No socket back box

[mjb]

I think I know the answer here, and it is fairly easily remedied - but it made me wonder.

In replacing some double sockets, it appears two of them have no metal back box. There is room for a box and in fact it appears they were originally present but have been removed. I think this was to make it easier to fit slightly bulky new sockets to these two positions. The sockets are attached by wood screws which go into wooden studs behind the opening. They are otherwise neatly fitted, with tidy wiring and sleeved earth etc.

It won't be difficult to replace these - which is of course what we will do. What I am wondering is - with plastic MK double sockets - what is the effect of not having an (earthed) back box? Presumably the fixing screws are at theoretical risk of becoming live? Any other possible dangers?

[David Hansen]

On 26 Feb 2006 00:28:33 -0800 someone who may be "mjb" wrote this:-

What is the wall made of?

The box is there partly to provide a non-flammable enclosure for the live parts.

[Stephen Dawson]

??? how does that make sense when uing a plastic box?

[David Hansen]

On Sun, 26 Feb 2006 12:40:11 GMT someone who may be "Stephen Dawson" wrote this:-

The cover of a typical consumer unit is made out of plastic too. Not all plastics are the same and the ones selected for electrical equipment are selected specifically for characteristics that include zero or low flammability.

[Derek ^]

It's a very old requirement going back to the days of rubber insulated cables and scruit connectors when I *think* the requirement was for an earthed metal or hardwood (oak) box. Presumably oak had sufficiently low flammability.

DG

[Lobster]

But that would be no different if you were to use a plastic back box, of the type commonly used in stud partitions...

David

[Andy Burns]

I think because oak chars rather than burns it is practically self-extinguishing, how well that applies to thinner pieces I don't know.

[meow2222]

if your wall is non conductive and non flammable, eg breeze, I dont think you'd gain anything by adding pattresses. Fixing screws are earthed by metal strapping on the sockets, though not always. The pattress just makes sure theres a non-flam barrier there, and makes sure the scerws are earthed.

NT