Wiring an office 35 meters uo the garden

[Ted Curly]

Hi all
I was just inquiring about the correct swa cable size for a office around 40 meter run, 15meters of which will be buried, this is to power 9 double sockets, 24 led spot lights and 3 dimplex heaters.
Would it be possible to install a 16mm swa from a new sub board in the house ran from a 60A kmf switch from the Henley block to supply the office in garden.
Thanks T.

 

[Bobster]

What do your calculations show?

 

[Pete999]

Hi all
I was just inquiring about the correct swa cable size for a office around 40 meter run, 15meters of which will be buried, this is to power 9 double sockets, 24 led spot lights and 3 dimplex heaters.
Would it be possible to install a 16mm swa from a new sub board in the house ran from a 60A kmf switch from the Henley block to supply the office in garden.
Thanks T.

Have you done any cable calculations to come up with 16mm2 or is that guesswork?

 

[bill01803]

I would like to see the termination of 16mm swa in a kmf

 

[telectrix]

16mm is way over the top, IMO. 10mm seems more appropriate considering the load and VD.

 

[Dustydazzler]

As above

A 16mm submain is probably way ott , even with the electric heaters

Without actually sitting down and going the proper cable calc , my best teeth sucking estimate would be 10mm off a 50a mcb

 

[telectrix]

snap. but with a bit of diversity thrown in 6.0mm on a 40A would probably do.

 

[Ted Curly]

Thanks guys, I was going to terminate the 16mm swa into a sub board in the house and at the other end in a 12way board in the outhouse office.
there is 3 rooms in the office each with 3sockets, lighting, hot water spur and heater spur. I know the 16mm is overkill but worried 10mm will have more voltage drop as the overall run for the swa will be around 40meters and thst being buried for 15or so meters effects the size.

 

[westward10]

Volt drop should not exceed 3% from point of source to the furthest point for a lighting circuit.

 

[Ted Curly]

Have you done any cable calculations to come up with 16mm2 or is that guesswork?

Hi Pete I have just estimated it at the minute standing in the rain, till I get home with the books out, I just imagined thst with the length at 40 meters it would be around 16mm, if the run was 5 meters less I probably would suggested a 10mm my self.

 

[Dustydazzler]

snap. but with a bit of diversity thrown in 6.0mm on a 40A would probably do.

If it were my own house I would possibly chance 4mm....

I’m a cheap skate

 

[Ted Curly]

Yh I will do the calculations later to find out the total design load, volt drop ect, I just thought 16mm couldn't do no harm (apart from the price) as its current carrying capacity has got to be around 70amps when in ground, can just down size the breakers

 

[westward10]

You need to apply some diversity to ascertain a realistic load but I doubt anything below 16mm will cut it for volt drop on the lighting circuits.

 

[telectrix]

this 3% for lighting is back in the dark ages with heat lamps. when LED drivers are happy with 90V input.

 

[Ted Curly]

Yes I have got the calculations to do for 24 spot lights, 9 sockets and 6 spurs 3 of them heaters, plus few other bits will present them later . I'm concerned about the size of the swa to use as the cable will be buried in the ground for a good 15-20meters and thus lowering the current carrying capacity 10mm in ground is around 58amps where as 16mm is 75amps.. Thanks guys

 

[davesparks]

I would like to see the termination of 16mm swa in a kmf

Why, it's not very interesting. I've got pictures somewhere of the times I've done it, but it's pretty simple to do.
My preferred soloution is to make off the SWA into a 2x2 steel adaptable box with one side cut out. The cut out side butt's up to the KMF with a paxolin plate between

The other option is a brass angle plate to hold the gland and cut the cable cover supplied with the KMF to suit.

 

[telectrix]

buried will not lower the ccc. due to the ambient temp.below ground being around 10deg.C, when the basic ccc calcs.are done for 20deg.C,