SWA for 130-180m distance?

[Darkness]

Doing alot of shed building at home and once the lot is built I will fit lights etc. Since the buildings are located 130m-180m away from source of electric I want to lay some SWA and have it ready for installation into the new buildings.

I want to lay the SWA this week cause I've dug the trench with the digger and I want to fill it in quickly to allow the laying of concrete for a new lane+surrounding area to these new buildings.

So really what size of SWA will I need for this distance. Useage of cable will be for a couple of sockets and a few indoor/outdoor lights.

Cheers in advance.

 

[plugwash]

i always advise specifying shed cuircuits to 40A to give you the some flexibilty of load in future especially if you wan't to fit say heaters

unfortunately due to the huge distance involved there are some issues

tlcs calculator only specifies cable sizes up to 16mm but i think for a 40A cuircuit over that distance you will need 35mm and its probablly a good idea to use 50mm so that there is some volt drop left for the final cuircuits

i always advise the use of 3 core with a core as earth for a variety of reasons

such cable is unfortunately not going to be cheap and you will have to find a supplier that can do you more than 100m in one peice

terminateing such a cable will not be fun either

 

[Lectrician]

Yup, def 50mm in my book - OTT for a shed

All wholesalers can get this direct for manufacturer, but yes, it will cost

It will be difficult for a DIY-er to terminate thats for sure, I would recommend you get a qualified spark to sort you out (get him to take a ganders before you lay the cable (or even buy it).

 

[supersparks]

Yup, def 50mm in my book - OTT for a shed

All wholesalers can get this direct for manufacturer, but yes, it will cost

It will be difficult for a DIY-er to terminate thats for sure, I would recommend you get a qualified spark to sort you out (get him to take a ganders before you lay the cable (or even buy it).

lol 50MM^2 3core
thats some shed

ss

 

[plugwash]

the problem is we are allowed a tiny 4% drop in our installs

so over nontrivial distances you get a huge cable

 

[Lectrician]

Does depend on what he is gona use, as 40amp may be OTT for some people.

 

[plugwash]

he does give the impression he is building multiple sheds

and while 40A may be a bit OTT you don't ever wan't to dig that trench again

 

[Darkness]

I am currently building 2x 90ft long sheds and there is currently one already there.

The only real power consumption I may use it for is like an electric welder but that might be once in a blue moon.

I will be getting a spark in as I haven't time....too much building etc and other things.

 

[Lectrician]

As soon as i hear welder.....

Get it done properly, and yepm 40amp may be more near the mark if you go the welder route. Once in a blue moon doesnt mean you can skimp now

 

[ban-all-sheds]

It might be worth asking the REC (sorry, DNO) about laying in a separate supply. Your fat SWA is going to cost a great deal - they might be interested in competing for the job. It might be a shame about the trench, though - if you do have a separate supply it might actually come from somewhere completely different.

 

[plugwash]

the thing is the rec can get away with much more volt drop thats why they can compete

if the rec set there transfomer to output 253V (the highest currently allowed) then they can drop 36.8V

 

[Darkness]

Puzzled now so I'd may better go and have a chat with a few sparks if they manage to find time.

50mm? That couldn't be right.

The shed that is already there has tempory power using 4mm T&E for power source to shed which is being used this minute for mixer/powertools/welder for the building of these new sheds and all is ok.

This for me is unsafe hence a refit is needed but 50mm, I'm not powering a street!

Better sort this SWA out quickly as the trench will be washed in if I leave it too long.

 

[plugwash]

hece you learn that there is a big difference between the volt srop allowed by the regs and the volt drop you can get away with in practice

 

[ban-all-sheds]

At, say, 10A, 180m of 4mm² is going to drop 20V. At 20A you'll be down to a 190V supply.

This is not good.

Darkness - I understand your concerns about the trench, but insufficient time is not a valid reason for not doing a proper design - you should have thought about this earlier, particularly as the trench is going to be concreted over and then have a road built over it.

As I see it you have 2 choices:

1) Bury some 35 or 50mm² cable, and worry about connecting it later.

2) Bury some reasonable-diameter pipes with rope already threaded through so that once you have got the design done you can then pull through the cable you need. Some inspection chambers along the run might be a good idea, particularly if there are bends.

 

[Lectrician]

Put in some 4" black cival engineering duct, comes in 6m lengths, with couplers, and you can put inspection pits at bends, and along the run every so often.

I would consider asking the REC, they may sort you easier. Just out of interest, get someone to turn everything on at the shed end, and get a spark to measuer the volts at the shed. Would like to see what you get.

I have seen some 4mm MICC run 100m, running 3 immersion heaters and lights/hand driers in a caravan park toilet block!! - i measured 205volt with the immersions on, and the park supply volts was 250v!!!!! (its been rewired now via a 50mm cable from a 185mm submain as part of the park rewire)