Garden Office Electrics

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I am looking for some advice in relation to installing the electrics in my garden office.

At the moment i have a fused spur from a twin socket in the house that leads into my garden. the armoured cable is approx 15mm dia. and runs approx 20m to the garden office. the cable will run into a small cu in the office.

My question is... can i use this spur to power 3 double sockets and 2 lights in the garden office or will i have to run a new cable directly from the CU?

Also how do i earth the office? i have a rod but do i connect just the cu to it or??????

Thanks in advance for your help!

 

[jj4091]

I am looking for some advice in relation to installing the electrics in my garden office.

At the moment i have a fused spur from a twin socket in the house that leads into my garden. the armoured cable is approx 15mm dia. and runs approx 20m to the garden office. the cable will run into a small cu in the office.

My question is... can i use this spur to power 3 double sockets and 2 lights in the garden office or will i have to run a new cable directly from the CU?

Also how do i earth the office? i have a rod but do i connect just the cu to it or??????

Thanks in advance for your help!

How many cores at what size each core(mm)

 

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Thanks for coming back to me!

I don't know as the cable was laid by the previous owners to supply power to the greenhouse and small water pump!

I will have a look and come back later with any details.

 

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The cable has 2 cores both of about 2mm in diameter.

If i need to replace it what do i need to use?

 

[breezer]

bigger swa cable.


exactl what will be connected at the other end? and winter will electric heating be required?

 

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Breezer:

What size SWA would you recommend?

I will connect pc, printer, telephone, small electric radiator on a themostat switch and maybe a coffe machine?[/quote]

 

[ban-all-sheds]

the armoured cable is approx 15mm dia.

That's approximately the size of 4mm² 2-core SWA.

The cable has 2 cores both of about 2mm in diameter.

2.5mm² has a diameter of 1.8mm.

4mm² is 2.25mm.

You are measuring the actual conductors, are you, not the insulation?

If i need to replace it what do i need to use?

The extra cost of 10mm² over 20m is £20-30.

If a mate asked you to dig a 20m trench, 40-50cm deep, and offered you £20-30, would it be:

1) Can I start today?
2) Sur ton velo?

For the sake of £20-30, do you want to risk digging your trench a 2nd time?

I'd say use 10mm² 3-core.

My question is... can i use this spur to power 3 double sockets and 2 lights in the garden office

You can, but you won't be able to draw more than 13A in total from the 3 sockets and the lights.

Also how do i earth the office? i have a rod but do i connect just the cu to it or??????

Do you mean you've bought a rod you want to use, or your house has a TT supply?

 

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You are measuring the actual conductors, are you, not the insulation?

I am measuring the copper conductors in the cable @ 2mm

Do you mean you've bought a rod you want to use, or your house has a TT supply?

I have a copper rod i want to bury next to the shed as i feel this will give extra protection?

Thanks for your input, i will change the spur cable to the 10mm² 3 core you suggest.

 

[Taylortwocities]

Thanks for your input, i will change the spur cable to the 10mm² 3 core you suggest.

There's no point doing that unless you are going to run a new circuit from the consumer unit. This would be notifiable work - you need to determine what your supply type is before doing anything with any earth rod etc.

 

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Taylortwocities

Thanks or the advice but, i am now a bit confused....are you suggesting that i should not change the spur that already exists in 2 core to 10mm2?

To explain in more detail:

The CU in the house is being changed by a qualified person however i do not want to run a cable directly from the new CU unless absoloutly necessary as it is located in the under stairs cupboard in the middle of the house.

there is going to be a small cu in the office which i was going to earth seperately from the house hence the rod purchase. this small CU will have the new curcuit of 3 twin sockets and the lights running from it.

I hope this helps to explain the situation a bit more?

 

[Chri5]

SWA can take the earth from house to office via the steel wire armour so the earth rod isn't required.

The power feed from the spur in the house is limited to 13A or 13 x 230v = 2990 watts.

Add up your requirements for the office and provided the total demand is less than this you can retain the existing connection via the fused spur.

SWA with 2.5mm conductors will run to a maximum of 35m before voltage drop becomes an issue.

For clarity you should find the SWA has a stamp embossed on the sheath to confirm it's current size.

SWA needs to be glanded and at the house it would be normal to terminate with these

on to a metal box such as

then the cores of the swa can pass through the back of the box, through the wall and terminate on the load side of the 13a fused spur.

The gland kit will provide the earth to the metal box which then requires an earth strap between the metal of the box and the fuse spur house earth.

So the earth sequence is at fused spur, strap to metal external box, metal external box to swa via the gland and then repeat in the shed office via another gland, another metal box and then on to the sub main / garage / builders style consumer unit.

 

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Chri5

Thank you thats a great help!

 

[ban-all-sheds]

Thanks or the advice but, i am now a bit confused....are you suggesting that i should not change the spur that already exists in 2 core to 10mm2?

What on earth would be the point when the FCU limits it to 13A?

The CU in the house is being changed by a qualified person however i do not want to run a cable directly from the new CU unless absoloutly necessary as it is located in the under stairs cupboard in the middle of the house.

Then you'll be limited to the 13A supply from the FCU.

there is going to be a small cu in the office which i was going to earth seperately from the house hence the rod purchase.

But why?

this small CU will have the new curcuit of 3 twin sockets and the lights running from it.

That CU needs to be installed by a registered electrician, as it's notifiable.

And anyway it's pointless - it's only a 13A supply - just have the sockets and a 3A FCU for the lights.