Puzzling installation

Dartlec · Apr 20, 2021

timhoward said:
I knew I'd read of this before once.

https://electriciansforums.co.uk/forums/forum/messageview.cfm?catid=205&threadid=46047
Some interesting comments about the span between metal conduit and the earliest PVC, apparently the cpc's were sometimes connected to the conduit using a threaded earth coupling.
1957 is suggested.

That links not working for me for some reason - what's the thread title?

Sounds about right - I guess it's better than it being VIR... And too early for green goo too...

timhoward · Apr 20, 2021

Dartlec said:
That links not working for me for some reason - what's the thread title?

Sounds about right - I guess it's better than it being VIR... And too early for green goo too...

It doesn't let me link to IET forum:

[ElectriciansForums.net] Puzzling installation

Grant1987 · Apr 20, 2021

Dartlec said:
That links not working for me for some reason - what's the thread title?

Sounds about right - I guess it's better than it being VIR... And too early for green goo too...

Yea I can’t open the link but I understand what you’re trying to display by the wording. I’ve come across a few older installs which were wired in singles and earthed through the conduits. Was great when I was rewiring them. Tied on and pulled through new pvc twin and earth and got paid per property these properties with conduits earned me mega £££ and the boys I worked with enjoyed the ? when we finished early ???

Dartlec · Apr 20, 2021

timhoward said:
It doesn't let me link to IET forum:
View attachment 84908
View attachment 84909

Ah yes, I'd forgotten that certain other forums are blocked, however sneakily you try to list them....

The house is older than that, but may well have been rewired from the original conduit installation - though no surface signs left of conduit - it might be hidden behind the skirting board I guess....

But that begs the question as to where the conduit is earthed - the Zs is too low for it to be acting as a rod, and possibly even too low for it to be directly using any pipes - but the main bonding may be increasing that.

The water main bonding wasn't visually available, just to add to the fun, though verified by testing...

Dartlec · Apr 20, 2021

If it is late 50s wiring then it goes to show how good comparatively PVC is since there was very little sign of 'aging'

What did the 13th say about RFC cpcs I wonder?

If this is run from a 'genuine' source, rather than via extraneous bonding, then can a single suitable sized earth at each point be considered safe for fault protection on an RFC? and if so what is that size?

Dropping it to a 20A radial would not be a major problem to be honest - it's 7 sockets in total - and the whole property is on a 60A fuse in any case...

loz2754 · Apr 20, 2021

You can use a URL shortener to post a link if you want. I've done it before and it worked.

timhoward · Apr 20, 2021

loz2754 said:
You can use a URL shortener to post a link if you want. I've done it before and it worked.

Of course! Thanks!

Here we are...

IET EngX

tinyurl.com

loz2754 · Apr 20, 2021

timhoward said:
Of course! Thanks!

Here we are...

IET EngX

tinyurl.com

Interesting thread. Thanks.

timhoward · Apr 21, 2021

Dartlec said:
If this is run from a 'genuine' source, rather than via extraneous bonding, then can a single suitable sized earth at each point be considered safe for fault protection on an RFC? and if so what is that size?

Taking your max Zs of 0.38, so fault current of 605 amps, I think I'm ending up with 3mm csa using adiabatic. I believe you said somewhere between 2.5 and 4mm.
I'm also reflecting there should be a way to tell the equation you've had 3 cans of 1664 though, so you'd better check my maths....

telectrix · Apr 21, 2021

timhoward said:
Taking your max Zs of 0.38, so fault current of 605 amps, I think I'm ending up with 3mm csa using adiabatic. I believe you said somewhere between 2.5 and 4mm.
I'm also reflecting there should be a way to tell the equation you've had 3 cans of 1664 though, so you'd better check my maths....

like your style. 1664 is 1 of the few available lagers that are drinkable.