Running Power to my Garage (prefab concrete external strutr)

[GJUK]

Hello, Morning all.

I want to run mains power to my garage (without killing myself).

I want to be able to run a couple of stip lights off one switch and maybe a double socket for use with a welder/grinder.

In my conservatior', I have a 13amp spur I could run some cable from, to the garage. This is currently being used to run off to two lights and an external security light.

Would it be viable to use this fused spur, to run in to the garage, then plubm it into a fused switch unit, then on to the lights and plug sockets?

Would the 13 amp blow if everything was being used at the same time :S

Any kits anyone recommends using for this kind of DIY job?

Thanks!

Jon

 

[Veglen]

Sorry Jon, its not that easy. Unless you use an extension lead of course!

You will probably find lots of threads on this topic if you do a search on the forum. However, this type of installation is notifiable which means you will have to involve your Local Authority Building Control Dept (LABC). All parts of the building regulations would have to be met too and in particular Part P.

In answer to your question, yes providing the ring final circuit is suitable for the additional load, the garage could be supplied from a fused spur inserted in the ring and a cable run out to a DP switch then to a socket-outlet in the garage. Another FCU could be installed for the lighting circuit after the socket outlet.

RCD protection should be provided for the socket-outlet to be installed in the garage if the circuit is not already protected. However, this could also be done using an RCD/FCU at the origin of the garage supply on the ring if required.

Obviously there are other ways of supplying the garage too. There are all sorts of factors to be taken into consideration. Such as your supply characteristics, any extraneous conductive parts, main bonding, etc etc. My advice would be to do some research on the subject of installations outdoors and of Part P of the building regulations first.

You don't have to take though

V

 

[jason1958]

You want...
- IEE Wiring Matters
- Autumn 2005
- ELECTRICAL INSTALLATIONS OUTDOORS: A SUPPLY TO A DETACHED OUTBUILDING
- By John Ware

It gives a good primer on the relevant aspects.

I have just been to the IET website and can not find it, perhaps someone has a direct link to the PDF document.


An extension lead can be less safe than a good fixed installation.
A bad fixed installation can be an order of magnitude less safe than an extension lead.

 

[GJUK]

Hello,
Thanks for the replies.

What I plan to do is to run armoured cable from a double socket in my sun lounge, through an external wall, up over a beam of wod above my gate and in to the garage.
Once in here I thought I'd connect it to this :

http://www.screwfix.co.uk/prods/631...x-IP55-Garage-Unit-40A-30mA-1X6A-1X16A-SP-MCB

Then from there I would use your 'normal' indoor electrical cable to go to some lights (off the 6 amp bit) and to a double socket for my welder/grinder etc.

Sound good?

 

[industryspark]

to be honest no it doesnt sound good. remember that you have to adhere to the wiring regulations so you must be aware of these before you do the job. you must also think about part p.

spurring from a socket to supply a garage is a poor way of doing this. what type of welder is this you are wanting to run? whats its power consumption? have you considered rcd protection of sockets in the garage as you need to. what earthing system is the installation, TT, TNS, TNCS? what zs reading are you expecting at the garage submain?

all these questions plus more are things you should be asking yourself.

regards.

 

[jason1958]

PROBLEM.
That could be what the end result "looks like".
However there are *MANY* critical technical details affecting the design.
These are related to compliance with BS7671 AND to safety.

There are no DIY kits due to those critical technical details.


SOLUTION.
1. Introduction.

Read the IET doc, join the following text & paste into webbrowser.

http://www2.theiet.org/Publish/WireRegs
/WiringMatters/Documents/Issue16/2005_16
_autumn_wiring_matters_electrical_installations_outdoors.pdf

2. Decide who does what.

From your posting I suggest you use option b).
a) you Design, Install, notify labc for I&T (inspect&test)
b) spark Designs, you Install, spark connects, I&T

The reason is you do not know what you do not know yet must know.
Not an insult, running an outside cable has many technical considerations.

I do not think your spur off (probably) a ring for a welder is sound.
You will probably need a dedicated feed from an RCBO in your CCU.


EXAMPLE - Technical Details.
1. Identify shed environment re earthing & house earthing type.

a) If the house is TT, you make the shed TT with its own local earth rod.
b) If the house is PME, you make the shed TT with its own local earth rod if any of i) concrete floor ii) class-1 tools iii) incoming metal service pipe.
c) If the house is PME, you export the earth to the shed if the floor is wood, no metal structure in contact with the soil, only class-2 tools, no incoming metal service pipes.

Technical details are critical.

Why?
Suppose you export your house PME earth to a shed and use a Class-1 earthed metal cased tool outside, eg, WELDER.
- WELDER metal casing is now at house PME earth potential.
- Soil at the shed may be at a different potential.
- Potential difference between tool & soil, hands & feet.

If the potential is sufficiently high 30ma could flow.
- Now that might trip your 30ma RCD, but if faulty you could die (30ma right on edge of ventricular fibrilation).
- Yes the test button may work, but that does NOT mean it is in spec re 0.5/1/5x at 0-180-degree phase tests etc.

2. Identify if MEB is missing or needs upgrading.

MEB is Main Equipotential Bonding
- MEB Must be present & sized correctly for your supply type
- MEB is a Gr/Ye earth wire linking MET (Main Earthing Terminal) to Gas & Water Pipes

If MEB were missing.
Street digger damages supply Neutral, fails months later.
- Earthed appliances in the house are now at Uo supply potential (230V)
- Water tap & Gas pipe fed by metal piping are at ground potential (0V)
- Hand on metal tap (Uo), hand on tap to lead water main (0V) = dead.
- Hand on metal WELDER at shed (Uo), feet on soil (0V) = dead.

That is why DNO have a fit if they see no MEB.
Even if the MEB is too small, it could be a problem (the copper could melt before the PME main fuse blows).

3. Voltage Drop, EFLI, Cable Sizing, Cable Factors for routing inside.

There are no DIY kits because of the *install specific details*.

These details are not "idealistic", but critical re safety.
Impossible to remote design without seeing an installation, so much information is needed.
- House supply type
- CCU type re age/rcd present/spare ways
- cable routing options
- shed load
- cable sizing after applying Ca Ci Cf Cg grouping factors within house for route
- Vdrop calculations
- EFLI calculations & verification at i&t re r1+r2, zs etc
- Earthing method re remote TT or export-PME
- Isolation
- CPD selection since it is a WELDER

Current welder (or future) may impose a load which may preclude use of Type-B trip characteristics.
That may necessitate other trip characteristics, with resulting cable re-sizing for Vdrop & EFLI to ensure the CPD trips. Fit a Type-C breaker in place of Type-B and if EFLI is not low enough your cable becomes the fuse protecting the CPD!

It really is not a trivial task, involving complex designwork particularly since a Welder is involved.
Hence easy answers or DIY kit are not quick to appear.

Go read the IET PDF document.
Then pick up an electricians guide.
Then speak to a spark, you will at least understand them better and WHY certain things are needed.

 

[Veglen]

Wow, bet you're are you sorry you asked!

Out of interest what power rating is the the welder you mention?

V

 

[GJUK]

Bloody hell.

*cries*

Wow, bet you're are you sorry you asked!

Out of interest what power rating is the the welder you mention?

V

My welder is a 150 amp semi medium type gas welder.

Assuming a glossed over the compliance and letting everyone know about the changes, say it was to replace existing wiring that was in place pre 2005.

What is the easiest way to do it then?

Does that change the situation?



J

 

[RF Lighting]

So having been told you need to comply with part P of the building regs, which is there for the single reason of making sure your installation is SAFE for YOU to use.

You are now asking the very same people how you can break the law, and avoid making sure the installation is safe for you to use

Do you try and avoid taking your car for its MOT too?

 

[ban-all-sheds]

What is the easiest way to do it then?

Given your design current, choose the correct size cable allowing for adjustments to its capacity for installation method and type of protective device.

Check that volt-drop is OK given its length.

Measure or assume Ze, add your calculated R1+R2, and check that the resulting value is within the limits for the type and rating of the protective device.

Ensure that when you install it you abide by the regulations for concealed cables, bend radii, support spacing and depth/height of buried/overhead cables.

When done, check continuity and measure R1 + R2, insulation resistance, and check polarity, including checking that any single-pole switching operates on the phase conductor.

Do all the above for each circuit in the garage as well.

Then energise, check polarity again, measure earth fault loop impedance, measure the tripping characteristics of the RCD. Do a functional test of all switching devices.

Then complete and sign your Electrical Installation Certificate and keep it safely.

 

[jason1958]

B-A-S - nice, concise, and considered reply

 

[bongos]

My welder is a 150 amp semi medium type gas welder.

If your welder was to draw 150A then it will be sadly disappointed if you run it from a spur on a ring main - or even if you ran it from its own dedicated single phase supply! Most single phase house supplies are in the region of 60 - 100A.

What is its actual power rating of the welder?

 

[RF Lighting]

I'm quite sure that the 150A is the output of the welder.

I have a 120A arc welder which runs on a 13A plugtop, but it is right on the limit for a 13A fuse.

My welder will trip a 16A type B MCB the first time you switch it on.