Lighting distribution circuit OK?

[1Justin]

Is there any reason under 17th why a lighting circuit (notionally a radial) shouldn't have a "distribution" tapped off it part way along, rather than looping in at each switch or luminaire? - By this I mean a junction box, which then serves power to sets of luminaires and switches off to the side.

What we effectively end up with is a star type arrangement, with perhaps four points, with the CU at one of the points. (Do we have a name for this other than "untidy"?).

For anyone not having a wiring diagram, it could lead to some harder to understand R1+R2 or R2 measurements. My guess is it's probably happened a lot in old installations which were added to, but if all cables are within limits, is there any 17th regs reason why this might be disallowed?

Justin

 

[wellshocked]

i could be wrong,ive only worked with these once,

but dont the klick boxes sort of serve as a distribution box , where you feed them and plug the lights in.

 

[wellshocked]

ive never heard of it not being a reg just bad practice,

 

[Des 56]

Is there any reason under 17th why a lighting circuit (notionally a radial) shouldn't have a "distribution" tapped off it part way along, rather than looping in at each switch or luminaire? - By this I mean a junction box, which then serves power to sets of luminaires and switches off to the side.

What we effectively end up with is a star type arrangement, with perhaps four points, with the CU at one of the points. (Do we have a name for this other than "untidy"?).

For anyone not having a wiring diagram, it could lead to some harder to understand R1+R2 or R2 measurements. My guess is it's probably happened a lot in old installations which were added to, but if all cables are within limits, is there any 17th regs reason why this might be disallowed?

Justin

It has been called before now a Spider

Pendants are only junction boxes that have visible cables

You could,if you want feed a junction box and spider the lot from there
You could make the junction box accessable or fit an enclosure on a wall/you can dream up many ways of wiring that are not as per the book as long as circuit tests are satisfactary

 

[Deleted member 26818]

Yes a spider circuit.
Not too common nowadays.
Came accross one recently on a PIR, only it was for socket-outlets, and was on a 30A fuse.
Changed the fuse for a 20A plug in MCB.

 

[needasparks]

Have never seen it on sockets but have on lighting, I could not work out why every light only had one cable in throught the whole bungalow. Then found a 300x300 box in the loft with every swichline, twoway cable and feed for the whole circuit in it.
At a guess about 30 cables. took ages to work out what was what.
I think the reason for this one was the loft was only about 18 inches high at the highest point so all the cables were fished to one point, must have taken ages to dress in and still looked like a box of worms.

 

[1Justin]

OK, it's nice to know A) It's "acceptable". And B) we call it a spider!

In this case the junction box here is inaccessible, under upstairs T&G. One leg feeds bathroom PIR, lights, fan, the other feeds hallway lights. So what I'll do is to dig it out and make a screw-down hatch in the floorboards. After that if it all measures OK, I'll leave the spidery thing as is.

Tell me one more thing. Old round JB's without cable clamps:
We use these now only when we can screw down the box and clip all the local cables?
When cables have been slung loose into the ceiling void (and they will mostly remain that way because I can't clip them), I'd need to at least replace the round JB with a chocbox having cable clamps (- as well as make it accessible)?

Thanks

 

[polo1]

Very common, especially in '70 new builds. Builder Geo Wimpey (or is it Wimpy?) used to make up the lighting wiring looms in the factory (typically one for the ground and one for first floor). Every cable was uniquely marked and then fitted to agreed positions e.g. pendant, switch. Bordering on works of art - I used to hate disturbing them when doing alterations.

The ground floor distribution box in these properties is typically located beneath the top hall floor, and the joiners were supposed to install the T&G flooring with an access hatch above....although often they didn't!

Regards.

 

[ackbarthestar]

Agreed, used to be very common once upon a time...
We used to take the longest spur from the 'octopus' JB often with more than socket attached and take a separate 2.5mm2 to that socket providing a new RFC.

 

[ezzzekiel]

came across one recently on a newish build (about 10 years) made picking up perm live for fan a nightmare, eventually found jam packed wiring centre buried in middle of loft.

 

[drew35]

I must admit I was doing spider lighting circuits in a barn conversion today, where all the voids, floors and ceilings, are packed with that bloody six inch celotex. I find myself a nook and run as many from one point as possible as there is no room to get a junction box anywhere else without mashing holes in the celotex. Especially where the ceiling height is 8 meters.