I contracted a landscape gardner to do a lot of work on our rear garden which inolved building a partition wall, filling in with hardcore and top soil to level everything off, followed by returfing everywhere. I requested cabling to be inserted so I can have an electrician hook up some garden lighting and connect to the cabling to our mains. Thing is the gardner has simply laid the cabling underneath the turf so what's that - about an inch and a half deep at most.
I'm no sparky and I'm concerned this isn't the best idea and when I do have a sparky come around to do the legit work and hook everything up they wont touch it.
If I was you I'd get on the phone to your landscape gardener and ask him to relay the cable properly. What he's done is probably more dangerous than just laying it across the surface of the grass - at least then you would SEE it before being electrocuted. I'm not sure what the regulations are, but I laid my armoured cable about 18 inches below the surface and the spark I used to connect it up seemed happy (ish) - maybe another six inches deeper would have been better!
For a lawn, 18 inches is reasonable. The Regs don't lay down a precise depth, but say sthg like 'beyond reasonably foreseeable digging depth'. That's widely accepted to be about 18inches in 'normal' bits of a garden, being 2 spade depths (so 'normal' digging won't touch it, and even full-on double-digging - wot I remember doing to very good effect in the end of the thankfully postage-stamp-sized garden in our first house!) will hit the "WARNING - BURIED ELECTRICAL CABLE BELOW" yellow warning tape and the bit of pea gravel the cable's laid in - these being the accepted form of Good Workmanship for buried cable.
Just below the turf is - as jd says - a *really* poor idea. It would be considerably better to run the cable - assuming it's SWA (steel wire armoured) which is what you need for direct burial - securely clipped
*above* ground, if there's a wall or robust fence (former is A-OK in Regs-land, latter gets rapidly iffier the more rickety the fence is!). That way it's clear where the cable is, rather than waiting for a spade or minidigger to Discover the cable...
Whether the OP's landscape gardener should be expected to know about cable-laying practices is not completely clear to me - if they advertise themselves as a full-service garden landscaping outfit and said 'yeah yeah' to the cable idea, they should have known how to do the job properly; if it's a jobbing gardener working under the explicit instructions of the OP without claiming any expertise, it's less definite, I'd guess...
No I didn't but it was pretty tough stuff - steel wired armoured. I'm not sure but I think you only need to use conduits if it is non-armoured. As Stefek has mentioned in his post, maybe you could simply run it above ground. But before doing that, maybe you should watch that episode of Curb Your Enthusiasm about the above ground cable.....
Everyone here has given you great advice on this subject.
Just as an extra thought- once you have the cable reburied correctly- make a rough sketch of your garden and mark on it where you burried the cable with some measurements from immobile reference points, like the corner of the house etc. Put this in a ziplock baggie and hang it on the wall next to your breaker box. Since markers will get lost over the years and memories do get a little fuzzy- this should make sure that if you need to do some digging in the area at some future date nobody gets a suprise or you don't accidently create more work for yourself by having to splice/repair a damaged power line.
I haven't checked the cable yet, it hasn't yet been connected so it's not live, but I'm guessing it's twin and earth because it was only =A31.50 a metre (so the gardner says).
Thanks for all your replies. I'm replying to my original post on 24th March with a couple further questions after consideration of posts so far and further study by myself.
My original post insinuated that 240v from the mains would be carried around the cable. If you read through the thread and posts so far the general consus is that this cabling is not sufficient for this purpose. I definately agree this cabling (it is by the way twin and earth looping around) is not sufficient or safe by a long way if I spur it directly off a mains - i.e. carrying 240v. However I've done some further studies and if I spur off a mains, hook it up to a 5A fuse box then through a transformer down to 12v would this be acceptable? i.e. the twin and earth that has simply been laid underneath the turf around the garden would only carry 12v - sufficient enough to power garden lighting? Please correct me where I'm wrong, I'm still learning about all this stuff, but as I understand it you can buy garden lighting that are already connected with thin wire and the plug has a built in transformer converting 240v down to 12v for the lighting. This thin wire is usually laid above ground. So again I'm assuming that twin and earth wire laid a couple inches below ground also carrying 12v should be safe also?
The second question I had related to the water feature our gardener has installed. The cable to the pump is separate to that cable I explain above, but it too has also been laid under the new turf, so again only a couple inches below ground at most. I have inspected the pump and the cable in to the pump is underwater (along with the pump). Is this normal? The cable looks like it was already connected to the pump, it looks again like twin and earth. I wasn't around when the gardener installed this but he suggested to my wife that a plug can be attached to the end of the cable so it can be plugged in to the mains just to test the pump. So my wife did that. We have only ever plugged the water feature in for a few minutes at most. But obviously this would mean that 240v is going through this cable, through what looks like twin and earth, just two inches below ground. I am concerned about that. So the questions I have about this then are 1. why is cable in the pump under water, 2. can I do something similar to the lights and run 12v to the pump instead of 240 and that way I can also use the existing cable the way it is? If not I'll definately lay armoured cable 18 inches below ground with warning tape above it etc..
It should be, but I would suggest using a proper garden lighting transformer unit rather than something intended for LV halogen lamps indoors, which might not be guaranteed to provide the necessary isolation.
At 12V however you will suffer voltage drop which will limit the demand you can carry - 5A for example will only give you 60W of lighting.
Ordinary T&E is not designed for direct burial regardless of the voltage.
It is normal for submersible pumps to have a length of *suitable* flex already attached. This must be connected to the fixed wiring outside the water by a *suitable* connection unit.
If it is ordinary twin&earth this is stupidity bordering on the criminally negligent. Most watertight cable glands work with circular flex/cable and will not form a long-lasting dependable seal with T&E.
What tests did he carry out on the wiring before connecting it to the mains?
To get to the pump, which is also under water.
You can run 12V (to a 12V pump, obviously) but the problem remains that the cable is unsuitable and may not last very long. You may also find that a 12V pump lacks sufficient oomph.
It really is the best way of doing it. To simplify wiring (subject to maximim loads etc) you can run one length of cable to everything and use X10 receivers in weatherproof boxes to switch individual things on and off by remote control (coloured lights, synchronised fountains, Handel on speakers concealed in the rockery, etc).
You would be well advised to ensure the wiring is inspected and tested by a competent electrician before connecting up, whether or not you intend to comply with Part P of the Building Regulations. You might prefer to do the trenching and cable laying work and get an electrician to supply and fit all the accessories.
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