Laying underground cable

[keith70]

i've just had a detached garage built and am in the process of constructing paths and walls as well as the driveway.
At the moment i am digging trenches for drains.
Can i now lay conduit to take the armoured cable to connect the garage to the mains so that when i get a leccy in(which i will be doing to wire the garage and connect to the meterbox) he will only have to pull the wire through and connect the ends rather than him having to lay the wire in trenches.
it also means i can carry on landscaping etc and sort the electrics out at a later date.
does this sound like a reasonable proposition
if so what is the minium depth that the conduit has to be
any other advice would be gratefully received
could i also put the cable in myself or would this start to infringe on part p regs
keith

 

[RF Lighting]

putting a duct in now would be fine, and i beleive it should be buried 600mm below the surface, and you should also place some 'warning electric cable below' tape in the trench. The diameter of the duct depends on what size cable you will be installing, but if you are putting in drains then it should be fine to use a spare length of drain pipe as the ducting (but make sure it is marked to avoid confusion). You will be fine to pull in the cable yourself, but you will need to discuss with your electrician what size cable you require.


HTH

Rob

 

[keith70]

cheers rob for that
600mm seems quite deep especially when i've got to dig the trench
i was thinking of using some 40mm waste pipe(only because i've got some spare lengths)
talking to a few people the popular concensus is to use 2.5mm2 swa cable but like you said i will consult a leccy before doing anything

 

[RF Lighting]

A 2.5mm² SWA will be OK for a normal garage with just a socket and a light, but I have a 16.0mm² feeding my garage. Now this is TBH a little overkill, but we have a couple of freezers, then all my workshop stuff, and the shed running of ours. It is easy to load the garage up (especially if you have a couple of welders, grinders, pillar drill table saw, chop saw, router, sanders compressor etc)

It depends if it really is a garage, or a workshop hidden in a garage

 

[keith70]

cheers again
i was thinking of having a couple of double sockets
2 lights poss flouresent
electric garage door
outside socket and some low voltage garden lights poss 3/4 20w
would love to have a workshop but unfortunitly costs and a wife prevent me
keith

 

[BigJon]

I did a similar installation recently, ran a 6mm SWA from house consumer unit in ductin under driveway to a consumer unit in garage, then had a lighting circuit and socket circuit with a 30ma rcd to cover the outside socket

 

[keith70]

thanks for that
the run from meter to cu in the garage will be about 7-8m long does this affect the size of swa?
keith

 

[BigJon]

No not in your case, thats quite a small run. You could up it to 4 or 6mm to cover any future additions. I used 3 core and used one core as an earth, but also earthed the SWA in the unlikely event a shovel went through the cable

 

[keith70]

ta again
do u think a leccy would have any reservations about me putting in the cable im thinking along the lines of part p regs and certifying the work off
i can understand people not wanting the job halfway through/finishing the job off so to speak it will just make my life alot less stressful if i know the cable is in place and i dont have to strat ripping the drive up because i laid the wrong stuff or a leccy wont sign it off because he has put it in himself
ive not contacted or got quotes from anyone yet
Keith

 

[ban-all-sheds]

Install the duct (it should really be black), and see here for info on depths etc.

Take photos to show what you have done.

And put a length of rope in the duct so that the electrician can pull the cable through himself.

 

[keith70]

i was wondering what size swa cable to put in whether to be 2.5mm2 or 4mm2
i will only be running couple of sockets 2 lights ,electric garage door outside socket and some low voltage lights
as i said before want to put cable in now then connect later in the year
what is the concencus on this
thanks

 

[Adam_151]

10mm² (incase of future expansion)

 

[keith70]

hi
i dont think i will be expanding in the future if i put in 10mm2 for a run of 7/8m what sort of stuff can i run without overloading it or would i be ok with 6mm2 there wont be any welding or heavy drilling etc
seem to be getting a lot of conflicting info throughout this and previous posts concerning size of wire
just want to know what size without going over the top or under so i dont have any probs later on

 

[JohnD]

10mm

I don't know what the ratings are for SWA underground in ducts but it must be about 50Amps!

 

[keith70]

ok ill take your advice and put in 10mm2
then there cant be any complaints (can there??????)