How to work out the total design load to find my swa cable size

[Ted Curly]

Hi all I am having trouble trying to work out the total load and swa cable size.
I have 10 circuits in a outhouse 40 meters from the mains power supply 1 x lighting with 10 lights, 1 x lighting with 10 lights.
1 x 2.5mm radial for 2 heaters, 1 x 2.5mm radial for heater. 3 x 2.5mm socket rings with 3 sockets on each ring, 1 x water heater radial for 2 instantaneous hot water... I have calculated the lights at 100w per light x 20= 2kw, the heaters are around 3kw x3 =9kw.
Water heaters 3kw each=6kw... The problem is the sockets as I'm not sure what's going to be plugged in apart from a kettle. working them out at 13amp x 230v gives me nearly 3kw per socket x9 = 27kw which seems unrealistic... Adding all that up before diversity is 44kw which seems way ott for that. Thanks all

 

[Ted Curly]

What is the reason you were given for converting to TT if its over a certain distance? And for that matter what value do you use for the distance at which you need to do this?
What do you mean by no extraneous parts therefore no need for PME?
None of this sounds 'old school' to me, more like nonsense!

Hi it was just the way was taught many moons ago regarding tt and outbuildings ,,, and the no extraneous parts was meant to indicate for this instance the out building is made of wood no metal, and if used tt would be no pme, but dnt worry about tt I going to use the tncs earth, sorry about the way I type not very good at typing on these small phones and new to forums cheers guys.. Also I will have update on what equipment is going to be used tomorrow so can make better assumption of ib of sockets,, sorry so late to reply had 12 hour day and at it again in 8

 

[Ted Curly]

Allowing for 63A over 40m and a 2% volt drop, this allows an extra 1% for your lighting to comply with a 3% requirement you will need a minimum 25mm cable.

I was hoping it wouldn't come to thst size the 40m swa will be clipped direct ,the lighting circuits max length run will be around 10meters,, 16mm swa Vd is around 2.6 mV/a/m

 

[Ted Curly]

I was hoping it wouldn't come to thst size the 40meters run of swa will be clipped direct ,the lighting circuits max length run will be around 10meters,, 16mm swa Vd is around 2.6 mV/a/m