convert a shed to a small workshop...

[Cablelength]

hello all,my name is barry, i live in mayo, ireland.this is my first post. im not sure if i should be making a post on this website since im not an electrician( im a carpenter). my query is that i have the use of a shed that i was thinking of turning into a workshop. it needs electricity and is about 200 metres from my house. now, i was planning to buy some heavy cable and do the groundwork myself(lay the cable so that its safe) and then find a spark to wire the cable into the fuseboard( thats if i cant just plug it into a socket...maybe).my question is what thickness of cable would i need to do the job, without the thing blowing fuses all the time...or without the voltage dropping so that it might damage the power tools.
im going to be using only single phase portable power tools( about 13amps)...no big machines
if anyone has any ideas on this then i'd really appreciate it
barry

 

[Dave]

Hello and welcome...of course you are welcome to post on here...

Hopefully one of our members will help you out on this matter..

 

[Mac]

Hi Barry and welcome to the forum

 

[Mr Mark Sparks]

welcome from me

 

[Smugley]

Hi Barry, here's how I'd work it out, perhaps someone will correct me if I'm wrong..

For sockets we normally allow a maximum voltage drop of 5%, which means for a single phase supply 5%x230V=11.5V. Voltage drop increases with the current being used, so let's say your load will be no more than 13A. You will no doubt be using SWA cable. Using the voltage drop table (4D4B in our 17th Edition regs), 16mm SWA would have a voltage drop of 7.2V over 200 metres. (0.0028x13x200) and 10mm SWA would be 11.4V, so right on the limit, and not great for lighting for which only a 3% drop is allowed .

Therefore 16mm SWA would be preferred, unless you can satisfy yourself that your maximum demand is going to be under 13A. Say for example you only have one socket and use just one power tool at a time and your most powerful tool is rated at 2000W (8.7A), then you could get away with the 10mm SWA cable and install a 10A MCB. The voltage drop for this load would be 7.6V for 10mm cable or 4.9V for 16mm cable. It depends whether you want to remain within the 3% limit for lighting (6.9V) or 5% for sockets (11.5V) and also what your expected load is. As you can see, much to consider. Especially once you look up the cost of that much SWA cable!!

You'll also want to consider your disconnect times, and may conclude that a TT system with RCD protection would be appropriate.

 

[acat]

The advice above works for me but just to complicate the situation a bit more BS 7671 is valid in England and Wales so check with a local sparky that the same rules apply. Also from a practical point of view make sure you have a sparky that will finishof your work as he will be assuming responsibility for everything on the circuit.



Chris

 

[kung]

Hello and welcome also

 

[Cablelength]

thanks smugley for the very helpful advice. i had another look at the distance and its only 170 metres, so 10mm cable should be ok...i think!(besides...theres a big hike in price from 10 to 16mm swa...im scanning the internet for some secondhand/nearly new stuff).
thanks everybody else for the welcomes
will let you know how i get on...
by the way, if i do find say 2 lengths of 100m cable, is it a big deal to joint them together safely, or is it just not advisable?
barry

 

[Smugley]

I would probably use an IP68 rated junction box if the junction is accessable for inspection, but if the junction is buried it shouldn't be joined with screw terminals. In this case you're better off using through crimps and a resin-filled joint - something like this Underground Joint Kit 2 - 2 Way / Through - Resin Joint Kit
Good Luck

 

[Risteard]

The advice above works for me but just to complicate the situation a bit more BS 7671 is valid in England and Wales so check with a local sparky that the same rules apply.

BS7671:2008 applies to the north of Ireland, however in County Mayo it would be the National Rules for Electrical Installations (4th Edition).

I should add that I have not yet done a course in the southern Wiring Rules (nor do I currently possess a copy of them) but I understand that one difference is that conductors must be identifiable throughout their length (and not just at the terminations). Obviously this might impact upon the PVC/SWA cable used.