wiring to garden sheds.

[SPECIAL LOCATION]

Hello johnstone1991..

quickly skip read the earlier posts..

I gather you are now going for 6.0mm SWA for the external runs between buildings.

Have you considered VOLT DROP? yet

you need to double check your realistic max simultanious demand at each shed.

e.g.

IF you were taking 32a at the far shed. total distance 45m

6.0 mv/a/m = 7.3 (pg 133 osg).

7.3x32x45 = 10.51volts

10.51/230x100 = 4.56% which exceeds the max 3% volt drop on light circuits?

you may need to increase the cable sizes or reduce the max permitted load at sheds?

example 2

put 1st 20M run of cable as 10mm,

put 2nd 25M run of cable as 6mm,

If you were taking 16A at each shed.

1st run has 32A load over 10mm 20M

4.4x32x20/1000 = 2.82v

2nd run has 16A load over 6mm 25M

7.3x16x25/1000 = 2.92v

Max permissible volt drop

3% lights = 6.9v

5% other = 11.9v

2.82+2.92 = 5.74v

with a little bit of tolerance for the last bit of cable to the light fitting itself,

1.16v over 1.5mmT&E @ 4A allows... about 10m internal shed run!

17th edition you do have to tick the box to say you have checked Volt drop!

Obviously if you know more accurate max demand figures you could re-calc

your original 4.0mm & 2.5mm would have dropped

7.04v & 7.2v respectively...

No way it would comply with appendix 12 pg 358 if taking 16a per shed.

 

[johnston1991]

hiii many thanks for the help with the calculations i dont have a copy of the regs yet but i will be gettin them soon..

i dont think the sheds will be runing 32 amps between them the top shed will be for a few patio lights and a 1500 watt tumble dryer

the second shed will have 3 standard strip lights not sure on wattage yet sorry. and will at most be powering a few light power tools would this not change things ?

sorry i really need to go through my notes from college

 

[SPECIAL LOCATION]

hiii many thanks for the help with the calculations i dont have a copy of the regs yet but i will be gettin them soon.. i dont think the sheds will be runing 32 amps between them the top shed will be for a few patio lights and a 1500 watt tumble dryer

the second shed will have 3 standard strip lights not sure on wattage yet sorry. and will at most be powering a few light power tools would this not change things ?

sorry i really need to go through my notes from college

If you get a copy of On-Site-Guide

page 133 has a table of volt-drop for all standard conductor sizes per Amp per Meter.

so you know your distances

you can roughly calc your loads

then using figures from Table 6E2 to see what you volt drop down each run would be.

When you get your regs book...

If you look at Regulation 525 this says about permissible Volt-Drop in Consumers Installations.



and as i said earlier

checking Volt drop is one of the new bits on 17th ed certificates!

so someone thinks its important!

your average runs inside a house are normally within volt drop limits...

but when you go outside up the garden you can start exceeding them..

especially if you have some heating or higher power workshop equipment!

 

[Badger]

can someone actually state a regulation because i have tncs here and exported the earth on 6mm earth direct from shed on armoured to seperate rcd c/u in garage, and showed the niceic inspctor, and havent been told there is anything wrong, and to be fair when the inspector checked things for my first inspection a couple of years ago he was extremely thourough.

 

[Badger]

and to be fair i thought anyhthing higher than20 amps externally was a big no no in domestic sheds etc.

 

[johnston1991]

ok im slowly building up a plan i need to check volt dropp ect in the morning when i go into college, heres what i think im surposed to be doing so far ..

its a bit of a mess and not to scale but i sort of get the idea of it..

 

[johnston1991]

also thanks for the on site guide and regs references special locations

 

[Andy™]

can someone actually state a regulation because i have tncs here and exported the earth on 6mm earth direct from shed on armoured to seperate rcd c/u in garage, and showed the niceic inspctor, and havent been told there is anything wrong, and to be fair when the inspector checked things for my first inspection a couple of years ago he was extremely thourough.

its generally bad practice to export TNC-S (but it can be done). altho its specifically banned for certain places (like caravans)\

ESQCR reg 9.4

 

[Andy™]

few points from your diagram.

your grey to the SWA - is that to the SWA or to a 3rd core? you can use a 3rd core for earth if you want, but the SWA must still be earthed.

CU in shed - they should have a main switch. either youve missed it on the drawing, or your going straight to the MCB

Volt drop will need checked, but other than that, it looks fine

 

[Robojin]

few points from your diagram.CU in shed - they should have a main switch. either youve missed it on the drawing, or your going straight to the MCB

I saw that too, thought it odd

 

[a1]

What is the earthing arrangement on your house supply? - Nice job on the diagram BTW.

What sort of loads are we looking at in Both sheds?

I'd wire the lighting in 1mm T&E or Use PVC Conduit and Singles (6491Y?)

Also, Don't like the idea of clipping to fence or the cable sizes that are proposed.

Personally - I would use 10mm for the first run (house to shed 1) and 6mm, perhaps for the second half of the run (shed 1 to shed 2) or better still

Knock Both sheds down and build a huge one.

 

[a1]

*** Note to myself ***

Finish reading all of the thread and all of it's pages, before commenting. :_|

I like the diagrams though. What did you use to do them?

 

[Badger]

*** Note to myself ***Finish reading all of the thread and all of it's pages, before commenting. :_|

I like the diagrams though. What did you use to do them?

the computer :^O :^O :^O :^O

 

[Subneural]

Didn't Wiring Matters cover this a while back and say it was ok to export the pme?

 

[Andy™]

http://www.theiet.org/publishing/wiring-regulations/mag/2005/16-elect-inst-outdoors.cfm?type=pdf

 

[Neilg5]

I am looking to do something simular. This is a great forum thanks.

 

[Zeespark]

You either need to have LABC involved or employ a Part P registered electrician to do the wiring to your garden shed Neil.

AndyGuinness

 

[moose man]

Dont forget about discremination between the two rcd S just a thought

moose man

 

[Couleddie]

can someone actually state a regulation because i have tncs here and exported the earth on 6mm earth direct from shed on armoured to seperate rcd c/u in garage, and showed the niceic inspctor, and havent been told there is anything wrong, and to be fair when the inspector checked things for my first inspection a couple of years ago he was extremely thourough.

I'd like to know this too as I raised this subject at my last Elecsa assessment and was told it was OK. Never once seen an outbuilding supplied by its own earth.

 

[steptoe]

Never once seen an outbuilding supplied by its own earth

come round mine sometime,