RCBO suitable for circuit with no earth?

[Sooby2]

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I've just started at a new church and the electrics are bit of a shambles. I'm not going to be touching them as I'm not qualified, but one thing I have been told is this, which I'm not sure is correct (and really doesn't sound right).

Sometime in the 90's the building was rewired by SEEBoard, who used twin core cable, the earth system being provided by the conduit which uses slip couplings. This failed in fairly short order and left many circuits with no earth - there's a very lengthy associated story of trying to get it rectified and failing.

To repair this now would mean ripping everything out and starting again, which they're keen to avoid. Apparently a few years ago an electrician stated it is fine to keep using these circuits, complete with metal faced switches and sockets, along with sockets now having no earthing system, as he fitted RCBO's to the circuit as and I quote "these are suitable for circuits without an earth arrangement".

Is that right? I've only done the EAL Level 3 and don't call myself an electrician, but this doesn't sound right to me? I'm aware of Regulation 411.3.1.1 & BS7671 which is why I'm struggling to believe this is correct. However I'm very happy to be put right if that is the case. Thanks.

 

[DPG]

No, the use of an RCD/RCBO does not mitigate the omission of a CPC for the circuit. No earth and metal sockets in use sounds like an accident waiting to happen.

I'm surprised that an electrician said they were safe for continued use.

Maybe have an extra little prayer this Sunday!

 

[timhoward]

This is intriguing for a few reasons as a lot doesn't really make too much sense at face value.
How exactly has the conduit installation failed? There's nothing wrong with slip-couplings if installed properly. A photo would probably be worth 1000 words!
I'm also surprised it's a big deal to fix. The regs allow a suitably sized earth to be shared by final circuits and I'd have imagined there would be a last-resort option of earthing the conduit further along.

Guessing a bit, it sounds as though the church needs to find the right sparks for the job. It isn't the right sort of thing for a mainly domestic sparks as a fair few of them would baulk at anything unusual and run a mile from galv conduit. That isn't to say that there aren't good all-rounders out there who do domestic work though!

From the time scales you mention I'd imagine that the installation is now overdue an EICR and hopefully this will provide a chance to put right this dangerous situation.

 

[littlespark]

Churches are getting into the same class as pubs and farms for dodgy installations.

 

[timhoward]

I got this IR result in a church last week which made me chuckle....

 

[Sooby2]

This is intriguing for a few reasons as a lot doesn't really make too much sense at face value.
How exactly has the conduit installation failed? There's nothing wrong with slip-couplings if installed properly. A photo would probably be worth 1000 words!
I'm also surprised it's a big deal to fix. The regs allow a suitably sized earth to be shared by final circuits and I'd have imagined there would be a last-resort option of earthing the conduit further along.

Guessing a bit, it sounds as though the church needs to find the right sparks for the job. It isn't the right sort of thing for a mainly domestic sparks as a fair few of them would baulk at anything unusual and run a mile from galv conduit. That isn't to say that there aren't good all-rounders out there who do domestic work though!

From the time scales you mention I'd imagine that the installation is now overdue an EICR and hopefully this will provide a chance to put right this dangerous situation.

We had a building team meeting this afternoon and I was able to get more detail. I could send you a photo of a wall with the conduit buried in it, although I'm not sure that would help! . The problem of the conduit being buried in the walls means we don't know where the joints are that have failed, but apparently there is no earth continuity along them. We're looking at running an earth to each socket (or line of sockets if there is continuity between them). We do have a proper electrical contractor now who is competent with commercial and he has done a proper job on the most recent parts of the building.

We are due another EICR next year and they're just working through the known issues. Like all old, extended buildings we have a mashup of systems. Back in the 90's SeeBoard rewired original building and made a complete mess of it, which is where "if installed correctly" falls down. Apparently it was so bad SeeBoard were reported to their trade body at the time.

It seems possible that somehow RCBO's were installed on those circuits affected, although no-one can remember when - and since then they've been missed out of testing as only a percentage of circuits were tested each time by different contractors (and we have a lot, it's a big building now). I've advised we get our current contractor in tomorrow and check the affected circuits to see if they are safe and compliant and I'm told is going to happen.

 

[DPG]

We had a building team meeting this afternoon and I was able to get more detail. I could send you a photo of a wall with the conduit buried in it, although I'm not sure that would help! . The problem of the conduit being buried in the walls means we don't know where the joints are that have failed, but apparently there is no earth continuity along them. We're looking at running an earth to each socket (or line of sockets if there is continuity between them). We do have a proper electrical contractor now who is competent with commercial and he has done a proper job on the most recent parts of the building.

We are due another EICR next year and they're just working through the known issues. Like all old, extended buildings we have a mashup of systems. Back in the 90's SeeBoard rewired original building and made a complete mess of it, which is where "if installed correctly" falls down. Apparently it was so bad SeeBoard were reported to their trade body at the time.

It seems possible that somehow RCBO's were installed on those circuits affected, although no-one can remember when - and since then they've been missed out of testing as only a percentage of circuits were tested each time by different contractors (and we have a lot, it's a big building now). I've advised we get our current contractor in tomorrow and check the affected circuits to see if they are safe and compliant and I'm told is going to happen.

Needs a full EICR now by the sounds of it, not next year. Be interesting to see what else is found.

Is there space in the conduits for new earths to be run inside them?

 

[Sooby2]

Churches are getting into the same class as pubs and farms for dodgy installations.

I moved from a 16th century flint church, that had some ancient, clunky and very sparky light switches! And spurs that were spurred off a spurred spur. Thankfully they're doing a full rewire now.

 

[Sooby2]

Needs a full EICR now by the sounds of it, not next year. Be interesting to see what else is found.

Is there space in the conduits for new earths to be run inside them?

True, although it's scheduled for January. I did ask if there was room or could we repull the cables with T&E but apparently the conduits are full and it's not an option. How that works for heat dissipation is another question.

 

[timhoward]

@Sooby2 thanks for explaining more. It sounds like things are moving in the right direction, but I'd agree that an EICR is needed asap.
The recent kids pub car park death through lack of earthing should help focus minds if minds need focussing, and I'd be advising socket circuits are locked off until this is rectified.

As you say, finding out what has continuity and where is critical; one thing certainly worth checking is how they joined the old conduit to a new consumer unit (if they did at all).
I've found MICC transplanted into a plastic CU once with no banjo or anything. That was in a church too thinking about it....