Running electricity to the greenhouse

[Dave_S]

Hi all,

I would like a bit of advice / some photos if possible. I want to run an electricity supply to one of my greenhouses, mainly to run a propagator, but also on very cold nights to run a electric heater too, then I can transfer some of my more delicate plants to this greenhouse rather than bringing them into the house over the winter. I know I need armoured cable and waterproof sockets, i would like some help on how to actually run it 'into' the greenhouse i.e drill through the slab floor (it is totally slabbed) or drill through the metal base (which I dont really think is a good idea), and how to attach the sockets to the greenhouse frame etc...The greenhouse I want to run electric to is approx 35m away from the house, so it will be quite a long run of cable, and i'm guessing pretty expensive too. Anyway, any help very much appreciated!

regards

Dave

[Phil White]

Dave,
Firstly you have to decide what load you need e.g. 3 or 4 kW ?? as this effects the size of armoured cable you need.
As for drilling ideally through the floor but it is not a big deal going through the frame & fitting a junction box inside the greenhouse. I am not sure how you would install an earth rod at the greenhouse end which is what I did but I am sure there are other people here who can help.
Fixing inside a greenhouse is always a pain you mostly have to improvise e.g. aluminium bars/angle etc....

[Chris43]

I don't want to be a killjoy, but I believe that these days (since 2005) such an activity would be classed as something that should only be done by a qualified electrician. Lots of new regulations covering what probably most of us have done ourselves previously. The minimum is that it should be inspected "officially".

However, before the rules came into play, I put 2 new feeds into my greenhouse. What I did was: - from two spare locations in my main distribution box I wired a 30 amp cable to each up into the loft and then out to a fully weather sealed junction box close to where the next set of cables were to exit the roof space. From this box onwards I used armoured cables, two of them, down the wall and underground to a depth of about 18" or so, out to where the greenhouse was going to be (I was rebuilding it so did it at he optimum time). This then went into a weathersealed and fused junction box, and then to weathersealed sockets. IP56, I think, were the standard for weatherproofing I used. So the each circuit had two circuit breakers in them, one at the main distribution box end and one at the greenhouse distribution box.

If you've got slabbed flooring in your greenhouse, I'd certainly drill a hole for the cable to come through, as close to where you want to site your distribution box as possible, and lift the slap to give yourself room to get the cable up from below.

I had had heating problems previously, which is why I put in two cables, as in fact one 3kw heater will normally keep me frost free. But I'd lost several hundred plants in 2000 while I was working abroad and my single heater failed mid winter. So redundancy was a priority. In fact I also have a 4kw propane heater set below the electric heaters thermostat level just in case of a major power supply issue. Maybe overkill, but t's taken a long while to restore what I'd lost.

[Ray_M]

Chris is absolutely right,your installation needs to be done by a qualified electrician as i've just found out.Chris,what size is your greenhouse and do you bubble wrap it?I ask as my electrician(a good friend)will not advise me on size of heater as he says there are too many variables and doesn't want me to thump him if he gets it wrong.My g/h is 10 x 8 with a poly carbonate roof and i'm thinking of tubular heaters.Cheers,Ray.

[Phil White]

Ray,
I am not sure that is correct. Chris stated - "The minimum is that it should be inspected "officially". "
Which I believe means that you can do the installation yourself but it then needs to be inspected by the relevant authority.

[Chris43]

My greenhouse is 30 x 10 and I do have it bubble wrapped. I keep it at about a minimum (on the thermostats) at 7C. I have 2 x 3kw Biogreen heaters with digital thermostats which are much more accurate than the older sorts. The 4kw propane heater is back-up. This appears from the recent years history to be more than adequate, but it does depend on where your greenhouse is situated, prevailing wind, likely lows etc.

But a useful calculator is at Jungle Seeds which will give you a rough idea anyway.

Phil is right, you can do it yourself, but it does need ot be inspected. So you will need to follow all the various guidelines - there's a lot on the web about these.

[DaveW]

As an amateur you could always plead ignorance of the regs, since I doubt many of the general public would know of them, so thousands of illegal installations are still taking place every year.

Also all regulations start on a certain date and usually legitimise installations that took place prior to them. It would be up to the authorities therefore to prove whether the installation was pre or post the new regulations and that would be difficult if not impossible for them if old cable were used.

See:-

http://www.gardenbanter.co.uk/showthread.php?t=178635

It's the same with installing new windows which now require certification, but that obviously did not apply to those installed before the act. If you sell a house therefore how can the buyer prove the windows were installed before or after a certain date so needed a certificate? Some laws and regulations are virtually unenforceable.

However electricity is not something to mess with if you don't know what you are doing since water is slopped around in a greenhouse, plus they are often metal structures.

DaveW

[Diane]

Unless you know exactly what you are doing, Dave, I would strongly advise getting a qualified electrician to do the work, expensive though it may be. As DaveW says, electricity and water don't mix, and the installation has to comply with current regulations. We had ours done professionally 16 years ago, it was expensive, but had peace of mind that it was installed properly.

[Dave_S]

Thanks all for your replies,just for clarification it would be done by a professional electrician, i wouldn't even attempt it myself . I didnt know about getting it inspected though, you learn something new everyday. it's only an 8' x 6' and its bubble wrap insulated already, heating wise i only need something to keep it frost free, nothing too big and powerful. I will have to ask some local electricians for quotes for the work. Thanks again all

Dave

[Chris43]

Check with your local council for a list of who they will accept as a Competent Person. Hopefully the electrical contracor you choose will have this accreditation, so you won't have to worry about getting Building Regs and their inspection - which can cost!