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

 

[snookgs]

It would be a note or code 3 a improvement

 

[7029 dave]

In all honesty, once the metre has been installed(self connect), who cares how long the tails are.

 

[Gavin A]

<snip>

seriously?

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'd be responsible for a call out fee to replace the fuse, as long as the tails conformed to their requirements there'd be nowt said about broken supply agreements etc.

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.

Perhaps you could go and have a look in the big green book and see if you can find that one size fits all rule. It is given as a guide in the on site guide, but that's just a generic guide for those who can't be arsed to actually do any thinking.

Why do people assume this agreement is automatic?

OK let's look at this a bit differently. When the supply agreement was first put in place there would have been a written agreement between the DNO and the customer at the time. It's fairly safe to assume that no DNO would put in place the meter without also having such an agreement, and that this agreement would cover the requirements needed for the customer's electrician to be able to safely connect their consumer unit to the suppliers meter via a set of tails that would be protected along their length by the suppliers fuse, as long as certain requirements for those tails were met, as without that agreement no installation could have ever legally been connected, and it'd have been a bit pointless for the DNO to have been paid to install the cut out and meter.

Or to put it another way, it's safe to assume that all installations must have had such an agreement in place, so there's no need to actually demand to see the paperwork prior to making / remaking any connection, as long as you're conforming to whatever guidance the local DNO has.

 

[Deleted member 26818]

There is no one size fits all rule in the Big Green Book, why should I go looking for one?
Yes the OSG is just a guide, what of it?
The one size fits all rule is a DNO stipulation, not anything to do with BS7671.
The reason why the DNO's now stipulate over sized tails is because of people like you who assume the DNO fuse is provided to protect the installation.

Do you seriously believe that the DNO's out of the goodness of their hearts will agree to provide protection when there is no statutory requirement for them to do so?
Do you seriously belive the DNOs will agree to protect a consumer's equipment, when they have no control over the installation?
Do you seriously believe that the DNO's would risk the litigation that would arise if their fuse failed to provide the promised protection?
The fact that there is a Regulation in BS7671 for the omission of overload protection if the DNO's agree that their fuse will provide protection, indicates that there are instances where the DNO's will not make such an agreement.
Why do you assume that such agreements are the norm, and not the exception?
Finaly, can you please explain why the Association of Meter Operators advise a maximum length of 3m and cite Regulation 434.2.1 for further guidance?

 

[Engineer54]

The 3 metre rule for consumers tails has been around ever since i've been in the industry and dating back to the early times of the old Electrical Regional Boards. Everyone and their dog knows about it, even if some DNO's allow a little more than 3 metres. A little common sense is needed here, no-ones going to lose any sleep or commit hari kari if the tails are a little longer than whatever the local DNO stipulate... But the fact remains if the tails are going to be longer than 3 m (or whatever) then a switchfuse of a suitable rating should be installed.... What's so difficult to understand about that??