Running a new SWA to supply a shed

[Helm-Electric]

Running a 4mm SWA to the shed, approx distance is 20m. Earthing is PME.

I plan to run the 4mm SWA out from the wall of the house and cleat it along the side until it reaches the back of the house. From there the cable will go to ground at a depth of 450mm all the way to the shed. I plan to fit a 2 way CU for lights and a double socket within the SHED. The SWA will be protected by 30mA RCD and MCCB at the CU within the house. Total load shall not exceed 2kW. The installation will be inspected and tested by qualified electrician who also happens to be my friend. I am making it easier for him by doing all the grunt work...

I am guessing there is no height restriction for the SWA?

Thanks

 

[malcolmsanford]

To be honest with your design criteria and protection devices in the shed CU you could get away with 4mm but personally I would go 6/10mm

 

[Helm-Electric]

Load wont exceed 2kW and volt drop is only 4.4V at 20A over 20m (4.6kW at 230V 1.91% VD).

The design is adequate for what I need to use it for. There will be nothing hefty supplied from it.

 

[Ryan Kavanagh]

yes doesnt really matter but the rcd is fine were it is

 

[Helm-Electric]

A tidier approach after a wee chat with a colleague.

 

[malcolmsanford]

An even tidier approach if you have that spare way is to connect the SWA direct into the CU, saves you messing with tailis and of course isolation of the installation to fit a new Cu ................

You can then if there is an unprotected way in the CU connect to that. and have your RCD local

 

[Guitarist]

Any reason why you aren't coming straight off an mcb straight to the shed if you intend to put an RCD protected 2-way CU inside?

 

[a1guvner]

i would use the spare way on your existing db

 

[Guitarist]

An even tidier approach if you have that spare way is to connect the SWA direct into the CU, saves you messing with tailis and of course isolation of the installation to fit a new Cu ................

You can then if there is an unprotected way in the CU connect to that. and have your RCD local

Just beat me to it... :smile5:

 

[a1guvner]

Just beat me to it... :smile5:

And me

 

[Helm-Electric]

It is a split board protected by a RCD on each side. Have various options in my head and looking at the pros and cons and great to get feedback from you guys for each proposal. The separate RCD would be on the side fed from a spare way in the board. Would be far easier to hook up than fit the SWA direct to the board using a 3 x 3 metal box for the glanding. I've not opened the CU up yet to see whats going on in there. Will do it when the Doris is out (so she doesnt complain about power being off) and post a pic up.

 

[malcolmsanford]

You may find with luck that it is an high integrity board and may have the 3rd Neutral bar, if it's a common make you may if it hasn't get a adapt kit to create it.

It really is better to have your RCD local if possible, especially for an outside installation. It become quite a chew in mid winter, to loose power and light, when your 20mts from the house and scrabbling about in a dark shed and garden, plus Doris might get miffed with the house being taken out.

 

[Engineer54]

Excellent solution Malc!! lol!! 41 posts on how to supply a shed with a couple of sockets and a light!!! This is getting way over complicated...

Follow Malcolm's suggestions and your installation will be better for it and an easier one to boot!! lol!! The RCD is always better downstream than at the house in these installations

By the way, You can run the SWA under the stones, just use a thick wall conduit or pipe and seal up the ends, (not your thin wall poly conduit, you have at the moment, save it and use elesewhere at a later date). That will stop any stones being forced into your cables sheathing. I would also be doing the same for your buried section, unless your prepared to sift all the stones and other rubbles etc, out of your backfill.

 

[Helm-Electric]

Thanks for the info. I have been asking a lot of questions to find the best solution. So... basically, from all the posts, it is best to run the SWA from a spare way fed from a mccb (40A and still need to get round connecting into the board) and have the RCD set up in the shed??

The cable can be just under the stones along the side of the house as along as it is in thick poly pipe (which I have and a bugger to bend).

The make of the consumer unit in the house is Hager.

 

[Engineer54]

The make of the consumer unit in the house is Hager.

I'm pretty sure they do an adapter kit to turn your CU into a high integrity format CU!! eg, one which will give you a couple of MCBs that aren't RCD protected, which is exactly what you need for your shed supply....

 

[mogga]

WHY do you keep refering to MCCB???

I realy worry about the "cable under stones in a plastic pipe" ffs No wonder DNOs are in the state they are if you are an "Engineer"