i am wanting to put three double sockets into my shed come undercover deck area, would run on it, two halogen heaters, each 1300w then possibly some low voltage garden lights, a hifi and two lamps, the type that you have in your living room.
was going to wire up the wall sockets in line and then have a trailing flex go through the window of my conservatory, 4mts max distance and just plug straight into the wall socket, any good or not?, basically it would be just like a 6 gang extention lead would it not?
failing that, in the conservatory i have built in air con unit that never gets used, it has it own supply from the consumer unit in the garage, wired via a FCU, could i just wire the flex into that and disconect the air con unit, that way the shed would be fused and on its own supply right?
First the Law. Under Part P any fixed installation in garden, kitchen and bathroom must get approval either by using some one who is a member of one of the clearing houses or from local authority building control who will charge £100 plus. In theory if you knock in one cable clip it's fixed so what you want to do will require notification under Part P. (The fact it is plugged in makes no difference.) I don't agree with Part P but you should be aware what you are intending to do will unless you pay the fees before you start break the law.
Now forgetting the above on to the work you want to do. The two halogen heaters will on there own exceed 2kW and really as such it should have a dedicated circuit. Likely you are just below 3kW so it likely would work but I would consider using only one heater per 13A outlet.
Water outside is a problem and specially with anything that produces heat. What happens is the heat expands the air and once switched off as it cools air or water is sucked back in. Often it is the latter and even the fuse in the plug gets hot so plugs and sockets left outside will likely fill with water.
So the British regulations BS7671 require all items outside will be RCD protected. Since 2008 this has been for all sockets under 20A but RCD outside requirement was long before that.
Any wire for outside will be black because of the sun light degrading the cable. The regulations don't say steel wire armoured must be used but go into loads of different ways to protect the cable. But I would not run any cable outside which was not SWA.
There are kits which the manufacturers claim do not require Part P. Seem to remember Blagdon who specialise in pond stuff make them so may be worth a trip to local pond and garden centre and see what is available. I don't approve of the system but it would be better than many DIY jobs I have seen.
The main problem as I see it is neighbours. If you upset them and they complain and you have broken the law then you may get found out. There are a host of Part building regulations including Part F which restricts the size of outdoor lights etc without planning permission.
Under British law there are loads of items that can be sold to but not used by the general public from radio transmitters to outside lights. Just because you can buy it does not mean you can use it.
What I would do is to get a registered electrician to give a quote for the work. Then one you will know how much to do it all to letter of law. And two how a professional would go about the job. You may well think it not worth the hassle of DIY. But at least if you do the work DIY you will do it in a safer manor.
In New Zealand I was told although not confirmed this that they repealed their laws similar to our Part P because so many injuries were caused by the use of extension leads.
I would always ensure all leads outside are feed with some sort of RCD be that in consumer unit or simple plug in type.
For more information on how you can be sure you're protecting yourself in your shed visit the Electrical Safety Council website where this is plenty of useful information.
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