SWA - Garden - Stables

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danny7299

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hi there

Just helping my old man out with some stuff...

I need to run power from the house fuse board to garden shed (30m) then from shed to stables (250m).

I only need about 20A at the stables and the only reason the shed is being wired is so it can have a light in it and so there isn't a horrible huge cable running up the house.... (3 core, 6mm to the shed, shed to stables= 25mm)

I just wanted to know, the board is the old BS3036 wylex fuses in the house and its full, i was just wondering what would be the best way to isolate and protect the run up the the stables.

The stables has a CCU and is just waiting for a feed...

I was thinking , coming out the old board into one of these

http://www.tlc-direct.co.uk/Images/Products/size_3/TLBS32SLASH6.JPG

then off the the shead... into and adaptable box, then off the the stables.

my questions are, firstly can any one think of a better way?

2nd) is there a better way of splitting at the shed?

hope that makes sense

please be gentle... :^O

Cheers

 

steptoe

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dont matter if you run a 240mm SWA from shed to stables, you still have to base all you calcs on the 6mm from house to shed.

SORRY.

prob about 4 1/2 amps, :D

you need to be running a 25mm direct from the incomer, just use a metal clad switch fuse beside the wylex board and split the tails with a pair of iscos.

remember to calc your earth size, and it might be an idea not to use the earth on this length of run, consider a TT to allow for the potential difference.

its really not a diy job unless you are confident in working out all these possibilities.

Albert, B)

 

danny7299

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OH right... thats interesting. i have spoken to my collage lecturer who told me that would be OK?? hum mm

also i am going to speak to my boss before doing job, but in all fairness , i would get a better and less condescending answer from this site... he is a right **** and wont explaining anything.

what are other peoples thoughts?

cheers

 

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hi thereJust helping my old man out with some stuff...

I need to run power from the house fuse board to garden shed (30m) then from shed to stables (250m).

I only need about 20A at the stables and the only reason the shed is being wired is so it can have a light in it and so there isn't a horrible huge cable running up the house.... (3 core, 6mm to the shed, shed to stables= 25mm)

I just wanted to know, the board is the old BS3036 wylex fuses in the house and its full, i was just wondering what would be the best way to isolate and protect the run up the the stables.

The stables has a CCU and is just waiting for a feed...

I was thinking , coming out the old board into one of these

http://www.tlc-direct.co.uk/Images/Products/size_3/TLBS32SLASH6.JPG

then off the the shead... into and adaptable box, then off the the stables.

my questions are, firstly can any one think of a better way?

2nd) is there a better way of splitting at the shed?

hope that makes sense

please be gentle... :^O

Cheers
I just have feelings there may be probelems with the volt-drop if you are hoping to run 20A at the stables...

250m is one long radial circuit from a domestic single phase supply.. :|

Not 100% sure the specific way to approach volt drop where the cable size changes part way up the run but these would be my assumptions.

{Just banging a few figures out for others to comment on..}

a) 30m 6.0mm (mV/A/m= 7.3)

B) 250m 25.0mm (mV/A/m= 1.75)

ref pg 125 O-S-G tab 6E

Using formula pg 116 VoltDrop = (mV/A/m) x Ib x L /1000

so looking at the two individual cable sections:

a) 7.3 x 20a x 30m/1000 = 4.38volts.

B) 1.75 x 20a x 250m/1000 = 8.75volts

Max permisable volt drop from origin to load equipment 9.2v

My conclusion..

Just the 250m length would be pushing the boundaries of volt drop on its own.

adding any further loss already encounterd from house to shed ???? ?:| ? :|

Also how long is the run fron the CU to where it leaves the house?

or is this included in the 30m figure?

Just seem to long for current and cable size?? :(

If the max currrent was limited to 16a it would be nearer 10.5v drop!!

Total length 250+30+ extras is a long radial circuit..

Comment..

suggestions..

have I missed somthing obvious? ?:|

SL.

 

steptoe

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I just have feelings there may be probelems with the volt-drop if you are hoping to run 20A at the stables...250m is one long radial circuit from a domestic single phase supply.. :|

Not 100% sure the specific way to approach volt drop where the cable size changes part way up the run but these would be my assumptions.

{Just banging a few figures out for others to comment on..}

a) 30m 6.0mm (mV/A/m= 7.3)

B) 250m 25.0mm (mV/A/m= 1.75)

ref pg 125 O-S-G tab 6E

Using formula pg 116 VoltDrop = (mV/A/m) x Ib x L /1000

so looking at the two individual cable sections:

a) 7.3 x 20a x 30m/1000 = 4.38volts.

B) 1.75 x 20a x 250m/1000 = 8.75volts

Max permisable volt drop from origin to load equipment 9.2v

My conclusion..

Just the 250m length would be pushing the boundaries of volt drop on its own.

adding any further loss already encounterd from house to shed ???? ?:| ? :|

Also how long is the run fron the CU to where it leaves the house?

or is this included in the 30m figure?

Just seem to long for current and cable size?? :(

If the max currrent was limited to 16a it would be nearer 10.5v drop!!

Total length 250+30+ extras is a long radial circuit..

Comment..

suggestions..

have I missed somthing obvious? ?:|

SL.
totally agree more SL,

as I said it would be of my opinion that it would have to be based on the smallest size cable, hence the 4 1/2 amp comment. I just didnt even think it was worth doing the calcs as it seemed too illogical for the distance.

also the Earthing arrangements are suspect,

I think it would require a TT setup, you couldnt possibly justify having a building 250m away as part of the equipotential zone, you would end up with the building being at a different potential to the ground(earth) surrounding it.

wonder what the DNO stance would be on this.? ?:|

I really think danny7299 that perhaps you need to get some1 in to at least give you some professional advice if nothing else.

 

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totally agree more SL,as I said it would be of my opinion that it would have to be based on the smallest size cable, hence the 4 1/2 amp comment. I just didnt even think it was worth doing the calcs as it seemed too illogical for the distance.
evenin steptoe:)

As you say it is quite obvious the run length will exceed volt drop limits..

just thought it may help danny to actually see some of the numbers crunched to see why we come to the conclusions we do!

And cuz, to be perfectly honest, you do not have to do these sort of calc's on a daily basis it is always good to check out the numbers once in a while..

bit like doin the crossword or sudoku!! :D

 

danny7299

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hi there

thanks for all of that... looks like the best route is to get the boss man out and see what he says... yes it is a huge run and to be honest 16amp would be ok for the stables , i was just trying to leave a little more.

like u said get the DNO out and see what they can suggest, ...

 

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i should just suggest to the old man to get a candle and box of matches!! B)

or move the stables.... or the house!

he he
Get a horse box!!! :D :D:D

Its got wheels....

roll it near to the house to use a plug-in extension lead..

then unplug..

and roll it back 280m away!!!!!!!! :^O :^O:^O:^O

 

steptoe

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as per usual SL correct.

Ive actually got very lazy on my calcs past while cos I been making my apprentice do them, :D

just making sure he understands why/or why not he can/cant do something.

one of the apprentices thought there was nothing wrong with putting 25 recessed 4tube grid fittings on a 6amp MCB with a 1.0mm cable!!!

and he alledgely completes his time next month!! :eek: :_|

He couldnt even explain ohms law to me, reckons he never learnt it at college.!!

I now have a meeting with the big boss next week to try sort out some of the problems left by the previous guy (whos job I have now).

 

kme

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Danny:

Just for added confirmation of information (if you need it.)

Mr Location (he`s special, he is), is absolutely on the button IMHO. TT the stables and put in a VERY large swa, or call DNO out for new supply. If you need size for swa, post on here and one of us will be able to suggest something.

p.s. Wind turbine may actually be cheapest option!!!!!

 
W

wabbitwabbit

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Split concentric 25 mm csa will just about do the job (4.6kW at stables). The cost is going to be blooming high, just for the split con. Henley block at the source and rcd + mcb it out of house direct to stables, stuff the shed for a moment. If the house is TNC-S/PME and am a believre in NO exporting of PME so TT the stables (which you should anyway).

Then you get to the stables. Animals and lecky don't mix so you need to treat it as agricultural.

 
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