Meter Tail Length

[enlighting]

Afternoon all,

Carried out an EICR yesterday, on the job I doscovered the consumer unit to be located in the kitchen and the incoming supply under the stairs. The tails feeding the board look to me to be just over 3 meters perhaps 3.5. But it is difficult to tell as they are ran in an internal wall.

What coding is recommended and what remedial action required.

Im thinking C2 with a fuse fited between the isolator and the consumer unit.

Cheers

Dave

 

[Deleted member 26818]

My thinking is, it is the dno that imposes the 3m rule.

For the purposes of the EICR, is the cable an immediate danger, potential danger or does it require improvement irrespective of the length. Here, the fact the cable is run through an internal wall makes it a probable C2, but onnly the OP can see the actual run so possibly no coding.

The DNOs have as already stated, a statutory obligation to provide a connection for an installation which complies with BS7671.
Yes they may well impose restrictions and stipulations, however from a legal stand point, unless they can show a real concern for the safety of the installation they have no basis for refusing a connection to a BS7671 compliant installation.

 

[andyelectric]

It is the unprotected hidden run through the internal wall that is imoprtant here I feel, and peeps are getting bogged down by DNO rules.

 

[Andy78]

BS7671 does not cover the distribution network.
As such the DNO protective device and the CCC of the DNO cable should be disregarded, although I would expect the DNO to use a cable with a greater CCC than is required for the supply and would always assume that a cable on the installation side would have a lower CCC than the DNO's side.
As for the 10m of unfused split con, how do you know that it is unfused?
Does it require fusing, even under the requirements of BS7671?

Exactly my point. BS7671 does not apply to distributor cables or fuses and they should be disregarded. So if they are disregarded there cannot be deemed to be a reduction in CCC. If there is no reduction in CCC then 433.2 and 434.2 do not apply.

I know the 10m feeds are unfused because there is none to be seen. No it doesn't require fusing IMO, but the link you provided me gave the "shorter than 3m or must be fused down" rule that I quoted.

Either we are on the same page but reading it from different angles, or the sat afternoon rioja is taking it's toll.

 

[Deleted member 26818]

You have to either accept that the 3m rule and the requirements of 433.2.1 etc apply, or consider some other Regulation as applicable.
You are left with the option of either omitting protection and complying with the requirements which would allow such omission, or tampering with the DNO equipment and installing protection at the start of the run.

 

[Risteard]

Couple of points:

There is no 3m rule. Different network operators have different policies on the maximum limit of the tails they will consider to be protected by their fuse without requiring an additional fuse on the consumer's side of the installation. (This might be 2m or might be more than 3m.)

Secondly, I still don't believe that there is a contravention of BS 7671 and therefore it must not be given any recommendation code. By giving it a code you are stating that it is in contravention of BS 7671, as well as your belief that it might potentially give rise to danger.

Thirdly, there is absolutely no relevance in whether something complied with the Wiring Regulations when it was installed. When you inspect to the current Edition of the Regulations it cannot be more or less safe depending on whether the Regulations allowed it at the time or not.

 

[Gavin A]

I know the 10m feeds are unfused because there is none to be seen. No it doesn't require fusing IMO, but the link you provided me gave the "shorter than 3m or must be fused down" rule that I quoted.

That be a new installation with new DNO supply, so presumably would have been subject to electrical design drawings being submitted to the DNO and agreed by them in advance.

3m is a rule to be applied without the DNO needing to be involved (unless the DNO in question has different rules).

The DNO will also be viewing the split concentric cable as being less prone to fault as the line is effectively mechnically protected by the neutral and earth cables surrounding it. May not exactly have that classification under 17th edition, but the DNO's don;t work to 17th and will take that into account I'd think.

 

[Deleted member 26818]

Well BS7671 limits the posistioning of a protective device to 3m where there is a reduction in the CCC of a conductor.
If you want to say that that is not a rule, or that the requirement doesn't exist, that's your option.
The DNOs take note of that particular requirement as can be seen in the FAQs on the Association of Meter Operator's website.
Can you provide any evidence to support your belief that the DNO's fuse protects any part of an installation, other than their equipment?
Of course there is relevance to installations complying to earlier requirements.
The Regulations are not retrospective, the Regulations indicate that installations which complied to earlier requirements are not considered as being unsafe.
The Regulations allow construction of an installation to earlier requirements to continue or even commence after the introduction of new requirements.
I have personal knowledge of an installation which was completed to the requirements of the 16th edition in March of this year. I know that the installation does not meet the requirements of the 17th edition.

 

[Gavin A]

Can you provide any evidence to support your belief that the DNO's fuse protects any part of an installation, other than their equipment?

It's a fuse, if there's a short circuit in the cable between it and any other protective device then the fuse will blow before the cable does, assuming the cable has been correctly sized relative to the fuse.

You seem to be relying on a semantic interpretation of various bits of guidance to attempt to refute basic physics.

eta Also, the CSA requirement for the meter tails comes from the DNO fuse rating. Why would that be if the DNO fuse wasn't viewed as protecting the tails.

This is a bit of a silly argument tbh.

 

[andyelectric]

Couple of points:

There is no 3m rule. Different network operators have different policies on the maximum limit of the tails they will consider to be protected by their fuse without requiring an additional fuse on the consumer's side of the installation. (This might be 2m or might be more than 3m.)

Secondly, I still don't believe that there is a contravention of BS 7671 and therefore it must not be given any recommendation code. By giving it a code you are stating that it is in contravention of BS 7671, as well as your belief that it might potentially give rise to danger.

Thirdly, there is absolutely no relevance in whether something complied with the Wiring Regulations when it was installed. When you inspect to the current Edition of the Regulations it cannot be more or less safe depending on whether the Regulations allowed it at the time or not.

Without seeing the installation it is hard to be certain. But....

There is definitely a section of cable neither mechanically nor rcd protected being run through an internal wall(I assume down the length of a stud as op cannot determine tail length). This will quite possibly be less than 50mm deep and therefore require a code 2. Otherwise no code.

 

[andyelectric]

It's a fuse, if there's a short circuit in the cable between it and any other protective device then the fuse will blow before the cable does, assuming the cable has been correctly sized relative to the fuse.

You seem to be relying on a semantic interpretation of various bits of guidance to attempt to refute basic physics.

eta Also, the CSA requirement for the meter tails comes from the DNO fuse ratingk. Why would that be if the DNO fuse wasn't viewed as protecting the tails.

This is a bit of a silly argument tbh.

Totally agree with you Gavin. Of course the dno fuse protects part of the installation. All the way through the tails, main switch in the cu to the devices for the individual circuits out of the cu. Or up to a switchfuse or similar if an extende run to cu.

 

[Guest77]

What a load of bollox, some providers are happy with 4 mtr tail lengths so that blows the 3 mtr rule out of the window, lets say for argument sake the tails are 3 mtrs and one inch, does that mean it is now dangerous and a C2 must be added to the sheet on a EICR? no of course not, it is a nothing code, I wouldn't even code tails 3.5 mtrs as a code 3, stuff and nonsence.

 

[andyelectric]

What a load of bollox, some providers are happy with 4 mtr tail lengths so that blows the 3 mtr rule out of the window, lets say for argument sake the tails are 3 mtrs and one inch, does that mean it is now dangerous and a C2 must be added to the sheet on a EICR? no of course not, it is a nothing code, I wouldn't even code tails 3.5 mtrs as a code 3, stuff and nonsence.

Exactly what I've said.
But what about the unprotected tails running through the stud wall. Doesn't sound like straight through so possibly a c2.

 

[Guest77]

Exactly what I've said.
But what about the unprotected tails running through the stud wall. Doesn't sound like straight through so possibly a c2.

when were they installed? the stud wall thing is only a recent amendment, I wouldn't give a code 2 to an old circuit if it complied at the time of install.

 

[andyelectric]

when were they installed? the stud wall thing is only a recent amendment, I wouldn't give a code 2 to an old circuit if it complied at the time of install.

Sorry, you are correct, definitely not a code 2. But possibly a code 3 for no rcd or mechanical protection for thr tails in stud.

 

[Deleted member 26818]

It's a fuse, if there's a short circuit in the cable between it and any other protective device then the fuse will blow before the cable does, assuming the cable has been correctly sized relative to the fuse.

If that were to happen, then you or whoever owns the installation, will have damaged the DNO's property and broken the supply agreement.

You seem to be relying on a semantic interpretation of various bits of guidance to attempt to refute basic physics.

This has nothing whatsoever at all to do with physics.
This is about legality and compliance with BS7671.

eta Also, the CSA requirement for the meter tails comes from the DNO fuse rating. Why would that be if the DNO fuse wasn't viewed as protecting the tails.

If that were the case, then the CSA would be determined by the rating of the DNO fuse. It would not be a blanket one size fits all, is is currently the case.

This is a bit of a silly argument tbh.

Yes it is a bit silly considering that you appear to refuse to accept the evidence that is clear to anyone who bothers to look.

The simple facts are that the Association of Meter Operators have provided guidance on the length allowed for meter tails, and made reference to Regulation 433.2.1. These are the people who can refuse a connection to the network, they can also disconnect an installation, and have the right of entry in certain circumstances to effect a disconnection.
Then there is Regulation 433.3.1 which allows the omission of overload protection, in circumstances where the DNO provide an overload device and agree that it affords protection for the tails.
Why do people assume this agreement is automatic?
Why would there be a specific Regulation for such circumstances if this agreement is automatic?