Hello,

Please could you tell me what is the correct way for a [part P] person
to cable to an external light?

The tidiest way is probably to run cable under the first floor
floorboards but this can be a nuisance to do, so if the cable is run
along the exterior of the house, should the twin and earth be run in
conduit or just clipped to the wall?

One person has told me that if clipped to the wall, the plastic will
degrade in UV light, so I was thinking conduit was the answer. However
a second person has told me T&E will "sweat" in conduit, whatever that
means. Who is right?

Thanks.

Stephen coughed up some electrons that declared:

Hello,

Please could you tell me what is the correct way for a [part P] person
to cable to an external light?

The tidiest way is probably to run cable under the first floor
floorboards but this can be a nuisance to do, so if the cable is run
along the exterior of the house, should the twin and earth be run in
conduit or just clipped to the wall?

One person has told me that if clipped to the wall, the plastic will
degrade in UV light,

That can happen. There are other types of UV resistant cable - one
called "HiTuf" would be very suitable. Nothing special to terminate, it's
basically a very tough flex.

http://www.tlc-direct.co.uk/Products/HT1dot5slash3.html

so I was thinking conduit was the answer. However
a second person has told me T&E will "sweat" in conduit, whatever that
means.

Rubbish.

Cables are rated to carry lower currents in conduit, compared to
being "clipped direct" to a surface, and clipped direct is lower than on
ventilated cable basket or ladders.

For most lighting circuit arrangements (6A or 10A MCB), you'll be fine with
1.0 or 1.5mm2 in conduit.

From the OnSite Guide:

1.5mm2: In conduit on a wall = 16.5A
Clipped direct = 19.5A
Conduit in thermally insulating wall (ref method A) = 14A
On perforated cable tray = 22A

In the same order, for 1.0mm2: 13A, 15A, 11A, 17A

A bit of black conduit can look quite smart on a wall - just put a bit in to
carry the main earth bond to the gas meter.

Cheers

Tim

On Tue, 21 Apr 2009 23:00:56 +0100, Tim S wrote:

A bit of black conduit can look quite smart on a wall

Thanks for all the replies. What do you put at the end of the conduit,
and should you finish the T&E in the conduit and run a short length of
flex into the light, since in theory the light can be moved through an
angle?

Stephen wrote:
On Tue, 21 Apr 2009 23:00:56 +0100, Tim S wrote:

A bit of black conduit can look quite smart on a wall

Thanks for all the replies. What do you put at the end of the conduit,
and should you finish the T&E in the conduit and run a short length of
flex into the light, since in theory the light can be moved through an
angle?

Depends on the light. Some will have a mounting box with 20mm knockout.
With these it is easy to terminate the conduit directly onto the box.
With others a flex outlet may be required.

--
Cheers,

John.

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Stephen coughed up some electrons that declared:

On Tue, 21 Apr 2009 23:00:56 +0100, Tim S wrote:

A bit of black conduit can look quite smart on a wall

Thanks for all the replies. What do you put at the end of the conduit,
and should you finish the T&E in the conduit and run a short length of
flex into the light, since in theory the light can be moved through an
angle?

If it's hanging downwards, you can use nothing (lets condensation out which
is a plus).

Or, use one of these:

http://www.tlc-direct.co.uk/Products/MT20FMAB.html

solvent welded on

and one of these:

http://www.tlc-direct.co.uk/Main_Ind...lon/index.html

for a tight seal (or the round equivalent for flex)

If you want to transfer to flex from T+E, you could put a besa box or
similar upstream

http://www.tlc-direct.co.uk/Products/MT20BX2B.html

and put a terminal strip in (assuming it is accessible to check the
terminals in future) or use crimps or solder and some heatshrink.

I wouldn't stuff crimps up a conduit without a box though - people really
wouldn't expect that.

Obviously ensure you fit a gasket to the besa box lid for outside use

HTH

Tim

Part P non-notifiable is...
- cable enters light from rear, no external connections (new light
fitting)
- cable enters however if light fitting pre-existing (cable
replacement)

******** really.
I prefer to plug lights into a Masterseal socket. A bit ugly I'll
grant you, but your mind will soon change when you can prewire a light
fitting (and its replacement) sat on the ground then walk up a ladder,
fit it to the wall & plug in. A lot better than trying to fiddle with
an upside down junction box, whilst balancing on a ladder, which is
usually metal, some 20ft up in the air.

No-one is going to plug a hedge trimmer into it and the supply can be
(S)FCU protected at 3A as necessary on the inside. You can not however
use this with more complicated 4-wire PIR lights. Don't think
Masterseal do a "T-earth" pin version.

If it is a PIR, they tend to last longer when sheltered under eaves.

Surprised no-one suggested the obvious cable...
- White 1.0mm NoBurn cable from TLC
- UV ok, outside ok, just adhere to 6x min bend radius

The red is not UV proof and tends to oxidise a bit pink over time.

DP Sw or FCU on the inside?
FTE from wherever into it, through rear via 20mm conduit spanning any
cavity, into 20mm galvanised BESA box on outside with 6491X earth fed
back through conduit to isolator, exit bottom of galvanised BESA box
via IP68 gland to drip-loop into light. Most lights are IPx4, or claim
to be whilst havin a larf, so do not forget the drip loop into the
light fitting.

If you did use FTE with any gland it needs to be a Pratley gland -
they are listed on TLCs website.

js.b1 coughed up some electrons that declared:

Part P non-notifiable is...
- cable enters light from rear, no external connections (new light
fitting)
- cable enters however if light fitting pre-existing (cable
replacement)

******** really.
I prefer to plug lights into a Masterseal socket. A bit ugly I'll
grant you, but your mind will soon change when you can prewire a light
fitting (and its replacement) sat on the ground then walk up a ladder,
fit it to the wall & plug in. A lot better than trying to fiddle with
an upside down junction box, whilst balancing on a ladder, which is
usually metal, some 20ft up in the air.

No-one is going to plug a hedge trimmer into it and the supply can be
(S)FCU protected at 3A as necessary on the inside. You can not however
use this with more complicated 4-wire PIR lights. Don't think
Masterseal do a "T-earth" pin version.

3 phase "red" commando? One earth, one neutral and 3 live pins to play
with

In article ,
Stephen wrote:
Hello,

Please could you tell me what is the correct way for a [part P] person
to cable to an external light?

The tidiest way is probably to run cable under the first floor
floorboards but this can be a nuisance to do, so if the cable is run
along the exterior of the house, should the twin and earth be run in
conduit or just clipped to the wall?

One person has told me that if clipped to the wall, the plastic will
degrade in UV light, so I was thinking conduit was the answer. However
a second person has told me T&E will "sweat" in conduit, whatever that
means. Who is right?

Personally I think TW&E run externally looks cheap. Best option is bare MI
cable which is small and neat and will blend in well with most stone or
brick. Otherwise HiTuf.
http://www.tlc-direct.co.uk/Main_Ind...Tuf/index.html

Thanks.

--
*A bartender is just a pharmacist with a limited inventory.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
"Dave Plowman (News)" writes:

Personally I think TW&E run externally looks cheap. Best option is bare MI
cable which is small and neat and will blend in well with most stone or
brick.

Should use plastic sheathed MI if the wall contains cement,
to prevent any reaction with the copper sheath (only
necessary outdoors).

Unfortunately, the plastic sheath on MI doesn't seem to be
protected against UV, and generally flakes and drops off.

Otherwise HiTuf.
http://www.tlc-direct.co.uk/Main_Ind...Tuf/index.html

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Andrew Gabriel wrote:
In article ,
"Dave Plowman (News)" writes:

Personally I think TW&E run externally looks cheap. Best option is
bare MI cable which is small and neat and will blend in well with most
stone or brick.

Should use plastic sheathed MI if the wall contains cement,
to prevent any reaction with the copper sheath (only
necessary outdoors).

Doesn't seem to be a problem in practice - I've got some over 30 years old
which is showing no corrosion. Just a nice patina.

Unfortunately, the plastic sheath on MI doesn't seem to be
protected against UV, and generally flakes and drops off.

Oh dear. ;-)

Otherwise HiTuf.
http://www.tlc-direct.co.uk/Main_Ind...Tuf/index.html

--
*The only difference between a rut and a grave is the depth.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Stephen writes:
Hello,

Please could you tell me what is the correct way for a [part P] person
to cable to an external light?

The tidiest way is probably to run cable under the first floor
floorboards but this can be a nuisance to do, so if the cable is run
along the exterior of the house, should the twin and earth be run in
conduit or just clipped to the wall?

One person has told me that if clipped to the wall, the plastic will
degrade in UV light,

That is often quoted as a theoretical possibility.
However, I've never seen it happen, even with PVC which has
spent decades in the sun. You could paint the cable if you
want, which would provide even more UV protection, and
blend it in better with the wall. Slip some paper behind it
to protect the wall, and then paint with oil based gloss
topcoat directly, without any undercoat. Slide the paper out
whilst the paint is still wet, so it doesn't stick.

so I was thinking conduit was the answer. However
a second person has told me T&E will "sweat" in conduit, whatever that
means. Who is right?

Possibly referring to considerations of condensation formation
and drainage in conduit?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Stephen wrote:

Please could you tell me what is the correct way for a [part P] person
to cable to an external light?

What is a part P person?

The tidiest way is probably to run cable under the first floor
floorboards but this can be a nuisance to do, so if the cable is run
along the exterior of the house, should the twin and earth be run in
conduit or just clipped to the wall?
One person has told me that if clipped to the wall, the plastic will
degrade in UV light, so I was thinking conduit was the answer. However

In conduit is better generally since it give mechanical protection as well.

It does degrade *slowly* in UV, but the actual amount will vary on the
amount of exposure and the particular cable used. Something sheltered
would probably last indefinitely. The main risk would be something in
full sun that is also prone to getting knocked. The T&E insulation may
get brittle with exposure and age.

HITuf is ok, but it is quite bulky for a given size, and as easy to
handle as bagpipes! (its very stiff, and the outer insulation takes some
stripping!)

a second person has told me T&E will "sweat" in conduit, whatever that

No it won't. As Andy says you may get some condensation though (which
basically means drilling the occasional drain hole in fittings)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/