Bit of advice off the more seasoned sparks :D

[mattmoo1974]

Been round to look at a job.
the guys got 3 CCU's
1 for the main house and 1 for garage 1 runs heating and a few other odds and sods.
Did IR on main house board(rewirable fuse) and its low on a few circuits.
So my plan is remove the 2 small units put a 4 way garage unit.
He also wants me to feed his extention, run swa around a out side wall.
then i was going to put a 8 way in there so iv got a few spare ways as well.
Theres going to be a 10Kw shower, Leccy cooker hob only, couple of leccy heaters on the wall, 2 lights 4 sockets.
I was going to use 10mm SWA poss 6mm.
i going to put a 50a MCB(in the 4 way unit) or do you think hes going to go over that?
Showers gunna pull 35+ when going, if the coookers on etc etc think this will trip?
Oh there putting a new supply in 60 to 100, there is zero space where the current 3 CCU's are.
Thought id ask your advice, As i dont want to get the wrong cable as it is dick turnip to buy these days. Hope iv supplyed enough info.
are there ne rules about SWA clipped to the side of a building?
Im going straight up and along under the sofit.

 

[telectrix]

i would use 3core 10mm XLPE SWA, rated 81A. that should be fine cleated to wall. 63A MCB front end.

 

[malcolmsanford]

IMO I'm not a great lover of having seperate boards in a domestic house, if there were any chance of getting it installed at the origin of the installation then I would, if there isn't any space then ok.Also as your having to take the sub main out around the house, that would be preferable than runing final circuits externally.

I would personally not feed a 8 way board off the small 4 way, I would much rather henly block the tails and then fit your protection devices for the sub main tails.

As for diversity just try an old rule of thumb, add your protection devices up and multiply by 0.4. It is not exact but it is pretty close.

Appendix 4 of the OSG will give you some good guidance on SWA erection.

 

[mattmoo1974]

When u say 63 front end the highest i have seen(Just looking on screwfix as dovendale dont have the tinternet option) is 50a.

 

[mattmoo1974]

IMO I'm not a great lover of having seperate boards in a domestic house, if there were any chance of getting it installed at the origin of the installation then I would, if there isn't any space then ok.Also as your having to take the sub main out around the house, that would be preferable than runing final circuits externally.

I would personally not feed a 8 way board off the small 4 way, I would much rather henly block the tails and then fit your protection devices for the sub main tails.

As for diversity just try an old rule of thumb, add your protection devices up and multiply by 0.4. It is not exact but it is pretty close.

Appendix 4 of the OSG will give you some good guidance on SWA erection.

Gunna pop that on a 50 and x32's for the other circuits taht are there now(ie out to garage 1 socket 1 light) the other Cir feeds a oil burner only.

 

[Engineer54]

Why not just replace the existing old CUs with a new one with enough ways to supply everything....4 CU in a standard house, ...is Crazy!!!

 

[telectrix]

no problem getting a 63A MCB. most manufacturers do standard din rail 63A

 

[mattmoo1974]

Why not just replace the existing old CUs with a new one with enough ways to supply everything....4 CU in a standard house, ...is Crazy!!!

I know if i do that im opening a can of worms. Low IR results on that board the other 2 are fine. Its a nice little cottage where they are nt gunna want me ripping floor boards etc etc

 

[Engineer54]

That would be leaving the installation in a less than safe condition mate. Have you explained/informed the owner of your findings?? Maybe he would want you to rectify those existing problems making his home safe, along with the other work. He certainly wouldn't have 4 CUs in a small cottage anymore ...lol!!!

 

[mattmoo1974]

Yeah iv said there is a Issue there he said "it works fine now" i cant force him to have it done, Jst advise him,thats why im leaving it alone. Im not going to fit a new CCU and end up down there every 5 mins cos the RCD keeps tripping. Hes just going to say "It was fine before you touched it".

 

[IQ Electrical]

I know if i do that im opening a can of worms. Low IR results on that board the other 2 are fine. Its a nice little cottage where they are nt gunna want me ripping floor boards etc etc

What are your values of low IR?

 

[mattmoo1974]

Aye 2 and a bit M ohms. they ve lived there 20 years and not had any leccy work done.
Not had a PIR in that time as well. But it works as he says!

 

[tony mc]

Was that on the whole board or cct's tested on thier own ???

Sorry just read original post again ???

 

[mattmoo1974]

Up lights low,down ring

 

[GT1]

Are you absolutely sure there's not a load still connected. ??
Do you get same readings when L+N tested connected together ?