Quick question on JB's needing to be accessible

[Hallsy]

As JB's are supposed to be accessible, how do we define this? Is lifting floorboards accessible? I presume so, this won;t give me a problem, BUT I am installing halogens under a flat roof, as they are halogens have to use JB's, these will be under the flat roof but above the ceiling so basically in-acessible unless you pulled the ceiling down or lifted the flat roof. Is this a problem?

Also, if a JB has only 4 entries must you only use 4 cables? I have a load of 20A 4 way 4 terminal JB's (but I don't like them as they are white & look cheap so may change them anyway!). The original wiring to the bathroom lighting was pretty poor and came straight from the CU. I intend to pick up the feed from the nearest ceiling rose, BUT this ceiling rose is being replaced by a JB to run two halogens in a hallway. SO....this JB will have a mains loop in, mains loop out, switch wire and cable going to lamp(s), if I want to pick up my feed for my bathroom from here I will be adding another loop out and so 5 cables. Is this OK, or would I be better breaking one of the loops that are already there and putting by JB in?

Or am I just worrying too much!!!

Also, do most people screw JB's to the side of the joists or leave them suspended by the cables?

 

[Lectrician]

A JB can have as many cables as will fit in the terminals. They usually say on the reverse (3x4mm is usuall for 30amps).

A JB under a floor, which can be drawn out through a down light cutout is accessable.

A JB under a laminet floor is NOT.

A JB under a carpeted floor.........according to the NIC.........is NOT. I await other views........

 

[andy]

A JB under a carpeted floor.........according to the NIC.........is NOT. I await other views........

even tho it could be accessable, its not obvious that it is there so you might not know about it

 

[Lectrician]

I am always happy to go with the NIC - Been enroled for 10yrs, so can't complain......I know others hate them!

Yup, a carpeted floor isn't ideal.......I think we have all done it in the past though

But for certed jobs......as they all should be......it's a no.

 

[Hallsy]

Right, so we're saying that as long as you can leave enough slack on the cables and the JB can be pulled down through the downlight hole that is OK.

Pretty stupid about the carpet, you might not know anything was under there, but you wouldn;t still with a bare floor until you started lifting boards!!

And I very much doubt that all these modernised homes with spotlights everywhere either have bare floorboards above them or enough slack to pull the JB through the cutout!!

Right, so the cable rating on the back of the JB is with regard to each terminal, so I could still have 5 cables going into a JB but only 4 cables terminated in each terminal.

 

[Hallsy]

Aha, BUT most std downlighters require a 60mm hole, yet most JB's are 80mm diameter. So unless I use fancy spotlights that require bigger cutouts due to having larger surrounds I still can't access the JB's.

This is ridiculous, by the book if I joined all these cables by say crimping all would be fine, but using JB's they must be accesible. I'm running out of ideas here, trouble is I'm going to have a few JB's in under this flat roof anyhow.

Currently I'm picking up a loop from the hallway light, as this ceiling is higher than my falt roof one I am having to go down through into the garage, along the garage then back into the flat roofed section of the hallway. This is the first JB used to allow connections for an outside light and it's switch, then I take the loop to another JB which supplies the two spots in the bathroom and their switch.

It seems I have two options, use spots that require massive holes even though they wouldn't be to my taste, and leave loads of slack on cables (mmmm, really tidy) so that they can be pulled down through the holes to be inspected

The other, is that I could move the JB's across into the garage as they share the same flat roof and so the same voids, this would keep the JB's accessible as there is no ceiling in the garage (under the flat roof anyway) then run all of the cabling back into the hallway/bathroom for final connections, BUT in time this may well be converted into a habitable room, it would have a pitched roof above it, but wouldn't be accessible.

What would a pro domestic spark do? I'm thinking they wouldn't actually worry that much.

 

[Qedelec]

Normally installing connections in a ceiling void I use terminal strips enclosed in chockboxes. Available from the great and wonderful screwfix at approx 99p. And no MOD I am not advertising.

 

[Hallsy]

Thanks, had considered them, but now realised that you can get J201 JB's, 20A 4 terminal but only 57mm diameter so would be able to pull through a std 60mm spotlight hole.

 

[Lectrician]

20A 4 terminal but only 57mm diameter so would be able to pull through a std 60mm spotlight hole.

You beat me to it!

 

[Hallsy]

Haha, just got some J201's from my local wholesaler. Was suprised to find that instead of four holes you have four knockouts. What is best method for getting the out cleanly? I used cutters on one which put a crack in the JB (oops!!) and used pliers on the others which did OK but left them a little rough.

 

[Lectrician]

I use side cutters as pliers (not as cutters), and snap in and out gently. They always leave them a little rough. A small file would help I suppose.....


In college, they teach to use a junior hacksaw to cut a section out the same size as the cable, (several vertical slits, then break them away with long nose pliers, and file smooth).


A tip to anyone using these JB's. Cut all conductors of all cables, irrespective of which cable entry to the same length. (approx 1.5inch). remove 10mm insulation.

Which ever terminal a conductor then has to goto, it will reach (either into the back of the closest two terminals to the entry, or in the front of the further two). No messing - easy.

 

[Hallsy]

Well, that's what I was doing, although I managed to put a hairline crack in the box. Should I discard this one? I could get my needle files out if I was being really anal!!