Plastic Mounting Boxes - With or Without Earth Terminal?

[Mad_Doctor_X]

Hello!

I'm planning a ring circuit and was wondering if there any guidelines about when you need a earth terminal in a plastic mounting box. The plaster on the walls is too thin to take a 25 mm metal box so I was hoping to attach plastic boxes directly to the masonry and then make good. This should make the sockets a bit more tidy and secure than if I just surface mount them.

Cheers

 

[RF Lighting]

Normally flush boxes are knocked into the brickwork, not just plasterwork.

You should not be half flush mounting plastic boxes.

 

[JohnD]

if this is a plastered brick wall, it is more usual to chase out the brick and fit metal back-boxes. Put the cable CPC into the sockets, and link the socket to the back-box earth terminal with a 150mm piece of 2.5mm or larger G&Y.

If you have not sunk into brickwork before, you use a club hammer and an electricians bolster. You can outline the hole with a row of drill-holes round the perimeter if you like. If the hole is a loose fit, you can use sand and cement mortar to pack round the box. this will hold it steady. But you must use at least one screw into a plasplug drilled into the wall.

Take it slow and easy, avoid cracking the wall or the bricks. Just pencil an outline on the wall and work slowly round it with your bolster, giving one or two blows in each position as you work round.

If the house is empty of people and furniture, and you don't mind great clouds of gritty dust, you can hire various motorised tools to work faster.

edited: bah, too slow.

 

[GaryMo]

Put the cable CPC into the sockets, and link the socket to the back-box earth terminal with a 150mm piece of 2.5mm or larger G&Y.

I'm curious as to why you think a minimum conductor size of 2.5mm is needed to earth the metal backbox when in fact it's not needed at all if a fixed lug is present?

 

[shortcircuit48]

Mad Dr

Its sounds like you want to partially flush a surface mounting back box. Rarely seen it done, but there are no reasons why not.

You do not need to earth the plastic back box and if metal boxes are used, then, providing one lug is fixed, you do not need to earth it either

 

[JohnD]

I'm curious as to why you think a minimum conductor size of 2.5mm is needed to earth the metal backbox when in fact it's not needed at all if a fixed lug is present?

for when the screw falls out or goes rusty.

 

[RF Lighting]

if metal boxes are used, then, providing one lug is fixed, you do not need to earth it either

Yeah but it's a bit kack innit?

 

[GaryMo]

I'm curious as to why you think a minimum conductor size of 2.5mm is needed to earth the metal backbox when in fact it's not needed at all if a fixed lug is present?

for when the screw falls out or goes rusty.

So >2.5mm cable is needed for that?

But you agree that it's not needed at all don't you?

 

[333rocky333]

Put the cable CPC into the sockets, and link the socket to the back-box earth terminal with a 150mm piece of 2.5mm or larger G&Y.

I'm curious as to why you think a minimum conductor size of 2.5mm is needed to earth the metal backbox when in fact it's not needed at all if a fixed lug is present?

I too would like to know
I have done it always , but cannot find any reference to it now,
The same rule said 2.5 was the minimum phase conductor for any socket, which at the same time outlawed 1.5 PYRO which was the norm for socket rings then, the same rule said ALL three conductors had to be the same size if not WITHIN the cable, which prompted the 2.5 earth link.
I am sure it was not long after I done my 16th edition course.
All I can find now is the conduit fly lead and the one fixed lug answer.
I think the nic like you to do it though

 

[GaryMo]

I think the nic like you to do it though

In the Snags and Solutions book by the NICEIC they state you don't need to earth the backbox providing there's a fixed lug present.

 

[JohnD]

I sell 150mm lengths of 2.5mm G&Y for 50p each

 

[GaryMo]

I sell 150mm lengths of 2.5mm G&Y for 50p each

Ahhh, penny drops!

BTW, I always earth metal backboxes

 

[JohnD]

For people restoring period properties, I supply 6" lengths for a pound.

 

[shortcircuit48]

Is that 7/029 or 7/036 ???? and price in £sd please

 

[333rocky333]

In the Snags and Solutions book by the NICEIC they state you don't need to earth the backbox providing there's a fixed lug present.

This was discussed before and an nic man said they like to see it even though it is not written,everyone i know does It, and if I find a socket without I will do that also.
AND NO before you ask ,do your own