electricity meter tails - length and routing

[Grov]

Hi all,

I'm hoping some of the electricty regs gurus can help with advice on meter tails.

Shortly I will be beginning an extension which forces a move of electricity meter. I have all of the info about getting the meter moved and where it can be located, but I cannot find any information about the meter tails. What I need to know is the maximum length allowed and what is / isn't acceptable for the routing of them.

My ideal position of the meter is not accepatable due to water pipes on the other side of the wall within 30cms of the meter so I have to go to plan B. Is it acceptable to run the tails vertically through the cavity into the ceiling void, horizontally for approximately 2 meters and then out of the ceiling void into the consumer unit?

Regards,

[Colin Wilson]

Usually within 6 foot of the cutout on the same wall in my experience. That does not include the meter being on the "other" side of the wall.

You might get away with it, but for that sort of run you might be better using a switched fused isolator to provide a little more protection (you`ll have to sort that out, RECs normally only supply a straight on/off switch).

[chris French]

In message , Grov writes

The maximum length that can be protected by the supplier fuse is their decision - it varies , but something like 2-3 m is the norm it would seem. Longer than what they allow, and you should protect it with your own switch fuse somewhere near the incoming supply.

You need to talk to someone at the company that maintains your local network (the company that was your old local elec.board), which of course may not be your supplier - though I think you need to go via them. when I enquired about this a few years back, trying to get to talk to someone who knew what I was on about took a little while.

[David Hansen]

On Mon, 3 Apr 2006 08:50:05 +0100 someone who may be chris French wrote this:-

How would this help? The customer's fuse would need to be able to discriminate with the "electricity board" fuse to be of much use. However, it would also need to be able to cope with the maximum demand. That would be fine if the "electricity board" fitted say

150A plus fuses and customers fitted say 80 or 100A fuses.

[Christian McArdle]

Generally the limit is 2m. If you need longer, then fit a 100A switchfuse unit next to the meter and then the consumer unit can go further down the line. Note that overlong tails can affect the available voltage drop on your final circuits.

Surely something can be done to make this acceptable. Mounting on some sort of waterproof sheet or something. I really can't think why 18mm ply protecting it from any leaks wouldn't be acceptable.

Christian.

[Christian McArdle]

It helps because as far as the supplier is concerned, your switchfuse is the consumer unit, so they no longer care where your actual consumer unit is.

There is no need for discrimination. Quite frankly who cares if it is the switchfuse or the supplier's fuse that blows.

Christian.

[John McLean]

is easily seen from the supplier's incomer fuse position, longer lengths are permissible; but this cable run (not meter tails), would require to be installed by yourself.and terminated near the meter position using a DP isolating CB. Discrimination with the supplier's fuse must be taken into account. This would be Part P notifiable. Jaymack

[David Hansen]

On Mon, 3 Apr 2006 09:38:19 +0100 someone who may be "Christian McArdle" wrote this:-

So, no real reason then.

Then I'm not sure that the two fuses are providing any more protection than one.

[Christian McArdle]

You get to choose a fuse that provides sufficient disconnection times to protect your tails. You can't rely on the supplier's fuse in case they choose something that is so slow blowing that your tails explode in flames. They might also upgrade your supply. They could come along and replace a 60A with a 100A cutout whenever they liked, for example.

However, in most cases, there isn't really a valid reason, you just need to do it to stay legal.

Christian.

[Grov]

Yes, I've tried that route. They have sent me their information pack and i have to supply drawings. Problem is I cannot do that until I know where I can mount the meter. They only response I get is to fill in the form and when the provision team contact me to arrange the work they will be able to answer any questions. Trouble is it will be a little too late then as it is my responsibilty to provide the trench, ducting and meter box.... Catch22 me thinks.

Thanks for your advice.

Regards, Paul

[Grov]

Thats what I thought - would need a hell of a lot of water to go through 9" engineering brick plus the meter box and board, but when I questioned it I was told that if that is what it states in the guidelines they sent me then it is not acceptable and they will refuse connection...

They also state it cannot go directly below a window (this was another option for me), but I *think* I've seen this done before on new builds. Perhaps the rules vary form area to area?

Regards, Paul

[Grov]

Looks like it will be the circuit breaker in the box then as I can't see any other possibility. They have already advised that they will not reconnect the meter tails regardless of length so no great issue there.

Thanks for the part p heads up - it's already covered on my building regs application, but was planning to use an electrician for this part as it also involves a CU move - not happy that I could do it not knowing all of the regs.

Regards, Paul

[Grov]

Thanks for the advice Colin. Looks like a seperate isolator will be needed. At least I know it is possible so can submit the application to the 'leccy company.

Regards, paul

[Christian McArdle]

Do you have space in front? If they want 30cm from the pipe and you've already got a 15cm thick wall, then will a 15cm thick stud framework mounted on the wall get past this bureaucratic buffoonery?

Christian.

[Grov]

Mmmmm thats a thought. Would prefer a flush mounted box as its facing the patio area, but if I cant find an alternative this may be a way around it.

I guess the other way around it would be to change the order of the works so there are no pipes present when they come to do the move :-)

Regards, Paul

[Andy Wade]

This is as much about demarcation of design responsibility as anything else. The distribution network operator's (DNO's) fuse is provided to protect _their_ equipment, not the consumer's installation. It is accepted that the DNO's fuse may be relied upon to provide overload and s/c fault protection to _short_ consumer's meter tails of up to 2 or 3 metres length, as in a normal domestic consumer unit type of installation.

Where a consumer unit is to be located at a distance from the supply intake the consumer is expected to provide 'main switchgear' (i.e. a switch-fuse, etc.) to protect the distribution circuit(s) between the meter and the consumer unit(s) and to satisfy the isolation requirements of BS 7671. It's the installation designer's responsibility to ensure that such distribution circuits/sub-mains are properly protected, regardless of the DNO's fuse. As others have pointed out it's not necessarily practical to obtain discrimination between the fuses in this situation.