Few questions ...

[Symztux]

Hi Guys,

Not posted on here before, but been reading for a few months and find it to be a great resource. Anyhow ...

Just been to see a job (consumer unit relocation & upgrade) and I have a couple of questions:

1 Currently, the consumer unit is located inside the house, essentially behind the outdoor meter box. I would imagine the current 16mm tails are approx 1.5m long to reach the unit inside. I need to move the consumer unit about 2m from it's current position, essentially out of the room it is currently in which will become a shower room. What is the correct procedure here? I presume that it is not acceptable to replace the tails and run them to the new position, as it would be approx 1.5m+2m = 3.5m which I believe is too long for meter tails? Is the correct solution here to add a switched fuse, then use say 16A T+E to run a submain to the new consumer unit? Are you allowed to locate switched fuses in a meter box? If so, does there need to be an IP rating for the switched fuse?

2 Earthing wise, there the main equipotential bonding is 10mm from the suppliers (TN-C-S) connection which the goes off to the water and gas supplies, and there is also a 4mm earth supplying the existing insulation which is obviously not acceptable. I presume that it is NOT ok to use the suppliers earthing connection as an MET (as there is essentially only 1 connection), and I would need to supply a new MET, whether that be stand alone or within a switched fuse. (And obviously upgrade to 16mm2 from the suppliers connection).

I am an NICEIC Domestic Installer, but relatively new to it all, and this is the first time I have come across this scenario of needing to move a consumer beyond the limits of the meter tails.

Looking forward to any help on this one.

Thanks chaps,

Simon

 

[nick611]

you cannot fit anything into the meter box,you would have to fit another one. i would go for 3.5 mts. 3 is the max indoors but i believe it may be 4 externally.if you run t+e submain you will need a 10mm e/wire alongside.hope this helps

 

[poirot]

Ask the electrical board to fit a isolater and run a 25mm 2 core swa to new.board
Position with seperate 16mm earth.

 

[Guest123]

You can fit a small switchfuse in the external meter cabinet, just not a huge wylex type one. Usually one of THESE is acceptable by all.

A DNO fitted isolator is no good because you need to fit additional overcurrent protection such as the switchfuse in the link as the DNO will not guarantee their service fuses over certain distances. The actual distance can vary but generally it is 3M or 4M depending on internal/external.

If you do use a T&E sub-main then you'll need to be careful how you install it as it may come under the requirement of 522.6 for additional RCD protection if it's just chased into the wall for instance.

The 10mm bonding is fine, you would need to run a seperate CPC with the T&E, a 10mm would do, some may say 16mm but as you are essentially creating a new circuit, that earth is not your MEC but a CPC. As long as the earth from the cut-out to the switchfuse is 16mm along with 25mm tails that is fine. Personally I would use a 16mm as a matter of course.

HTH.

 

[Symztux]

Hey Guys,

Thanks for your suggestions, I have a couple more:

Just say for instance I used 2 core SWA ... I presume at the meter box end I could make it off with a SWA gland into the switched fuse ... what would I do at the other end? Could I use a plastic adaptable box with a gland to essentially terminate the outer protections, then run the 2 x 25mm cores into the consumer unit? (This could be placed beneath the floor boards just above the new consumer unit location)

If I used 3 core SWA, could I use one of the cores as an earth, if correctly sleeved at either end? I imagine the answer to this is no, as I imagine it would be extremely difficult to terminate that 25mm into the earth terminal in the consumer unit.

If I did use 3 core SWA (some have mentioned it might be less expensive as it is more common), and didn't use the 3rd core, what would I do with that? To cut seems stupid as it could always be a spare if one of the other cores ever got damaged.

Thanks guys, it's really interesting coming across a problem I have not yet encountered and finding the solution to it.

Cheers,

Simon

 

[ezzzekiel]

an adaptable box would be fine and can be hidden out the way providing its accessible for future inspections, 3 core swa could be used but may prove difficult to terminate

 

[nick611]

check you cut out fuse.no need for 25mm if its a 60amp cut out.and once again you are not allowed to mount anything in the suppliers meter cupboard.also its fine to use 3rd core as cpc as long as its sleeved,25mm will fit into an earth bar

 

[Symztux]

Hey Nick, to be honest, in talking to the suppliers earlier today re changing the tails, they told me I would have to install the isolator into their cupboard. I can't see how installing a relatively small switched fuse will be a whole lot different to that, other than the fact it is fused, and protecting the SWA that will be feeding the new consumer unit.

The current meter cupboard is sunk into the wall, and adding another cupboard beside it for a small switched fuse, would be unsightly and frankly unnecessary.

Thanks for your help though )

 

[nick611]

ok fella.but my neck of the woods they will allow nothing in their box.not even a dp block.all the best