upgrade

[5amp]

Hi All,
Glad to be aboard.

I want to upgrade my garage electrically, by means of a c/u.
At present, i've just got a buried cable coming from the house,
into an isolator. 3 d/sockets and 3 strip lights are then run from this.
I want to increase the number of d/sockets to 6 ( on a ring ) and add a couple of lights.( on a circuit )
Can i just add a c/u or do i need to know if it is a direct feed from the house and/or anything else i'd need to know/do?

Cheers 5amp
___________________________________
Moderator

split from hi-jacked post

 

[Damocles]

You do kinda need to know whether the power is coming from your house, yes. Or from a nearby lamp post. And what is limiting the current....e.g. 10A mcb.....and the size of the conductors inside the cable.

Thing is, assuming this was installed by someone who knew what they were doing, then it likely is protected by a low current fuse/mcb. A ring is normally a 30/32A circuit for sockets. Sounds as though you do not have 30A to play with, so likely you will only need a radial circuit (like a ring, but the end does not have to go back to the CU).

What do you want to plug in, so how much power will you really need? If its more than the existing cable can carry, then you will have to start from scratch.

 

[plugwash]

Or from a nearby lamp post.

btw this is why electricians use insulated tools all the time and are paraniod about touching stuff without testing it first

you may think that all power to your site/building/whatever is dead but you can never be sure that there isn't another cuircuit feeding from elsewhere (legally or illigally)

 

[5amp]

Thanks Damocles,
It does come from the house, but what i meant was i don't know if
it's direct from the main c/u. I don't think it is.
The garage use is just general, but i will want a 16a socket and some
spares.
By radial, i assume the same as a light circuit?

Cheers 5amp

 

[ban-all-sheds]

I want to upgrade my garage electrically, by means of a c/u.
At present, i've just got a buried cable coming from the house,
into an isolator.

It does come from the house, but what i meant was i don't know if
it's direct from the main c/u. I don't think it is.

If you've got a cable running to the garage that does not come off the main CU, and only has an isolator in the garage, then this is dangerous.

If the cable does not come off any sort of CU or switchfuse in the house then this is very dangerous, as there is absolutely nothing to protect the supply cable, or the ones in the garage apart from your main service fuse, and I can guarantee that they will not be big enough for that to be their only protection.

You need to identify the source of the supply to the garage.

 

[Damocles]

For starters you need to find which circuit is powering the shed.

Most likely it is spurred off a ring if there is no separate fuse/mcb. I would suggest you switch off mcbs in turn until you find which is powering the shed, and report back. You will also have to investigate the kind of cable feeding the shed, but I suggest you find out how to switch it off first. If the power is coming from a ring, you will have to find out where it joins in and how exactly it is connected.

If you have fuses not mcb, then take care removing them... because there will be flashes and bangs if the power is sitched on when you pull out a fuse. So switch it off first.

 

[securespark]

5amp

You should change your CU for a modern one, then you would become 6amp......

 

[5amp]

Hi all,
Yes, it is spurred off the g/floor ring, by means of a j/box.
It's standard t/e in an armoured conduit.
Trouble is, i've not got any free mcb's in the main c/u.
My spidey-senses tell me this isn't good!

5amp

 

[ban-all-sheds]

Your spidey senses are working.

1) You have 3 sockets and lighting powered by an unfused spur
2) You have ordinary T/E cable buried underground

1) you can fix immediately by replacing the J B with a fused connection unit
2) will require you to replace the cable with SWA (steel wire armoured) - this can be buried directly - do a search here for detail of all that.

 

[5amp]

Thanks B.a.s,

I have an update

1) The spur IS from a fused connection,but then, for whatever
reason, a j/box is used just before the cable goes through the wall.
(maybe the cable was connected to the j/box in advance of outside work)
So, does this mean i can replace the iso. in the garage with a 4 way
c/u? If yes, do i have to run it as a radial circuit?

2) The (protected) cable runs deep under the entire length of my new(ish) wall Therefore, it won't be coming out

5amp

 

[Lectrician]

You say it is in tube?? What size tube?? Can you pull a new cable in??

 

[ban-all-sheds]

Thanks B.a.s,

I have an update

1) The spur IS from a fused connection,but then, for whatever
reason, a j/box is used just before the cable goes through the wall.
(maybe the cable was connected to the j/box in advance of outside work)
So, does this mean i can replace the iso. in the garage with a 4 way
c/u? If yes, do i have to run it as a radial circuit?

1a) it is a radial - there is 1 cable running to the garage. You can put a CU in there, but there seems precious little point, as you've only got a 13A supply - just use a switched FCU for the lights. Why do you want a CU in the garage? What will it buy you?
1b) You say above you want a 16A socket - remember the FCU in the house has a 13A fuse
1c) How long is the cable from the house to the garage?
1d) Does the circuit from which the garage spur is taken have RCD protection?

2) The (protected) cable runs deep under the entire length of my new(ish) wall Therefore, it won't be coming out

OK - disconnect it and leave it there - you really should replace it with armoured cable - T/E is not designed to be buried, even in conduit. And anyway, depending on what capacity you need in the garage, and how far away it is, the existing cable may be no use. When you said "standard t/e", did you mean 2.5mm²?

 

[5amp]

Hi B.a.s,
Yes it is 2.5mm.
no RCD protection
Cable run is about 4m.
I wanted the c/u for RCD, convenience of separate MCB's, ie, so that
if a fuse goes i haven't got to fiddle about behind the kitchen units.
Also, as it's a spur, i'm worried about running the lights and say two sockets at the same time.
I may or may not need a 16a socket in the future, but i take it that i'd
have to rewire into the main c/u if i did.(Don't worry,not me)

Cheers 5amp

 

[ban-all-sheds]

Hi B.a.s,
Yes it is 2.5mm.
no RCD protection
Cable run is about 4m.

OK - that size cable is perfectly OK for a 13A load over that distance. Bit worrying that you don't also have RCD protection on the ground-floor sockets though.

I wanted the c/u for RCD, convenience of separate MCB's, ie, so that if a fuse goes i haven't got to fiddle about behind the kitchen units.

OK - makes sense - the RCD is essential, and you will probably get discrimination between an MCB in the garage and the fuse in the FCU behind the kitchen units. What MCB values do you plan to use?

Also, as it's a spur, i'm worried about running the lights and say two sockets at the same time.

It's all going through a 13A fuse - 2 sockets or 200, makes no difference, you won't be able to overload the 2.5mm² cable.

I may or may not need a 16a socket in the future, but i take it that i'd have to rewire into the main c/u if i did.(Don't worry,not me)

You would indeed - that is if you wanted to be able to draw 16A from it. But as you are going to replace that T/E cable supplying the garage with SWA, which you only want to do once, why not install 6mm², or even 10mm², on its own 40/50A supply, then you'll be able to do whatever you want in the future.

 

[5amp]

Thanks B.a.s, most helpful.
I'm assuming i'll use a 6 and a 16 at the moment.

Btw, excluding the c/u, how much to install a new 6 way in the
house,do you reckon?