RCD Hell
 

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.

In all fairness, he is yet to start troubleshooting this one. Thus has moved
it over to the non RCD protected side of the CU.

The other more pressing issue that needs to be resolved is this;

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.

So far the electrician has advised that we remove the bulbs from the two
offending lights which resolves the issue.

We are expecting a visit this coming Saturday for some extensive
troubleshooting. Therefore, if I can get some ideas in the mean time I might
be able to help him out and also reduce my bill.

I am not an electrician or even pretend to be, so if I have misinterpreted
any of the above please do not be offended.

Answers and suggestions greatly appreciated.

Cheers.

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

Answers and suggestions greatly appreciated.

It's likely that the cretin who originally wired your house decided to
borrow neutrals left right and centre. A borrowed neutral from the RCDed
ring main used on the two way lighting would cause these issues. Anyone
cretinous to devise such a system is quite capable of a whole load of
faults. I would do a complete test of the entire installation, checking ring
continuity, insulation resistance (you've may have a neutral-earth short in
there somewhere) etc.

Christian.

In article ,
diynovice wrote:
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.

In all fairness, he is yet to start troubleshooting this one. Thus has
moved it over to the non RCD protected side of the CU.

I'd just say that any sparks worthy of the name would have tested an
existing ring before connecting it. Just because it 'worked' before on a
fuse protected circuit doesn't mean it will be satisfactory for an RCD
protected one. For example, both neutrals have to go to the correct 'RCD'
busbar - where before there was only one.

--
*Lottery: A tax on people who are bad at math.

Dave Plowman London SW
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