Can I use metal socket with dry lining knockout box?

[Mr Sparkle]

I'm looking to replace my existing plastic sockets with some metal ones.

However, my walls are of plasterboard construction and thus I have drylining knockout boxes throughout.

Question, is it okay/safe to use metal sockets with drylining knockout boxes?

Or is it mandatory to replace the the drylining boxes with metal ones, then earth the backbox to the socket?

Per my understanding and from watching a JW vid many moons ago earthing the back box is good practice but not compulsory

Have I got this right?

 

[RandomGrinch]

Question, is it okay/safe to use metal sockets with drylining knockout boxes?

Yes!

 

[plugwash]

Question, is it okay/safe to use metal sockets with drylining knockout boxes?

That's fine.

Metal accessories need to be earthed. It's always good practice to check the earthing when doing electrical work, but you should be particularly careful with light switches. Lighting circuits were supposed to be earthed since sometime in the late 1960s, but what is supposed to happen isn't what always happens.

Per my understanding and from watching a JW vid many moons ago earthing the back box is good practice but not compulsory

As I understand it.

"Exposed-conductive parts" need to be earthed, where "Exposed-conductive part" is defined as

Exposed-conductive part: Conductive part of equipment which can be touched and which is not normally live, but
which can become live when basic insulation fails

If a backbox is not made of conductive material it is not an Exposed-conductive part and does not need to be earthed.

If a backbox is made of metal and exposed to touch then it needs to be earthed. Backboxes burried in the wall are more questionable. By a literal interpretation of the regulation you could argue that they are not exposed conductive parts because they are not exposed. However, it is still generaly considered that they should be earthed, because masonry cannot be relied on to be a good insulator.

If the back box has at least one fixed lug (most backboxes have one fixed lug and one floating lug) and the accessory screwholes are electrically connected to the accessory earth terminal (if the accesory has an earth terminal, the screwholes are usually connected to it) then it is normally deemed adequate for the back box to be earthed via the mounting screws. Some electrians like to fit a flylead anyway but there is no compulsion to do so.

Note that the reverse is not true. The regulations explicitly require an earth flylead where conduit/trunking is used as the earth path, and while they don't explicitly prohibit earthing the accessory via it's fixing screws in other scenarios the implication is pretty clear.

 

[Mr Sparkle]

@RandomGrinch thank you.

That's fine.

Metal accessories need to be earthed. It's always good practice to check the earthing when doing electrical work, but you should be particularly careful with light switches. Lighting circuits were supposed to be earthed since sometime in the late 1960s, but what is supposed to happen isn't what always happens.


As I understand it.

"Exposed-conductive parts" need to be earthed, where "Exposed-conductive part" is defined as



If a backbox is not made of conductive material it is not an Exposed-conductive part and does not need to be earthed.

If a backbox is made of metal and exposed to touch then it needs to be earthed. Backboxes burried in the wall are more questionable. By a literal interpretation of the regulation you could argue that they are not exposed conductive parts because they are not exposed. However, it is still generaly considered that they should be earthed, because masonry cannot be relied on to be a good insulator.

If the back box has at least one fixed lug (most backboxes have one fixed lug and one floating lug) and the accessory screwholes are electrically connected to the accessory earth terminal (if the accesory has an earth terminal, the screwholes are usually connected to it) then it is normally deemed adequate for the back box to be earthed via the mounting screws. Some electrians like to fit a flylead anyway but there is no compulsion to do so.

Note that the reverse is not true. The regulations explicitly require an earth flylead where conduit/trunking is used as the earth path, and while they don't explicitly prohibit earthing the accessory via it's fixing screws in other scenarios the implication is pretty clear.

That's brilliant! Thanks for the explanation.

 

[SUNRAY]

That's fine.

Metal accessories need to be earthed. It's always good practice to check the earthing when doing electrical work, but you should be particularly careful with light switches. Lighting circuits were supposed to be earthed since sometime in the late 1960s, but what is supposed to happen isn't what always happens.


As I understand it.

"Exposed-conductive parts" need to be earthed, where "Exposed-conductive part" is defined as



If a backbox is not made of conductive material it is not an Exposed-conductive part and does not need to be earthed.

If a backbox is made of metal and exposed to touch then it needs to be earthed. Backboxes burried in the wall are more questionable. By a literal interpretation of the regulation you could argue that they are not exposed conductive parts because they are not exposed. However, it is still generaly considered that they should be earthed, because masonry cannot be relied on to be a good insulator.

If the back box has at least one fixed lug (most backboxes have one fixed lug and one floating lug) and the accessory screwholes are electrically connected to the accessory earth terminal (if the accesory has an earth terminal, the screwholes are usually connected to it) then it is normally deemed adequate for the back box to be earthed via the mounting screws. Some electrians like to fit a flylead anyway but there is no compulsion to do so.

Note that the reverse is not true. The regulations explicitly require an earth flylead where conduit/trunking is used as the earth path, and while they don't explicitly prohibit earthing the accessory via it's fixing screws in other scenarios the implication is pretty clear.

I don't rely on the fixing screw(s) as I've found one or two where the screw hasn't made contact/got dirty or rusty/broken through the laquer etc