mete tails in cavity wall

[tu1982]

hello

im doing a house rewire and currently the fuse board is directly on the other side of the meter(which is outside) this means its in the kitchen cupboard at low level.

This is a daft position for a fuse board and i was thinking about moving it to high level, so that any future addition circuits can be easily added without trunking or chasing that will ruin the kitchen!!! i am wondering if its ok to put the meter tails in the cavity wall only up about 2 metres?, its also stupid to chase them in the wallobvious reasons!!, so any advice is much appreciated?!! i presume this way is ok as long as there is no cavity wall insulation to afect able rating.

im mainly a commercial electrician and will get this certified via my boss. it just means im not clued up on the domestic regs.

cheers for any help!

 

[Andy™]

id avoid it

what happens when they decide to get wall insulation next year?

 

[a1]

Welcome to the forum, Tu.

 

[Andy™]

see this thread for more info

Electrician Forum

 

[tu1982]

thanks andy c ive read that thread it not very clear!

some people say seem to think its ok some people dont, if the people are 100% sure of not having cavity insulation in the future does it matter? its a family member so its not like i cant tell them! and they wont be moving!

it also says in one of those posts that meter tails are exempt, (wozz say this)

thanks and its good to be on the forum

 

[Andy™]

thanks andy c ive read that thread it not very clear!some people say seem to think its ok some people dont, if the people are 100% sure of not having cavity insulation in the future does it matter? its a family member so its not like i cant tell them! and they wont be moving!

it also says in one of those posts that meter tails are exempt, (wozz say this)

thanks and its good to be on the forum

anything before the meter, i.e service cable, cable from head to meter is upto DNO. anything after than is BS7671.

even though there is no insulation in there now, there is a good chance there will be at some point, so if you do decide to install it there, you should assume that there is insulation and re-rate as required.

inside of cavity's is also fairly rough, so consider some extra protection. copex, conduit etc (mostly for the install - you may not notice if you have sliced away a large section of sheath)

 

[tu1982]

so basically if i get some 32 mm copex (i presume this will fit 2x 25mm tails and 16mm earth) and upgrade the 16mm tails to 25mm tails that should be adaquate (descrimination etc meaning no need to go bigger)? and within the regs?

thanks andy you have been a great gettin back so quickly.

 

[Andy™]

so basically if i get some 32 mm copex (i presume this will fit 2x 25mm tails and 16mm earth) and upgrade the 16mm tails to 25mm tails that should be adaquate (descrimination etc meaning no need to go bigger)? and within the regs?thanks andy you have been a great gettin back so quickly.

may be tight with 32mm copex, but use a draw rope, keep it straight and it should be possible

too cold to go outside and gets regs....but maybe install 35 tails....

 

[tu1982]

if i install 35mm tails what size does the copex go upto!?!?

 

[tu1982]

and as ive never done this before am i supposed to seal the cables on entry into the fuseboard and in the meter box? so that the cavity wall is sealed?

 

[Apache]

if i install 35mm tails what size does the copex go upto!?!?

35mm copex - maybe?

 

[SPECIAL LOCATION]

thanks andy c ive read that thread it not very clear!some people say seem to think its ok some people dont, if the people are 100% sure of not having cavity insulation in the future does it matter? its a family member so its not like i cant tell them! and they wont be moving!

it also says in one of those posts that meter tails are exempt, (wozz say this)

thanks and its good to be on the forum

Hello Tu1982.

Meter tails in cavity walls is a building regs guidance NOT wiring regs..

wiring regs you just got to ensure things such as

mechanical protection, thermal de-rating, max volt drop,

etc..

building regs bits...

Building Regulations 2000, Approved Document C, 2004 Edition, Section 5: Walls, paragraph 5.13 b Cavity external walls, requires, amongst other things, that a cavity external wall is at least 50 mm wide, and the cavity is to be bridged only by wall ties or by cavity trays provided to prevent moisture being carried to the inner leaf.A cavity is intended to provide a gap to prevent water penetration. Cables could bridge this protection if they touch both the inner and outer leaves of a cavity wall. Furthermore, the cables could provide a route for water to drain directly into accessories, with potentially dangerous results.

Then NHBC Requirements:-

It is noteworthy that the National House-Building Council states, in Section 8.1 - S2 of NHBC Standards, that no cables other than electricity meter tails are to be located in the cavity of an external wall. Where meter tails do have to pass through the cavity, however, this does not preclude the requirements of BS 7671 referred to in this topic having to be met.

 

[SPECIAL LOCATION]

if i install 35mm tails what size does the copex go upto!?!?

Whats you max demand????

if no more than 80A I think 25mm will be fine?

Ref method 'A' enclosing in conduit & thermal insulation

25m single core non-armoured with or without sheath single phase 80A

 

[Nicky Tesla]

you're not supposed to bridge gaps inside cavities cos the moisture will run along the cable and onto the wall creating damp patches....this is the theory

but what the hell just do it anyway... plus the cables will be heading towards the outside wall on the way down anyway.

 

[SPECIAL LOCATION]

may be tight with 32mm copex, but use a draw rope, keep it straight and it should be possibletoo cold to go outside and gets regs....but maybe install 35 tails....

two lenghts of copex?

individual tails one down each.

16mm earth no need for extra mechanincal protection IMHO.

if going 35mm tails, need bigger earth as well!

min half CSA of phase conductors.

 

[Andy™]

two lenghts of copex?individual tails one down each.

just make sure the copex isnt made from metal!

 

[Stevie h]

Electrician Forum

chase them in the wall , cover them with steel plate

Ste

 

[SPECIAL LOCATION]

just make sure the copex isnt made from metal!

nice bit of flexible PVC corrugated 25mm dia conduit..

just to guide it through the wall

and keep insulation off the tails

and stop you damaging the sheath

 

[Andy™]

Electrician Forumchase them in the wall , cover them with steel plate

Ste

dont forget to earth it!

 

[tu1982]

cool i think thats sorted then? some pvc flexi conduit in the wall to protect the cables from damage pulling cables in? and also protect from any future wall insulation damaging cables etc.

As i wrote earlier i presume its best to seal the cavity up from either side after the holes have been made?

i will check the cut out and if its 80amp i will proceed with 25mm tails if its 100amp i will upgrade to 35mm in this day and age with low energy everywhere and massive electric bills i cant see any future scope for more than 80amps anyway! even with a cooker and electric shower!

sound about right?

i must say ive never come accross this forum before im loving the quick accurate replies, much appreciated guys,