New CU but RCD problems!

[GrahamS666]

Hello!

Having just moved to a new house and finding an old wylex push button CU, I decided to change it for a new one with RCD.
Disconnected old CU and connected new one no problem, but the RCD keeps tripping instantly.
Having tried all the different circuits in the house:
Up Lighting
Down lighting
Cooker main
Shower
Ring circuit
all show the same symptom, trip straight away.
Having disconnected every thing from each circuit the RCD will stay on, until any circuit has any load put through it. e.g. Shower switched on, Cooker switched on, anything plugged into a socket and switched on.

So decided RCD must be faulty and changed RCD from a contactum to a squareD. However this still gave the same result.

Perhaps all the cables leading from the CU had become damaged (Checked for resistance and continuity : these are all OK), however I replaced the cable to cooker and still same result.

I have noticed the test switch on both RCD's do not work. Could both RCD's be faulty, both brand new and never been used?
Do the test switches only work when a load is passed through them?
I have an TN-S earthing system would this cause a problem?

Thank you for your help.

 

[DESL]

sounds like you've got a neutral for the RCD connected to the non RCD side instead

or you need to remove the link between the two neutral busbars if there is one

Also check all the neutrals for each circuit are in the correct busbar

 

[jj4091]

sounds like you've got a neutral for the RCD connected to the non RCD side instead

or you need to remove the link between the two neutral busbars if there is one

Also check all the neutrals for each circuit are in the correct busbar

presumeing it is a split load one.

 

[THRIPSTER]

http://www.memonline.com/rcd4.html



This may help you.

 

[JohnD]

I decided not to answer this one last night but here goes:

It is tripping like that because you have made some mistakes.

There area variety of mistakes that you could have made so I can't guess. But I think you have made at least two.

Changing a consumer unit is notifiable under building Regulations in England and Wales (if you are in Scotland I believe you need a building Warrant). One of the reasons for this is that it requires a certain amount of skill and knowledge to do it safely, and the testing is quite involved. I have formed the opinion that you do not have the necessary skill and knowledge.

If you post a digital photo showing the CU and the area around it, so we can see how you've connected it, we may be able to spot the cause.

But I would advise you to ask your friends and neighbours for recommendations of a good local electrician, and check that he is a member of a self-certification scheme. He would doubtless be able to find and correct the error.

I hope that this is a property for your own sole occupation because I am concerned about the risk to others.

 

[GrahamS666]

I had a qualified electrician round for three hours on the 11th dec, and he could not find the problem.
However, upon replies to this forum, i have managed to correct the fault. The neutrals connected to the RCD were the wrong way around. Everything now works fine!
Thank you all for your posts!
I am an electronic engineer not a domestic electrician, cabling is cabling on whichever level!
Thanks again

 

[GrahamS666]

P.S. the consumer unit also had the 100A switch and the RCD already wired in. So i am now writing a complaint to supplier!!!

 

[dingbat]

I had a qualified electrician round for three hours on the 11th dec, and he could not find the problem.

Hmmm... 'qualified' and 'competent' are clearly not the same.

 

[didthathurt]

"Qualified as what, if he couldn't find that fault?" I ask myself...

 

[DESL]

"Qualified as what, if he couldn't find that fault?"

Exactly - first thing you go for on a split load board is misplaced neutral under those fault conditions.

 

[securespark]

It still does not fully explain why the test button on either RCD would not operate the device.

 

[JohnD]

Aaaaaaaaaaaaaaaah, if only we had a picture!

 

[jj4091]

P.S. the consumer unit also had the 100A switch and the RCD already wired in. So i am now writing a complaint to supplier!!!

I do not think you will have a complaint with your supplier as every consumer unit I have ever installed has had sheet or label saying it should be checked & installed by a competant person.(I presume the definition of competant is someone who knows how to do it.)