Distribution Circuit issues!

[Charlie_169]

Hi guys, new to the forum and hoping I can gain some useful information to help me out!

I have just put in a distribution circuit into a garage, with the following specs:

6.0mm cable, 3m in length from consumer unit to new installation.

B32 circuit breaker in the consumer unit to the distribution circuits.

30mA RCB in the garage unit

B6 circuit breaker in garage unit

B32 circuit breaker in garage unit

the existing consumer unit is a 10 way split board, containing 2 30mA RCDs. I have moved the first RCB from the main switch to allow space for a single B32 circuit breaker. Reason for this is to ensure that the other two breakers aren't affected by the garage circuit.

The issue here in arises! There is power to both the consumer unit and the new distribution circuit. you fire live the board and the distribution circuit. Go to turn the garage light on and it blows the RCB in the house consumer unit. the garage lights and RCB's are fine.

The continuity tests all came back OK and the insulation resistance tests all came back at <999M ohms. I'm thinking its something to do with where the power is coming from in the board. at present it is coming off the bottom of the main switch, and the neutral into the first neutral bar (attached the RCB1 in the house consumer unit) and the earth is attached to the main earth electrode.

Any help is much appreciated! Cheers guys!

Charlie

 

[NozSpark]

Now, I'm assuming that the installation type and wiring methods allow for the ommison of RCD protection to the sub main?

I'm guessing that you have moved the first RCD over to allow for the sub main?

I'm also guessing that you have connected the MCB line to the outgoing of the main switch?

If the above are correct, where have you connected the neutral to?

Welcome to the forum by the way

 

[Charlie_169]

Firstly, thanks very much! Been meaning to do it for a while!

the installation types and wiring methods all allow for this adjustment. You are right on both counts to do with the Line connections and the Moving of the RCD repositioning. I have connected the Neutral to the first neutral bar on the consumer unit. This is the one where the neutral from the first RCD is connected.

 

[daveygh]

Firstly, thanks very much! Been meaning to do it for a while!the installation types and wiring methods all allow for this adjustment. You are right on both counts to do with the Line connections and the Moving of the RCD repositioning. I have connected the Neutral to the first neutral bar on the consumer unit. This is the one where the neutral from the first RCD is connected.

there lies the problem

 

[NozSpark]

Firstly, thanks very much! Been meaning to do it for a while!the installation types and wiring methods all allow for this adjustment. You are right on both counts to do with the Line connections and the Moving of the RCD repositioning. I have connected the Neutral to the first neutral bar on the consumer unit. This is the one where the neutral from the first RCD is connected.

I'm now guessing that the CU only has 2 neutral bars for outgoing circuits?

 

[betty swollocks]

I have connected the Neutral to the first neutral bar on the consumer unit. This is the one where the neutral from the first RCD is connected.

You should have connected the neutral to the neutral bar FEEDING the first

Rcd

If there isn't one ....... How about slipping it into the outgoing neutral of the main switch

 

[Charlie_169]

yes it only has two neutral bars for outgoing circuits, and its connected to the first neutral bar that serves the first 5 circuit breakers. I will connect the Neutral cable to the outgoing neutral from the main switch tomorrow and give it a whirl.

Many thanks guys! will keep you updated as we go along!

Cheers All!

 

[steptoe]

you do realise that by modifying the design of the CU it no longer complies with BS7671 and therefore the householders insurance will be void,?

and the work you have done will require notifying, and the non compliance noted on the cert along with the alternative measures taken to ensure type testing eqivalency has been met.

the other thing is this,

you have an earth electrode, which indicates a TT system, but you have a circuit that you have decided to remove the RCD protection from?

why? and how safe is that?

 

[betty swollocks]

All good points steps

however because of the initial problem I don't think the op has enough understanding and experience to

1) complete and test the new work correctly

2) understand the very relevent points you have made

Sounds a little DIY to me

 

[Bacon]

I allways carry out some basic tests prior to a CU change and explain to the customer as to why i'm doing them as,

Because it works now but may not show a fault,

But with a new CU and MCB's it may identify a fault thats not apparent until changed,

Like the borrowed neut on lights.

Plus it doesn't make you look like a numpty when some think doesn't work after you've done the change.

But because you have'nt you now look like a NUMPTY trying to work out whats wrong.

 

[Charlie_169]

I totally understand your points here, and equally respect your opinions however what I have given you is a mere over view of the work that has been carried out on the property.

So just to clear up any potential confusion, and misunderstanding I'll explain.

ALL CARRIED OUT BEFORE THE WORK WAS STARTED:

1. I ascertained the supply characteristics, in this case a TN-C-S system. Not a TT as previously stated by another member.

2. I then checked the earth suitability of the property to ensure that this was suitable for the additions planned by running a prospective fault current test. while doing this also checked the supplementary bonding was correct in the vicinity that I was working as it was next to the gas meter

BUILDING CONTROL NOTIFIED AND WORK COMMENCES:

3. The board has been modified and all non compliance has been noted on the certificates, as has the fact that as I have adjusted the CU I am now fully liable for all of the circuits in the property.

4. the dead tests were carried out on the new circuits, and have all passed prior to the work being commissioned.

5.Building control have been notified of a new circuit being installed at the address and they have arranged for the work to be checked at the end of the job as at present I am in midway through my Napit registration.

6. there is nothing wrong with asking for a bit of assistance when you need it, I have no issues in doing this so to ensure that the job gets done as quick as possible with the minimum disruption to the customers.

I'd just like to take this time while you're reading this to say thanks to the guys who helped out genuinely with their advice that helped resolve the issue and to also say thanks to those who didn't.

Once again,

Thanks guys

 

[steptoe]

#1 main earth electrode

What is that then if its not a TT system?

 

[Charlie_169]

Its a main earthing terminal, my error in terminology, Sorry.

 

[M107]

I'd have split the meter tails rather than bodge the cu.

Also what about discrimination

B32 circuit breaker in the consumer unit to the distribution circuits.30mA RCB in the garage unit

B32 circuit breaker in garage unit

Its not supplimentary it is main equipotential bonding.......did you check the water & other services also?

supplementary bonding was correct in the vicinity that I was working as it was next to the gas meter

The board has been modified and all non compliance has been noted on the certificates, as has the fact that as I have adjusted the CU I am now fully liable for all of the circuits in the property.

If you've gone to all that trouble why did you not just change the board for a HIGH INTEGRITY board giving you some non-rcd protected ways & the 3rd neutral terminal..........or as I've said rather than bodging a standard dual rcd board, why did you not split the tails & use a stand alone switch fuse or the like.

Building control have been notified of a new circuit being installed at the address and they have arranged for the work to be checked at the end of the job

Do they not check the first fix now? (this is a genuine question not a dig).

I am in midway through my Napit registration.

I wouldnt use this job for an assessment, but good luck with the registration process.

 

[betty swollocks]

I'd just like to take this time while you're reading this to say thanks to the guys who helped out genuinely with their advice that helped resolve the issue and to also say thanks to those who didn't.

Once again,

Thanks guys

Hey Charlie don't take offence or let this put you off using the forum, people have varied opinions and to me that's what makes the forum what it everyone here has been stumped at some point and what puzzles us is often a simple solution for others, I've just repaired a heating system today that a friend of mine has been stumped on all yesterday a quick look and simple solution, two heads and all that

P.s for a Napit assessment I wouldnt be worried he will only be interested in 3 things

1) your money

2) your money

And

3) oops I've over stretched myself there!

 

[Charlie_169]

No worries guys, all is working now, and tested. Thanks for the help, and advice. I will look into the high integrity boards in future, but the customer didn't want change the board as she'd only had it changed a 2years ago when the loft conversion was done. Just awaiting the inspection from building control now. In response to the inspection question, normally they want to see the work at the first fix but I've been onsite and dealt with the local building inspector who comes to inspect the work and he was happy with the evidence he'd seen previously that the first inspection wasn't necessary.

Charlie

---------- Post Auto-Merged at 18:01 ---------- Previous post was made at 17:58 ----------

Hey Charlie don't take offence or let this put you off using the forum, people have varied opinions and to me that's what makes the forum what it everyone here has been stumped at some point and what puzzles us is often a simple solution for others, I've just repaired a heating system today that a friend of mine has been stumped on all yesterday a quick look and simple solution, two heads and all that P.s for a Napit assessment I wouldnt be worried he will only be interested in 3 things

1) your money

2) your money

And

3) oops I've over stretched myself there!

Not a worry mate, many thanks for the advice and pointers. Hopefully there will be more than just two heads on here at a time to help us all out

Just out of curiosity which scheme are you with?

 

[betty swollocks]

No worries guys, all is working now, and tested. Thanks for the help, and advice. I will look into the high integrity boards in future, but the customer didn't want change the board as she'd only had it changed a 2years ago when the loft conversion was done. Just awaiting the inspection from building control now. In response to the inspection question, normally they want to see the work at the first fix but I've been onsite and dealt with the local building inspector who comes to inspect the work and he was happy with the evidence he'd seen previously that the first inspection wasn't necessary. Charlie

---------- Post Auto-Merged at 18:01 ---------- Previous post was made at 17:58 ----------

Hey Charlie don't take offence or let this put you off using the forum, people have varied opinions and to me that's what makes the forum what it everyone here has been stumped at some point and what puzzles us is often a simple solution for others, I've just repaired a heating system today that a friend of mine has been stumped on all yesterday a quick look and simple solution, two heads and all that P.s for a Napit assessment I wouldnt be worried he will only be interested in 3 things

1) your money

2) your money

And

3) oops I've over stretched myself there!

Not a worry mate, many thanks for the advice and pointers. Hopefully there will be more than just two heads on here at a time to help us all out

Just out of curiosity which scheme are you with?

Napit

 

[M107]

Out of interest how did you get it working? again not a dig or poking fun just interested to know in case I have the same issues

Edited because i cant spoll

 

[SLIPSHOD & SLAPDASH]

Do Napit inspectors favour fig rolls ?