UK How do we solve the long meter tail problem?

[Snailspark]

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.....

 

[Andy78]

What exactly was the problem ? Was it not protected apart from DNO fuse ?

 

[Snailspark]

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]

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]

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

 

[Snailspark]

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]

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.

 

[Dustydazzler]

If the tails are in the cavity without being in earthed metal containment , then they would require rcd prot3ction

 

[Snailspark]

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]

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]

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.

 

[cliffed]

Unprotected the tails can be Swa,without Rcd protection,otherwise a time delay Rcd @ front.
Then I would supply rcbo’s for outgoing circuits.

 

[Mark Wright]

max length is 3m ?

 

[mattg4321]

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]

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
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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.