Installing floorbox, power and networking

[industryspark]

Got a job to do in an office at the weekend which involves installing a floorbox. The floorbox will have 2 double gang socket outlets installed in it and 4 x RJ45 network outlets. The floorbox is going to be an extension of the ring circuit and has got to come from a surface mount moulded socket on the wall about 4 metres away.

The office is a first floor building with joists covered by chipboards, the bottom chipboard being the roof of the ground floor. These chipboards can't be lifted so i have to feed a cable (parralel to the joists) from the surface socket to the floorbox along the void through small cutouts (one at floor box location and other by removing a section under the wall surface socket).

I dont want to have to just lay the twin and earth cables in the roof void and just grommetted into the floorbox so thought about steel flexible conduit. With this though i have the problem of how i connect the conduit at the surface socket end without it looking rubbish and being visible. How do others usually connect to floorboxes and has anybody had a similar problem before?

The cat 5 data cables are a similar predicament.

I want to avoid having to notch the chipboard for the 4 metres so i can clip to the joists.

Regards.

 

[Lectrician]

Just chuck it in!

 

[electronicsuk]

If you're worried about mechanical stress on the terminations in the floorbox then why not use compression glands on the incoming cables?

 

[plugwash]

is the existing surface socket plastic or metal and how is it wired already? conduit? trunking? surface clipped cable?

 

[industryspark]

Lol electrician, im tempted!

Not the mechanical stress im worried about really. The chipboard on the bottom of the void is the roof of the ground floor building-dont want anybody hanging any future light fittings screwing up into the cable. Id much rather it run in conduit or be clipped to the joist out of the way, likewise the data cables. There's plenty of thermal insulation down there aswell to make life more difficult.

I was always taught not to run cables in voids like this, am i being overly cautious?

 

[industryspark]

Plugwash

The existing socket is a surface white plastic moulded socket supplied via surface mini trunking containing twin and earth.

 

[ColJack]

get the SBC out and go for it...

if it's stuffed with insulation, how do you intend on getting the conduit down there?

couple of lenghts of solid plastic fed in through the floor box hole might be a better idea than flexi steel..

radiused bend on the socket end and swap the surface box for one with a conduit knockout...

 

[industryspark]

There is insulation in the void put i think a lot of it could be pushed out using a rod of some type, although i consede it wouldnt be easy.

Thats a good possible solution Coljack, its about as good as anything else ive though of. Its either that or chop a wide enough channel in the chipboard so i can get the twin and earth clipped direct to the joist.

So tempting to just lay the cable in there though!

 

[ColJack]

if there's insulation then try to fish the T+E over the top of it...
the likelyhood of screwing into the floor is less that someone mounting a new light in the ceiling below..

if you're going to try the conduit, might I recomend a bw20 SWA gland "boot" taped on the end... ..

 

[industryspark]

Just laying the cables in the void is definitelly the easiest option. Lets face it-the chance of it ever being screwed into or damaged is very slim indeed. Frustrates me sometimes thinking about some of the stuff ive seen done by people, and here i am going on about a 4 metre run of cable in a void!

Think ill go with just laying it onto the insulation and take the easy option for a change

 

[ColJack]

YOU CAN'T DO THAT!!! and I never said you should.... ( ahem... ) ...

 

[industryspark]

I know i shouldnt, save me a hell of a lot of hassle though........

''Its clipped to the joist guv, honest''

 

[oharaf]

I have had a similar problem in the past my solution (and it worked well)

Get some PVC capping, slide this over the top of the insulation (channel side up to the underneath of the floor.

Nice and flexible, plenty of tape on the front end edge to 'smooth' its progress.

Once inplace 'ram' the T&E along the channel or for the ladies use the cable rods.

Bobs your uncle fannies your aunt.

'Cable underfloor in insulation, touching' DONE!! as Ramsey would say

 

[kjacko]

Surely conduit is better not least for shielding the power away from the network cabling. I've seen a few installs like this where dubious fitters have just parallel trailed power and network cabling together (often cabled tied together) without any conduits or shielding at all.

Our guys use the metal flexible stuff (i think)

 

[industryspark]

Have settled on some PVC conduit secured to the joist at either end, one conduit for the data cables and one for the ring cables.

A steel beam runs between the points im going between which has made life harder-have had to drill holes in the beam to pass my conduit through.

When lifting the chip boards around the beam we had a bit of a suprise-on lifting them we could see underneath that we'd chopped through a twin and earth that was just run ontop of the steel guirder! Doh!

Thats the downstairs lighting needing repair then!

what idiot would run a cable ontop of the steel guirder directly under the chipboard. Ive yet to inspect and test the existing ring but im already having visions of interconnections, spurs on spurs ect.