metal conduit damaged - advice please

[martmax]

some info up front: keen DIY'er, got usual tools and basic electric multimeter, knowledge of basic electrics and a little experience

been redecorating my late mum's house to prepare it for sale; house built late 60's; went to change worn faceplates of 2 single power sockets on living room wall, thought it would be a simple 5min job;

1st socket noticed the backbox was loose and it came out by hand; a twin and earth cable comes out of a solid metal tube (which runs vertically up the wall, buried in plaster); the end of this metal tube looks damaged

2nd socket - the backbox had one of the screwholders sheered off so thought this backbox should be replaced. however this box was extremely resistant to come out being mechanically attached to the solid metal conduit, which also got damaged as I used a chisel to pry open the flanged bits gripping onto the metal box (stupid design - how did they expect people to replace backboxes if they get damaged ?)

both sockets are fed by a twin and earth cable exiting the conduit; there was no earth cable attached to the backboxes at all;

I can't be sure whether or not the conduit is acting as a cpc and if I need to repair the conduit somehow (how???) to attach it to the new back boxes or if there's an easier solution that still complies with regulations ?

thanks in advance

 

[rebuke]

If you attach some pictures of the conduit etc, then it will be much easier to determine what's going on...

 

[Chri5]

Remember that the earth in the socket connects to the face plate screw.

Since the faceplate screw screw on the back box lugs, then there is an earth to the conduit via this tenious route.

Best bet and general good 'code' is to have an earth strap between the back box earth terminal and the socket earth where the cable CPC terminates.

If it was a floating lug thats lost it's thread you could simply remove one from a good back box and retro fit in the old back box.

 

[ColJack]

alright, we heard you the first time...

 

[Chri5]

Odd one. I edited the original post and the site multiplied it x 2.

Site has been a bit flaky, as in screen loads not happening and back button use required.

I assure you I didn't post x 2

Mod informed to remove duplicate post

 

[martmax]

thanks for the responses

here's a pic:
View media item 13249
it's a twin and earth coming out of a rock solid metal pipe (steel ?) with 2 tags (?) on it that I've bent down with some difficulty in order to be able to pull out the backbox

the backbox screw lugs, one of them was completely sheared off, can't see any way to reattach a lug without welding equipment, would rather put a new backbox in but am wondering if I need to earth the conduit ?

thanks

 

[flameport]

The conduit should be earthed, but there is no way to correctly attach anything to the end of that without causing serious damage and destruction to the wall.
Depending on what that 'conduit' actually is, it might not be possible to attach anything to it.

The cpc should be the wire in the T+E.
Using the multimeter on continuity, is there any reading between the metal conduit and the earth wire in the cable?

 

[ColJack]

as there is a cpc in the cable, there is no requirement to earth the conduit, it's there strictly for mechanical protection now ( or so you can easily rewire ) ..

you've got those "dust and spit" blocks making up that wall.. you can cut it with a fingernail...

 

[martmax]

ok thanks

I'll report back on what the earth continuity is later today

it's probably pure coincidence but after I removed those sockets and turned leccy back on (sockets and wires secured of course), our Centroller 3000 central heating control unit went up the swanny constantly buzzing (relays probably) and totally unresponsive;

 

[SUNRAY]

The conduit should be earthed, but there is no way to correctly attach anything to the end of that without causing serious damage and destruction to the wall.
Depending on what that 'conduit' actually is, it might not be possible to attach anything to it.

The cpc should be the wire in the T+E.
Using the multimeter on continuity, is there any reading between the metal conduit and the earth wire in the cable?

Remember to check for voltage between conduit and CPC before continuity to save damage to the meter

 

[martmax]

didn't think about checking for voltage between conduit and cpc

I tested for continuity and it's open circuit so I'm assuming the conduit isn't earthed, this was tested while the fuse box was off so there wouldn't be any voltages present

since there is no way I can envisage cutting off the end of the steel conduit, and because I do not want to lower the new socket (part m?), or offset it left or right (because vertical runs are supposed to be directly in line with the socket ?) I take it's ok to slip the end of the conduit into the new backbox and leave it be ?