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

 

[alasdairp]

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

Thanks for the links - they clarify things. I talked with the head of BASEC at an IET meeting on ring vs radial wiring some years ago and he wrote to me and confirmed that FP200 and similar BASEC approved screened cables could be used running almost anywhere - but always on a standard type B 30 mA RCD protected circuit. Now fire-alarm supplies should not be RCD protected (as the voltinium article states) - so they have to be run in "protected" areas to avoid the likelihood of later nail or screw damage.

 

[JK-Electrical]

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

Flexishield is what I've always used when a BS 8436 compliant cable was required:

The Original BS8436 Cable | Flexishield - http://www.flexishield.co.uk/

FLEXISHIELD Cable - https://www.electriccable.co.uk/flexishield.php
https://www.electriccable.co.uk/flexishield.php
There are some older threads to be found elsewhere on the forum for anyone who's interested:

Flexishield Cable - http://www.electriciansforums.co.uk/threads/flexishield-cable.4722/

Flexishield cable - http://www.electriciansforums.co.uk/threads/flexishield-cable.101007/

 

[Cadgey123]

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

25mm if you want to fit tight boxes and cheap plates.

10mm for a decent job..... pfft laziness

 

[ED17]

Considering the low prices that some sparks do the new builds for, I'm surprised that they can even afford to fit a box!

 

[DPG]

Thanks for the links - they clarify things. I talked with the head of BASEC at an IET meeting on ring vs radial wiring some years ago and he wrote to me and confirmed that FP200 and similar BASEC approved screened cables could be used running almost anywhere - but always on a standard type B 30 mA RCD protected circuit. Now fire-alarm supplies should not be RCD protected (as the voltinium article states) - so they have to be run in "protected" areas to avoid the likelihood of later nail or screw damage.

I'm not sure you've got the wording right there.

 

[alasdairp]

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

Thanks for the links - they clarify things. I talked with the head of BASEC at an IET meeting on ring vs radial wiring some years ago and he wrote to me and confirmed that FP200 and similar BASEC approved screened cables could be used running almost anywhere - but always on a standard type B 30 mA RCD protected circuit. Now fire-alarm supplies should not be RCD protected (as the voltinium article states) - so they have to be run in "protected" areas to avoid the likelihood of later nail or screw damage.

I'm not sure you've got the wording right there.

Thanks for pointing out my mistake. The voltinum article:
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
actually points out that no routing of screened cables should rely on RCD protection alone with regard to cable protection - whatever the supply purpose of the cables. The article then goes on to point out that both FP200 Gold and FP Plus have thick aluminium sheaths that do pass the nail/screw penetration tests - so they may be run more freely (though of course with common sense!). Some other screened cables have an aluminised plastic screen and they cannot legally be run so freely as they do not pass the penetration test requirements.