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Just seen a you tube video by Artisan, he mentions there is a 15 meter run that goes in the fabric of the building from the meter/100amp cut out to the consumer unit.
it started a debate as to whether to code it a c2 or c3. The question that I have is how would you fix/solve the problem?
the house was a relatively new build as well so how did it pass initial verification?
Discuss.....
 
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  • Thread Starter Thread Starter
  • #3
What exactly was the problem ? Was it not protected apart from DNO fuse ?
That’s correct - the tails were unprotected - just run directly from the dno fuse to meter then long run into fuseboard
 

Andy78

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Solve that issue by fusing the tails correctly 👍
I've seen it a lot on new builds. Most don't have a clue what they're doing, just copy other examples of quick and shoddy work.
 

Ian1981

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That’s correct - the tails were unprotected - just run directly from the dno fuse to meter then long run into fuseboard
No there was a switch fuse in a separate cabinet, the issue was that the tails are potentially unprotected in the wall but for all he knows they could be mechanically protected, a limitation in my opinion, you can’t possibly know how they are installed
 
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  • #6
No there was a switch fuse in a separate cabinet, the issue was that the tails are potentially unprotected in the wall but for all he knows they could be mechanically protected, a limitation in my opinion, you can’t possibly know how they are installed
Let’s just assume they are unprotected in the wall for the sake of argument. The question I have is how would you correct the problem?
 

davesparks

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Let’s just assume they are unprotected in the wall for the sake of argument. The question I have is how would you correct the problem?
If the problem is that they are unprotected then the solution must logically be to protect them.

Dig them out and install a heavy gauge metal plate over them would be one soloution, and possibly ideal from an electrical point of view, but not so ideal from the customer point of view.
 
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  • #9
If the tails are in the cavity without being in earthed metal containment , then they would require rcd prot3ction
That’s what I thought too but how / where would this be installed. I’ve never had this problem yet Myself but wondered how I would resolve it in the most efficient way.
 

Andy78

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That’s what I thought too but how / where would this be installed. I’ve never had this problem yet Myself but wondered how I would resolve it in the most efficient way.
You can't really as then you'd be putting the whole installation under a single RCD, which is not compliant with section 314.
Another method from 522.6.204 would have to be considered if the cables were less than 50mm deep.
 

Lister1987

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Put in the smallest fuse board (4 way?) and take it from/to the db.

If it's feeding the install then have the new enclosure with RCBO (or RCD & MCB) at the servicehead other have it off the main board by a suitable sized RCBO.

I'm probably wrong in my ideas but I'm happy to be properly guided.
 
Unprotected the tails can be Swa,without Rcd protection,otherwise a time delay Rcd @ front.
Then I would supply rcbo’s for outgoing circuits.
 

mattg4321

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Time delay RCD won’t comply if it’s for additional protection (which it is).

Your options are protect the cables in the wall with a thick metal plate that can’t be drilled through with sds

or

Replace meter tails with swa
Both options require you to have a switchfuse at the intake position. You can’t rely on DNO’s fuse at that length

Fitting an RCD won’t comply as you risk losing the whole installation in the event of a fault.
 

Ian1981

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Time delay RCD won’t comply if it’s for additional protection (which it is).

Your options are protect the cables in the wall with a thick metal plate that can’t be drilled through with sds

or

Replace meter tails with swa
Both options require you to have a switchfuse at the intake position. You can’t rely on DNO’s fuse at that length

Fitting an RCD won’t comply as you risk losing the whole installation in the event of a fault.
There’s a switch fuse at the origin, that’s not the concern
Post automatically merged:

As the inspector it is impossible to say for certain that the tails are installed incorrectly, cables concealed in the fabric of the building cannot be inspected and are a limitation on the report, as it’s already written for you.
 
Just curious - something like this is a suitable Switched fuse?

and then ideally you would use SWA?
 
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  • #17
There’s a switch fuse at the origin, that’s not the concern
Post automatically merged:

As the inspector it is impossible to say for certain that the tails are installed incorrectly, cables concealed in the fabric of the building cannot be inspected and are a limitation on the report, as it’s already written for you.
I Understand that and it would be an easy out for the inspector by putting a LIM, however, in this case we are assuming that we already know the cable is unprotected - it may even be a job being picked up following an inspection. My question is all about how to fix the already identified problem.
i haven’t yet had this problem myself and when I thought about it all I could come up with is to fit a small switched fused 100amp unit after the meter or isolator if there was one? Would we then still need to replace the tails? If so, how if the consumer unit is at the other end of the building?
 
My understanding is an Isolator would not be correct for tails over 3m it would need to be a fused.

but it might be better to add a consumer unit at source and this as second CU in SWA also giving Earth fault protection by RCD yes it take out all circuits in Earth fault but would still be safer.
Post automatically merged:

Skip that stick to a Fused isolator at source > SWA > Consumer unit

a RCD at the other end (not source ) protecting the SWA is that possible?
 
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Ian1981

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Swa does not require fault or additional protection by an rcd in TN arrangements, buried in a wall or not.
A switch fuse for a distribution circuit to a CU over 3 meters is all that’s required for swa.
 
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  • #20
Swa does not require fault or additional protection by an rcd in TN arrangements, buried in a wall or not.
A switch fuse for a distribution circuit to a CU over 3 meters is all that’s required.
Which would probably be a much easier option - and cheaper for the customer too.
The extra question is - how did this get signed off in the first place. I’ve heard it happens regularly - this being a property less than 10’years old so 17th edition regs - they still required this protection didn’t they?
 

Ian1981

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Which would probably be a much easier option - and cheaper for the customer too.
The extra question is - how did this get signed off in the first place. I’ve heard it happens regularly - this being a property less than 10’years old so 17th edition regs - they still required this protection didn’t they?
You don’t know the installation method of the tails, it was possibly signed off because they were installed in compliance with bs7671, there’s a switch fuse at the origin and the tails could be installed with mechanical protection in accordance with 522.6.204 indent iv, so if maybe compliant, you can’t condemn something that you think might be wrong without evidence, is the customer happy for you to bash the wall out to see?
I have installed a short length of meter tails buried in a wall using this method, except I write this down in the comments section on the EIC.

I can’t imagine the customer would be happy for you to bash holes in ceilings/ walls and take up the chipboard floor to run in another cable, or have an ugly swa clipped externally to the house, if it’s not necessary.
 
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telectrix

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surely, RCD protection is only required for the tails if they are <50mm deep from wall surface and not SWA or otherwise mechanically protected. if they are > 50mm from wall surface, they are compliant. ( not referring to TT earthing btw).
 

Ian1981

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I’ve got no doubt that installers think that if there’s a CU in zone then they can install the tails in a wall without the required precautions, but I also know that some people install them to the regulations, my point is you can’t see them so can’t possibly code them based on a hunch and certainly can’t deem them potentially dangerous and have them renewed without knowing.
The fact that he guy on the video commented that tails don’t have an earth incorporated into them like a sheathed cable was irrelevant and showed lack of understanding of the regulations as there’s no requirement for a cable to contain a cpc, then asked his video audience what he should code it as .
 
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Andy78

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Which would probably be a much easier option - and cheaper for the customer too.
The extra question is - how did this get signed off in the first place. I’ve heard it happens regularly - this being a property less than 10’years old so 17th edition regs - they still required this protection didn’t they?
Because new builds are thrown up by gangs of trained chimps directed by baboons working for fat cats.

I worked on a house where this problem existed. SWA used but not glanded or earthed at either end, no fuse, approx 12m run.

House was that new the road wasn't even tarmacked.

One socket circuit for upstairs, another for whole downstairs including kitchen, all appliances, hob and oven.

I noted it on the cert for my work. Customer didn't want the hassle. I assume the entire estate was the same. Not what you want in your £400k house.
 
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  • #25
You don’t know the installation method of the tails, it was possibly signed off because they were installed in compliance with bs7671, there’s a switch fuse at the origin and the tails could be installed with mechanical protection in accordance with 522.6.204 indent iv, so if maybe compliant, you can’t condemn something that you think might be wrong without evidence, is the customer happy for you to bash the wall out to see?
I have installed a short length of meter tails buried in a wall using this method, except I write this down in the comments section on the EIC.

I can’t imagine the customer would be happy for you to bash holes in ceilings/ walls and take up the chipboard floor to run in another cable, or have an ugly swa clipped externally to the house, if it’s not necessary.
I understand that. I also get the fact that it would be a LiM in an inspection in this case. However, my query was based on us discovering that there was no protection and how we would resolve the problem - not specifically the one in the video.
The video just posed questions in my head that I was looking for different suggestions, ideas and solutions should I ever come across this myself.
 
Unprotected the tails can be Swa,without Rcd protection,otherwise a time delay Rcd @ front.
Then I would supply rcbo’s for outgoing circuits.
I think the problem with that is is that the tails would need 30mA RCD protection and i’m not sure a 30mA type S RCD will achieve selectivity with a standard 30mA RCD or RCBO. 🤷‍♂️
 
So if it's 50mm deep and 6181Y it doesn't need any extra protection and is "technically" compliant ?
 

Risteard

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The fact that he guy on the video commented that tails don’t have an earth incorporated into them like a sheathed cable was irrelevant and showed lack of understanding of the regulations as there’s no requirement for a cable to contain a cpc
Indeed. I always ask why singles cables are manufactured if their belief was correct. Each point in the wiring requires a cpc - not each cable. I don't understand how this can be so misunderstood.
 
he might have something actually - singles not run in containment should have mechanical protection and there own earth 6241Y like when you run that neutral to the upstairs light it has it's own earth.
 
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