I want to run power to a garage and would welcome advice please. The total run is about 30 metres, with 5 metres inside & 25 metres outside. I propose directly burying 3 core SWA but what size cable should I use and what are the latest conductor colours please? The CU is RCD protected but what should I use in the conservatory where the outside cable meets the inside cable? What should I use in the garage where the the armoured cable terminates and I distribute power to the lights and sockets? Thanks.
Electricity to a garage
- Thread starter coastalchris
- Start date
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First thing.
Please remember that what you are thinking of is notifiable work, if you want to do it yourself. So you'll need to aquire some technical skills, do a lot of reading and buy some calibrated test equiopment.
For stuff like this it is much better to use a registered electrician - he'll probably be hoppy for you to do the grunt work under his supervision.
Second thing
You are starting at the wrong end. The important first bit of information is what will be powered in the building
Power lift
Engine hoist
Lathe
MIG welder
Missile launcher
Much much later comes decisions about cable size and what happens in the conservatory (why the conservatory? Is the consumer unit there - very strange place for it).
Please remember that what you are thinking of is notifiable work, if you want to do it yourself. So you'll need to aquire some technical skills, do a lot of reading and buy some calibrated test equiopment.
For stuff like this it is much better to use a registered electrician - he'll probably be hoppy for you to do the grunt work under his supervision.
Second thing
You are starting at the wrong end. The important first bit of information is what will be powered in the building
Power lift
Engine hoist
Lathe
MIG welder
Missile launcher
Much much later comes decisions about cable size and what happens in the conservatory (why the conservatory? Is the consumer unit there - very strange place for it).
Have a look at 'similar topics' at the bottom of this page.
Every one you look at will have the 'similar topics' at the bottom of that page.
Have a look at them too
Every one you look at will have the 'similar topics' at the bottom of that page.
Have a look at them too
etc.
Every one you look at will have the 'similar topics' at the bottom of that page.
Have a look at them too
Every one you look at will have the 'similar topics' at the bottom of that page.
Have a look at them too
etc.
The size of the cable will depend on the load which is required in the garage as Taylortwocities has stated this is where you need to start your calculations form.
For example a simple installation with a number of sockets and a lighting circuit may require something like 32A for sockets and 6A for lights.
So total load on maximum demand would be 38A, then the next stage would be to calculate the voltage drop over 30 meter run.
The voltage drop for 3 core SWA buried underground at a length of 30 metres would be 3.4% 7.75Volts. This would allow a maximum load of 39.2A. So you would require 6mm cable
But I would put 10mm in.
Ideally this example circuit should be terminated within the house at the consumer unit, protected by a 40A MCB there would be no need for RCD protection at this point, then terminated at the garage within a small garage consumer unit with RCD protection, then your socket and light circuit can be distributed from that point.
For example a simple installation with a number of sockets and a lighting circuit may require something like 32A for sockets and 6A for lights.
So total load on maximum demand would be 38A, then the next stage would be to calculate the voltage drop over 30 meter run.
The voltage drop for 3 core SWA buried underground at a length of 30 metres would be 3.4% 7.75Volts. This would allow a maximum load of 39.2A. So you would require 6mm cable
But I would put 10mm in.
Ideally this example circuit should be terminated within the house at the consumer unit, protected by a 40A MCB there would be no need for RCD protection at this point, then terminated at the garage within a small garage consumer unit with RCD protection, then your socket and light circuit can be distributed from that point.
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I prefer to have the supply cable non rcd protected and the rcd protection within the outbuilding. Are you planning to connect to a socket outlet in the conservatory?
Thanks Dum SS and others. It will not be anything energy heavy and then not all at the same time, DIY power tools, lawn mower, car battery charger, garage lights, radio etc. The conservatory is just where the interal and external cables will meet. From there, there is another 5 metres or so to the CU under the stairs. Again, thanks all and ESP Dum SS
Dum SS?
- //www.diynot.com/wiki/electrics:mcbtocable
- http://www.tlc-direct.co.uk/Book/4.3.1.htm (all subsections)
- http://www.tlc-direct.co.uk/Book/4.3.11.htm
- http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
- http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
- http://www.tlc-direct.co.uk/Book/5.3.1.htm
- //www.diynot.com/wiki/electrics:mcb2
- http://www.tlc-direct.co.uk/Book/7.13.3.htm
- http://www.tlc-direct.co.uk/Book/8.1.1.htm
- //www.diynot.com/wiki/electrics:swa-gland
- http://electrical.theiet.org/wiring-matters/16/elect-inst-outdoors.cfm?type=pdf
- //www.diynot.com/wiki/electrics:part-p
Re the conservatory. There are sockets already there on the house circuit so I thought I'd just use a connection box of some sort, possibly switched so that the garage can be isolated when I am away.
Yes you could run from there, but it would need to be a fused connection so that would limit the maximum total current for the garage as 13amps.
That would a severe limitation for future use.
Also any fault in the agarge would trip the house power, so bang goes your freezer when you are on holiday.
SO you wouldn't then have a separate fusebox in teh garage, what would be the point as all of the protection would be in the house.
Best is to run the feed from a special separate connection on the consumer unit.
All of this is really ouside the scope of DIY. Get an electrician - he'll sort out the tricky stuff and probably let you do most of the grunt work.
That would a severe limitation for future use.
Also any fault in the agarge would trip the house power, so bang goes your freezer when you are on holiday.
SO you wouldn't then have a separate fusebox in teh garage, what would be the point as all of the protection would be in the house.
Best is to run the feed from a special separate connection on the consumer unit.
All of this is really ouside the scope of DIY. Get an electrician - he'll sort out the tricky stuff and probably let you do most of the grunt work.
Ah.
Sorry - never seen anybody reply to someone by calling him a Latin proverb before, as if it were some kind of name.
I think he's taking the term "signature" too literally.....
Sorry - never seen anybody reply to someone by calling him a Latin proverb before, as if it were some kind of name.
I think he's taking the term "signature" too literally.....
It is a good read and has been referred to many times.
Several points:
1. The article is several years old and was written under during the 16th Edition of the Wiring Regulations. Its good for general guidance though.
2. The "Wiring Matters" publication comes from the (then) Institute of Electrical Engineers. Its written on the assumption that the reader has a reasonable level of competence in electrical installation.
3. The work to be carried out requires SKILL in its design, SKILL in its installation and SKILL in its testing and bringing in to service. None of these skills can be acquired by asking questions on an Internet forum.
Several points:
1. The article is several years old and was written under during the 16th Edition of the Wiring Regulations. Its good for general guidance though.
2. The "Wiring Matters" publication comes from the (then) Institute of Electrical Engineers. Its written on the assumption that the reader has a reasonable level of competence in electrical installation.
3. The work to be carried out requires SKILL in its design, SKILL in its installation and SKILL in its testing and bringing in to service. None of these skills can be acquired by asking questions on an Internet forum.
Thank you all for your advice. The cable has been installed (buried to the correct depth, warning tape used etc) and terminated in the garage using a 2 way garage consumer unit. Cable glands are good and earthed. I will leave the connection at the other end (house CU) and testing to a local electrician but at least with your help I have broken the back of it. Thanks again.
A
Alarm
How will he sign it off then?
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