Backbox size for USB socket plate

[VickyBH]

Hi,
Anyone know if it’s ok to fit sockets with USB ports into a 20mm backbox when the installation instruction says backbox should be 30mm.

I am supplying my own socket plates for partial rewire and noticed 20mm backboxes were installed in the wall. Electrician says it’ll be fine, is it true? Thanks.

 

[flameport]

Box depths are normally 25mm or 35mm.
If the instructions require one thing and you have something less, then problems are inevitable.

Some USB outlets will fit into 25mm boxes - plenty will not.
Even for those that do, 25mm is likely to be difficult and require very careful placement of the cables.

 

[AndyPRK]

The likely hood is that they won’t fit!!

You can get usb sockets for 25mm boxes if you look in screwfix.

Maybe not meet fancy requirements though!

 

[EFLImpudence]

How far below the finished surface are the back boxes?

 

[VickyBH]

Ah, you guys are right, the boxes are 25mm, so only 5mm short from the instruction requirement.

Most backboxes are 3-5mm below surfaces but several are flush with wall. If I remove the 25mm box, chased it a bit deeper so that it's at least 30mm from surface, will it be ok then? Getting him out again will cost another £200+ I think.

 

[AndyPRK]

There is probably a good reason why they have fitted 25mm !

You could have a go if you want though and see.

 

[boringoldcodger]

Just a suggestion, could you use a spacer such as:
https://cpc.farnell.com/bg/817/pattress-box-1g-10mm-spacer/dp/PL08924

It's supplying 10mm when you're after 5 (but it might be all we can find).
I'm sure other suppliers are available.

 

[seasickstevie]

There is probably a good reason why they have fitted 25mm !

I'm trying to think of one.

 

[AndyPRK]

Well in modern houses 25mm and they will sit up against breeze block

 

[donrkebab]

There is probably a good reason why they have fitted 25mm

Because it's easier than fitting a 35mm.