CU change indoors for assessment

[m4tty]

Hi,

Im going to change my CU indoors for my assessment with Elecsa/NIC and want to ask the following questions.

View attachment 528

If the picture has worked above the earthing conductor from TNS sheath to MET is only about 3" long but uncovered/uninsulated wires. Is this normal and OK?

Also the main protective bonding conductors are 6mm with main earthing conductor being 6mm too. OSG recommends 16mm MEC and 10mm MPBCs so will these have to be upgraded. (Concrete floors/Walls and gas meter and water meter on wall outside maisonette so will be a nightmare to get there)

Also all the wiring is in conduit which is being used as the earth and im trying to find where the conduit is bonded to MET and have found some BS951 clamps but lookn like 4mm cable has been used.

It would have been installed approx 1974 with CU being changed approx 1994 I recon.

View attachment 529

Thats the CU if that helps any?

Thanks for any help you give me

Cheers

 

[Danny]

The connection between the MET and sheath would normally be a metal strap or similar .. length is about right ..

Take a Ze and if the result is above 0.8 then contact the DNO to upgrade .. it's their bit of kit after all ..

If you're replacing the CU then 16mm MEC it is ... the main bonding is 10mm regardless of how tricky it is to get to ... i saw one recently that took a right old jolly route around the outside of the house before it got to the outside meter box, but it's got to get to the water/gas inlet somehow ...

Each circuit is going to have to be tested to see if the Zs can be met in any case ... you'll have to take each circuit in turn to see if the conduit is helping the situation .. do the circuits have CPCs?

 

[m4tty]

Thanks for replying Danny.

No circuits have cpc's, it is earthed through the conduit with bushes going into backboxes etc.

Cheers

 

[Danny]

If there are no CPCs then you might have a job on your hands ..

What are the cables like ? If they're old rubber cables you're knackered as you'll need to replace ..

 

[m4tty]

It was built in 1974 (No VIR)so all cables are Red/Black stranded singles 3/029 and 7/029 i think. The whole block is the same and my pal who lives upstairs had his CU changed when he moved in without the place being rewired (but he has a nice 10mm earth cable in trunking run around the ceiling :_| )

 

[batty]

Lighting should not need RCD protecting apart from bathroom although it looks like you only have one lighting circuit which is not ideal. There should be no problem with main earth. I would sleeve it with green/yellow sleeving into earth block on meter board then take 16mm to c/u .

 

[m4tty]

I think theres only 1 lighting circuit cos its a maisonette which is all on one floor and tbh most rooms have got 11W low energy bulbs which are poo but cheap to run when the kids and mrs leave them on headbang

 

[Lurch]

I'm sure I read on here somewhere from a respectable source that if you can confirm that 6mm is fine for the main bond then you can leave it in. Can;t remember exaxctly what the criteria was or where it was, or who said it. I just remember being quite happy as my 6mm bonding (that was staying anyway ) looked like ti might be fine to leave anyway, otherwise I'd have forgotten probably.

 

[tom1]

I'm sure I read on here somewhere from a respectable source that if you can confirm that 6mm is fine for the main bond then you can leave it in. Can;t remember exaxctly what the criteria was or where it was, or who said it. I just remember being quite happy as my 6mm bonding (that was staying anyway ) looked like ti might be fine to leave anyway, otherwise I'd have forgotten probably.

http://www.talk.electricianforum.co.uk/showthread.php?t=5693&highlight=6mm+bonding

 

[ianmacd]

http://www.talk.electricianforum.co.uk/showthread.php?t=5693&highlight=6mm+bonding

And as I said on that thread its not to 7671 so I would not be supprised for you to either have non-conformaties or fail the assessment.

 

[Lurch]

And as I said on that thread its not to 7671 so I would not be supprised for you to either have non-conformaties or fail the assessment.

Well as the thread says it's come from the NIC, but is more for minor works rather than a CU change so not applicable in this case. I know it's not to BS7671 but I can;t see my 6mm bonding conductors being a problem.

 

[ianmacd]

Well as the thread says it's come from the NIC, but is more for minor works rather than a CU change so not applicable in this case. I know it's not to BS7671 but I can;t see my 6mm bonding conductors being a problem.

Are you goign to pay for M4tty's retest if he fails becasue of your advice?

 

[Lurch]

Are you goign to pay for M4tty's retest if he fails becasue of your advice?

I think you have misread something. I never told M4tty to not upgrade the bonding. I said someone mentioned something about it being acceptable to leave it in under some circumstances, which was linked above by tom1, which confirmed that I was half right so said it wasn;t applicable in this case.

I don;t see anywhere where I said to leave it in and you'll be fine, nor would I pay for or be held responsible for anything someone else does following advice given on this forum, or any forum.

 

[wozz]

the information originates from a ESC guide, which some people say is the NIC. As far as im concerned its about as close to the horses mouth as you are likely to get.

 

[ianmacd]

the information originates from a ESC guide, which some people say is the NIC. As far as im concerned its about as close to the horses mouth as you are likely to get.

Actually the horses mouth in this case says different as its the IET. NIC do not write the regs.

 

[wozz]

i said some people consider ESC to be the NIC i personally dont. The guides are put together by all the scheme providers all having input.

 

[ianmacd]

But ESC are not IET.

 

[mr_writer]

hi, i too am going to change my cu for my assessment, i have a 10mm earth to the gas which i can locate but my water incoming is buried in the wall with just the tap sticking out. I have got a suitable reading for continuity to confirm it is bonded and it too is in 10mm i just cant trace the actual connection, would this be satisfactory for the assessor or will i have to find the clamp?

thanks

 

[kme]

You need to find the clamp, in order to verify that the MBC is connected at the correct location. Plus, as others have discovered, you can have 10mm leaving the CU, and some numpty connects to the existing 6/4/2.5mm bond - so it looks alright, but in reality isn`t.

Sorry

KME