Brick built workshop consumer unit

[bigray1]

I'll try and give as much info as possible, so please bear with me....

I have just moved into a new house that has a brick built outbuilding halfway down the garden. At the moment, there is a 4mm armoured cable which appears to have been spurred from the downstairs ring in the dining room. The outhouse side of the armoured is straight into a a double socket (Power Breaker Safety RCD type). This then supplies a single wall mounted light. The armoured run is approx 10m form spur to outbuilding.

I want to turn this building into a workshop so would ideally want 2/3 pendant lights with 60w bulbs max and 3/4 double sockets. I have a brand new MK 2 way CU with 63A RCD 30ma and a 6amp and 32amp MCB which I would like to fit. Is it possible to take a 2.5mm te from the power breaker into the new CU then use the breakers for the lights and sockets. 1.5mm for the lights and 2.5mm for the sockets on a radial???

Many thanks in advance

Ray

 

[Luckyphil]

I`ll start like a lot of others do - This work is notifable if you are not Member of a Part P Scam - all done

Ideally I`d take out the Dual RCD Socket and run the SWA straight into the 2 gang Consumer Unit , then run Circuits from that , If the Ring Main that Feeds the Armoured is RCD`d at the House consumer Unit you don`t need an RCD at the Outbuilding.

Ideally the Armoured Cable should be extended in the House and took back to the House Consumer Unit and have its own MCB at source.


Lucky

 

[Taylortwocities]

What is the point of a mini-consumer unit in the shed?
I see this lots and its mostly pointless.

I am assuming that the circuit that the 4mm is connected to is RCD protected at the house end?

Also, you say "spurred". I hope that you mean the 4mm is connected to a fused connection unit with a 13amp fuse in it? It had better be.

If the above are true then you can connect the sockets in the outbuilding to the 4mm and just have an FCU with a 3A fuse in it for the lights.

<There's no point having a mini CU with a 32A MCB for the sockets in the shed. 32A MCB on a radial... Hmmmm>

 

[bigray1]

I realise that I will need someone to carry out/test/cert the work but just thought if I had an idea of what I wanted then it would save some time when I get the leccy in.

On further inspection, it appears as though the 4mm SWA is simply piggy backed onto the back of a standard single socket in the dining room. My main house CU appears very old. It has a single on/off switch with 4x plug in fuse wire modules (2x 30amp and 2x 5amp). These are labelled inside the cabinet as:-

1- 30amp - nothing
2- 30amp - elec - heating - workshop -cooker - tv
3 - 5amp - downstairs lights
4 - 5amp - upstairs lights

To me, this seems very basic. Is it safe/correct???

 

[Luckyphil]

What is the point of a mini-consumer unit in the shed?
I see this lots and its mostly pointless.

If its a Workshop and you have a Fault there , The RCD will trip at the Outbuilding Board , it saves traipsing back upto the House to reset an RCD which "may" have been in the House Consumer Unit

As a result of the Posters response , it would seem there is no RCD Protection on the System at all ? , So as I said before ideally the SWA should be extended back to the House Consumer Unit area , then maybe a seperate Supply Unit (Non RCD assuming the extended SWA supply meets 50mm regs etc) for the Outbuilding , You can bet your bottom Dollar that the Bonding needs upgrading etc etc .....

Lucky

 

[ban-all-sheds]

That type of CU is still sold, and is still, per se, compliant with the Wiring Regulations, and there is no reason why it should be unsafe.

But - it's rare for the rest of the wiring to have never been fiddled with in all the years that it's been in, and it's possible that all sorts of unsafe things have been done there.

You have no RCD protection in the house, which is not as safe as it could be, and which precludes a lot of additions/changes to the installation.

Do you have any idea how old it is? What sort of cables are installed - modern PVC? Old Imperial size PVC (they'll be stranded, and the copper conductors will be tinned, so will look silvery grey)? Really old rubber insulated?

Does the lighting circuit have an earth?

Basically you have just moved in, you have inherited an electrical installation which could well be of a certain age, you have at least one change you want which will need an electrician to do - I suggest your first step should be to find a reputable one and have him carry out an inspection.

 

[ban-all-sheds]

If its a Workshop and you have a Fault there , The RCD will trip at the Outbuilding Board , it saves traipsing back upto the House to reset an RCD which "may" have been in the House Consumer Unit

There is no guarantee of that whatsoever.

And if there's no RCD at the house, and a CU in the outbuilding is pointless because of supply constraint an RCD FCU there would be cheaper - does raise the old "plunged into darkness whilst still holding the spinningwhirringchoppinggrindingslicingmachine" issue though...

 

[Taylortwocities]

Ahh so NOT

a new house

then?

New to him but not new.

 

[dhutch]

I would certainly look at having a new consumer unit putting in in due course, infact on my own house, although Im aware it can still leave issues down stream, i had it changed as a condition of sale.

Simularly I would look at extending the 4mm back to the consumer unit and putting it on its own feed, particualtly if your planning to run a fair bit off it. For instance, a 2kw heater along side power tools. Certainly stuffing it into the back of an existing socket is far from best practice if not in itself overly dangerous.

The argument of should there be a rcd/mcb in the workshop could go on for ever. In my parents garage we have a pair of MCBs (power and lights) so the lights are protected corrently but no RCD.


Daniel

 

[ban-all-sheds]

If you want "should", then it's

Meter tails, split, switchfuse, SWA to outbuilding, CU with RCD protection on sockets and no RCD on the lights.

 

[DetlefSchmitz]

If you want "should", then it's

Meter tails, split, switchfuse, SWA to outbuilding, CU with RCD protection on sockets and no RCD on the lights.

Trouble with that is finding a switch fuse rated at less than 60A. If you can't, you'd probably need 16mm² SWA. If you can - let me know!

 

[Iggifer]

could you not just use a TP+N switch fuse and just use L1 with L2 and L3 empty? I have seen plenty of them rated at 20A

I have no idea if thats allowed, obviously it's not cheap or compact but it would work.

 

[DetlefSchmitz]

Oh, not bad! I hadn't thought of that. I've been using DIN rail mounted HRC fuse holders - but people look at you funny when you buy them.

 

[Iggifer]

i bet you a DIN rail HRC + other stuff needed is a boatload cheaper than even the cheapest TP+N switch fuse though. A hager Contactum one is £74+VAT on TLC.

Can you not just put a 20a fuse in a 60a SPN isolator and label accordingly?

 

[DetlefSchmitz]

Probably never researched this properly but I had the impression that the fuses were physically different sizes. If that isn't the case then it explains a lot.