Greenhouse Eletrics

[Liamas]

Can someone suggest the best cable for this, I need at least two double sockets, would love more but that might be pushing it.

At the moment there are two extension leads cable running to the greenhouse which appear to be wired into a double socket in the downstairs kitchen.

I'm looking to improve this as it can't be that safe?, although it works, well one line does the other blows the electric with overload.

P.S I did not wire any of this in, it was already there.

I need to run:

A 3kw heater (normally on 2kw setting)
My grow lights which are:
12, 54watt floresent grow light bulbs. Thats one 8 tube which is 4 ft long, and one 4 tube which is 4 ft long.
Warming cable.. About 75 watt
Propagator..About 22 watt

3745 max watts?
Greenhouse is approx 15-20 foot away from house.

 

[RF Lighting]

Right, the first thing you need to do is work out the desired load for this circuit.

What are you planning on running from it?

Will it just be to plug a radio into now and again, or are you wanting some form of heating in the greenhouse?

Do you plan on installing any lighting into the greenhouse?

Can you post us a picture of your existing fusebox, and any associated equipment around it such as the cutout which supplies the meter?

 

[Liamas]

Ok most of what you asked Is in my updated edited post. As for pictures I'm not at the house at the moment, so I will upload tomorrow.

Your help is appreciated, cheers.

 

[ericmark]

It seems the government does not agree and they have introduced Part P which means if you alter any wiring in your garden then you have to pay the local authority building control (LABC) a fee of £100+. However electrician who are registered pay a lot less around £5 depending on how much work they do as annual fee so for small jobs it is now cheaper to get an electrician to do it than to DIY.

Of course you can break the law but that would also effect insurance. When the electrician calls he will look at the existing insulation and he we need to ensure your supply is protected by an RCD. He will likely use steel wire armoured cable (SWA) and either a fused connection unit (FCU) or a combined FCU/RCD but he may also take it back to your consumer unit.

Likely he will want to bury the cable and likely if a trench is provided by you he will use it. But he must see cable in trench so don't back fill until inspected. For a green house he will likely use 2.5mm sq cable as rated around the 20A mark which is well above the 13A a fuse will limit supply to. He will also select glands for outside which also seal the outer as well as inner cores.

It seems the pricing of Part P is under review and I would say this is right time to complain to MP they want your vote. The problem is the minimum charge is for £2000 worth of work so although fair for re-wire it is daft for small jobs. However the electrician will likely visit once but LABC will likely come 2 or 3 times and you pay for his fuel with fee. On the plus side he also has to test your work to ensure it is safe and then issue you with completion certificate. The electrician will not only issue completion certificate but also other paperwork giving all readings needed next time house electrics are inspected.

 

[RF Lighting]

Right, from that, you need at least a 20A supply, but for the difference in cost I'd definatly want to install a 32A supply just to give you a bit of future proofing incase you ever want to upgrade one of your components, or you have forgotten something.


You should be fine to run this on a 4.0mm² SWA cable.

Now the tricky bit is to work out what sort of earthing system you need to use in the greenhouse.

Is the greenhouse metal framed, and is there or do you plan to have a water supply into the greenhouse?

We will also need a photo of your mains incommer to determin your current supply type as this may have a bearing on what sort of earthing system you need to use at the greenhouse end.

 

[333rocky333]

Can someone suggest the best cable for this,

Proberly looking at a lump of SWA cable
"steel wired armoured".

 

[Liamas]

Thanx for the help, all very usefull and interesting.

My greenhouse is made from aluminum and water is supplied via a hose in summer, watering can in winter.

I shall get some pics up when I'm at the house next.

 

[ericmark]

When writing first reply did not see load requirement it is over 13A so FCU is out and it's back to consumer unit job and as already said at least 4mm SWA see Issue 16 Autumn 2005 and PDF Electrical installations outdoors: a supply to a detached outbuilding a little out of date but still a good start.

 

[Liamas]

Thanx, just reading the pdf file, looks very usefull.