Rewiring of garage circut

[bothyhead]

Hi All,

First of all this is my first post to this group so please excuse me if I make
a mistake or two.

My garage currently has one single socket, and one light which my Dad installed
sometime in the early 80s. I want to extend this to 3 double sockets, and 2
light fittings.

I have bought a garage cu which consists of 1x6A mcb, 1x20A mcb, 30mA RCD,
and a 63A single pole isolator switch, with an incorporated 35A fuse.

I plan to use 2.5mm cable for the socket radial circut, and 1.5mm for the
lighting. I also plan to use metal clad sockets & light switch and to route
the cables in metal conduit (at least for the vertical runs.)

The main cable coming into the garage from the house looks like 6mm (7
individual strands) and terminates into a 30A junction box. I want to position
the new cu about 15 feet further on from this.

Can I use 2.5mm cable between the jb and the cu, or should I continue on with
the 6mm?

Do I need to earth the metal conduit, and if so, is it ok to it via the earth
screw in the light/socket mounting boxes?

Finally, can anyone advise me on a wiring plan? A rough layout is as follows:


CU------------------------------------JB



Socket 1 (doorway) Socket 2 (window) Socket 3


Someone was advising me to go from cu to socket 1, cu to socket2, and cu to
socket 3, With the wires in the cu end going into the one mcb. After
researching this forum I realise that this is an old Star configuration and is
a no-no.

The way that I am thinking about is cu to socket 1, then up and over the
doorway to socket 2, and finally up and over the window to socket 3. The only
drawback with this is that it's about 20 feet between cu and socket 1, so
daisy-chaining to socket 2 will mean an extra 20 feet of cable, that would not
be required if the wiring was done as a star. That said, I want to do the job
properly.

Note: I have not included the lighting in the above diag.

Thanks in advance for any help that you may be able to offer.

 

[Steve]

metal conduit is a good idea for protection, but would need earthing. Are you going to use a connector to connect the conduit to the fittings?

You only need 1mm cable for the lights.

and a 63A single pole isolator switch, with an incorporated 35A fuse

what is one of these? do you have a picture you can post?

continue the existing 6mm cable feed in 6mm, not 2.5. What rating fuse/mcb is this cable protected by?

 

[bothyhead]

Thanks for the reply!

metal conduit is a good idea for protection, but would need earthing. Are you going to use a connector to connect the conduit to the fittings?

Sorry, you've kind of lost me with regard to the connector that I should be using. I was planning to use metal wall-boxes & face plates as well. I thought that I could earth the conduit via the circuit earth?

and a 63A single pole isolator switch, with an incorporated 35A fuse

what is one of these? do you have a picture you can post?

Basically it's a single pole switch that's rated for 63A. It plugs on to the DIN rail of the cu. In the off position, the 'middle part' of the switch can be physically pulled out. The 'middle part' contains a small ceramic 35A fuse. I guess that the idea of it is that you can quickly isolate the cu, and keep the switch in your pocket to prevent anyone else from switching it on. I'll try to post a pic tomorrow.

What rating fuse/mcb is this cable protected by?

The cable is protected back at the house fuse board by it's own dedicated 25A fuse (the old ceramic type.) I plan to get the whole board upgraded later on in the year with a modern cu and mcbs, so this can be changed if required.

 

[breezer]

bothyhead, i am sorry to ask but do you know how to "terminate" steel conduit?

 

[bothyhead]

Hi Breezer,

To be honest, I don't know how to terminate steel conduit. One of the reasons that I'm posting here is that I want to learn. If it is beyond my capabilities then I will definitely employ a professional to do the job - but it's in my nature to ask questions and to try to understand the problem.

With regard to the steel conduit, I am more than willing to use plastic if this is the safer option.

 

[mapj1]

Cutting threads on steel conduit is hard work, and needs the hire of the right dies and tooling, and a little knack.
Plastic might be better, as a stanley knife and hacksaw are more readily available I suspect..

 

[bothyhead]

Lovley stuff mapj1 - plastic it is then! thanks

 

[bothyhead]

crafty1289 - here is the image you were looking for.