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I'm in the process of moving a reasonable sized shed in order to build a detached garage / workshop / guest annex, and need some help with wiring. I'll get a proper sparky to bolt the cable to the consumer unit, or whatever it is they do, but the cost will be far reduced if I bury the armoured cable in advance of his visit. However, I need to know what sized stuff I need to buy.
The shed will have a few strip lights (only 2 or 3...) and a couple of sockets for a drill and a bench grinder or similar. I guess I could get away with fairly small section stuff?
The garage is another matter - there will be an electric shower, multiple lights and power tools galore in the workshop - lathe, milling machine, table saw etc, plus there'll be a spur to the sewage treatment plant (only 50w, but on all the time). Clearly not everything will be on at once, but Regs will probably mean I have to cater for a high load.
I'm sure the Sparky will have an opinion, but he can't even visit for a few weeks and I'd like an idea of how much I'm going to have to spend on this element of the project. Each building will be about 30-40m from the consumer unit.
Lastly, is there a problem with running armoured cable in the same trench as central heating oil and / or mains water?
I'd be asking have you got enough ways/juice left in your current consumer unit. Decent electric shower will require at the other end a 10mm feed on a 40a breaker probably.
A good point indeed - but I figure if that needs changing its a simple enough job. I'd hate to buy and bury cable, only to be told its a few mil too small....
[i]I figure if that needs changing its a simple enough job[/i]
chinny reckon 😉
just make sure nothing's going to need 3 phase or a massive amperage supply.
I'm no spark but obviously involved with all that kind of stuff. You will want minimum 6mm for the small shed feed I'd say over that distance. The other I wouldn't want to take a guess at. Regarding trenches Id run the heating oil on its own and have water and electric together. Water should really be 750 deep to protect from frost but that is a little overkill. I'd then half backfill then put the cable in. Nice idea is to surround the armoured in sand just to give it a bit of protection.
[url= http://hto.power.schneider-electric.com/CBT/Apps/cables.aspx?lang=en-GB ]Cable Size Calculator[/url]
Well if it needs three phase its a new supply anyway because I doubt he'd have that coming in to the house currently.
Unless you forgot to mention that you have a trade account with your electrical wholesaler, why on earth do you think you can get the cable cheaper - it's not something you can get from B&Q...
If I were you I would find the spark you are going to use and let him do the cable calcs and supply cable for you to bury (I don't know many who would actually want to do that bit of the job anyway) then return to connect up once it's in.
Diversity is what you use to calculate what you current requirement is.
Your work shop sound quit full so I would be tempted to go along the of small shop / business premiss.
For motors 100% of largest + 80% 2nd largest + 60 of remaining.
Water heaters instantaneous. 100% largest + 100% second +25% remaining.
Let the tradesman do the cable calcs, that's what you pay the money for.
40m is quite a distance but there are loads of other factors to take into account.
House earthing system, supply voltage, maximum demand, diversity etc etc.
The distance is probably going to be the biggest factor, you might well need 3 core 16mm or even 25mm due to the voltage drop along the length of the conductor.
Just a rough guess btw, need more info.
just make sure nothing's going to need 3 phase or a massive amperage supply.
Three phase is no problem. IGBT based inverter can give you a nice 3 phase supply with the bonus of motor speed control via variable frequency.
I'd leave this one with your electrician, he's the guy who's going to be signing it off as being compliant with the current regulations and will (probably) be getting discount from his supplier which you won't. You will have to bury it at a minimum depth and there is a derating factor for it being buried, personally can't see it being less than 16mm^2 SWA. Haven't got my reg's book handy otherwise would add to this response. Ryan