Shared Neutral?

[andyww]

Hi All

Recently installed a supply to a new consumer unit for an outbiulding. All tests fine. The outbuilding c/u is a 5 way rcd mainswitch Wylex and has it's own TT earth, the armour on the SWA is earthed to the main house c/u. The main house c/u is a dual rcd 17th edition 10 way Hager, and the distribution circuit for the outbuilding is on the same rcd as the shower in the main house. When the shower is turned on the RCD's in the main house and the outbuilding trip. I called the NICEIC helpline and they said it was due to a 'shared neutral' problem and that I needed to place the MCB for the dist circuit on a non rcd protected circuit. Problem is, the Hager only has rcd circuits and is not as adaptable as a Wylex for example.
One idea I had was to put the MCB next to the main switch and move the first RCD along, and take a supply from the mainswitch to the MCB ( currently there are two cables form the mainswitch, one to each rcd )- can anyone see any problem with adding another straight into the mcb? - other question then is, the neutral is still 'shared' so will this alleviate the problem?

 

[44ALLAN]

He disconnected the outbuilding neutral and was holding it when they tried the shower, the RCD didn't trip, but it blew the bejesus out of his pacemaker...hence the silence!

Not funny at all from someone with a pacemaker fitted 3 year ago and still an active spark !!!!!

Every metal part is now a potential mA route through the 2 wires going in to my heart :shocked3:
Thanks for reminding me you..............:63::evil:

 

[GLENNSPARK]

Hi Andy

Had trouble with lighting circuits with shared netuals, but not showers etc! Try swapping the shower over to the other RCD. Perhaps theres a fault on the shower itself, were IR readings ok? not sure what eles to suggest.

Steve

then if shower suspect...IR when cold....then IR again just after being used....compare the differences...