RCD Hell

[mrmark]

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…

 

[ban-all-sheds]

These are the classic symptoms of circuits being wired with the live on the RCD side and the neutral on the non-RCD side, or vice-versa.

Lights sound odd - was it just a straight CU replacement, or was any rewiring done as well?

 

[mrmark]

Thank's for the quick response.

That's an interesting point. I would hope to god that he would know better than that.

As far as the CU installation goes, it was a straight swop with an old 6 way Wylex. Three down lighters where installed about a week ago, but other than that no additional wiring or rewiring.

 

[dw3101]

Borrowed Neutral?

 

[mrmark]

Can you please elaborate a little on that dw?

 

[Adam_151]

1) neutral earth short
2) Lighting neutral borrowed from ring main

would be my guess

 

[Adam_151]

An RCD senses inbalence between live and neutral, if there is an inbalence, something is wrong and it shuts off, in the way that there are two live busbars, one that goes through the rcd, one that doesn't (so you get rcd protected, and none rcd protected sides of the board), you also have two neutral connection blocks, one on rcd, one not, as long as everything that is on the rcd uses the rcd neutral, and everything that isn't dosen't, then eveything works fine, but if you take a live from after the rcd and a neutral from before it, or vice versa, it'll trip out. A borrowed neutral is where a device uses a neutral from a different circuit than its live connection is from, always a bad idea, but rcd tripping out will result if one of the two circuits involved is rcd protected, and the other is not..

 

[ban-all-sheds]

Borrowed Neutral?

From a socket circuit for those lights? Could be.

The traditional borrowed neutral on landing lights shouldn't cause RCD problems, as all the lights would be on the same side..

mrmark - see here: //www.diynot.com/forums/viewtopic.php?p=123427#123427 for a description of borrowed neutrals.

 

[mrmark]

I see. Certainly sounds logical enough.

Did I mention the fact that sometimes you can switch the lights on and off several times before the RCD trips!!! Other times it will do it constantly.

As I said before, it only appears to be affecting the kitchen and Hall way/landing lights.

I'm assuming that taking the bulb out of the fitting breaks the connection!!! Could the problem with the lights be down to something as silly as a dodge bulb. Something that was suggested by a colleague of mine?

Thanks for all the go advice so far. Especially the diagram Ban-All-Sheds...

 

[mrmark]

Well I guess we will just have to wait and see what the weekend brings. I'll be sure to post my findings back here for future reference.

Thanks to all who have input so far.

Any further advice much appreciated...

 

[Adam_151]

Upstairs ring - check the permitted cable routes (straight up, down or sideways from an accesory and corners of rooms) for fixings which could be attached by screws nails which could have gone through a cable

 

[Scoby_Beasley]

I have just had a new Wylex split load CU installed by a local sparkie

A Sparkie ? and he can't sort it ?????? I suggest now is a time to PANICPANICPANIC
(unless you still have the cheque, you don't live in london do you ?)

 

[andy]

A Sparkie ? and he can't sort it ?????? I suggest now is a time to PANICPANICPANIC

just what i was thinkin. first thing to look for if the RCD trips when a circuit is used is the neutral on the wrong side

 

[mrmark]

No, Manchester.

Well, Saturday is exhaustive testing day. So we will see what happens. I'll be sure to report back...

 

[Scoby_Beasley]

let us know how it goes mrmark, always nice to know the outcome (crossed N sounds good to me too0