External lighting with conduit.

[Lectrician]

We use a rubber sealing washer never had one leak yet.

You mean you have never been back or never had a fuse blow!

Even with the gaskets water is going to ingress into the conduit.

I prefer to use 4x4x2 or the next size down of "Gewiss" box or equivelent make. Conduit entry left and right and flex from the bottom via a TRS gland.

What light fittings are you using? It hugely depends on the fittings as to how the final connection would be made.

 

[IJWS15]

This parallels something I need ot do and had been thinking about expansion - how do you deal with it?

 

[holmslaw]

..

 

[ColJack]

use expansion couplers..
or only glue one side of a coupler and don't push the other side in tight.. ( little bit of grease / vaseline keeps it sealed and stops it sticking.. )

 

[Lectrician]

Use the correct expansion couplers if the run is excessive.

These have a short side for gluing to the conduit (like half a standard coupler) and then a longer side which is slighty oversized to allow the conduit to move in and out. To keep the conduit system water tight you should use jelly on the expansion side....

http://www.marshall-tufflex.com/shop/product.php/1660/expansion_coupling___20mm

 

[ColJack]

rasberry or strawberry?

 

[ricewind]

all this advice and end of day if you you use steel or plastic at some point,
you will get water penetrating into the system, why not tell them to go and use 1.5mm 3 core MICC sheathed cable this way you get all of the factors which you are talking about cut straight out expect:-
1. water will still enter in the conduit boxes,
2. MICC much costly them the other two options.
3 It will still sag between clips.

plus for Plastic conduit are :-
1 cost effective
2, easy to install
3 want rusts
4 easy to bend.
5 no need to run extra CPC through and bond every box.


let the lad be and let fit plastic.

 

[RF Lighting]

you will get water penetrating into the system,

Not if it's sealed properly

why not tell them to go and use 1.5mm 3 core MICC sheathed cable this way you get all of the factors which you are talking about cut straight out expect:-

MICC seems a bit overkill, and you average DIYer will not be able to buy it and will not have the tools, test equipment or the knowledge to terminate it

1. water will still enter in the conduit boxes,

Not if they're sealed properly.

2. MICC much costly them the other two options.

Yep

3 It will still sag between clips.

Not if you use the spacings recommended by the manufacturers.

plus for Plastic conduit are :- ............ 5 no need to run extra CPC through and bond every box.

I don't understand. You don't have to run any more CPCs with steel than you would with PVC.

 

[SparkyFromTheValley]

theres also conduit glue which will seal any joins between conduit and connectors