**CU Changes And YOU**

[BP Electrics]

The tails and earthing conductor are the customers/your responsibility, the DNO's won't change them.

I recently completed a 1st fix re-wire where as part of the job I had changed some dusty old 10mm tails for a nice new set of 25mm brown and blues. In between then and returning for the 2nd fix, the DNO had sent an engineer to upgrade the meter. To my surprise, I returned to find my new shiny copper tails had disappeared, only to have been replaced by a pair of red and black 16mm tails supplying from a BS88 100A fuse.

 

[Des 56]

Out of interest
Is that the tails between the meter and cut out,or between the meter and your consumer unit ?

 

[BP Electrics]

They were from a Henley block bridging between the meter into the new CU.

 

[Ohmyword]

I recently completed a 1st fix re-wire where as part of the job I had changed some dusty old 10mm tails for a nice new set of 25mm brown and blues. In between then and returning for the 2nd fix, the DNO had sent an engineer to upgrade the meter. To my surprise, I returned to find my new shiny copper tails had disappeared, only to have been replaced by a pair of red and black 16mm tails supplying from a BS88 100A fuse.

I've never known any DNO engineer to get anywhere near touching a consumer unit (they are not allowed to). I would even consider asking all who has access to this mains equipment if they know who has "nicked" your tails.

On the subject of 16.00mm or 25.00mm tails. The EDF engineers I "come across" here in West Cornwall will not use 25mm tails at all! (Only 16's) Regardless that I have installed 25's into my c/u.

 

[Octopus]

I recently completed a 1st fix re-wire where as part of the job I had changed some dusty old 10mm tails for a nice new set of 25mm brown and blues. In between then and returning for the 2nd fix, the DNO had sent an engineer to upgrade the meter. To my surprise, I returned to find my new shiny copper tails had disappeared, only to have been replaced by a pair of red and black 16mm tails supplying from a BS88 100A fuse.

Are you saying you changed the tails from the DNO fuse to the meter?

 

[Deleted member 26818]

Would using 16mm² tails instead of 25mm² limit the Ze to any apreciable amount?

 

[BP Electrics]

Are you saying you changed the tails from the DNO fuse to the meter?

No Sir, correct me if I'm wrong, but I am of the opinion that everything up to the distributor's meter is within their own jurisdiction? The tails I'm referring to were connected directly into the CU main switch via a Henley block. I was a tad perplexed as to why they changed them, but never chased it up as I got very drunk that night and forgot about it until now.

 

[daiplayer]

perform an IR test between the earth an neutral bar (ensure the main earthing conductor has been disconnected)

this is likely to be done so that when you install RCD's or RCBO's with your new CU then your not likely to get any nasty susrprises with the RCD's tripping all the time due to a previous issue that is irrelelevant to your new CU change

Never knew that !!!! ?? ...how come it dont damage anything then ?

 

[Spudnik]

Because you should test at 250V and in theory the two should not be connected.

 

[RobMax]

Very useful info

 

[Boberto]

Really interesting thread. There is alot of mixed opinion on what you are responsible for with regards CU changes/upgrades.

I would be interested to know peoples opinions on the following scenario...

What if you carry out a CU change and there is a N-E fault that causes the RCD to trip. The fault is on the downstairs ring but due to the way it was wired years ago (not a perfect ring), lots of additions and spurs, possible interconnections, junction box minefield - it is not easy to pinpoint the damaged leg of cable just by splitting the ring etc without taking up floor boards and tracing the cables. You manage to narrow it down to the kitchen which was wired by a kitchen fitter when the kitchen was done 12 months ago. Cables buried. The RCD holds when two kitchen sockets are dead/removed from the ring so it seems the fault is a cable spurring to these from the ring final.
You explain to the customer the fault, remind her that you did say there would be fault finding work as you carried out some pre board change IR tests. Customer isnt happy that 2 sockets dont work in her kitchen, nor is she keen to have a new cable installed to over come the problem. Her kitchen is nice and new and those sockets were working fine before I installed the new board. She doesnt want trunking or walls chased to install a replacement cable. You remind her that you are working to regs and that she agreed to the board change because it complys and makes the whole installation a lot safer.

I have read in this thread of fellow sparks saying that in the long run they have improved the safety of the overall installation by upgrading the CU. The individual wiring of every circuit does not become their responsibility. All the other circuits in this scenario are now RCD protected. The fault remains on the ring but the customer doesnt want her two kitchen sockets left out of service, regs or no regs. In order to keep the customer happy and get paid, how would you resolve the situation?

 

[Deleted member 26818]

The simplest method would be to remove the RCD protection.

 

[Boberto]

Agreed. But is it acceptable to notify the customer that the ring would therefore not be RCD protected, configure the CU, leave the ring unprotected and make a note on the certificate of the fault, reason for outcome and advise the fault needs to be rectified in the near future??

 

[Ohmyword]

Well Boberto, it's probably not what you want to hear, but, 'horse, stable door & bolt' comes to mind!
I have been 'caught' in this situation myself on more than one occasion, therefor I carry out some 'basic prelimary' tests before completely dismantling and removing the existing consumer unit(s).
If one discovers any 'problems' that cannot be easily overcomed, or the customer is not in agreement with the possible extent of the work and/or price involved, then one can walk away from the job. You can make a report and statement that you had provided the householder with all the relevant information (and report) and quote for the remedial works needed, but they had declined.

I'm sorry that this doesn't help you with your current problem, but it could be the way for the future?

 

[Octopus]

Agreed. But is it acceptable to notify the customer that the ring would therefore not be RCD protected, configure the CU, leave the ring unprotected and make a note on the certificate of the fault, reason for outcome and advise the fault needs to be rectified in the near future??

How about asking your customer to see the certificate that the kitchen fitters gave her?

 

[Boberto]

Just to clarify. Its not a situation I am in now. I experienced it in the past. Just wondering what your opinions were and where we stand as competent people if we were to leave the Ring unprotected on the new board?

 

[Boberto]

Murdoch, from memory there was no certificate. Surprisingly.

 

[malcolmsanford]

To be honest most sparks now, after the extensive use of RCDs in domestic installation will not, or should not be faced with this now. I'm sure in the beginning a few sparks were caught out like this but now we are 4 yrs down the line with extensive RCD protection, and most guys will test for this as was posted above.

But for your hypothetical question I think I would split the ring into radials, and give the at least one of those radials RCD protection, and the other one would be marked down on the EIC under "comments on existing installation" and quote the reg your deviating from and leave it on it's own. I would prove though that it did disconnect within the 0.4secs by doing the Zs and that would be me.

 

[BP Electrics]

To be honest most sparks now, after the extensive use of RCDs in domestic installation will not, or should not be faced with this now. I'm sure in the beginning a few sparks were caught out like this but now we are 4 yrs down the line with extensive RCD protection, and most guys will test for this as was posted above.

But for your hypothetical question I think I would split the ring into radials, and give the at least one of those radials RCD protection, and the other one would be marked down on the EIC under "comments on existing installation" and quote the reg your deviating from and leave it on it's own. I would prove though that it did disconnect within the 0.4secs by doing the Zs and that would be me.

+1 to this solution.

Historically, whenever my pre-change IR tests have shown poor results and I advise the client, they usually think I'm making up crap just to bloat the quote, and the job gets lost. I should brush up on my people skills...

 

[Ohmyword]

+1 to this solution.

Historically, whenever my pre-change IR tests have shown poor results and I advise the client, they usually think I'm making up crap just to bloat the quote, and the job gets lost. I should brush up on my people skills...

Tell them to get a 2nd opinion. Better that, even if you lose the job, than creating an 'enemy'.
You know how the saying goes? "Do a good job and 5 people hear about it! Do a bad job and 50 people hear about it!" ;-)