Puzzling installation

I do seem to pick only the weirdest properties to inspect...

Victorian terraced house today - with up front RCD to a Wylex fuse board and main bonding all in place to current standards....

No cpc on lighting, but all pendants and plastic switches - so far so fairly standard.

Then remove the CU cover and find this:



I'm guessing somewhere originally early 60s given the lack of cpc and tinned stranded connectors?

With 2 main issues:

1. Kitchen feed run from CU (30A 3036) in 6mm T&E (probably to an old cooker feed) - and then kitchen sockets run post 2005 in 2.5mm twin and earth.

At first I thought it was a lollipop arrangement, but not even that when testing at the sockets (No ring in sight)

Even so, that can be sorted for now with a drop to a 20A plug in MCB - not ideal for a kitchen with oven, but it's only doing 2 double sockets and a dishwasher in addition....

2. The rest of the sockets (only 1 in most rooms, with 2 in master bedroom) though are run in what I guess would be called "Twin" from another 30A 3036 - 2.5mm (imperial equivalent) with no earth. Perfect continuity of live conductors and when checking at the (very few) sockets - each one has a separate earth run to it, in bare twisted tinned copper imperial somewhere between 2.5mm and 4mm from eye.

Zs is fine at each socket, but the earths do not appear to run from the CU, so not possible to do R1&R2 at each socket. R1&RN fine at each socket though.

A RFC would have 2 x 1.5mm CPCs at each point - this has something akin to that at each point in a single conductor, with unknown source, but zs tests suggest adequate to deal with the short fault currents liable to occur before the RCD cuts in.

So do this count as a C2 for not having cpc continuity on a RFC - or is not technically a RFC but a hybrid that is non-ideal but safe? or in need of downrating to a radial to be safe for continued use? Or a C2 regardless of the OPCD?

How would you code that little lot?

Clearly the place needs rewiring sooner rather than later, but in terms of an EICR it ticks most of the boxes that older properties usually fail on...

RCBO board would fit nicely in the cupboard, replacing the up front RCD with an isolator switch, but not entirely happy reconnecting wiring with no CPC to a 'new' install - and I don't really want to do the rewiring job (it's not that local).

Baffling! someone has gone to the trouble of replacing the meter tails though - Brown and Blue (Not 60's)!

Probably C3 as there is evidence of some sort of earth connection as you've managed to get a Zs reading at the socket outlets, otherwise C2

DefyG said:

Baffling! someone has gone to the trouble of replacing the meter tails though - Brown and Blue (Not 60's)!

Probably C3 as there is evidence of some sort of earth connection as you've managed to get a Zs reading at the socket outlets, otherwise C2

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Was there ever a period when 2.5mm equivalent 'twin' pvc without earth would have been used in domestic? I'd have thought by the time PVC came in (post 50s VIR?) that earths on sockets were very much a requirement already?

No idea where the earths run to/from though, it certainly wasn't visible in the meter cupboard, which had an RCD installed and meter tails upgraded, along with main earth and bonding, at some point...

Seems to have been done properly too (though no date visible on the installation sticker). Meter was changed 2015ish it seems.

I have seen many two core lighting circuits with a separate bare tinned cpc strung around them but not power circuits. It is normally evident at the consumer unit but yours is not so you have to question where it is connected, a water pipe maybe? I personally think it warrants an FI.

westward10 said:

I have seen many two core lighting circuits with a separate bare tinned cpc strung around them but not power circuits. It is normally evident at the consumer unit but yours is not so you have to question where it is connected, a water pipe maybe? I personally think it warrants an FI.

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FI makes sense - except I'm not sure how one would get the information - the downstairs is fully hardwood/laminate floors, so no floorboards to easily take up. The sockets are surface pattresses attached to skirting boards, clearly where original single sockets would have been so it would appear it may have originally been installed like it.

Can you physically see it is a two core cable at the consumer unit.

westward10 said:

Can you physically see it is a two core cable at the consumer unit.

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yes - it's 100% 2.5mm (imp equivalent) twin with no earth, not cut back short or anything.

Not a great picture - but this is at one of the sockets...



The cpc runs in separately through the skirting board as bare tinned - then sleeved (but only one feed at the sockets I checked, not looped in/out).

R1+RN was exactly as expected and in line with R1 and RN of 0.19... Zs tested as 0.87 maximum (on an extension lead run from behind a bed with someone in it so couldn't investigate fully....), but more like 0.38 ish on the ring - Ze was 0.15, so it all makes some sort of 'sense'.

IR on that circuit (L&N -> MET) was 30+ MOhms, though not sure exactly what that proves.... I wasn't able to completely isolate everything.

I didn't do a resistance test from MET to each earth with the wander lead, which looking back now might have been useful, but like you I expected to see the CPCs back to the CU.

The sort of job that needs multiple people ripping it apart for days to get full information I guess, but domestic EICRs don't usually allow for that sort of effort...

It is possible to prove a connection to an extraneous part and probably not that difficult with so few points. Isolate power, remove the earthing conductor and all cpcs at the consumer unit but leave the main protective bonding in place. If they have a boiler or immersion ditch the cpcs at the isolators then do a continuity check to the bonding.

Dartlec said:

yes - it's 100% 2.5mm (imp equivalent) twin with no earth, not cut back short or anything.

Not a great picture - but this is at one of the sockets...

View attachment 84896

The cpc runs in separately through the skirting board as bare tinned - then sleeved (but only one feed at the sockets I checked, not looped in/out).

R1+RN was exactly as expected and in line with R1 and RN of 0.19... Zs tested as 0.87 maximum (on an extension lead run from behind a bed with someone in it so couldn't investigate fully....), but more like 0.38 ish on the ring - Ze was 0.15, so it all makes some sort of 'sense'.

IR on that circuit (L&N -> MET) was 30+ MOhms, though not sure exactly what that proves.... I wasn't able to completely isolate everything.

I didn't do a resistance test from MET to each earth with the wander lead, which looking back now might have been useful, but like you I expected to see the CPCs back to the CU.

The sort of job that needs multiple people ripping it apart for days to get full information I guess, but domestic EICRs don't usually allow for that sort of effort...

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These are the EICRS I hate, you can argue that it is compliant based on test results but in my mind it’s not and needs upgrading is there any RCD protection in here? It’s well outdated and I would recommend the consideration of rewiring the property it’s well overdue isnt it. Many will argue that it’s not needed right now but when will you change that thought process? When it’s too late?

Grant1987 said:

These are the EICRS I hate, you can argue that it is compliant based on test results but in my mind it’s not and needs upgrading is there any RCD protection in here? It’s well outdated and I would recommend the consideration of rewiring the property it’s well overdue isnt it. Many will argue that it’s not needed right now but when will you change that thought process? When it’s too late?

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These are the sort of EICRs you need they build your knowledge and experience.

Grant1987 said:

These are the EICRS I hate, you can argue that it is compliant based on test results but in my mind it’s not and needs upgrading is there any RCD protection in here? It’s well outdated and I would recommend the consideration of rewiring the property it’s well overdue isnt it. Many will argue that it’s not needed right now but when will you change that thought process? When it’s too late?

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I know I'm mad but I like this sort of a challenge! (there is up front RCD btw)

westward10 said:

These are the sort of EICRs you need they build your knowledge and experience.

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Yes true but you need to have your books to hand don’t you. Or even better post on here and guys like yourself help out. (I HOPE) i will be going through that process in the next year or so when Wales puts it in legislation to have an up to date EICR like our compatriots in England and Scotland.

timhoward said:

I know I'm mad but I like this sort of a challenge! (there is up front RCD btw)

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Right ok I missed that. RCD does help out in many situations

westward10 said:

These are the sort of EICRs you need they build your knowledge and experience.

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I'd rather it wasn't the ones that were an hours drive away though!

I knew I'd read of this before once.
EDIT doesn't seem to let me link to an IET forum article....
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.
I'll beat the system....!