Consumer Unit Location ?

[the_constructor]

I am going to be having my house rewired hopefully within the next 12 months, but I have a couple of questions that I would like to get some thoughts on in the meantime.

A. Does the consumer unit have to be in the same location as the electricity meter ?

B. What is the maximum distance a consumer unit can be away from the electricity meter.

The reason I ask this is this. All the cables at present come out of the wall between the downstairs ceiling and the upstairs bathroom floor onto a small landing.

I personally think it would be daft to run all the cables down the wall, through the landing floor, through the downstairs cupboard is tot he consumer unit. I would be happier for the consumer unit to be on the landing wall and just have the tails go to the electricity meter.

Your thought gentlemen please.

Jim G

[A.Lee]

No.

There is no set distance. However, anything over 3 metres has to have a 'switch fuse' (or maybe just a fuse) fitted, to protect the tails between the meter and the CU, you would typically fit the Sw/F near to the meter.

Switch fuses for domestic use are typically £20 for a 80/100a Sw/F, so not at all expensive. Tails are ~£3/metre each.

Alan.

[the_constructor]

Ah yes, I forgot to mention that there is a 3ma trip switch after the meter and before the consumer unit Jim G

[The Natural Philosopher]

ITYM 30mA

just abut any appliance with RFI suppression will trip a 3mA trip..

[jgharston]

[Snip: Consumer unit at a distance from supply]

Essentially, you've got a one-flat version of this (old colours):

[A.Lee]

That would be a 30mA RCD I suspect. You will still need an additional fuse for tails longer than 3 metres, as the RCD is for fault / additional protection, the fuse will be for over-current protection.

Basically, with only RCD protection, you can hold the line(live) and neutral in your hands, and it will pass current through you until you are fried. It will not trip until some of the current goes to earth, which, if you are wearing rubber soles, on a wooden floor etc, could take a long time.

With the fuse, if you do it, once the relevant ampage is reached (~

1000Amps with a 100A fuse) the fuse will break in half a second, and hopefully you will not be toasted.

Different types of protection. Tails are more likely to need over-current protection than fault protection, as they are, usually, quite short, and quite noticeable, hence few people would try to drill through them etc.

Alan.

[Dave Liquorice]

Varies by DNO and/or meter supplier. The DNO's responsibilty now stops at the main cut out and earth terminal. Connections from there to the meter is the responsibilty of the company you buy the electicity from.

[John Rumm]

That sounds like a "whole house RCD" which is somewhat undesirable in itself (when it trips, you lose all power to everything), and secondly it does not alone provide adequate protection for the tails since it only protects from earth faults and not short circuit faults.

[the_constructor]

Yes, sorry everyone, it was a type error. It should have read 30mA trip.

Any recommendations ?

I take it that the fuse goes between 30mA trip and consumer unit.....

Jim G

[A.Lee]

The cheapest one here is fine for domestic use:

TT install? - yes.

TN - doesnt matter.

[Dave Liquorice]

Where ever it goes in the relation to CU and 30mA trip it must go at the DNO cut out/meter end of the tails. B-)

If you are messing about with the tails it might be useful to replace that whole house 30mA trip with a time delayed 100mA device and adding 30mA trips at sensible places in the CU.

Be aware that with the cheap switch fuses mentioned there is sod all room inside for routing the tails, hence the seperate covers that can go top/bottom.

[Stephen H]

I am also interested in moving my CU unit. There is nothing on the meter tails between the electricity boards fuse and the old CU.

I have three questions:

Is there such a thing as a 100mA trip 100A rated RCBO? this would protect against both L-N and L-E shorts between main supply fuse and the new CU, but not be a nuisance enough as the new CU will be using 30mA RCBO's for the various circuits.

Now if a switchfuse is fitted, can any part P reg sparky do it or does the electricity board have to put in this switchfuse?

The earthbonding for the gas and water pipes run back to the old CU. Obviously there is a 10mm earth cable from the meter cupboard to tee old CU. Now can I put a earthing connector block in the mter cupboard and connect all the earth wires back to this point rather than taking them to the new CU location?

Regards,

Stephen

[Tim Watts]

I have never seen such a beast.

Even for a breaker, you are into MCCB territory for that current - big, ugly and expensive (usually used main distribution panels).

Anyone can do it.

But to do it safely, you will want to remove the cutout fuse unless the meter is a modern one with inbuilt isolator. Technically only the meter operator/DNO can touch the cutout fuse...

Yes. It is what I have done and is both acceptible and quite normal.

[ARWadsworth]

The mains fuse will take care of both a L-N and a L-E short on the tails - unless you have a TT supply and then you would use a 100mA time delayed RCD that is rated to carry but not switch off 100A