Lighting lengths on radial circuit

[andemz]

Hi everyone. Just been reading through some very old posts on this forum, excellent reading. I then went to a few websites to cross reference the points that had been debated. Here goes.

With 1 mm sq. cable, one circuit may serve up to 1200 Watts (12 X 100 Watt lamps) and must not exceed 95 m of cable length measured without the switch length. However, where there are long cable lengths, use 1.5 mm sq. cable instead which allows a maximum cable length of 110 m measured without the switch length.

Ok here is the problem. If you have been watching the programme grand designs, you may have noticed that some of the domestic electrics are like nerve centers. I am aware of a couple of houses where the room sizes are very large and therefore even 110m wouldn't go very far.

For arguments sake let's say we had a very long corridor. We have a consumer unit and we run a 1.5mm2 T&E, we then come to our end of 110m and so naturally speaking we couldn't go any further. Yet for me to continue i would need to go back to my consumer unit for the supply but would be faced with the same problem.

I know this is a bit way out but is the answer that if you did wire up a very long corridor or area that you would need to feed a cable to a new supply to start you off again. Just couldn't get my head around that one.

Anyway just as a comment, i think on one of the grand design houses they used over 3 Kilometers of cable WOW and they call that domestic, that would have cost the earth, it was intelligent electrics as well.

I bet FWL would have loved that contract

 

[AdamW]

The Grand Designs house with the bird's wing roof had 11 kilometres of wiring in it! If I recall each half of the building had it's own full system, which must aid installation in such a complex installation.

 

[Big_Spark]

Had that problem here

That place is across the road from where I live..literally..and we are often on the estate doing works, either as FWL or CEL, depending on the works.

The corridors did present..shall we say unique..challenges when the place needed some serious work done last year..more is needed but the owner needs to fit such work into the busy schedule of the estate.

Anyway we came up with a novel way to solve the problem.

3 core 2.5mm MICC run in the ceiling voids to an position adjacent to the lighting circuits to be fed, this terminated in a small enclosure that contains a 25A BS88-2.1 fuse, immediately adjacent to this enclosure are six unswitched fused connection units with integral neon indicators. Each of these has a 3A or 5A fuse in it, and these go off to form the final circuits for the lights.

Should a fault occur on a circuit, it takes out the local fuse and the neon goes out. Each of these setups is above an accessway in the cieling, and in an emergency the Butler knows where they so he can change a fuse..if it blows again, they'll phone us.

Before we installed the system, we ran it by the NICEIC and the IEE technical boys to see if they had any objections, an NICEIC inspector looked over it once complete and was more than satisfied it meets the requirements of BS7671 and their requirements for good design.

 

[ban-all-sheds]

If you have enough money there is always a solution. The Pentagon for example has 17.5 miles of corridors, 16,250 lighting fixtures, and they make that work.

And they employ enough full-time people to change 250 bulbs per day...

 

[kendor]

Ban all sheds wrote:
And they employ enough full-time people to change 250 bulbs per day...

Over here that would be ONE Person