Wiring a Garage


Postby Hobie21 » Wed Feb 01, 2012 4:51 pm

Hi, I have just acquired a garage that is not attached to my house but is very close. I want to wire the garage for no more than 2 strip lights and 2 double sockets. The electrical supply will come from an extension lead run from a sock in the house.

Can anyone suggest were I start, I will probably do the work myself and get it check by an electrician.

your suggestion are all welcome.
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Postby ericmark » Thu Feb 02, 2012 5:56 pm

There is not location but likely you will need to notify under Part P. Now that's out of the road the first question is what is the loop impedance on the socket you intend to use. This will tell you how thick the cable needs to be to comply with volt drop etc. You will need to know how much cable is required before you can start to calculate. Often one can look at an installation and realise if it's near the limit or not but that's not much help with DIY where you don't do many jobs of this type.

Also of course RCD protection will be required likely this is already in any house wired after 2008 but older houses may require them. If so you have to consider again the cable type. With SWA cable fitting the RCD in the garage would likely be best option but using other cable for outside it may mean the RCD needs to be in the house. Do remember nearly all cable for use outside will be black in colour to resist UV light so if it's not black likely it should not be used outside.

The normal is to use a fused connection unit (FCU) in the house with a second switched FCU in garage for lights the latter with just a 3A fuse. This means no need for consumer units in the garage. By using metal clad type FCU in house and at least the first socket or FCU in garage being metal clad it is easier to terminate the SWA cable gland.

In a garage or container I have often used SWA for all so it is reasonably protected from knocks and bangs. Really depends what you are going to do in the garage.

I seem to remember the IET in their publication "Wiring Matters" in 2005 did cover the wiring of out buildings it's a free down load from their web site in PDF format. It is a little out of date but does cover the main bits and the complex issue of earthing. Again you have not stated if you are on a TN or TT system.

The big problem I find is the cost of hiring the test equipment and LABC charges which means you need to pay around £250 more than an electrician doing the same job. So in the main it is cheaper to employ a scheme member electrician.
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Postby Hobie21 » Fri Feb 03, 2012 7:24 pm

Hi ericmark,

Thanks for getting back to me, I didn't realise that it was so involved. I think on second thought I better get a proper electrian to look at the job.

Once again thanks for the advice.

Hobie21
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Postby sparx » Fri Feb 03, 2012 7:31 pm

As the OP states to be supplied from an extension lead, then the total load can only be 13A which if taken from a socket in house using an RCD plug with a 2.5mm2 flex makes the whole thing no different from an appliance, assuming the lights are to be plugged into one of the garage sockets with 5A fused plug! so no reporting required.
HOWEVER this is at best a bodge job way and not to be recommended.
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Postby Hobie21 » Wed Feb 08, 2012 6:17 pm

I've had a think about this and can anyone tell me the pros and cons of powering lights from a portable generator.
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Postby ericmark » Fri Feb 10, 2012 10:02 pm

Earthing is a problem if done correctly however many do not do it correctly. I have worked on and lived in many houses with only a generator supply. (Lived on the Falklands for 4 years) To get a generator to work for a long time one needs a low revving type normally around 1500 rpm Lister was the norm. Diesel was also the normal fuel. The smaller high revving generators are noisy and also don't last as long. However much smaller. The revs are locked to frequency so tends to be 1500rpm or 3000rpm with little between,

However there are now inverter generators which unlike the old type I used can change their revs according to load these combine the benefits of both high and low revving types.

The price also varies and as one goes for the better generator so the price goes up. So if for example you look at one sold in Lidi and compare with a diesel inverter type one has to look at the different and work out how much fuel will the difference buy and how many times would you need to replace the cheaper one. Sorry you need to work that out.

The other option is 12v. Caravan lighting and an inverter may be enough and just have two batteries one being charged in house the other being used.

However it may be better to go for 24v as 24v inverters tend to work better.

I got a cheap China inverter 3kW with 6kW peak 12v at £150 but it burnt out. So learn from my mistake and don't buy from China. Although you say two double sockets you don't say what power you need. At 5A I would consider an inverter and battery at 13A I would go for generator.
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Postby Hobie21 » Tue Feb 28, 2012 6:44 pm

I'm sorry to bore the kind people who offer numnuts like me advice. I am trying to wire a florescent light in my garage. The garage is not attached to my house, it stands about 35 metres away. I am going to power the garage with an extension cable with a RCD breaker on it.

I have bought 1.5mm T&E cable an enclosed metal light switch and a florescent baton tube 1500mm, I am connecting to the extension lead via a three pin plug. The back of the switch has 2 live, 2 neutral and 2 earth connections which I have wired up correctly I think. As far as I can see I have wire everything up correctly but the light does not work.

my next step is to buy a new baton lamp and fuse for the plug. Can anyone please advise how I should wire the switch and light.

cheers
Hobie21
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Postby ericmark » Sat Mar 03, 2012 9:42 pm

I read the back of switch have line, neutral, and earth connections. The only switch like that I can bring to mind is a switched fused connection unit. If so has the fuse blown?

This site does not allow links to images. Asking the same question on a site which allows links with a picture may help. But this site does not have guys who will tell you in no uncertain terms when your breaking the law and any fixed installation be it plugged in or hard wired which goes into the garden comes under Part P. So expect to be told that and read between the lines.
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