Power to a greenhouse

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soup

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Sep 17, 2007, 9:51:36 AM9/17/07
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I am thinking of putting power out to the greenhouse (only for one light
and possibly a (small) heater, say, in total, 1100 watts worth) was
thinking of using a domestic outlet in the living room running the cable
through the living room wall via a vent (this cable would be some sort
of SWA) then down the garden (buried say a foot down) to the greenhouse,
cable terminated in some sort of trailing socket.
Anyone have any experience of running power out? I do not wish to
go the full; dedicated CU with armoured cable terminated in glands route.
--
'S rioghal mo dhream
Ciamar a tha sibh
www.cheesesoup.myby.co.uk

David Hansen

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Sep 17, 2007, 10:30:27 AM9/17/07
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On Mon, 17 Sep 2007 13:51:36 GMT someone who may be soup
<1...@invalid.com> wrote this:-

>I am thinking of putting power out to the greenhouse (only for one light
>and possibly a (small) heater, say, in total, 1100 watts worth) was
>thinking of using a domestic outlet in the living room running the cable
> through the living room wall via a vent (this cable would be some sort
>of SWA) then down the garden (buried say a foot down) to the greenhouse,
>cable terminated in some sort of trailing socket.
> Anyone have any experience of running power out? I do not wish to
>go the full; dedicated CU with armoured cable terminated in glands route.

How would the SWA cable be terminated in the plug and socket?

--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

soup

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Sep 17, 2007, 10:39:21 AM9/17/07
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David Hansen wrote:

> How would the SWA cable be terminated in the plug and socket?

AIUI BICBW the SWA cable is like a normal cable but with wires laid on
the outside then more insulation over that. I would take back the outer
insulation cut the wires around it at the end of the exterior insulation
then inside of this should (?) be a regular cable this I would deal with
as normal, ie remove outer insulation to expose three insulated wires
strip them and screw to terminals obviously all lengths etc so the unit
looks neat and is non dangerous. Possibly a piece of heat shrink tubing
over the lot just to neaten.

Andy Hall

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Sep 17, 2007, 10:35:03 AM9/17/07
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On 2007-09-17 14:51:36 +0100, soup <1...@invalid.com> said:

> I am thinking of putting power out to the greenhouse (only for one
> light and possibly a (small) heater, say, in total, 1100 watts worth)
> was thinking of using a domestic outlet in the living room running the
> cable through the living room wall via a vent (this cable would be
> some sort of SWA) then down the garden (buried say a foot down) to the
> greenhouse, cable terminated in some sort of trailing socket.
> Anyone have any experience of running power out? I do not wish to
> go the full; dedicated CU with armoured cable terminated in glands
> route.

You could run the power from the living room as a spur using a spur
unit with RCD either inside or a weatherproof one just outside.
Perhaps an outside socket at the living room position is useful as
well? If so, you can use one of the 20mm knockouts and fit the
cable terminating gland into that. Otherwise there are IP65 plastic
enclosures with terminal strip available that can be used to do the
same thing. Position the box over the hole in the wall and run T&E
through the back to the RCD.

A similar arrangement can be done at the greenhouse end. You can
terminate the SWA into a weatherproof socket outlet and FCU for the
light connection.

Have a look at MK Masterseal for a range of suitable wiring accessories.

If you are going to use SWA, you really need to use glands to terminate
the ends. This isn't difficult or expensive.

Steps are:

- Cut cable generously to length
- Cut tip off of the flexible shroud and place on cable
- Fit upper parts of fitting, up to and including ferrule onto cable.
On most connectors the ferrule is not cylindrical and goes one way
round.
- Cut around outer jacket of cable at the joint position and cut from
there to end using a utility knife
- Snip off steel wires using cutters. Leave the required length for
the fitting. The conical part of the lower part of the fitting
indicates that but usually around 20mm or so. Splay the wires
slightly.
- Assemble fitting laying the wires around the cone and pushing ferrule
over them.
- Tighten the two main parts of the connector together using two spanners.
- Tighten the top cable clamp
- Fit the fitting to the enclosure using washers, tag and nut.

John

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Sep 17, 2007, 10:40:55 AM9/17/07
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By using a socket outlet, you're creating a spur. If it's not fused,
the cable should really be rated at the same as the ring main for that
distance.
A buried cable should be deep enough to avoid the possibility of
damage including future changes to your garden layout. One foot down
is unlikely to achieve that. I would bury it at least two feet down.
The cable should be surrounded by sand and have a marker tape far
enough above it that it will provide a warning before the cable gets
damaged.
Greenhouses also get hot so your cable (and any other electrical
equipment) must be capable of withstanding that.

Andy Hall

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Sep 17, 2007, 10:42:46 AM9/17/07
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Not really safe.

The inner insulation is not intended for this purpose.

John Rumm

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Sep 17, 2007, 12:55:45 PM9/17/07
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soup wrote:

> I am thinking of putting power out to the greenhouse (only for one light
> and possibly a (small) heater, say, in total, 1100 watts worth) was
> thinking of using a domestic outlet in the living room running the cable
> through the living room wall via a vent (this cable would be some sort
> of SWA) then down the garden (buried say a foot down) to the greenhouse,
> cable terminated in some sort of trailing socket.
> Anyone have any experience of running power out? I do not wish to go
> the full; dedicated CU with armoured cable terminated in glands route.

You don't have to go for a full CU, but you do need to think through the
available alternatives and see what best suits your circumstances. You
can find most of what you need to know here:

http://wiki.diyfaq.org.uk/index.php?title=Taking_electricity_outside

--
Cheers,

John.

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

David Hansen

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Sep 17, 2007, 1:07:54 PM9/17/07
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On Mon, 17 Sep 2007 14:39:21 GMT someone who may be soup
<1...@invalid.com> wrote this:-

>> How would the SWA cable be terminated in the plug and socket?


>
>AIUI BICBW the SWA cable is like a normal cable but with wires laid on
>the outside then more insulation over that. I would take back the outer
>insulation cut the wires around it at the end of the exterior insulation

Then the armour of the cable will not be earthed and it needs to be
earthed at one or both ends.

The way to terminate SWA is with the appropriate glands at a
suitable location. This could be a box, from which say twin & earth
emerges. I suggest that you don't use SWA as I don't think you would
be able to do it properly.

You could wire the greenhouse by installing plastic conduit in the
ground and threading a suitable cable through it. Something on
http://www.screwfix.co.uk/app/sfd/cat/cat.jsp?cId=A331822&ts=48412
would be suitable, with appropriate accessories at both ends. Note
that if you are in England or Wales Mr Prescott's daft idea applies.

Electricity and the outdoors is a reasonably safe combination,
provided appropriate cable systems and equipment is selected and
installed properly. If this is not done then one is more likely to
come across a dead human or animal, a five year old nice or
grandchild perhaps, or a beloved pet.

Owain

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Sep 17, 2007, 1:01:13 PM9/17/07
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Which would leave the armour wires unearthed, negating much of the
protection offered by SWA.

Owain


jkn

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Sep 17, 2007, 1:33:18 PM9/17/07
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This thread has prompted me to read that useful section on the FAQ.
There I see it stated that

"SWA is frequently not brought right into the building at the head end
since it is relatively inflexible and difficult to work with."

What is done instead then, please? I was thinking of an outbuilding
supply using SWA and would be interested to learn about the options.

Thanks
J^n

John Rumm

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Sep 17, 2007, 1:42:09 PM9/17/07
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jkn wrote:

If you read on a bit to the section on installing the sub main it gives
some of the options:

http://wiki.diyfaq.org.uk/index.php?title=Taking_electricity_outside#Installing_the_sub_main

The usual solution is to fix a waterproof box of some description
outside and run the SWA into that with appropriate glands. You can then
drill straight through the wall from the box to allow a cable to
continue to the supply. This can be in T&E which is much simpler to
route and work with than SWA.

Andy Hall

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Sep 17, 2007, 2:26:00 PM9/17/07
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On 2007-09-17 18:42:09 +0100, John Rumm <see.my.s...@nowhere.null> said:

> jkn wrote:
>
>> This thread has prompted me to read that useful section on the FAQ.
>> There I see it stated that
>>
>> "SWA is frequently not brought right into the building at the head end
>> since it is relatively inflexible and difficult to work with."
>>
>> What is done instead then, please? I was thinking of an outbuilding
>> supply using SWA and would be interested to learn about the options.
>
> If you read on a bit to the section on installing the sub main it gives
> some of the options:
>
> http://wiki.diyfaq.org.uk/index.php?title=Taking_electricity_outside#Installing_the_sub_main

The
>
> usual solution is to fix a waterproof box of some description outside
> and run the SWA into that with appropriate glands. You can then drill
> straight through the wall from the box to allow a cable to continue to
> the supply. This can be in T&E which is much simpler to route and work
> with than SWA.

Spelsberg A-Boxes are good for this. There are a number of sizes,
plus different sizes of terminal strip inside suitable for terminations
of the range of conductor sizes likely to be used. The terminals can
be located in several positions inside the box to make termination of
the cable conductors easy. There are 20mm and 25mm knockouts on all
sides and at the back. The lid with seal This brand is
available inexpensively from RS and I think Farnell as well as
electrical wholesalers. I've also seen similar products from
manufacturers such as Fibox which are essentially the same thing.


Having said all of that, I have just done an SWA installation where I
didn't want to have an exterior box. This was for power to some
exterior lighting whereby the cable is run under the drive to a fixture
at the end. 2.5^2mm 4 core was used and has an overall diameter of
just under 15mm so fairly chunky. The supply for it is from an
installation in the garage and the cable position is very much on view,
so I didn't really want the box solution. As John suggests, turning
the cable through 90 degrees wouldn't have been a good solution either.

The solution I came up with was to determine a cable entry position one
course of bricks above the DPC - about 250mm above the ground. Knowing
the exact thickness of the wall plus internal insulation and paneling,
I was able to calculate an internal position for a hole drilled
downwards at an angle of about 25 degrees or so relative to the wall
surface. I used a long, thinner SDS drill to make the initial hole
and then a 16mm one to complete it, thus avoiding breakout of the brick
on the outside. However, I did chip away a slight groove below the
hole on the outside to take the curve of the cable.

Threading the cable through proved to be a challenge. Even this stiff
cable tends to bend. I cut the SWA well over length and then cut
about 500mm of outer insulation from the end. The steel wires were
then snipped off. From inside, a piece of 15mm copper tube was fed
downwards through the hole to the outside. The inner insulated bundle
of conductors fits neatly inside the tube so can be thread upwards.
I put a layer of tape where the outer insulation had been cut to avoid
snagging. The tube could then be withdrawn in stages as the SWA was
fed inwards and upwards through the wall.

Finally, the SWA was terminated at a box inside as before, with a short
length of 20mm conduit connecting that to the centre compartment of
some 3-compartment trunking that runs around all the walls. The final
wiring back to the CU in the workshop is then done in singles.
Obviously this part could be done in T&E if preferred.

The final result is a short length of SWA close to ground level
entering neatly through the wall.

jkn

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Sep 17, 2007, 3:42:32 PM9/17/07
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Thanks John & Andy - that's really useful.

J^n

Dave Gordon

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Sep 17, 2007, 5:28:59 PM9/17/07
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"jkn" <jkn...@nicorp.f9.co.uk> wrote in message
news:1190050398.9...@o80g2000hse.googlegroups.com...

I attached an outdoor box
http://www.screwfix.co.uk/app/sfd/cat/pro.jsp?cId=A331873&ts=63869&id=11549
to the wall with screws and a substantial bed of mastic and ran the SWA into that from underneath
using
http://www.screwfix.co.uk/app/sfd/cat/pro.jsp?cId=A331873&ts=64018&id=14198
Then standard 13A T&E through the wall from the back of the box to a 6A fuse inside. The fuse linked
the spur to the ring main.
The cable powers a pond pump and a socket for the lawn mower, and a couple of pond heaters in winter.


John Rumm

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Sep 17, 2007, 5:55:58 PM9/17/07
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jkn wrote:

> Thanks John & Andy - that's really useful.

As an aside, I used one of these the other day:

http://www.tlc-direct.co.uk/Products/LB9045.html

And was surprised to find it came complete with a boiled sweet waiting
inside for the lucky installer. I don't think it was an accident either,
since the wrapper bore the makers "ELS" logo and details!

Andy Hall

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Sep 17, 2007, 6:51:54 PM9/17/07
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On 2007-09-17 22:55:58 +0100, John Rumm <see.my.s...@nowhere.null> said:

> jkn wrote:
>
>> Thanks John & Andy - that's really useful.
>
> As an aside, I used one of these the other day:
>
> http://www.tlc-direct.co.uk/Products/LB9045.html
>
> And was surprised to find it came complete with a boiled sweet waiting
> inside for the lucky installer. I don't think it was an accident
> either, since the wrapper bore the makers "ELS" logo and details!

It's worth putting them underground just so that one can play with the
epoxy gunk :-)


John Rumm

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Sep 17, 2007, 11:30:01 PM9/17/07
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Must admit to never having had the need to pot a junction box yet...

jkn

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Sep 18, 2007, 3:52:10 AM9/18/07
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damn, having to reply to my own posting. Nevertheless, I've just
realised I have a supplementary question:

How are you supposed to join the steel wire part of the SWA to eg.
earth if you are using one of these junction boxes? TBH, considering
the admonitions elswhere about only connecting T+E using proper crimp
connectors, I'm a little surprised that these 'glorified chocolate
box' connectors are considered OK in the first place.

Ta
J^n

On Sep 17, 11:51 pm, Andy Hall <an...@hall.nospam> wrote:

Andy Burns

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Sep 18, 2007, 4:02:38 AM9/18/07
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On 17/09/2007 22:55, John Rumm wrote:

> As an aside, I used one of these the other day:
>
> http://www.tlc-direct.co.uk/Products/LB9045.html
>
> And was surprised to find it came complete with a boiled sweet waiting
> inside for the lucky installer.

The A-boxes I've bought from B&Q and screwfix had no sweeties :-(

Andy Hall

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Sep 18, 2007, 4:12:41 AM9/18/07
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On 2007-09-18 08:52:10 +0100, jkn <jkn...@nicorp.f9.co.uk> said:

> damn, having to reply to my own posting. Nevertheless, I've just
> realised I have a supplementary question:
>
> How are you supposed to join the steel wire part of the SWA to eg.
> earth if you are using one of these junction boxes?

Gland packs come with a tag, an extra nut and a serrated washer which
fits over the 20mm threaded part of the fitting inside the box.

An earth wire can be soldered to the tag or fitted using an extra
crimped tag, bolt, nut and serrated washer through the small hole in
the tag

> TBH, considering
> the admonitions elswhere about only connecting T+E using proper crimp
> connectors, I'm a little surprised that these 'glorified chocolate
> box' connectors are considered OK in the first place.
>
>

They are rather better than chocolate box connectors.

However, the point about using crimps is for cases where the connection
is not going to be accessible in the future - e.g. buried in a wall.

For wiring accessories, which are accessible, screw terminals are OK.

In the particular application of the little box, one could crimp the
connections

Andy Hall

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Sep 18, 2007, 4:31:33 AM9/18/07
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Staff pilferage.


jkn

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Sep 18, 2007, 5:51:33 AM9/18/07
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Hi Andy

[much useful stuff snipped]

OK, Ta.

Jon N

John Rumm

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Sep 18, 2007, 6:22:34 AM9/18/07
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Andy Hall wrote:

> Gland packs come with a tag, an extra nut and a serrated washer which
> fits over the 20mm threaded part of the fitting inside the box.
>
> An earth wire can be soldered to the tag or fitted using an extra
> crimped tag, bolt, nut and serrated washer through the small hole in the
> tag

I must admit to being a fan of these:

http://www.tlc-direct.co.uk/Products/PRPEN20.html

You discard the backnut and solder tag, and use this much more
substantial nut in its place (which has small teeth on one side to grip
the inner wall of the box - allowing the gland to be tightened with one
spanner). You can then crimp a eye terminal on the end of your earth
wire, and screw it to the side of the new nut with the supplied screw.
Seems much simpler than needing to solder to a heavy tag "in the field"
so to speak.

John Rumm

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Sep 18, 2007, 6:26:03 AM9/18/07
to

I suppose in a world where one wants to try and create unique selling
points for what is otherwise a "me too" product, it is quite a clever
idea. If you are ordering the things on a regular basis, you may opt for
the one that gives you a bonus each time you use it!

(having said that, they are nice boxes anyway - the knockouts are made
of a rubbery type material that you can easily trim out with a knife
rather than needing a hole drill, decent terminals, and a sealing strip
built in).

Andy Hall

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Sep 18, 2007, 6:42:43 AM9/18/07
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On 2007-09-18 11:22:34 +0100, John Rumm <see.my.s...@nowhere.null> said:

> Andy Hall wrote:
>
>> Gland packs come with a tag, an extra nut and a serrated washer which
>> fits over the 20mm threaded part of the fitting inside the box.
>>
>> An earth wire can be soldered to the tag or fitted using an extra
>> crimped tag, bolt, nut and serrated washer through the small hole in
>> the tag
>
> I must admit to being a fan of these:
>
> http://www.tlc-direct.co.uk/Products/PRPEN20.html
>
> You discard the backnut and solder tag, and use this much more
> substantial nut in its place (which has small teeth on one side to grip
> the inner wall of the box - allowing the gland to be tightened with one
> spanner). You can then crimp a eye terminal on the end of your earth
> wire, and screw it to the side of the new nut with the supplied screw.
> Seems much simpler than needing to solder to a heavy tag "in the field"
> so to speak.

Ah. Now those are a good idea.


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