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.
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.
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.
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:
On Mon, 17 Sep 2007 14:39:21 GMT someone who may be soup wrote this:-
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
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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.
If you read on a bit to the section on installing the sub main it gives some of the options:
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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.
the wall with screws and a substantial bed of mastic and ran the SWA into that from underneath using
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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.
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!
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.
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