Cable advice | on ElectriciansForums

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T

toothsome

I need to purchase some cable to lay whilst my garden is being dug up, to be connected later when the outbuilding (a 30 square meter log cabin) is built. I have two questions I could use some advice with!

1. The cable will be run through a 'standard industrial duct' (my landscaper's words). Do I still need to get armoured cable, or will standard 'outdoor' type cable suffice as it is in a duct?

2. Is it better to use 2 core cable and drive a new earth spike in, or run the earth back to the house using 3 core?

Thanks
 
USE SWA!!!

ask the builder what his duct is!!!! is it plastic or metal...!! if plastic USE SWA, if METAL still use SWA as metal corodes and can rot later..!!

get the hint SWA!!

earth rod is good idea as any earth faults will be delt with by the rod and not transported back to the house!

2core SWA depending what your fitting in teh cabin then 10/16mm would be ample! just fit a switch fuse at meter / supply to power cabin..!
 
Wont have time to answer your query at the moment. A few more questions will need answering first, what type of earthing system do you have in the house. Total distance from your consumer unit to log cabin. What are you going to be using in the cabin ie what is likley to be your maximum demand and what type of consumer unit do you have at the moment.


Hopefully someone else will pick up on this and give you the answers you need.


Chris
 
Thanks both. I shall use SWA then :)

In answer to your questions acat, the house is 30 year old but I have just had the house completely rewired, with new earths and everything. Brand new consumer unit with plenty of spare slots. Usage will be a small heater, TV, lighting etc. I've calculated not more than about 3000w so am looking to use 4mm. The house is 25 meters away.

I'm looking at using this: 4.0mm 6942X 2 core SWA Steel Armoured Cable
 
4mm will supply 3kW at 25 metres but be aware that if you stick a kettle on while you are watching TV with your little heater on that you will likely be way above 3kW. Also it is not the distance from the house to the chalet that is important but the length of the run that the swa takes from your CU to the chalet.
 
I was going for 4mm because the charts I've seen, such as:

Common domestic electric cable types used in the UK

say that this will be ok up to 7000 watts... is this not the case?

Also, the cable will go line of site to the cabin...

It is where it is going immediately it leaves your CU that is more important

There are several calculations involving tables from either a regs book or onsite guide that a proper electrician will do when working out which cable to install. Method of installation is very important as this can affect the current carrying capacity of the cable. eg running the cable through as little as 5cm of insulation affects it and as little as 50cm of insulation can derate it by 50% ! Also there will be a voltage drop at the end of the cable, which has to be within certain percentages, and this affected by the size of the cable , the current it is carrying and the length of the run from the original consumer unit. I think this is what "acat" was getting at... that you consider everything first and then choose the cable to suit when everything has been considered not choose the cable first.
4mm may well be a suitable cable but it will be a severe hassle and expense to you if you install it and a year down the line it turns out that it was the wrong one or it does not have the extra capacity because you need a bit more power in your chalet. Equally if you go immediately for a larger cable than you would ever need you are wasting quite large amounts of your hard earned cash - this is why it is sensible to get the advice of a proper electrician.

Also any circuit going into your garden is an example of notifiable work.

Hope this helps.
 

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