Large house 2.5mm or 4.0mm

[grandfortune]

Hi all,

Used to doing small 2 bed and 3 bed new builds so cable sizing is never an issue

got a huge 7 deb house 5 floors to do in the next 6 months, had a quick look and now wondering what cable size to use, before i get the book out i thought id post here for more advice

4.0mm legs for ring then 2,5 or 4,0mm all the way, seems to be quite a bit more expensive than 2,5mm also on the lighting 1.5mm to feed the first point then 1.0mm after.

or other option is radials, seem to be getting more common now and some favor over rings.

putting a large 24 way board in for the extra rings and lighting circuits

any advise would be appreciated , also told me he wants the cables capped ggrrrr, you guys use oval tube or channel for this these days?.

Cheers
Grand

 

[snowhead]

putting a large 24 way board in for the extra rings and lighting circuits

Is the builder aware of the size of the 24 way and the number of cables that will be going into it?

Sub DB for me.

 

[westward10]

35mm boxes for me.

 

[Leesparkykent]

35mm boxes for me and 47mm boxes on Euro plates.

 

[Ian1981]

So I must be the only person who fits 25mm boxes for sockets?
I don't think so

 

[Deleted member 9648]

Why? What was the logic?

No idea.

So I must be the only person who fits 25mm boxes for sockets?
I don't think so

No you are not, but on quite a few occasions I've had to tell someone newly moved into their shiny new house that I cant change the cheap crappy plastic accessories for quality flat plate without chopping out the boxes and inevitable damage.
Just because the original installer doesn't give a ---- what happens once he's done.

 

[Ian1981]

No idea.



No you are not, but on quite a few occasions I've had to tell someone newly moved into their shiny new house that I cant change the cheap crappy plastic accessories for quality flat plate without chopping out the boxes and inevitable damage.
Just because the original installer doesn't give a **** what happens once he's done.[/QUOTE

 

[Ian1981]

[/QUOTE
When I'm breaking regulations please feel free to condemn me and call me a poor electrician.

 

[westward10]

So I must be the only person who fits 25mm boxes for sockets?
I don't think so

You are Ian if you stopped production would cease

 

[Ian1981]

You are Ian if you stopped production would cease

But my shares would tumble

 

[JK-Electrical]

For all the time that it takes to go 10mm deeper with an Armeg box-cutter into brick, I don't see there being any great problem installing 35mm metal boxes throughout on rewires. I once used 16mm boxes for switches and 25mm boxes for sockets, but came a cropper when a customer invited me back two years after I had rewired her house to replace all the original white accessories with flatplate equivalents. She was most disappointed that she couldn't have all those shiny new sockets and switches that she'd bought installed without walls being damaged to accomodate deeper boxes, and felt that I should have taken this into consideration when the rewiring was being done. Know what? .... she was quite correct. Customer lost, painful lesson learned.

 

[alasdairp]

Why? What was the logic?

I agree. Sub-boards in a large house can make a lot of sense, reduce final circuit lengths (and can then keep to 2.5 mm2) and cable bundles and make getting to resetting the RCD or MCBs if they trip quicker and easier. Depends how big or how long the house is, of course.

 

[alasdairp]

Hi all,

Used to doing small 2 bed and 3 bed new builds so cable sizing is never an issue

got a huge 7 deb house 5 floors to do in the next 6 months, had a quick look and now wondering what cable size to use, before i get the book out i thought id post here for more advice

4.0mm legs for ring then 2,5 or 4,0mm all the way, seems to be quite a bit more expensive than 2,5mm also on the lighting 1.5mm to feed the first point then 1.0mm after.

or other option is radials, seem to be getting more common now and some favor over rings.

putting a large 24 way board in for the extra rings and lighting circuits

any advise would be appreciated , also told me he wants the cables capped ggrrrr, you guys use oval tube or channel for this these days?.

Cheers
Grand

Wants cables capped - oval tube or channel? I would consider costing FP200 GOLD or (not quite as good) No Burn Platinum screened fire-proof cables in white. These cables are fully protected against damage due to their ally foil screen, bend easily, outer strips more easily than standard twin&E (score lightly, bend twice and pull). Yes, they are a fair bit dearer but installation is a relative doddle and much quicker than capping or conduit. You can run them without worrying about wall position (though be sensible) and they are BASEC approved. The also work brilliantly with the Hager (and other) push-connect 'maintenance free' junction boxes (which can be in concealed locations) - that way you can avoid doing the switch connection inside the light fitting, reducing cable lengths and making installation quicker and easier. Can't use this on budget jobs, but very worthwhile on large or quality jobs. I would still use large size PVC twin&E to feed any sub-boards in a large domestic installation.

 

[bigspark17]

Where is this 24way db going? I would certainly be running a sub board to accomadate top 2/3 floors where electrical consumption will be minimum assuming theyre mainly bed/bathrooms. I agree with installing 35mm especially if its stud/D&D walls.

 

[Deleted member 9648]

I was under the impression that for a cable to be installed outside safe zones the earthed screen must be compliant as a cpc in it's own right. This would not be the case with the foil screen on FP200.

 

[Leesparkykent]

I was under the impression that for a cable to be installed outside safe zones the earthed screen must be compliant as a cpc in it's own right. This would not be the case with the foil screen on FP200.

Fire alarm cables for use in thin walls or partitions - http://www.voltimum.co.uk/articles/fire-alarm-cables-use-thin-walls-or-partitions-0


http://www.napitonline.com/downloads/CP 3 08 P 11-12 BS 8436 Cables.pdf