rec cable size and type selection

[Steve]

I was looking at the side of my house earlier, and had a thought. some of these cables dont look any thicker than 10mm, how are they thick enough to supply up to 4 houses???

(top cable actually comes overhead from next door, right cable goes to our house, left cable goes next door and to the next house too) The one coming from next door (the 2 cores at the joint) doesn't look any thicker than 10mm! same cable used next door that goes underground to the street, supplies 5 houses!
also been having questions about the cables at my meter

the cable from the cutout to the meter, im pretty sure is concentric. why did they use this here? surely easier to just use meter tails? the other cable from the top of the cutout, seems to loop back into the cutout. what is this for? Just curious, im not planning any work, dont worry !!!!

 

[plugwash]

i do agree that some of those cables are a little on the small side what size is your service fuse? (bear in mind the recs seem happy about putting a 100A fuse on a 16mm service cable).

as for the concentric it seems recs do this sometimes i've no idea why (possiblly cost). the cable you see looping over is probablly the neutral side of the concentric looping over to the cutout neutral.

 

[Lectrician]

They use those concentric meter tails for safety and security and speed - anything pre-meter. The little loop is indeed the neutral. These are seen widely in my area.

 

[plugwash]

i can't see how concentric meter tails would improve any of theese things can you explain?

 

[Steve]

yes, its a 100A fuse, at least thats what it says on the cover, im not going to be taking it off to look inside. i suspect that the rest of my neighbours have similarly rated fuses. how do they get away with the small cables when you are forced to use 25mm SWA for meter tails on long runs?

A few years ago, the rec came and put most of the supply cables underground. They used to run overhead on the street on wooden poles, with a branch to every 5th house. When they did this, some houses got their own branch from the main cable in the street. and some still had to share a branch with 5 other houses, us being one of them It was mainly those across the road (their side of the road where the main cable runs) who got individual supplies, and obviously it was cheaper to just do, say, 4 runs under the road than 18.

 

[plugwash]

afaict the recs won't replace anything until they absoloutely have to (ie they tend to take notice when smoke starts coming off it)

 

[Lectrician]

i can't see how concentric meter tails would improve any of theese things can you explain?

Well concentric is much safer than tails when you consider damage etc, the live conductor is kept conceiled and protected through the entire run to the meter.

They also come ready prepared and stripped - loosen the terminals, stick it in.

They do also look alot neater.

 

[mapj1]

Remember that the whole LV network is sized on an AVERAGE load of about 2kW per house - a 0.5Mw tranny will feed perhaps 200 houses, 60 to 70 on each phase plus a few with 3 phase feed. However, being outdoors and well coolled a few 100% overload for the odd half hour doesn't matter as much as you might imagine.
The chance of all 4 houses on the branch line drawing full load for lots of heaters or something long enough to do cable damage is quite small, and if they do it'll most likely be cold outside. It is this assumption that is so dangerously wrong in terms of air conditioning, which tends to be on in the summer, but fortunately not poular in the UK.
You like to might be happier to think that what we do indoors is over engineered, rather than the otherway about.

 

[ban-all-sheds]

Remember that the whole LV network is sized on an AVERAGE load of about 2kW per house - a 0.5Mw tranny will feed perhaps 200 houses, 60 to 70 on each phase plus a few with 3 phase feed. However, being outdoors and well coolled a few 100% overload for the odd half hour doesn't matter as much as you might imagine.

Did I post this already?

http://www.stupidvideos.com/?VideoID=828

can't remember..

 

[plugwash]

i'm positive i've seen a better quality version of that exact same video somewhere...

 

[ban-all-sheds]

Probably - the site does indicate that if you subscribe you get access to higher quality clips.