New ring main - RCD & MCB keeps tripping - Help!!!!!!!!!

[jazzbhatia]

Hi,

I have just rewired my newly built extension and my electrician confirmed the wires were run correctly safe zones, depths etc. the plasterers are due to come in over the weekend and render and multi finish the room.

Due to this I called my electrician to come and test the circuits however he is on holiday for another week. Due to this I connected all the lights – working fine and the sockets - ring main seems to have a fault.

It is connected to a 32a MCB and every time I switch it on the MCB and RCD trips. I have done the following

Tested for a short between each socket (except for the legs which are buried in conduit in the screed) - MCB and RCD trips
Tested with all sockets disconnected - MCB and RCD trips
Tested with both legs disconnected on the extension side (leaving them connected at the CSU) - MCB and RCD trips
Removed the legs from the CSU - MCB and RCD do not trip
Tested the new circuit in a known working MCB - MCB and RCD trips

I have an external socket but don’t think this makes any difference as the circuit trips even when the legs are disconnected from the extension side.

In testing the wires between the sockets I set my multi meter to ohms and confirmed there is no link between the L and N.

Any suggestion would be appriciated

 

[plugwash]

Have you tested between live and earth and between neutral and earth?

 

[Chri5]

If the board has 2 x rcd rails, I'd look at the neutrals and make sure they are terminated on the correct neutral rail for the rcd.

If the neutrals are on rcd 1, then they MUST terminate on the neutral bar for that rcd.

 

[jazzbhatia]

I have not tested between live and earth and between neutral and earth - thought about doing that whilst driving into work this morning - I will test tonight.

Both legs run through my old kitchen (current utility room) and into the extension. Sorry if this sounds silly but if I left both legs disconnected on the extension side and the circuit still trips would a test between the live and earth and between neutral and earth prove anything or would you expect the circuit to trip when the legs are left open ooops disconnected?

The consumer unit that I have is a pre 17th edition. wylex and it has what seems like one neutral bar however I did ensure that the wire terminated in the corresponding connector.

Is there anything else that I should be checking.

 

[securespark]

YES!

Insulation Resistance!

Check there is nothing plugged or hard-wired into the circuit. Then disconnect all conductors for that circuit from the board. Then test IR between all conductors.

If it is low, then you need to strip the circuit down to its component legs and IR test each piece of cable until you find the fault. Most likely a nail or screw through a cable.

You don't mention the results of your tests...

Maybe the cables in the conduit buried in the screed are down? Have they been replaced?

If so, how did you do this?

 

[ban-all-sheds]

I have just rewired my newly built extension

When you applied for Building Regulations approval, what did you say would be the way that the electrical work would be done to comply with Part P?

and my electrician confirmed the wires were run correctly safe zones, depths etc.

Err... theres a huge amount more to get right than just where the cables are.

I connected all the lights – working fine and the sockets - ring main seems to have a fault.

Could you post the results of all the tests which are needed before energising is done?

In testing the wires between the sockets I set my multi meter to ohms and confirmed there is no link between the L and N.

Very funny.

What results do you get from the proper installation testers you must have access to if you're to do wiring work like this?

Any suggestion would be appriciated

I suggest you get someone in who actually knows what they are doing.

 

[jazzbhatia]

I have just rewired my newly built extension

When you applied for Building Regulations approval, what did you say would be the way that the electrical work would be done to comply with Part P?

The works have been checked by a qualified electrician but just not to hand right now. What is the difference between a “qualified electrician” leaving worker onsite to do the work whilst he has his back turned as I am sure is a normal practice because in theory they are working under the supervision of a competent person.

and my electrician confirmed the wires were run correctly safe zones, depths etc.

Err... theres a huge amount more to get right than just where the cables are.

I am sure there is a lot more to it but it has been checked. You don’t have to be qualified to chase the wall or run wires.

Commissioning the circuit yes, but I have a problem with getting him onsite as he is somewhere on a beach I guess.

I connected all the lights – working fine and the sockets - ring main seems to have a fault.

Could you post the results of all the tests which are needed before energising is done?

not to hand as im at work.

In testing the wires between the sockets I set my multi meter to ohms and confirmed there is no link between the L and N.

Very funny.

What results do you get from the proper installation testers you must have access to if you're to do wiring work like this?

i am a network engineer and work part time as a gas engineer, please explain what is a subnet mask or how to use a FGA and what the readings mean.

Without forums like this you would not know, its called sharing knowledge which we were not born with except you.

By the way you will find the answer on table 10.1 of the onsite guide (page 83)

Any suggestion would be appriciated

I suggest you get someone in who actually knows what they are doing.

If it’s someone like you id rather not, Thank you Mr know it all.

Read the other posts, unlike you others are trying to help rather than be a silly Billy

Thanks anyway

 

[JohnD]

I called my electrician to come and test the circuits however he is on holiday for another week.

I know the one you mean, his customers are always on here asking for help. I don't know how he makes a living, with all those holidays and his persistent sickness.

 

[PrenticeBoyofDerry]

jazzbhatia;
Could you take a photo of the consumer unit you have, ideally with the cover off?
When you have one particular circuit taking out the RCD the two most common problems on an unloaded circuit are that the neutral has been terminated on a split side or you have insulation resistance failure.
The first problem can be resolved by a visual inspection and conformation or correction of the termination.
The second (IR) you will need the correct test equipment, a knowledge on how to perform the tests correctly and safely, then how to fault find if you have a none compliance.
As the circuits are newly installed the expected value should be really high and an infinity reading of your insulation resistance tester should be measured.
Some IR testers will measure >200MΩ, >299MΩ or >1000MΩ depending on which model you use. On new cabling the highest possible reading, given model type should by expected.
If your board only has one RCD and one neutral bar, I expect an IR fault to be your problem, these faults can be caused by a number of issues:
Cable damaged along route and inside accessories, moisture at accessories/joint are the normal culprits.
But as BAS has mentioned/pointed out, in his polite way, test procedures on the circuits are made in a particular order. Starting with dead tests, then moving on to live test. The last test would be a functional test. If your system has not under gone or failed any test prior to the functional test, it should have never been energised! As much as you may not want to hear that, it is a simple truth!

 

[ebee]

"If your system has not under gone or failed any test prior to the functional test, it should have never been energised! As much as you may not want to hear that, it is a simple truth!"

Correct.

This is, in essence, what our Mr Sheds has been trying to tell you.

You have committed that old chestnut formerly known as "The Bang Bang 240 test"

 

[davelx]

i am a network engineer and work part time as a gas engineer, please explain what is a subnet mask

CIDR or Classful?

or how to use a FGA and what the readings mean.

No idea - but the point is that you should not even TRY until you know exactly how to do it and all that is required.

 

[ban-all-sheds]

...work part time as a gas engineer, .

OK - put that hat on and imagine reading this on a DIY forum.

I've installed the pipes and flue for my new gas fire, but I can't get the engineer who was going to fit it to come as he's on holiday, so I went ahead and did it myself.

The flames are yellow, not blue, I can smell gas and if I sit by the fire for more than a short time I start to get a headache.

Any suggestion would be appreciated.