Hi I am looking for some advice in installing an outside plug socket
and security light in the garden. This is what I though I would do:

1.Take a spur from the downstairs main ring.
2.Connect the spur to a RCD.
3.Connect a cable from the RCD to a junction box
4.Connect 2.5mm armoured cable (about 12 meters) to the junction box
and lay under the lawn
5.Connect to a waterproof socket
6.From the waterproof socket spur to a 150W security light.

Does this sound expectable? Also I'm not to sure what size RCD I
should install. The only things that would be connected to the outside
sockets would be garden tools, or maybe a radio. (not forgetting the
150W light)

Could I use 1.5mm cable? or should I stick with 2.5 to reduce the
voltage drop?

Also I read somewhere that I may need to install an extra earth in the
garden near the socket. Is this correct. My supply is a TN-S.



Thanks

John

wrote:
Hi I am looking for some advice in installing an outside plug socket
and security light in the garden. This is what I though I would do:
1.Take a spur from the downstairs main ring.
2.Connect the spur to a RCD.

You may not need an RCD, if your socket ring is already RCD protected.
Cascading two RCDs in series will not usually provide discrimination (ie
either may trip in the event of a fault).

You can get Fused Connection Units with inbuilt RCD. You will need to
fuse the spur at 13A as you are supplying two points, and an unfused
spur on a ring can only supply one point.

3.Connect a cable from the RCD to a junction box
4.Connect 2.5mm armoured cable (about 12 meters) to the junction box
and lay under the lawn

With some 'buried cable below' tape between the surface and the cable.

5.Connect to a waterproof socket
6.From the waterproof socket spur to a 150W security light.

You may need to fuse down to 3A for the light (assuming the spur from
the ring is fused at 13A).

Does this sound expectable? Also I'm not to sure what size RCD I
should install. The only things that would be connected to the outside
sockets would be garden tools, or maybe a radio. (not forgetting the
150W light)
Could I use 1.5m m cable? or should I stick with 2.5 to reduce the
voltage drop?

I would stick with 2.5mm - voltage drop /might/ be an issue especially
at motor start. More importantly, digging up the lawn is the sort of job
you only want to do once, and the marginal cost of the larger cable is
insignificant.

Besides, 2.5mm lets you use the George Forman outside :-)

Also I read somewhere that I may need to install an extra earth in the
garden near the socket. Is this correct. My supply is a TN-S.

Probably not at 12m with TN-S.

(Part P will apply.)

Owain

On 27 Jun 2005 13:09:50 -0700,it is alleged that
spake thusly in uk.d-i-y:

Hi I am looking for some advice in installing an outside plug socket
and security light in the garden. This is what I though I would do:

fx: Mentions the existence of part P of the building regulations and
its effect of making this kind of DIY work illegal in passing, then
assumes the OP is in Scotland and thus not affected by them.

1.Take a spur from the downstairs main ring.
2.Connect the spur to a RCD.

Make sure the spur is *fused* not just a 'normal' unfused spur as if
it was another socket on the inside of the house.
( http://www.tlc-direct.co.uk/Products/CM4904.html ) is probably what
you'd be after on this count.

3.Connect a cable from the RCD to a junction box

Your solution of using a junction box outside to terminate the SWA
sounds reasonable, although you'd have to ensure a good seal around
the (presumably) T&E feeding the box, TLC supply glands for this
purpose for NotMuchMoney:-)

4.Connect 2.5mm armoured cable (about 12 meters) to the junction box
and lay under the lawn
5.Connect to a waterproof socket
6.From the waterproof socket spur to a 150W security light.

The light should be protected by the fuse recommended by the
manufacturer which is *probably* 5-6 amp maximum, which would not be
ok for the socket, given high loading of some garden tools.

I have thought of various ways round this without excessive expense,
the simplest (if clunky) solution is a double outside socket, of the
type with the in-use covers that can be occupied when wet, with the
light plugged into this using a 3-5amp fuse in the plug, outside FCUs
are available from TLC but the price made me go 'ouch'.

Does this sound expectable? Also I'm not to sure what size RCD I
should install.
(see points 1-2)

The only things that would be connected to the outside
sockets would be garden tools, or maybe a radio. (not forgetting the
150W light)

Could I use 1.5mm cable? or should I stick with 2.5 to reduce the
voltage drop?

Over 12m, volt drop shouldn't be a major issue at 13 amps or below,
but 2.5 is not much more expensive than 1.5 and it's less fragile.

Also I read somewhere that I may need to install an extra earth in the
garden near the socket. Is this correct. My supply is a TN-S.


To my knowledge, a TN-S supply is not the one that requires extra
earthing, you run into issues with TN-C-S (aka PME) when feeding
outbuildings/external equipment but I have never heard of requiring it
with a TN-S supply, although I am sure to be corrected if wrong g.

* Heavy disclaimer: Please, if you're not confident, and/or concerned
about complying with part P if not in Scotland, don't do this. If you
are confident etc, HTH:-) *

Also, I have no affiliation with TLC, they are just generally good
guys, and my closest wholesaler, and the one I am familiar with. Other
suppliers undoubtedly have the same things maybe at lower prices.

--
You cannot shake hands with a clenched fist.
- Indira Gandhi

Thanks for you help guys