diynovice wrote:
Help required...

Guys an Gals

I have just had a new Wylex split load CU installed by a local sparkie.
Since then, two problems have occurred that he is struggling to resolve.

The first one being;

As soon as the upstairs Ring is connected to the RCD protected side of the
CU the RCD trips.

If it trips the moment it's connected, with no load, there's likely to
be a neutral-to-earth fault on the ring wiring. If it trips once there's
a load, he's probably got the neutrals connected to the non-RCD N busbar.

Whenever one of two light switches are pressed, one being a two way switch
in the hall the other being a one way switch in the kitchen, the RCD trips.
The lights are NOT on the RCD protected side of the CU. Which I believe is
normal practice. But the downstairs Ring for the sockets are... Therefore,
how would the two relate to each other unless there where to be an inter
connection between the two circuits.

It's possible he's wired the N for these lights to the RCD N, while
taking the L from the non-RCD side; but not if there are other lights on
the same circuit which don't pop the RCD. Other possibilities include a
'borrowed' neutral for these lights (some previous mumpty's used a
'handy' connection to a nearby socket to take the N).

I am not an electrician or even pretend to be,
No - but your "local sparkie" is pretending to be. These are not
massively subtle faults we're concerned with here, and a bit of logical
thought and a meter should be all a real sparkie would need. Relying on
an existing installation to be up to scratch is naive, and your sparkie
should've been testing each final circuit before connecting it to the
new CU. By the sounds of it, he's replaced like-for-like, possibly got
some of his N cores muddled, and (if I understand your "help him out and
also reduce my bill" comment), expecting *you* to pay for his
incompetence. So, when you say,

so if I have misinterpreted any of the above please do not be offended.

- we're not offended, but you should be, at your 'sparky's' antics. But
they're probably entitled to self-certify under
Part-Prescott-Takes-The-Pee, so that's alright then: good ol' 'Two
Fuses' (or was it 'two planks'?) keeping us all safe...

Stefek