OK. In that case, as I said, 10mm² SWA will be more than adequate for your present requirements and also incorporates a appreciable degree of 'future proofing'. However,as I hinted before, if there is the slightest possibility that you might ever have greater load requirements (more than 32A / ~7.4 kW power) in the future, it might be worth thinking about 16mm - since even a 40m trench is mighty hard work to dig, if you're doing it manually (in answer to your previous question, a minimum of about 450mm deep).It will John, right the way to the consumer unit.
Now we are down to 40m, under normal circumstances I would say that 10mm² cable (allowing you up to around 32A power) would probably be adequate future proofing. However, given the size of your shed, I suppose there are possibilities that 'unusual' larger loads may arise in the future. The marginal difference in cost of 10mm² and 16mm² cable is not enormous, so it might be the way to go.I think you're right with the 16mm being the best for the future John, and yes I will be digging the trench by hand. Although going down to half a metre might make me reconsider. I am looking at installing ground source heating in the near future, so I may well combine the two jobs and rent a digger.
I wouldn't personally even think of attempting to terminate 16mm² SWA (or, frankly, SWA of any size) directly into a consumer unit, particularly a 'flimsy' plastic one. Far better to terminate it in some sort of box/enclosure close to the CU and take T+E cable (or singles) from there into the CU.The other thing that I was thinking of with the 16mm is how the heavier cable attaches to a domestic consumer unit. Is there enough room for a cable that size?
Given the short length of cable concerned, voltage drop is not really an issue, so current-carrying capacity is the only issue. On that basis, if it's being run from a 32A MCB or RCBO, then 4mm² (maybe 6mm²) would theoretically be OK. However, it is arguably 'nicer' to stick to the same cable size as the SWA, not the least in case someone decides that more power is required in the future and 'upgrades' the 32A RCB/MCBO for something larger.Good idea John. Can you let me know what size cable you would use to link the box to the CU?
Don't really want to go around the houses but, with definitions being a little ambiguous. If we calculate VD from Main CU, why would we not calculate it from sub-main or beyond.I have to ask you yet again ... if you do believe that VD (for the purpose of the regs) can be calculated from an 'origin' which is at the end of a (consumer's) distribution cable or sub-main, then why on earth do you think we calculate (as you did, even if with errors) the VD in such a distribution cable/submain, and why do you think that discussion about VD arises so often in relation to lengthy supplies to outbuildings
Err - hello? Anyone there?Oh, now I'm a bit confused! It looks like I can make the run 40m - so does anyone have a definitive answer on the cable size?
While we're here guys, do you know if there's a minimum depth the cable must be buried?
Below are the main points you need to cover
.
.
- //www.diynot.com/wiki/electrics:mcbtocable <- CABLE SIZING
- http://www.tlc-direct.co.uk/Book/4.3.1.htm (all subsections)
- http://www.tlc-direct.co.uk/Book/4.3.11.htm <- CABLE SIZING
- http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf <- CABLE SIZING
- http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html <- CABLE SIZING
- http://www.tlc-direct.co.uk/Book/5.3.1.htm
- //www.diynot.com/wiki/electrics:mcb2
- http://www.tlc-direct.co.uk/Book/7.13.3.htm <- BURIED CABLES
- http://www.tlc-direct.co.uk/Book/8.1.1.htm
- //www.diynot.com/wiki/electrics:swa-gland
- http://electrical.theiet.org/wiring-matters/16/elect-inst-outdoors.cfm?type=pdf
- //www.diynot.com/wiki/electrics:part-p
FFS.Good idea John. Can you let me know what size cable you would use to link the box to the CU?
Far better to terminate it in some sort of box/enclosure close to the CU and take T+E cable (or singles) from there into the CU.
That's what I assumed (a 32A MCB or RCBO in the house consuimer unit) - does anything I said appeare to be incompatible with that?I was going to feed the SWA from an MCB in the house consumer unit, and then use a two way CU in the shed for the lights and ring main.
Yes, that would be fine, although, if it's 16mm² SWA,some might want to avoid the hassle of manipulating 16mm² conductors within the CU (and terminating them in an MCB) by using something smaller than 16mm² from box to CU (give or take my caveats). There would obviously also have to be a connection from the SWA armour to an appropriate 'earthing' place (CU/MET).Personally i would just strip the tails longer and pass the tails through the box uncut to the CU terminals.Far better to terminate it in some sort of box/enclosure close to the CU and take T+E cable (or singles) from there into the CU.
Don't take it personally - it's an ever-present part of the forum's customer relations dept which most of us have encountered and learned to live with! In fact, if you can grit your teeth and see past the bolier-plate responses and rudeness, he is (believe it or not!) generally very well intentioned and he does have a lot to offer.Blimey - that's quite a reaction! Have I found the customer relations department? I didn't know the cable size to use - that's why I asked. I do have a desire to learn - that's why I asked. Thankfully John has been very helpful and pointed me in the right direction.
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local