underground junction box

[jim23]

Got some lights to wire in a garden. Plan is to run an swa underground to each point and then use a flex up to each fitting, as the fittings will only accept flex and not swa.

Looking at 8 fittings so at some points an incoming and outgoing swa will be present , as well as the flex. It is desired to keep the junctions out of sight so bringing the swa's out of the ground into a local jb is not wanted.

Im sure ive seen some maintenance free junction boxes that can be buried and filled with a gel/resin, thus allolwing burial of swa and flex. Anyone come across such a beast or have i dreamt it?

Cheers

 

[flameport]

Resin filled underground joints exist.

However as flex isn't suitable for burying in the ground, your idea isn't going to happen.

 

[jim23]

Im aware flew isnt suitable for burying but in the situation i have i could probably get round it. The lights are to be mounted on wooden sleepers sunk into the ground. The idea was to fit an underground jb to the base of the sleepers and flex up the sleeper into the fitting. The flex would then only be 'buried' for 600mm and vertically straight up with the sleeper. Could even give some mechanical protection to the flex if need be. Could use hituf flex. Still pushing the boundaries a little maybe?

 

[ban-all-sheds]

What sort of cable entries do the lights have?

Are they sold to be installed as you plan, i.e. directly onto a ground-level surface with the cables underground? If so, what do the makers say about how they can be cabled in a way which complies with the Wiring Regulations?

 

[jim23]

Fittings are designed to be installed at or near ground level yes BAS. The cable entry is a 'diaphram' seal inside on overall enclosure. Believe it or not the literature instructs the use of silicon to seal the outer enclosure. Fittings are IP44. No mention of wiring methods in literature but fitting 2 x swa's into the fitting isnt possible.

Im aware that this install is difficult in terms of assurring compliance with bs7671 but i started the thread to discuss ways of making it compliant and to see if it could be done, or if anyone had previous experience of such jb's ect.

Cheers.

 

[ban-all-sheds]

Believe it or not the literature instructs the use of silicon to seal the outer enclosure.

Oh I can believe it.

Fittings are IP44. No mention of wiring methods in literature but fitting 2 x swa's into the fitting isnt possible.

What about one SWA cable?

Im aware that this install is difficult in terms of assurring compliance with bs7671

IMO a light which cannot be installed in a way which complies with BS 7671 is not fit for purpose, and anybody selling them should be prosecuted.

but i started the thread to discuss ways of making it compliant and to see if it could be done, or if anyone had previous experience of such jb's ect.

Hence my Q about cable entries - is there no way that a 20mm gland can be fitted?

 

[bernardgreen]

You could use a trouser box with the SWA into the legs and the "flex" from the top.

 

[ban-all-sheds]

I've seen that photo before...

It's got 3 SWA glands...

 

[RF Lighting]

Isn't that a Y box? I thought a trouser box didn't have the left hand entry as you look at the photo?

 

[jim23]

BAS

no way even one swa gland could be fitted into the lights. As with a lot of these fittings today, not much thought has gone into the installation. I agree with you that some lights on sale today seem barelly 'legal' but the fittings have been purchased already (not by me).

Regarding the trouser boxes, surelly these arent suitable for burying? Im sure ive seen some underground jb's similar to these though that are resin filled. I would have to have a box/jb that accepted 2x cw swa glands and a stuffing gland for the flex.

Cheers

 

[bernardgreen]

Regarding the trouser boxes, surelly these arent suitable for burying?

They are not intended to be buried but be just above ground where they are

ACCESSIBLE

Im sure ive seen some underground jb's similar to these though that are resin filled.

Resin filled is good for underground non accessible boxes, but a real pig if you damage a cable and need to change one or more of the cables going into the box. The cable from the buried box gets nibbled by a rodent, dog or otherwise damaged and you have to dig down to the box, laying on the wet ground head first down into the hole chipping away at the resin and so on.

 

[sparkwright]

Isn't that a Y box? I thought a trouser box didn't have the left hand entry as you look at the photo?

That's a U box.

A trouser box is the same as a Y box as far as I know.

 

[sparkwright]

It isn't recommended to bury the conduit box.

You could fix the conduit box onto the sleeper above ground level. You could also fix the box to a separate stake driven into the ground.

Be sure to use waterproof swa glands, and don't strip to much outer sheath from the armour as when you tighten the weatherproof gland the armour will be exposed.

On the other hand make sure you strip enough sheath so the armour is in contact with the gland, as the armour must be earthed.

Make sure a 4 mm screw is inserted in the hole in the back of the box to prevent water getting in, particularly if you don't fix the box to anything.

Use a gasket between the box and the lid.

If possible, try to avoid cable entries at the top of the box as water may find a way in.

Keep the flexes on the lights fairly short.

 

[ban-all-sheds]

I hope the lights were really expensive, or this solution will not look good in comparison...

3-way underground Pratley boxes.

People say they leak, but the makers say otherwise. No harm in filling them with Magic Gel though.

Circuit SWA in and out, and SWA out to the light, but not glanded into it - just take it in as if it were normal cable. True the armour will only be earthed at one end, but it will be earthed, and it will be armour, so the best of a bad job, really. I'd rather have armour earthed at one end than no armour at all.

 

[holmslaw]

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