Meter Tails - Again!

[ben2012]

Not quiet the same as the other recent threads i believe, ive been to look at a new extension that's been built, the mains is being moved from is current position which is on the current outside wall to the outside wall on the new extension, so the plan is to fit a new consumer unit to supply the new extension and then from an 80A switch fuse to run a pair of 25mm tails and 16mm earth to the existing consumer unit to resupply. the tails would be run under the floor of the new extension and through the wall to the board, its approx 10-12mtrs in length. can anyone see any problem with this? part of me thinks i should run SWA but given its going to be under the floor i cant see any way it would get damaged.

thanks

ben

 

[davesparks]

Why not just extend the existing circuits to serve the new extension and alter them a little to be fed from a new board at the new mains position?

Unless this is some kind of mansion and actually needs 80A to feed the existing CU and it has no capacity to feed the extension?

 

[ben2012]

The current board is full and the new extension has 2 beds, utility, snug and kitchen hence having a new board would be easier and either way tails would have to be run from the new meter position to the existing board

 

[shanky887614]

The current board is full and the new extension has 2 beds, utility, snug and kitchen hence having a new board would be easier and either way tails would have to be run from the new meter position to the existing board

?

why not just extend the circuits, extend ring and lighting and be done with it

 

[davesparks]

The current board is full and the new extension has 2 beds, utility, snug and kitchen hence having a new board would be easier and either way tails would have to be run from the new meter position to the existing board

Just fit one new board in the new position and alter the existing circuits to be fed from that board.
Take the existing rings out of the board and close the ring at that point, open the rings where they are closest to the extension and extend them around the extension as required and to the new board.

Remove the feed from board to first light on lighting circuits and then extend feed from nearest point to extension to serve new lights and connect to new board.

Unless they are having 2 kitchens the old one will be coming out and all new electrics to the new kitchen anyway.

Come on, this is the basics of domestic electrical work!

 

[joe.ninety]

Have you spoken to the DNO regarding this? Are they happy to have you extend the tails for 10-12m? Have you made plans for incorporating a switchfuse to accommodate the need to have tails >3m?

 

[Engineer54]

Just fit one new board in the new position and alter the existing circuits to be fed from that board.
Take the existing rings out of the board and close the ring at that point, open the rings where they are closest to the extension and extend them around the extension as required and to the new board.

Remove the feed from board to first light on lighting circuits and then extend feed from nearest point to extension to serve new lights and connect to new board.

Unless they are having 2 kitchens the old one will be coming out and all new electrics to the new kitchen anyway.

Come on, this is the basics of domestic electrical work!

This is typical of what's going on out there.... Mention any form of building extension and it's a second CU straight off the cuff...

 

[Scornio]

In my opinion I don't think what he is doing is a bad option. His questions was about the tails anyway, not what others may or may not do. Every electrician is different and I respect other peoples work if all well and safe.
If he starts messing with original installation he may open a can of worms and is deemed liable. Just change the tails, don't bother asking dno for permission; stick your own KMF switch in; make sure they're run in, in an approved manner and be done with it. Nothing wrong with it.

 

[7029 dave]

In my opinion I don't think what he is doing is a bad option. His questions was about the tails anyway, not what others may or may not do. Every electrician is different and I respect other peoples work if all well and safe.
If he starts messing with original installation he may open a can of worms and is deemed liable. Just change the tails, don't bother asking dno for permission; stick your own KMF switch in; make sure they're run in, in an approved manner and be done with it. Nothing wrong with it.

Err, I think there is plenty wrong with having 12mts of tails running under the floor boards. Fit sub/ KMF.

 

[Scornio]

Please enlighten me.

 

[davesparks]

In my opinion I don't think what he is doing is a bad option. His questions was about the tails anyway, not what others may or may not do. Every electrician is different and I respect other peoples work if all well and safe.
If he starts messing with original installation he may open a can of worms and is deemed liable. Just change the tails, don't bother asking dno for permission; stick your own KMF switch in; make sure they're run in, in an approved manner and be done with it. Nothing wrong with it.

Installing a new feed to the existing board means he will have to check that all of the circuits still comply as he will have changed the Zdb so the Zs will be affected.

Surely it is better to find any faults in the original installation and put them right rather than turning a blind eye and pretending they aren't there!

And he wouldn't be messing with the original installation, he would (hopefully) be working safely and in line with good workmanship.

 

[Johnuk]

put sub-main in. 10 to 12 meters of tails is a bit to long

 

[Scornio]

I'm not sure what the notification implications are for replacing tails are as I've never had the pleasure. I'm sure there is nothing wrong with him taking the zs readings down prior to such work. I can't see replacing for 25mm/16mm tails is much more than 30mohm off top of head.
Obviously if you visually come across faults then recommend for rectification or do so depending on severity. That isn't your installation and not your work so why get involved? That is a different job for a different quotation, preff a ecr.

 

[Flanders]

Max tails length in normally about 3 meters, you have not said what power you need in the new extention but if it only lights and sockets a 10mm twin and earth could be big enough for you requirements don't forget you may need an upfront RCD depending on how you run the cable

 

[Flanders]

Sorry just red you post again so you are creating a sub main circuit you may be better running a SWA and it may be cheaper

 

[davesparks]

The meter is moving so the new sub is to feed the existing board.

Personally I just can't see the sense or necessity for 2 boards in 2 different locations in the average house.

 

[Scornio]

Well personally without looking at the job it is not within my ability to impose my view, thus is why we should just answer his original question as I've mentioned before.

 

[davesparks]

It's a house, the whole installation might just about draw an average of 20A, the DNO will have allowed 2 or 3 KW for it.
There'll likely be an upstairs ring and a downstairs ring, an upstairs lights and a downstairs lights, a cooker supply and an immersion heater supply.

The OP wants to run an 80A SP supply in 25mm sheathed singles to feed this at approx 12mtrs length.

The extension includes a new kitchen and the new meter position so the cooker will no longer be on the existing board nor will the main bonding.

The existing board will likely not see the current reach double figures after this, so I'd say 80A is well and truly OTT.
32A down a 6mm T&E will more than likely be OTT.

Without further information and assuming that it is a regular house I'd say the OP is either a bit clueless or delusional about how much power a house needs.

 

[sparksburnout]

Can I just ask a simple question, going back to the original post, as this thread seems to have lost the plot to me. Why are you moving the intake and existing CU??

 

[Scornio]

Ok, just to clarify. The answer I have given was to his question, where he asked is it suitable to run a cable of his choice 10-12m- to which I replied, Yes with a KMF switch or similar. (if they are tails being over the 3m rule) They must be also suitably installed regarding installation methods. This is a simple answer to a simple question. However, as he has not specified any other such information which gives us any right to say what he can and cant do, then we should trust he knows what he has done regarding design and answer the simple question. Ok, so you maybe right regarding the AMD, but you cant assume the main protective bonding has also been moved, meaning he would still need a *10mm at the existing board. I did not answer any questions regarding his new sub main he has planned for the extension other than its a good idea, and not un-usual.