PVC Conduit sizing

[SS9]

I'm currently planning out some improvements to my garage lighting and sockets. I planned to do it in 25mm pvc conduit with singles to make it easier to pull cables and for future upgrades. I can't for the life of me find any good 1-gang/2-gang steel surface mounted backboxes with 25mm knockouts. I don't really want to use reducers everywhere and worry drilling out the knockouts to 25mm is just going to be messy and throw up complications.

Has anyone solved this?

[MajorMantra]

I don't know the answer but following as I'm planning something similar and haven't yet worked out the details.

[119]

SS9 said:

I'm currently planning out some improvements to my garage lighting and sockets. I planned to do it in 25mm pvc conduit with singles to make it easier to pull cables and for future upgrades. I can't for the life of me find any good 1-gang/2-gang steel surface mounted backboxes with 25mm knockouts. I don't really want to use reducers everywhere and worry drilling out the knockouts to 25mm is just going to be messy and throw up complications.

Has anyone solved this?

The reason you cant find then, is because the 25mm conduit is the same depth as the back box so the nut fixing the bush thing would stick out too far for the socket to go back in the box.

If you are using singles, i would think 20mm would be plenty big enough!

[Belle427]

There shouldnt be a need to go 25 with singles but if you choose to you can reduce the final drops to sockets etc to 20 with an adapter.

[4Q]

119 said:

The reason you cant find then, is because the 25mm conduit is the same depth as the back box so the nut fixing the bush thing would stick out too far for the socket to go back in the box.

If using surface mount metal clad back boxes, which I would in a garage, they’re usually between 35-45mm deep.

[119]

4Q said:

119 said:

The reason you cant find then, is because the 25mm conduit is the same depth as the back box so the nut fixing the bush thing would stick out too far for the socket to go back in the box.

If using surface mount metal clad back boxes, which I would in a garage, they’re usually between 35-45mm deep.

Oh I didnt know that!

All mine are plastic.

[megaphone]

20mm tube will be fine with singles. If you do want to open up the metalclad boxes to 25mm, use a step cutter.

[SS9]

Thanks folks, I’ll stick with 20mm. I’m doing separate lighting and socket runs so I’m probably over thinking it with 25.

[JoshSm]

Depends on your layout but a dado trunking with the sockets put wherever might work better instead of plain surface mount + conduit. Lots to choose from and not too bulky, and easy to change socket layouts.

https://www.tlc-direct.co.uk/Main_Index/Trunking_P... for example.

[DorsetSparky]

25mm conduit is probably overkill; I'd use 20mm.
Regardless, MK Grid Plus metal clad have a combination of 20mm and 25mm knockouts if I recall.