Galv. steel loop in boxes - fixing & earth connection

[pw1123]

Afternoon all.

Looking at surface mounting a loop in box which will in turn have a dome/spout cover installed to route lighting circuit out of a wall (existing wall light location).

One thing that is unclear to me, apologies if this is a super rookie question, but how would you fix this to the wall? The only holes in the rear of the boxes I'm seeing are the 20mm cable entry and typically an M4 threaded hole for earthing.

Also, with the earth connection, what length of screw would you normally use? It only needs to firmly hold a crimp lug in place...

Appreciate any comments you may have.

 

[sparkwright]

Sounds like the box with a 20mm hole in the back is a pot box.

You can drill some fixing holes into the back to fix it to the wall.

Typically one would get a 4mm brass screw, and cut it down to about 5mm length to fix to the earth terminal.

 

[securespark]

https://www.tlc-direct.co.uk/Products/MS4slash6.html

 

[pw1123]

https://www.tlc-direct.co.uk/Products/MS4slash6.html

Many thanks.

For fixing the loop in box I'm wondering if it might just be a case of drilling the fixing holes myself...

 

[securespark]

Absolutely, yes.

I usually drill a couple of 5mm holes in a diagonal to the boxes fixing holes.

 

[333rocky333]

I thought loop in boxes had a curved back edge and would not fit flat to a wall.
can you not screw the domelid straight to the wall.

A bit harder to earth but you can get these, or thinner ones
https://www.electrical2go.co.uk/20mm-galvanised-conduit-extension-ring-10-pack.html

 

[pw1123]

I thought loop in boxes had a curved back edge and would not fit flat to a wall.
can you not screw the domelid straight to the wall.

A bit harder to earth but you can get these, or thinner ones
https://www.electrical2go.co.uk/20mm-galvanised-conduit-extension-ring-10-pack.html

The loop in boxes I've looked at have been flat based - essentially conduit boxes without any apertures in the side walls but one in the base to use as rear cable entry. I could put the dome lid direct to the wall but may need to step it out a bit as from that I'm taking a bend to a threaded lampholder.

The extension ring could be a sound alternative though provided there's enough depth to house the electrical connections....I could tap the fixing tab for earthing.

 

[333rocky333]

It must vary with makers then, a lot of them now are pressed steel, whereas you may have the old style cast ones.
The extension rings are the same, theres nice ones and others with an ugly seam down the side.
.
Would like to see a pic of your fitting when complete.

 

[pw1123]

I'll try and remember to stick some photos up

 

[Echo the husky]

What is the purpose of the pressed steel boxes? Useless trash!