Hmm. Sounds like an idea for an "installation" to me. I could call it "socket to me". Plug in a TV in the middle and have it showing that electrical safety movie from the 60's. Damien Hirst, eat your heart out.
Back-boxes?
Are we talking a quality job all of a sudden?
Owain
earth loop impedance. It's high, but within the recommended max (which I forget).
dont forget the bit about conning the public purse into paying for it all.
NT
well 100m^2 of floor might be 100meters long and one meter wide, which is 200m of perimeter. Plenty of room for a couple of doors now.
And by stacking the sockets on top of one another to fill the regulation space between 450mm and 1.2m or whatever it is, I reckon you could get about 10,0000 sockets on a ring.
Ive seen some computer rooms like that... ;-)
Uh? Table 7.1 appears on page *42* of the blue edition OSG and also of the current brown edition.
The 84 m figure for 2.5 mm^2 cable and a Type B MCB is voltage drop limited on the assumption that the whole 32 A loading occurs at the mid-point of the ring. For general lightly loaded household rings, kitchens excepted, no great harm is going to come about if the 84 m figure is exceeded a little. 84 m of 2.5 conductor will have a max. resistance at 20 deg. C of 0.62 ohm, so if your r1 & rn end-to-end test figures exceed that value you should at least consider whether any remedial action is necessary.
There's nothing to stop you using 4 mm^2 cable if necessary for long rings, but you do need to do the usual calculations to check Zs (for disconnection time) and to check for adiabatic compliance of the CPC. (4 mm^s T&E has a 1.5 mm^2 CPC.)
Be practical! If you actually want to wire them up you will need a finite length of cable between sockets. Let's say 200 mm between doubles. Then allow one metre at each end to connect to the dis-board. Then, observing the 84 m length limit, you could have (84-2)/0.2 + 1 =
411 double sockets - a far more reasonable number.Now the practicalities of testing such a circuit. High continuity test resistance reading - oh dear, which socket has a loose terminal screw...
Your right.
No idea how I missed that but probably because I never considered it and it wasn't evident in Appendix 8.
Anyway just rechecked the ring and it is 81m from the ring impedance and
1.5sqmm CPC from the CPC measurement. Measured earth fault loop impedance is 0.55ohms so false alarm really.Thanks for pointing out the table.
Jim A
Don't cut the conductors at any point in the ring, just loop in and out of the terminals.
Owain
And just imaging installing the buggers in cheap dry lining backboxes... I get fed up after doing ten of them!
If I'm installing a new ring, my personal challenge to myself is to do so without cutting any of the conductors. I think it's about 5 years since I've installed a whole ring from scratch, but the last two I did, I managed using a single piece of cable without cutting the conductors.
Which begs the question, why is there not a dedicated tool for slitting neatly down the middle of T&E without the risk to hands and cable posed by a knife. They make something similar for round flexes....
On Sun, 27 May 2007 03:58:07 +0100, John Rumm mused:
They do. One of those Jokari strippers with the rotating blade.
Oh, that was a given ...
Are they any good, and can you use them on the middle of a cable rather than just the end?
On Sun, 27 May 2007 12:57:51 +0100, John Rumm mused:
Never tried it tbh, just used it on SWA, but I see no reason why it wouldn't work. Might need some attention paying to how it does it and some practicing first.
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