Weatherproofing an outdoor socket outlet cable entry

[kwikfix328]

I am going to add an outdoor socket outlet to the wall of my wooden shed. The socket outlet will be at the end of a short ( approx 2 metre max ) radial circuit of 4mm T&E protected by a 20A MCB and 30mA RCD.

The socket outlet assy is rated at IP55. I have a waterproof 20mm Glandseal that i can use for cable entry to the socket enclosure. I was going to do it so that the socket outlet enclosure is screwed to the wall in the normal manner, i was going to run a bead of exterior silicon sealant around the top and sides of the enclosure and leave the bottom open ( to allow any drainage and a bit of air circulation).

As the enclosue will be hard up against the wall I was going to use a plastic waterproof gland to seal the cable entry on the rear face of the enclosure. Due to the thickness of the wall (approx 12mm ) i would imagine that some of the gland seal assy will be inside and some outside, in this way non of the cable will actually be exposed outside of the building.

The glad seals the cable by compressing a rubber seal around the cable as a lock nut is tightened.

My main question is:
Is it OK to use T&E cable with these types of compression seals, they seem more suited to round section cables than oval shaped ?

 

[ban-all-sheds]

1) 4mm² is bigger than needed for a 2m 20A radial - 2.5mm² will be fine.

2) Instead of entering the rear, why not go in through the bottom? Angle the hole through the wall downwards as it goes out, and take the cable down and then bending up to form a drip loop and water won't get in. (you should really use something other that T/E though.)

With no hole in the back of the socket you won't need silicone around it, but you can use some around the cable where it goes through the wall to stop draughts.

3) You can get compression glands with inserts suitable for T/E,

but as I said you should ideally use a different cable type anyway.