Something missing here...?

[sparkinlee]

Got called out to a tripped RCD yesterday, opened up the consumer unit and...



What, no CPCs anywhere, in any circuit?!

Closer inspection revealed that the whole house is built with singles in metal conduit providing the earthing, and Zs readings are satisfactory, but still a bit of a surprise when I first opened the CU - I expect others have seen this before, but a first for me.

But I have a couple of questions about a socket I need to replace. I found a brass fronted socket where the guts of the socket was not securely fixed to the front plate, and as the earth connection is via the mounting screws and the front plate, the plug earth pin was not getting a good connection. The socket was mounted into its back box using thicker screws than current M3.5 socket screws, so that I cannot use M3.5 screws, and the thicker screws are too thick for the M3.5 holes in new sockets. So:
- any suggestions for how to fix a new socket onto the existing back box (which I do not want to replace as it's a conduit box built into the wall)
- any suggestions for getting a decent earth connection off the back box, which does not have an earth terminal in the back of it (this may depend I guess on the answer to the first question)?

Ideas welcome...

 

[Knobhead]

The socket screws will be 4BA. As to bending the box lugs you’re more likely to break them. There is an easy but not cheap way around the screw problem that is to heli-coil the holes.

 

[telectrix]

more room on that CU than we can ever expect in a modern unit and only 6 circuits. still the installer has managed to make a right mess-- looks like a demented rat has been making a nest.

 

[sparkinlee]

A quick update in case you're interested...

Fixed the socket discussed above this morning - tapped holes in the back of the box and long M3.5s worked a treat, so thanks for the suggestion. Only light hiccup was that the spacing between the fixing holes was different in the new socket plate, so had to knock off one of the original lugs, and the screws are slightly angled, but no real problem as I had to use 75mm screws anyway!