Supply to Garage ???

[richard1600]

just finishing my workshop/garage at the end of my garden, its 10m away from the house.. i want lights and sockets in there and will be having a trip in there too.

my question this: what is the standard way this is done to provide a supply?? is it taken from our original cct breakers in the house or off the main input before the junction boxes..

also i would like to dig it into the ground, whats the legalities involved here, how deep and what exact cabling should be used??

also earthing,, do i just do a return to house or does the garage need a dedicated earth, if so legalities on this.


i know most will say just get an electrician, lol, i am an electronical/electrical engineer in the army so fully happy with what am doing and will get it inspected and signed off after, i just dont know standard practice and legalities with regards housing.

thx

 

[HullMarc]

SWA, more often than not from a non-RCD protected MCB in the consumer unit. There are no specific legalities, can't remember the wording but BS7671 says adequate depth so as not to be damaged, best practice is considered 18".

What's your earthing system? TN-S, TN-C-S, TT? You shouldn't export the earth on a TN-C-S system, I suggest you find out what yours is.

If you're getting it signed off then an electrician won't do it as s/he hasn't installed it - the only way to get around this would be to contact him/her before you start work, talk through what you want to do, s/he'll tell you how to do it and if s/he agrees to sign it off s/he'll want to see everything before it's buried/covered up.

 

[17thman]

i think that 500 to 600 mm is the suggested depth with a marker tape 150 mm above swa, you can export a tnc-s system if there is no extraneous conductive parts in the shed/garage (water, gas, oil pipes etc or structural metalwork, youll need the correct csa steel wired armour cable 4mm wouls probably be good.

 

[Taylortwocities]

Two things for you to read

1. Legalities about what you are planning to do

2. wiring outdoors
This was published before the new regs came out, but it is mostly still relavent

 

[Steve]

just finishing my workshop/garage at the end of my garden, its 10m away from the house.. i want lights and sockets in there and will be having a trip in there too.

A trip? You got a first aid box? What do you mean by a trip? Do you know?

my question this: what is the standard way this is done to provide a supply?? is it taken from our original cct breakers in the house or off the main input before the junction boxes..

It depends how much power you need really.

also i would like to dig it into the ground,

Thank god, a DIYer not afraid to dig up his garden. I swear some people think power can be transmitted wirelessly across gardens.

whats the legalities involved here, how deep and what exact cabling should be used??

18 inches minimum. 24 inches if ground is likely to be cultivated. The deeper the better. Steel Wire Armour or Split Concentric cable.

also earthing,, do i just do a return to house or does the garage need a dedicated earth, if so legalities on this.

What type of earth does the house have? TNS, TNC-S, TT, this is important in determining the type of earth. Does the garage have a water supply in metal pipe? Or a steel frame? Or a gas or oil supply in metal, or metal drains?

i know most will say just get an electrician, lol, i am an electronical/electrical engineer in the army so fully happy with what am doing and will get it inspected and signed off after, i just dont know standard practice and legalities with regards housing.

Go to this site's WIKI (link at very top) and into electrics UK, and read up on Part P. Also any articles with regard to earthing and external building supplies.

 

[ban-all-sheds]

i know most will say just get an electrician, lol,

Yup - and this is why:

just finishing my workshop/garage at the end of my garden..... i want lights and sockets in there

You aren't yet competent to do this, but (presumably) you want to press on and get it done, so unless you do want to wait until you are competent, an electrician is what you need.

i am an electronical/electrical engineer in the army so fully happy with what am doing

Well you shouldn't be - you're not worrying about your unknown unknowns.

You asked a series of questions which you thought covered everything you didn't know. But what about things you didn't ask about because you have no idea you don't know them and no idea they even exist?

and will get it inspected and signed off after

It doesn't work like that.

 

[Taylortwocities]

Donald Rumsfeld is alive and well and living at DIYNOT.COM

 

[ban-all-sheds]

Donald Rumsfeld is alive and well and living at DIYNOT.COM

Whatever else you may think about that lying mass murderer, his concept of "unknown unknowns" was sound.

 

[EddieJ]

What type of earth does the house have? TNS, TNC-S, TT, this is important in determining the type of earth. Does the garage have a water supply in metal pipe? Or a steel frame? Or a gas or oil supply in metal, or metal drains?

I've never thought about this.
When I went to college we studied putting a supply to an outside garage from a house with a TNCS, the solution was a TT system the reason being that the earth in garage was not to connect to the earth in the house but no one said anything about water or gas, the water pipe from the garage would connect to the house and so the two earthing systems would not be separate.
What is the solution to this problem?
Thanks.

 

[ban-all-sheds]

http://www.theiet.org/publishing/wiring-regulations/mag/2005/16-elect-inst-outdoors.cfm?type=pdf

[edit]Out of date link corrected.[/edit]

 

[EddieJ]

http://www.iee.org/Publish/WireRegs/WiringMatters/Documents/Issue16/2005_16_autumn_wiring_matters_electrical_installations_outdoors.pdf

Sorry the link doesn't work, maybe I have to be a member of the other forum

 

[ban-all-sheds]

No - they just changed their site. Link above is now correct.

 

[EddieJ]

From the above link:

An exposedconductive-
part connected to one means of earthing
must not be simultaneously accessible with an exposedconductive-
part connected to another means of earthing
(Regulation 413-02-03 refers). Where the installation in
the garage is supplied by an armoured cable, the armour
or any protective conductor in the cable must not be
connected to and must not be simultaneously-accessible
with any exposed-conductive-parts in the outbuilding

My question is, the water pipe will connect to the water pipe in the house and so both earthing systems will be joined.
If a TT system is used it is said the earth in the house must not connect with the earth in the garage and yet the water pipe will provide a path between both installations.
I am confused, could someone enlighten me please.

 

[chapeau]

In this case, both the house and the garage have their own equipotential zones.

I suppose the theory is that if you correctly bond the water pipe to earth* where it enters each equipotential zone, then what is in between those zones will not matter.

*whatever that earth is, doesnt matter, as long as it's the same throughout that zone. Might not even be 0.00000 volts with respect to an earth somewhere else.