Running electricity to the greenhouse

[Peter]

My 40ft x 21ft greenhouse was'wired up' by a local electrician in a morning. That included 4 x waterproof double sockets (ex Wickes), six fluorescent lights (again ex Wickes), almost new distribution box (supplied by the electrician), fed by a dedicated breaker on the house distribution box. There is a spur off the armoured cable to feed three sockets and a lighting circuit in my shed.

The electrician charged £100 and the job is very professional in appearance. The greenhouse was expensive and I wasn't about to spoil it with loose and twisted wiring all over the show!

[Julie]

Me and my dad, on the advice of my uncle who is a retired electrician, laid ours to the shed some years back... 5-10 years? Before Health and Safety got the nappies out.

We got semi armoured cable and threaded it into reinforced garden hose with the help of Fairy liquid... although only 6m at most, and it was hard when we got to the end. I would recommend fully armoured cable in your case! It is about 9 inches deep and under a little soil and in some places big gravel.

Me and the parents have also installed a boiler and then got an electrician to check it over afterwards.

Don't be put off from using your brain, just because there are new rules to prevent chavs from frying themselves. Do what you feel able to do, then pay £70 to get an electrician to check it out. I bet the cable costs more than that anyway.

Electricians have a licence to print money... your money. Spend it on plants instead!!

[iann]

Sounds like you got a bargain, Peter!

Its a bit of a nightmare with everyone confused about how the new regulations work. At one level, its a bit like the CORGI (now Gas Safe, how much did they pay for that re-branding?) for gas fitters. Electricians now have to be registered under the Part P (catchy ) regulations to do most jobs. But you can legally do it yourself and have it inspected afterwards. Any Part P electrician can do this, but apparently also your local authority can do it although don't expect them to necessarily know about that. First port of call would probably be the planning office to try and get someone to come out. As Dave says, if you know what you're doing (do you, really?) then it would be simpler to do it and say it was done 5 years ago

[iann]

Lots of variables on heating a greenhouse, not least how warm you want it and how cold it gets where you live. For that 10x8, 2kw should be enough to get by, 3kw would be better. Another variable is how your thermostat works, whether it lets the temperature drop quite a lot before kicking in and having to warm everything up again.

[Vic]

Dear Moderators


I am not a BCSS member, but I am writing in response to a forum thread "Running electricity to the greenhouse".


To install mains electricity anywhere in a garden, you must use a "Part P" qualified competent person. Ask a trade association such as NAPIT (napit.org.uk) for details of competent members in your area.


Cables under the ground must be:
. armoured or enclosed in a duct
. buried at least 20" / 500mm below the surface, on a layer of sand with more sand above
. marked by a marker ribbon 6" / 150mm below the surface
. terminated in a weatherproof enclosure or socket outlet rated IP54 or greater
. electrically earthed by the armoured shield as well as any protective earth conductor in the cable
. supplied by a 30mA RCD-protected power source.


All equipment used in greenhouses or outside must be Class II insulated.


I hope that this will be of use to your members.


Malcolm Chisholm

[Mike P]

As has been noted above there is now a section of the Building Regulations (Part P) which covers external wiring and most internal wiring now (Kitchens and bathrooms particularly).
I ran a supply to mine just before the regs came in using some relativly cheap armoured cable - I shopped around and found a supplier who was having a clearance sale and it was just over half the price I was quoted generally.
The biggest problem I found was trying to bury cable in a fully stocked suburban garden when the cable is very rigid and has a mind of its own...and its very difficult to bend it to anything like a sensible radius when you bring it into the house and greenhouse.
You could probably install the cable yourself and then employ an electrician to make the connections at each end.

[Agavegeoff]

Hi, all.
So what rule apply If you run a cable over the garden on a pole.

[Diane]

That's a catenary wire, Geoff. This might be useful to know!

[Chris L]

As my plants have suffered again with the very cold weather. I'm thinking of installing an electrical heater in my greenhouse over the summer ready for next winter. I used to use paraffin until I nearly set the greenhouse on fire ( )

I have a 6x4 greenhouse that is about 20 feet from the house.

My concern is that it would be very difficult (i.e. impossible) to bury the cabling underground (there is a concrete path and a wall between the house and the greenhouse - can supply pictures for clarification if needed). Would it be acceptable/allowable to have the cabling housed within some kind of metal/plastic piping that is then fastened to the garden wall ? Obviously I'd get an electrician to do all the work.

Am I correct in thinking I'd need somewhere between a 1kW and 2kW heater, with 2KW being too much?

And also if I was thinking of concreting the greenhouse floor (20 square feet?) how much would it roughly cost?

Many thanks for any help and advice.

[iann]

Strangely enough, I think you are allowed to run outdoor cabling above ground subject to certain conditions. Obviously that isn't just a wire running across the lawn! Your electrician should be able to advise you more reliably.

If your plants are mostly hardy and you just want to keep them from freezing too hard then 1kW is plenty in a small greenhouse. To maintain frost free you would probably need 2kw. Small greenhouses are not very efficient to heat. Your electrical connection should be for more, probably 13A would do if you only want a max of 2kW. Or get even more, or two circuits, since it won't cost that much more once you have someone there.