66]

pontys right.I had a mate of mine whose a builder with this prob.The live for landing light was taken from the downstairs circuit but neutral and earth from upstairs circuit.Talked him through it on the phone,he called me an hour later to say prob sorted.

 

[Nicktric]

Thanks, at the moment I have put both MCb's on one rcd and neutral bar and all is as it should be though not to BS7671. As Ponty says, it is only a CU change not a rewire and I could note in the existing comments box but it feels like half a job. Also when ground lights MCB is off landing light flickers. Haven't come across this before and I'm sure many of you have and fixed quickly. I need a neat quick solution as it's an HMO with limited access and paper decor everywhere. Can I just run my plan past you? Check neutrals are on correct circuits which I am sure they are as they are in the ceiling roses cpc's can be on either circuit in this case. Separate downstairs two way supply from other upstairs landing light two way switch, run in new live from loft to landing switch? Job done? Thanks for your help.

 

[mark80]

It wont work as you need a 3 core between the 2 switches for the strappers. At the moment only a twin and earth will be used for that. If she doesnt want to lift floorboards etc then i would put both circuits in the same MCB and note on cert reasons.

 

[mickys86]

But y is the light flickering....

 

[truckster]

Possibly back feeding through a lamp and up the neutral?

 

[Nicktric]

It wont work as you need a 3 core between the 2 switches for the strappers. At the moment only a twin and earth will be used for that. If she doesnt want to lift floorboards etc then i would put both circuits in the same MCB and note on cert reasons.

Thanks Mark needs further investigation then. It's all run in singles. I haven't looked yet but was hoping the L1L2Com between switches were right, I know there is only a switch wire and neutral in the landing ceiling rose so suspecting/hoping it's live is linked from the hallway 3 gang in which case break the link and run in a new live from the landing ceiling rose to light switch upstairs. Like you say probably not as straightforward.

 

[Nicktric]

If it is not feasible to run new strappers due to disruption and cost (HMO access), and if I was thinking of using this as an assessment... Which would be the best option please, your advice is greatly appreciated.

1) Separate the two two way switches and re wire as single switches to allow mcb on each rcd and just lose two way options up and down.

2) As there are two two ways (same gangs), Rob a switch wire from one so that downstairs two way works and rewire landing light to a single (easy and my preferred option, the tenants couldn't care less and client would be happy with this as no disruption and could be noted on EIC or with a cover note?)

3) put both MCB's on one rcd and note in existing installation comments EIC?

Thanks guys.

 

[Richard]

It is possible to run a single neutral from the board to the upstairs light? just park the 'upstairs neutrals' and then the new single netrual is in with the downstairs lights.