Garden Lighting - filling junction box with resin/gel?

[Nigel Watts]

Two electricians and I spent the best part of the day today working on repairing our garden lighting system.

The system comprises four separate circuits. Four 240 volt reinforced cables extend from a central box (remotely controlled) to different parts of the garden, connect to buried transformers which in turn connect to 12 volt cables ending in spike lights (moveable spot lights in the flower beds) and wall lights. The system is about 9 years old and has been out of action for the last three. The final straw was when the scaffolders smashed the main box last year.

One light was found to be incapable of being fixed but three of the four circuits now work. A key problem was that water had got into a buried junction box on one of the 240 volt circuits. The box was nearly eighteen inches deep and under the roots of a nine foot tall hornbeam. I nevertheless managed to extract it (my fingers are now so sore I can barely type this) and the electricians cleaned it out and got it working. They suggested that before burying it again I could fill the junction box either with resin or with some kind of gel. Encasing the connectors inside the box in this way would, they said, greatly increase the water resistance, but the resin option would be irreversible. Is this good practice and should I follow their advice?

 

[Zebra]

Yes. Excellent stuff that, you pour it in and it solidifies around the connections, protecting them from further water ingress even if the junction box leaks.

 

[Feltwell]

That's pretty much the process the electricity companies use when joining supply cables underground. They form a physical joint, put a hinged plastic mould round it and pour a resin in to seal the whole thing. The mould remains but doesn't actually serve any purpose once the resin has gone off.

 

[Flyfisher]

Also, I wouldn't be too concerned about such joints being irreversible. It's rare that such joints would ever want to be undone, but even if that were the case it would be quite easy to cut out the joint and make new ones. There's really no other practical way to repair broken cables anyway.

 

[Penners]

Years ago we had a complete failure of the underground power supply to our house (on Christmas Eve - of course!). The electrical engineers traced it with a sensing wossname (stop me if I'm getting too technical) and then dug up our drive. They fixed the breakage in the way you describe - used a big junction block, encased it in a plastic "torpedo" and then filled this with some sort of foaming gunge, which hardened. They finished at about 3.00am on Christmas morning - Gawd bless 'em!

 

[markm]

Resin encapsulated joints are very useful. Under 16th Ed (I haven’t done my 17th), they could be used under floor boards, along with brazed and crimped joints (all of course enclosed in a CE or BS marked non combustible container).