I need to install an external socket and a few garden lights (mixture of LV
LEDs and GU10 halogen fittings) in my garden (approx 5m from the house) and
have a few questions:

1.) For one of the cable runs in the garden I will need to run 3 separately
switched circuits for the deck LEDs, pond pump and step lights (LED).It will
need to run underground so I was thinking of using polypropylene conduit
(http://www.toolstation.com/index.html?code=20536) with 3 lengths of single
core conduit cable for each of the switched live circuits. If I bury at the
recommended depth (450mm) and cover with slabs, presumably this will offer
comparable mechanical protection to SWA as interpreted by the regs? The
neutral and earth I would run separately (probably in some left over 2 core
SWA)

2.) I need to work out how to power the external socket/lights from the
house. The easiest option is to run a spur off the ground floor ring (using
a 13A RCD FCU -
http://www.screwfix.com/app/sfd/cat/...14770&ts=48780) and then from
that a branch with a 3A FCU for the external lights.
Looking at the Collins DIY interpretation of the wiring regs they seem to
state that if an external power socket (or light for that matter) is NOT
located on the external wall of the house then it has to be run in a
separate (RCD protected) circuit direct from the CU. This seems overkill for
one outdoor socket and a few lights, and wonder if they are talking about
power to an external outbuilding (where potentially the loads would be much
higher with separate ring circuits etc)

3.) As part of the lighting, I will be installing three recessed ground
lights in the patio
(http://www.screwfix.com/app/sfd/cat/...04 2&ts=49971)
These come preinstalled with 1m of flex to a waterproof junction box which
will accept PVC flex. The instructions are rather vague about installation
in the ground, presumably the 1m flex will need mechanical protection since
the whole light is buried in the patio? I wanted to run SWA to each of the
fittings but they won't accept SWA so I was thinking of running the SWA to a
IP box on the wall and then run flex from there to the junction box (below
ground) if that is permissible? Again difficult to interpret from the regs.

PLS

On Mon, 02 Apr 2007 23:15:18 +0100, Owain
mused:

You *must* run the lives, neutral and earth together in one conduit or
cable.

Says who?
--
Regards,
Stuart.

On Mon, 02 Apr 2007 21:44:27 GMT, "pls" mused:

I need to install an external socket and a few garden lights (mixture of LV
LEDs and GU10 halogen fittings) in my garden (approx 5m from the house) and
have a few questions:

1.) For one of the cable runs in the garden I will need to run 3 separately
switched circuits for the deck LEDs, pond pump and step lights (LED).It will
need to run underground so I was thinking of using polypropylene conduit
(http://www.toolstation.com/index.html?code=20536) with 3 lengths of single
core conduit cable for each of the switched live circuits. If I bury at the
recommended depth (450mm) and cover with slabs, presumably this will offer
comparable mechanical protection to SWA as interpreted by the regs? The
neutral and earth I would run separately (probably in some left over 2 core
SWA)

I''d run a couple or 3 SWA cables out, or a 7 core SWA.

2.) I need to work out how to power the external socket/lights from the
house. The easiest option is to run a spur off the ground floor ring (using
a 13A RCD FCU -
http://www.screwfix.com/app/sfd/cat/...14770&ts=48780) and then from
that a branch with a 3A FCU for the external lights.
Looking at the Collins DIY interpretation of the wiring regs they seem to
state that if an external power socket (or light for that matter) is NOT
located on the external wall of the house then it has to be run in a
separate (RCD protected) circuit direct from the CU. This seems overkill for
one outdoor socket and a few lights, and wonder if they are talking about
power to an external outbuilding (where potentially the loads would be much
higher with separate ring circuits etc)

Coming off the socket circuit via an RCD spur is fine. Even if your
sockets are already protected by an RCD then the additional RCD spur
will hopefully provide some descrapncy.

3.) As part of the lighting, I will be installing three recessed ground
lights in the patio
(http://www.screwfix.com/app/sfd/cat/...04 2&ts=49971)
These come preinstalled with 1m of flex to a waterproof junction box which
will accept PVC flex. The instructions are rather vague about installation
in the ground, presumably the 1m flex will need mechanical protection since
the whole light is buried in the patio? I wanted to run SWA to each of the
fittings but they won't accept SWA so I was thinking of running the SWA to a
IP box on the wall and then run flex from there to the junction box (below
ground) if that is permissible? Again difficult to interpret from the regs.

I wouldn't use a junction box underground. If the provided flex is too
short replace it with a longer length and use flexible conduit for
some protection, but keep the runs from the lights to juncrtion boxes
as short as possible.
--
Regards,
Stuart.

In message , Lurch
writes
On Mon, 02 Apr 2007 23:15:18 +0100, Owain
mused:

You *must* run the lives, neutral and earth together in one conduit or
cable.

Says who?

The feed and return of any given circuit should be paired in metal
conduit or armoured/screened cable to prevent eddy current issues.
Whether this is a supply or two switch wires it's important they be
contained together.

It's a similar scenario to making sure that the three phases in
distribution equipment are all run through a single hole.


--
Clive Mitchell
http://www.bigclive.com

On Thu, 05 Apr 2007 23:05:22 GMT, Clive Mitchell
mused:

In message , Lurch
writes
On Mon, 02 Apr 2007 23:15:18 +0100, Owain
mused:

You *must* run the lives, neutral and earth together in one conduit or
cable.

Says who?

The feed and return of any given circuit should be paired in metal
conduit or armoured/screened cable to prevent eddy current issues.
Whether this is a supply or two switch wires it's important they be
contained together.

It's a similar scenario to making sure that the three phases in
distribution equipment are all run through a single hole.

Yes but the OP was on about using flexible PVC tube. I know about
using a single hole in metal enclosures for live and neutral etc...
but Owain said live, neutral and earth together in any conduit or
cable.
--
Regards,
Stuart.

On Sat, 07 Apr 2007 20:12:55 +0100, Owain
mused:

Lurch wrote:
You *must* run the lives, neutral and earth together in one conduit or
cable.
Says who?

"Single-core cables (without armour) enclosed in conduits or trunking
must be bunched so that the outgoing and return circuits are enclosed in
the same conduit or trunking. This must be accepted as a gnereal rule
for all ac circuits ... If single-core cables are enclosed in separate
metal conduit, trunking or metal armouring, the resultant induction
losses could be very marked, and cause considerable voltage drop and
overheating of the cables and the enclosure. A voltage drop of 90%, and
consuderable overheating, has been known when single-core cables,
enclosed separately in magnetic metal have been connected to an ac
supply" "Modern Wiring Practice", Steward & Stubbs, 10th Ed

Okay they talk about metallic conduit, but I think it would be Good
Practice to adopt anyway.

Yes, where possible\practicable, but I was under the impression it was
for metallic conduits and enclosures only so was just wondering what
your source was.

Cheers for quoting the source.
--
Regards,
Stuart.