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Author: Subject: Rewiring My Shed Advice Needed
Surrey Dave

posted on 9/4/14 at 12:18 AM Reply With Quote
Rewiring My Shed Advice Needed

My ancient orange pyro that runs from a socket in my dining room to my shed has finally given up.

So I'm going to replace with SWA armoured cable , will 1.5 mm ( 16amps max) be enough , or should I go to 2.5mm (31amps max)?.

Also I guess i should fit an RCD indoors?

The old stuff is just a fused spur from socket.

Advice gratefully received ,thankyou............

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JoelP

posted on 9/4/14 at 05:58 AM Reply With Quote
Cable size depends on how big your shed is and what you do in it! If it's like a workshop then id lean towards 2.5mm.

Rcd is always a good idea tbh.





Beware! Bourettes is binfectious.

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cliftyhanger

posted on 9/4/14 at 06:35 AM Reply With Quote
I used 6mm on the basis I will be using a welder and compressor etc. Then a small consumer unit with a main switch, a 32a and 6a MCB.
The garage runs off a 32a rcbo in the house.

Anyway, well worth getting bigger than what you anticipate needing, as the extra material cost is small compared tho the cost and grief of having to do it again later.
Yes, definitely fit an RCD type device or maybe an rcbo which will offer overload protection too.
You say you are on a fused spur at the moment.
This has me thinking. Most of the above would mean changes to what you have inside the house. But no reason not to pur the bigger cable in, it will be ready for when/if you have a rewire.
Besides, have you done the calcs for voltage drop? There is a handy tool for doing that on the TLC website...

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owelly

posted on 9/4/14 at 09:00 AM Reply With Quote
I'm more intrigued by the pyro that has given up.....
We have pyro that was installed in 1959 and it's still sound. Even stuff that has been hammered flat still tests OK!





http://www.ppcmag.co.uk

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dhutch

posted on 9/4/14 at 09:46 AM Reply With Quote
quote:
Originally posted by Surrey DaveSo I'm going to replace with SWA armoured cable , will 1.5 mm ( 16amps max) be enough , or should I go to 2.5mm (31amps max)?.

Also I guess i should fit an RCD indoors?

The old stuff is just a fused spur from socket.

It depends what you want to be able to do in the shed, clearly. You need to work out what you are going to want to use, and what you can attach the other end to. Buying the cable is the really easy bit.

About the highest spec you would see, is to have a 30amp switched fuse of the main incoming supply upstream of the consumer unit for the house direct into the SWA, then an consumer unit in the shed/garage, either a split-way '17th ed' twin rcd setup, or a main switch and a set of rcbo's. Two radials, or a ring, a lighting circuit or two, 16 or 32amp socket for a welder. The earth may need to be TT'd locally, or bonded back to the house MET with 10mm^2 earth, depending on the earth type of the house and the construction of the garage/shed, if it has water supply, etc. You get good dicrimination between the fuse, and the breakers in the shed/garage, dont get any trips in the house, and have bags of power available. But it costs money, and is over kill for something you just keep the lawn mower in!

Lowest spec short of an extension out the window, is a 13amp fused spur (fcu) off the house, which if the ring main is not rcd protected already, can be a rcd protected fcu. Down to the shed, with a few sockets, and a 5amp switched fcu for a light or two. Assuming the shed does not contain 'extraneous paths to earth' such as a steel frame, water supply etc, you can most likely 'export' the earth two it. But clearly, you only have 13amps to play with, an overload would cause a trip to the house to reset it, and would cause the lights to go off on you. Although you can solve the latter with emergency battery backup light, which is wise if you might be using power tools. The only benefit in having two RCDs rather than one is to remove the single point failure, you cannot provide discrimination against two 32mA RCDs/RCBOs hence the one to trip first will be random.

I have gone for a half way house for my garage. Taking a dedicated feed from the house consumer unit (17th ed twin rcd unit), over an old 4mm cooker feed cable to the back wall, into some 4mm SWA, down to the garage, where because its a metal frame garage, I have a local TT earth setup, with garage consumer unit, with two 16amp radials, and 6am lighting circuit, and an emergency light (£8 from TLC) to give me some light should I trip the supply in the house. I would have modified the house consumer unit to give me a single non-rcd way for the garage to decrease the change of that tripping remotely, but the would then have required running the SWA back all the way, or for the cooker feed to by buried 50mm or more into the way, to give the required protection for a non-rcd protect cable. Which it is not, and I didnt fancy running a cable round the front of the house.


Daniel

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dhutch

posted on 14/4/14 at 12:26 PM Reply With Quote
Just as disclaimer on the above, that I am not a qualified spark, and that the information has largely from information I had before hand or gathered for and from doing my own garage, much of which came from the diynot forums.

It is my understanding that I was extending an existing circuit, that both ends of the swa terminate inside, and the garage is build from non-flammable materials, none of the work I did was notifiable as under part-p of the domestic regs and hence should be done by any competent person in which I include myself. Obviously it is up to you to understand what the situation is for your own installation.


Daniel

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whitestu

posted on 14/4/14 at 03:56 PM Reply With Quote
quote:

Just as disclaimer on the above, that I am not a qualified spark, and that the information has largely from information I had before hand or gathered for and from doing my own garage, much of which came from the diynot forums.

It is my understanding that I was extending an existing circuit, that both ends of the swa terminate inside, and the garage is build from non-flammable materials, none of the work I did was notifiable as under part-p of the domestic regs and hence should be done by any competent person in which I include myself. Obviously it is up to you to understand what the situation is for your own installation.


Daniel



Don't forget any installation needs testing and most folks won't have the kit needed to do it properly.

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