Summer house power supply 50 metres away

[pablo4321]

Hi there just wanting a bit of advice here, been asked to put a power supply to summer hoiuse down bottom of the garden which is approx 50 metres away
i was thinking of using 6 mm armour cable from a mini rcd fuse board beside old consumer unit as this is a old wired wylex board althiough someone has put an exterior 30ma rcd to cover whole installation. so into the mini db connect to the 20 amp mcb from there run down to the summer house connect into the mini board rcd then run a couple of sockets of a radial 16 amp and one light of 6 amp mcb also this is a tt system would it be advisable to put a rod in next to summer house.would it be advisable to put a 100 ma rcd timed delayed at the house side, any advise would be appreciated

 

[Guest55]

No point having rcd's at both ends of the swa cable , choose one end only.
And if youre using 6mm i'd connect to a 32a mcb at the house otherwise you wont get discrimination from a 20a mcb to the 16a mcb in the summer house.
Extra rod sounds good.
I wouldnt swop the 30ma for 100ma rcd at the mains , youre reducing the level of protection.

 

[pablo4321]

so would you just put the rcd at the the summer house end,also does the swa not need protection at house end

 

[Guest55]

swa needs no rcd protection so use rcd at the summerhouse only.

 

[pablo4321]

thankyou biff for your time much appreciated.

 

[Guest55]

no prob :-D

 

[stevesullivan]

Hi pablo,
If your run is 50mtrs backed by a 32 amp mcb your swa would need to be 10mm to allow for the volt drop of 7.04. you are only allowed 9.2v on a 230v supply, a 6mm comes out at 11.68v or downrate to 20amp mcb giving you a volt drop of 7.3v

 

[Taylortwocities]

This link
http://electrical.------.org/wiring-matters/16/elect-inst-outdoors.cfm?type=pdf
will cover some of the points that you have asked. It was written before the 17th edition came out but is still relavent.

If you are doing this for reward you should be aware of the legal requirements for electricity outside and
(as important)
you should already have the competence to undertake the job without resorting to a DIY fourm to ask (with respect) rather basic questions.

 

[Engineer54]

It's always advisable to add another rod on a TT system. So long as you are talking about installing a rod and not a twig!! lol!!

Oh, and take note of post 7....

 

[Richard]

this is a tt system would it be advisable to put a rod in next to summer housed

swa needs no rcd protection so use rcd at the summerhouse only.

I would think that it is likely that the SWA would need RCD protection in this case.

 

[Guest55]

I would think that it is likely that the SWA would need RCD protection in this case.

why is that ?

 

[Richard]

Presuming you were suggesting protecting the submain with a B32 BS60898, then the maximum allowable Zs for that circuit would be 1.15ohm. I would be suprised if you could achieve a stable Ra to get that.

The Op's original idea of protecting that submain with a 100ma s type followed by 30ma in the summerhouse would be better IMO.

 

[Guest55]

Presuming you were suggesting protecting the submain with a B32 BS60898, then the maximum allowable Zs for that circuit would be 1.15ohm. I would be suprised if you could achieve a stable Ra to get that.

The Op's original idea of protecting that submain with a 100ma s type followed by 30ma in the summerhouse would be better IMO.

Youre right , i read it wrong.
oops lol.

 

[Richard]

Well, hopefully the OP will spot the problem when he comes to test it. Hmmm, we'll see...