Outbuilding and shed installation

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I would like to install power to my outbuilding and then onto my shed.

The outbuilding will have a washing machine and dryer plugged into a double metal socket with one additional double socket for the occasional power tool use, etc, in a radial circuit and a single batten light overhead.

The shed will again have two double sockets and an overhead batten light.

Distance from house c/u to outbuilding is 4 metres and from outbuilding to shed is 12 metres.

The only way to get the cable there is via catenary, house to outbuilding and then again to the shed.

My existing c/u has a spare place in the RCD side.

What would be the most suitable SWA to use and would it be better to use a 'garage unit' or metalclad?

Would I need to install the 'garage unit' or metalclad in both the outbuilding and shed?

Best way to earth both of them?

I'm a little confused about the RCD, as the feed will come my house c/u that will be protceted, does that mean I do not need RCD in the small c/u in the outbuilind and or shed?

Please advice?
 
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For that run & load I would use a minimum of 4mm cable.
If you are connecting to the rcd side of your board you dont need another one but i would put feed on the non RCD side of the board and have an rcd in the garage.
This will eliminate the possibility of the garge tripping the house supply if there is a fault (not good if u are on holiday as the freezer tends to melt).

Assuming the garage cu is away from areas of possible damamge then not necessary to use metal.

You will obviously have water feed to the washiong machine and there are special bonding requirements. In view of this and as this work is notifiable to the local authority I strongly suggest you use, or work with, a competent electrician..

Get one near you at www.competentperson.co.uk
 
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Ok, so better to use a supply from the house c/u that is not protected, no problem.

Then an RCD protected small c/u for the outbuilding, then I want to link the shed to that.

Its 12 meters away, do I take two feeds from the same MCB in my house C/U or add a junction box and continue where the outbuilding finishes? I think the latter.

Then have another small c/u in the shed.

And last question, do I need to earth these small c/u's and if so, is it simply a yellow/green wire to an earth rod?
 
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then I want to link the shed to that.
Its 12 meters away, do I take two feeds from the same MCB in my house C/U or add a junction box and continue where the outbuilding finishes? I think the latter.

Firstly I'd use 10mm swa, take supply from spare mcb on house cu non rcd side.
Earth the armour from the house end (assuming you have PME) & terminate into insulated enclosure at outbuilding.
Terminate swa at first outbuilding into henly's via an insulated enclosure then take second run of swa from henley's to second out building ensuring continuity of armour earth.
Or
Come off of a spare way in the first outbuilding cu.

[/quote]And last question, do I need to earth these small c/u's and if so, is it simply a yellow/green wire to an earth rod?
Use cu's with 30mA rcd as main switch in both sheds.
Set them both up as a TT system, that will involve installing a earth rod at both outbuildings.
Connect the rods to cu with 2.5mm green/yellow if cable is protected or do as most sparks do just use 10mm green/yellow.

Dont forget the installation will need testing !!!!

As said here & on SF (no I didnt post there just viewd) this is notifiable work & possibly beyond some diyers (no dissrespect intended to diyers) so consider getting a pro in.
 
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Ok, so once I do this install, do I leave the MCB out of the house CU before I get it tested.

Who would I call to 'sign it off'

Our electrics were brand new 2 years ago, so will this method be suitable, ie, earthing the two small c/u's.
 
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You have 2 choices. If you take the DIY route notify your LABC and pay their fee before you start the work.
They will inspect at various stages and should (note should) test and sign off the work.

Your second option is to find a local qualified spark and have him do the technical bit including testing, certification and notification.

Most electricians are only allowed to notify work that they have done themselves. You will find it hard to get a spark to take on legal responsibility for work they didnt do.

See Part P info in the WIKI

Re connection. you should understand the sequence for testing and connection. You have to do 'dead' tests like continuity, R1+R2, insulation resistance, earth fault loop impedance using calibrated test equipment.
Then connection is made and then live tests including making sure the RCD trips withn certain limits (again needs specialist test gear).
 
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So to clarify, I run 2.5mm? twin from MCB 16/32amp? at non RCD side outside house where I will connect it to SWA using waterproof gear and into 1st building.

Im fairly happy with everything now, except the earth.

Do I connect the T&E in my house consumer unit to the SWA, and continue that throughout the instillation, ie, earth the swa to both garage units AND earth both garage units in shed 1 and 2 to an earth rod?

The garage c/u's are complete with 40A 30mA RCCB, 2 MCB 16A and 6A.

Please answer, if you can, if correct T&E and MCB are being used and the earth question too.

Many thanks.
 
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From 32amp mcb on house cu run 10mm T/E to metal adaptable box, join T/E to 10mm swa, swa to be glanded to metal adaptable box.
Run swa to first shed terminate into plastic adaptable box (make sure the box is big enough for two swa terminations), pull phase & neutral tails through and terminate into a henly block (leave swa earth terminated in adaptable box).
Terminate second 10mm swa into same insulated adaptable box taking tails through to henley block (use banjo's of both swa's joined at insulated adaptable box for earth continuity of armour), run swa on to second shed.
Take phase & neutral tails from henley block to new shed cu rcd main switch, run 10mm green/yellow from cu earth terminal down to a earth rod.
At second shed terminate swa directly into insulated cu & terminate phase & neutral (terminate earth into chock block not cu earth terminal) into rcd main switch, run a 10mm green/yellow earth from earth terminal of cu down to a rod.

in sheds use 16 or 20amp mcb's & run 2.5mm radials for sockets & 6amp mcb's for lighting.
Think about protection for cables, such as conduit or trunking with in the sheds.
Water pipes (washing machine) if metal will need bonding.

Test / inspect & certificate.

The above is assuming that the house earthing arrangement is pme.

Thats one way I'd think about doing it.
 
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Thanks, that makes sense to me.

EXCEPT:

1. DO I CONNECT T&E EARTH TO HOUSE C/U? I suspect not as we will be creating our own TT earthing arrangements for this install.
2. WHY USE A METAL ADAPTABLE BOX IN THE FIRST PART OF INSTALL?
3. WHY TERMINATE THE END OF THE SWA INTO A CHOCK BLOCK?
4. IS IT OK TO USE 2 RCD's IN THIS CIRCUIT, AS IN THE LAST EXAMPLE BOTH SWA's WERE INSTALLED INTO THE RCD's?

Also I dont ever think I will use the load those cables are designed for.

1st building will use washing machine and dryer, family of 4, so quite busy, and the odd use of batten light if ever in there on a night, rare!

2nd building will really only have 2 batten lights used most often, no heating etc, its been built to house some built in rabbit cages and the rest is for storage.

Both sheds will have very occasional socket use, ie, lawnmower. I have a workshop elsewhere.

Based on this, would you really advise such big cables?

Washing machine is fed by plastic pipes.

By illustrations of different earthing arrangements I have seen, I believe mine to be a TT set up, as we have an earth rod as well as plumbing earthing. New install 2 years ago.

Thanks for taking the time to reply, I will not undertake anything untill I fully understand what I am doing, I am almost there.
 
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By illustrations of different earthing arrangements I have seen, I believe mine to be a TT set up, as we have an earth rod as well as plumbing earthing. New install 2 years ago

So you have a non rcd side in the house cu ?
If so you need a 100mA S type rcd as a mainswitch.

1. DO I CONNECT T&E EARTH TO HOUSE C/U? I suspect not as we will be creating our own TT earthing arrangements for this install

If your house had pme then yes you would need to connect the earth for the submain, this would be because you are not wanting to come off the rcd side & your wanting to get the Zs as low as possible (will be high if using a rod).


2. WHY USE A METAL ADAPTABLE BOX IN THE FIRST PART OF INSTALL?

Because you are wanting to have continuity between the earth of the T/E & swa armour, just makes it easier to terminate with ring terminals to the banjo nut/bolt (But it's mostly just habbit to use a metal adaptable box)


3. WHY TERMINATE THE END OF THE SWA INTO A CHOCK BLOCK?

Because if using one of the swa cores as an earth aswell as the armour from the house pme for the sub, you dont want to mix pme with with the shed cu TT system (if that makes sense). I tend to terminate the swa core into a ring terminal & connect to the swa armour via banjo at the outbuilding.



4. IS IT OK TO USE 2 RCD's IN THIS CIRCUIT, AS IN THE LAST EXAMPLE BOTH SWA's WERE INSTALLED INTO THE RCD's?

Not a problem as the rcd's will be in paralell not series.
If they were in series one would ideally need to be time delayed.

Also I dont ever think I will use the load those cables are designed for.

Well do the calcs & go for a smaller csa cable, but you may regret not having the bigger csa if you want to expand circuits in the sheds at a later date.


Make sense?
 
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Yes I have a non rcd side, lights, central heating & smoke alarms. Mainswitch is a MK 6180s 80A 100mA.

Not sure about pme, so I do need to connect earth to house c/u?

I understand the metal box, it will indeed be easier to earth but mine is outside so I will be using a waterproof MK adaptable box, but I can terminate all those connections no problem.

I am still unsure about the earth though, I think beacuse I dont understand some of the terms used in your descriptions, although yours have been great comms, and what pme is too.

Your help is fantastic, thank you once again.

I do have a sparky frined who I am hoping will cert this job, he is quite young and just qualified, so a few pints down the pub should do the trick, I hope he is able to cert??

[/quote]
 
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Yes I have a non rcd side, lights, central heating & smoke alarms. Mainswitch is a MK 6180s 80A 100mA.

So it's not a non rcd side, it does infact have a standard 100mA rcd as a main switch.
The mainswitch/rcd should be a time delayed type on a TT earthing system such as you have. MK part number as follows
Time delayed
80A, 230V 100mA 6980s
100A, 230V 100mA 6400s

I understand the metal box, it will indeed be easier to earth but mine is outside so I will be using a waterproof MK adaptable box, but I can terminate all those connections no problem.

To make life easier I use these instead of the nuts supplied with swa glands.
http://www.tlc-direct.co.uk/Main_Index/Earthing_Index/Piranhna_Earth_Nuts/index.html

and what pme is too

Protective Multiple Earth
 
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I have two RCD's in my C/U.

The first one I have mentioned and the other is a MK 5780s 80A 30mA and runs the sockets, cooker, fridge and another circuit thats not named.

Based on this information, whats my best install?
 
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I have two RCD's in my C/U.

The first one I have mentioned and the other is a MK 5780s 80A 30mA and runs the sockets, cooker, fridge and another circuit thats not named.

Based on this information, whats my best install?

Now we have established you have a TT earthing system at the house, albeit with the wrong type of 100mA main switch rcd.

1. Dont worry yourself about pme you've not got it.

2. Come off the 30mA rcd side of your house cu for the submain to the outbuildings (or change the 100mA for a time delayed one then come off that side), just do the rest of the install as already described.

3. Just use normal double pole main switches (not rcd's) for outbuilding cu's if you run submain off house 30mA rcd side.

4. Might be just as easy to get a sparks out to advise & show you what is required, as it is difficult to explain properly over the net.
 

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