Garden Cabin

[BirchCrafts]

I have built a garden cabin for use as an office/photo studio. Distance from the house is about 45 metres.
With heater, lights, computer, etc., all on at the same time, I estimate that highest current will be 20 amps.
I will get a qualified electrician to check out the wiring and do the final connection to the main consumer board to make it legal.
Questions:
1. Will 2.5 armoured cable from the house, buried in the ground, be heavy enough for the whole project.
2. Should I use a garage consumer unit (with earth leakage)?
I was advised by an electrician that new regulations state that there should be an additional earth rod and connection at the cabin.
There will only be two circuits - a plug circuit and lighting circuit.
3. Is it possible to put the consumer unit in a weather proof box outside the cabin and then to take the cabling outside to the lights and plugs? Ideally, I would like to take the cables along the back and one side of the cabin where they will not be seen.
Thanks for your help.

 

[davelx]

1) I think you are going to need 6mm cable to meet the voltage drop requirement at that distance. 4mm is just outside (20*45*0.011=9.9V i.e. 4.3%) and 2.5mm is way off (20*45*0.018=16.2V)

2) What is the earthing system in the house (piccy if you are not sure)?

3) ------ I'll leave that to someone else!

 

[bernardgreen]

Well worth considering a duct for the cable to ease replacement and while the trench is open put in a second duct for things like telephone, intercom, door bell repeater. alarm cables etc etc.

Solvent welded PVC pipe ( rain water or waste system pipes ) are a good option.

 

[Steve]

in answer to question 2, to my knowledge there are no new regulations regarding earthing. And as long as there are no metal water or gas pipes or metal structure in the building, you can export any earthing system from the house (though with TT, it would be best to provide a second earth rod due to the high resistance of TT earths).

If you're not sure, post a picture of your mains intake, including the meter, mainfuse, incoming cable, and the surrounding wires, and preferably the consumer unit too.

 

[BirchCrafts]

Thanks for the help and advice given so far. Very useful and much appreciated.

The idea of ducting is a very good one. There is a problem though and that is that the main consumer box is on the other side of the house (inevitably!), so I will have to give that careful thought.

 

[bernardgreen]

There is a problem though and that is that the main consumer box is on the other side of the house (inevitably!), so I will have to give that careful thought.

Use PVC twin and earth of the correct size through the house and then connect to the steel wire armour in the house at a point convenient to the ducting route.

I use a die cast box terminate the SWA

 

[BirchCrafts]

I need further clarity, please:
If I lay ducting for the cabling and use separate conduit wiring rather than three-core cabling, what size would be correct? 2.5 conduit wiring cable?
Thanks for your help.

 

[breezer]

no, they are saying if you lay ducting it will make life easier in the future if you wish to upgrade the cable. you cant use singles in a drain pipe, the size you mention (2.5) is as already said too small