New supply to new build

[steviethespark]

Ok guys im wiring a house atm and was wondering if this set up met regulations ?i have a meter cubicle installed at the side of my garage were nie supply enters ,from there i have a set of 16mm double insulated tails feeding a set of iscos inside of garage located beside garage db ,from there i will install a 80ma time delayed trip feed from iscos using 16mm double insulated tails and 1 way incloseure ,the under ground cable i propose to use is 16mm split in 4inch sewer duct piped 30m to main house ,once entered the house will be installing 2 no 16 way hager db ,all circuits will be distributed between 4 x30ma 80a rcds with exception of smoke dection and alarm system ,the 16mm split may have to terminate into main 80a isolator and 2nd 16 way db will be fead from a 63 a mcb on same board ,hope this makes sense guys ?

 

[telectrix]

what's your calculated load for the whole house, allowing for diversity? you may want to consider 25mm tails for a job that size.

 

[steviethespark]

Na mate 16mm should just about be ok done math on that one

 

[telectrix]

hmm. just about? what if just about is not enough? have you calculated VD as well?

 

[steviethespark]

Yea did voltage too and that should be fine on 16mm supply

 

[telectrix]

@ 80A i got a VD of 6.7V, so it's borderline at 80A. if your load is below 80A, fine.

 

[HandySparks]

What's providing the overcurrent protection to the 30m underground cable?

 

[davesparks]

Isn't nie an Irish DNO?

 

[Octopus]

Na mate 16mm should just about be ok done math on that one

Matey - always fit 25mm on a new build or rewire

 

[Risteard]

Isn't nie an Irish DNO?

Yes, but in the north where BS 7671 applies. The ESB is the DSO in the south where ET 101 applies and BS 7671 has no jurisdiction.

 

[telectrix]

just wondering what an iscos is when it's at home.

 

[Risteard]

just wondering what an iscos is when it's at home.

An ISCO is a service connector.

 

[davesparks]

just wondering what an iscos is when it's at home.

ISCO was WT Henley's original range of cast iron cutouts, service fuses and service connection boxes.
I think genuine Henley service connector blocks still have ISCO on the lids.

So basically just another name for henley blocks, Lucy blocks, mains blocks, service connector blocks etc by

 

[Risteard]

So basically just another name for henley blocks, Lucy blocks, mains blocks, service connector blocks etc by

Precisely, although ISCOs are all you will ever hear them called over here.

 

[steviethespark]

What's providing the overcurrent protection to the 30m underground cable?

Mate the time delayed rcd back in garage will cover the cable ,and yea guys i have a rethink bout cable size and do maths again just in case ,

 

[davesparks]

Mate the time delayed rcd back in garage will cover the cable ,and yea guys i have a rethink bout cable size and do maths again just in case ,

Why do you need the time delayed RCD?
It won't protect the cable for OL or SC fault

 

[steviethespark]

Why do you need the time delayed RCD?
It won't protect the cable for OL or SC fault

So that if the 30ma trips in the house trip it wont trip out in garage all the time

 

[davesparks]

So that if the 30ma trips in the house trip it wont trip out in garage all the time

I mean why does the sub main require an RCD?

 

[telectrix]

I mean why does the sub main require an RCD?

it shouldn't if it's installed properly.

 

[steviethespark]

I was covering the sub mains because the cable will be live from a very early stage and there will be quite a bit of digging around it for sewers ect at a later date

 

[Leesparkykent]

I was covering the sub mains because the cable will be live from a very early stage and there will be quite a bit of digging around it for sewers ect at a later date

smacks of bad design though to have an upfront RCD don't you think?

 

[steviethespark]

smacks of bad design though to have an upfront RCD don't you think?

No i dont think ,can u explain

 

[davesparks]

I was covering the sub mains because the cable will be live from a very early stage and there will be quite a bit of digging around it for sewers ect at a later date

It's a few years since I last worked on a new build house, but when I did they always completed that kind of ground works a lot earlier in the job than the point when we started livening up the circuits. We only had the temp supply board live at that time.

And if it's being buried then split con doesn't comply as it doesn't have a complete earthed metallic layer,

 

[davesparks]

No i dont think ,can u explain

Leaving the whole installation with overall RCD protection for no other reason than poor coordination and project planning during the construction stage is not good installation design.

 

[steviethespark]

It's a few years since I last worked on a new build house, but when I did they always completed that kind of ground works a lot earlier in the job than the point when we started livening up the circuits. We only had the temp supply board live at that time.

And if it's being buried then split con doesn't comply as it doesn't have a complete earthed metallic layer,

U might want to check that because split does comply

 

[davesparks]

U might want to check that because split does comply

Split concentric does not, a buried cable should have an earthed metallic sheath or armour. Split con does not as over 50% of the outer layer is neutral, not earth

 

[Leesparkykent]

U might want to check that because split does comply

check what? you want to feed a new board with a cable that has an RCD at the front of it...........

edit: just realised the quoted is on about split concentric cable lol

 

[HandySparks]

Split concentric does not, a buried cable should have an earthed metallic sheath or armour. Split con does not as over 50% of the outer layer is neutral, not earth

The OP says it's in 4" soil pipe, not buried direct.

 

[HandySparks]

It won't protect the cable for OL or SC fault

Indeed, hence my question. No answer on that one yet.

 

[davesparks]

The OP says it's in 4" soil pipe, not buried direct.

But still underground and needing an earthed armour or similar

 

[steviethespark]

As far as im aware the spilt is ok to run underground via a duct something to do with the neutral and earth wrapping aroung the live conductor ,and as far as the rcd on the mains side of the submains i can drop it i was just looking little advise so cheers lads

 

[HandySparks]

But still underground and needing an earthed armour or similar

If the duct provides equivalent protection against mechanical damage as armour or metal sheath, then it's not required. BYB 522.8.10. I'd say that typical soil pipe probably does, although in most cases I'd use SWA anyway.

Interestingly, it doesn't seem to matter that the duct doesn't provide the earthing to a conductive tool that an earthed armour would.

 

[HandySparks]

As far as im aware the spilt is ok to run underground via a duct something to do with the neutral and earth wrapping aroung the live conductor ,and as far as the rcd on the mains side of the submains i can drop it i was just looking little advise so cheers lads

Any thoughts on this question?:

What's providing the overcurrent protection to the 30m underground cable?

 

[Risteard]

If the duct provides equivalent protection against mechanical damage as armour or metal sheath, then it's not required. BYB 522.8.10. I'd say that typical soil pipe probably does, although in most cases I'd use SWA anyway.

I wouldn't claim that the protection is the same as earthed armour, however, unless you had a considerably dense steel duct to actually prevent penetration. It is the fact that the armour is earthed which is pertinent.

As for split concentric there is a live conductor surrounding the phase conductor in places, so this couldnt really be considered to be "protecting" it.

 

[Simonslimline]

What's providing the overcurrent protection to the 30m underground cable?

OP please answer this question, it's quite important. I hope you are aware that an RCD does not provide OL or SC protection to the cable!