Topic: Electricity in the greenhouse

[macmac]

My friend has just had a new greenhouse and wants electricity installed.does anybody know anything about this dos and don'ts.She's had three electricians look at and each gives her differing info as to whether the cable can be attached to the adjacent fence or must be buried. ::)

[Trevor_D]

Mine went in nearly 30 years ago and we had a choice between burying it (which is what we did) or an overhead cable. (It's only 10 feet away from the house, so no problems either way.) But regulations on everything electrical have tightened up a lot since then. It's illegal to put in an extra socket, which we used to do as a matter of course.

I'd check the current regulations, but go for burying it. And put in a circuit breaker at the GH end.

But yes, electricity: GH heater; heated sand-bench; Radios 3 & 4....

[Baccy Man]

All work has to be carried out by a qualified electrician to comply with Part P to the Building Regulations.
Normally for a shed/greenhouse/garage supply the reccomendations are to bury the cable 2' below ground level, it should be steel wire armoured cable & ideally should run through a pipe to give extra protection from digging tools.

[siandc]

The cable (armoured) if buried should be 18" deep, in soft sand or pea shingle with a tape above it warning about the buried cable. Similar to this...

Fixing to a fence can be done but it depends on the construction.
Personally I'd lay the cable on the surface at the bottom of the fence, this way it is visible and away from "traffic"
It will be ESSENTIAL to have the cable protected by RCD. Also, depending on the distance from the house the greenhouse may be classed as a seperate equipotential zone and require its own, independant earthing.
The installation will be covered under Part P of the building regs and must by law be notified to local building control.

[grawrc]

This is a bit alarming! I have a switch in the house for an outdoor cable which goes to a shed about 70 feet away. The cable runs along the top of the fence. It has been there for a long time. It is pretty stout cable. Is it OK or not? What happens when I need to replace the fence? Can I just put the cable back along the new fence or do I need to start excavating under it?

[Chrispy]

Yes grawrc, you probably will.

What I would recommend to anybody who already has outdoor power, is if it was fitted more than a few years ago, it is probably legal, but legal or not, if it does not have an RCD, get one fitted, it could save your life.

[Baccy Man]

If the cable was there before 2005 then it is exempt from building regs so you don't legally have to do anything to it. When the cable eventually has to be replaced then it would have to comply with the new regs.

[grawrc]

Thank you for those replies. The cable was installed by my FiL in 1994. Formerly the outside power  was used for my FiL's "workshop" where he did lots of carpentry. Nowadays it is used for recharging batteries (strimmer and lawnmower) and for using appliances like hedge trimmer. Clearly those could be done from inside the house, especially if I replaced  my current hedge cutter with a battery owered one (might be a good idea since I regularly slice through the cable  :-[ :-[). The only other thing is light in the shed. Not sure I really need that either? Oh just remembered! The fountain in one of the ponds is also powered from the shed.

[Tee Gee]

My supply is by overhead cable supported on support wire (fencing wire) then it is carried along a 6ft high trellis fence to the greenhouse!  see pic below

It has an RCD at its source and goes into a  fused control box then each socket (5) has it own dedicated fused spur.

From these I power my light, hotbed, fan, radio and one for outdoor appliances e,g lawn mower.

So none of my sockets are ever overloaded ( so far as I know)

[macmac]

Thanks for all the information ,'though some of it very technical ???Tee Gee when was your power connected ? 'cos we've got supply running from the garage along the garden fence but it was over 5 years ago and the rules seem to change constantly.Which is probably why the electricians my friend has spoken to are giving different information ::)

[tartonterro]

I take it the regulations only apply to installations that connect into the wiring circuit of the home.  The connection i am planning on making to my mums greenhouse uses a RCD plugged into kitchen socket, run out to greenhouse and connected to Fully weatherproof socket (weather proof with cable plugged in and switched on) = as this is in theory an extension lead it wouldnt require approval by local building control department - or am i wrong?

[macmac]

My friend will be connecting to her garage supply. Does this make a difference  ???

[chriscross1966]

According to the now current 17th edition rules (superceding 16th/Part P) all fixed electrical installations (new sockets anywhere connected to the mains) have to be installed by a qualified electrician....
Glad I did the shed long before that cos I habitually use massively over-specced cables for the feeds and by using the old house breaker box (we replaced the original one to give us the extra breakers) in the shed I have two independant lighting circuits, two independant mains sets of sockets and another independant feed to my lathe and mill and the exterior socket is on a seperate trip (and RCD) of its own.....  I couldn't afford to get a sparks to do all that....

chrisc

[Tee Gee]

Tee Gee when was your power connected ?

Can't recall exactly?? 10+years I supppose.

Another thing to watch is that you don't overload the existing ring main.

Like CrissX I have use the circuit breaker that I pulled out when I had the new box and RCD fitted.

The other thing I did was took a new ring main from the 30amp cooker connection that became superfluous when I switched to gas. So my extension & greenhouse is on this and the rest of the house is as it was!

Trouble is now: we need a new oven and there is more choice with 'electric' models than gas so it would mean some lengthy electrics to refit a 30amp supply so it looks like we will have to pick from a very limited choice............so much for progress!! >:(