Log cabin...... again

[Norv]

Spent a couple of days digging the trench for the cable to the log cabin. Measured it & it is 120meters, take a few metres, from where we are getting the power from. Calculated it & if I use 25mm SWA over this distance with a 50amp design current it gives a 9v drop. Would you say this is ok & any suggestions where I can buy this amount of cable (I know it will be expensive... )

 

[ColJack]

if you've already dug the trench then i still say a dedicated supply from the DNO would be better..
makes the cabin independant from the workshop if the owner ever decides to sell one or the other..

what is this log cabin to be used for?

if it's just an office etc then 50A should be ok, if it's going to be a holiday home etc then a larger supply would be better..

 

[Lectrician]

You must not drop more than 9.2v between the SUPPLY ORIGIN and the furthest point of utilisation, so the volt drop is included in any submains and any final circuits.

you are leaving .2v to drop in the cabin.

What are you anticipating fitting in the cabin? Exactly?

 

[Norv]

When the cabin is finished my mate is going to live in it until his house is built. Its got the usual bits & bobs, washing machine, fridge/freezer, oven/hob in the kitchen & water is heated by an immersion. DNO wont fit a supply unless we dug up a 3ft thick concrete slab which wasnt happening.

 

[Lectrician]

3 ft thick


Sounds like you need to run atleast a 50amp supply, as you have elec? hob, immersion, micro etc.

25mm is obviously too small, and 35mm may still be.....need to calc properly.

35m of 25mm 4c was £205 on wednesday

 

[JonB]

Sounds a good case for a generator.

 

[Norv]

Using this little tool here -
http://www.pandpelectrical.com/mpm/voltcalc.htm

35mm SWA should do the trick with the design current at approx 65A

 

[RF Lighting]

You need to set the calculator to 2 core SWA, which gives you a minimum of 50.0mm² SWA.

Even if you install 3 core SWA using the 3rd core as earth, you still do the calcs as if it is 2 core.

If you do the calcs for 3 or 4 core then it assumes a TP supply.

Do you know what split concentric cable is? You can get this in upto 35.0mm², but I'm not sure of its current carrying capacity

 

[Lectrician]

Not keen on burried split con unless ducted.....and ducting that length isn't easy!