SWA or Conduit under floors?

[Mouseman]

Hi, I have been reading this sight for some time now and find it very useful and entertaining. I particularly like the way a lot of threads wander off the OP and fall in to such banter. I have a couple of points I would like opinions on. I am relatively new so please be gentle.

I am about to do a complete installation on a rebuild which will have a ground floor half solid concrete and half block and beam over a basement.

1, I need to run a cable to a sub unit in an outhouse which is attached to the main house but the opposite side of the site to the CU, about 10 mtrs. This sub unit will feed a boiler in the outhouse and a shed about 18 mtrs away, both the outhouse and shed will need lights and the shed will need sockets, which may be used to power workshop equipment. Obviously I will need to do the calc for sizing etc but I would like opinions on what cable to use. Would you run SWA from the CU to the sub unit and then on to the shed or conduit T&E to the SU and then SWA to the shed? One complication is that there may be UFH, so would it be ok to route under the floor insulation or should I find an alternative route? As the outhouse will only be a boiler room cosmetic appearance is not too important, I could use a commercial sub unit to make SWA installation easier. I have read this post which seems to imply SWA all the way would be preferred. http://www.talk.electricianforum.co.uk/showthread.php?t=12374&highlight=swa

2, As this is a completely new installation, would you choose to split the supply before the main CU or take a feed from inside it?

3, Due to the concrete floor and after calculating the floor areas and cable lengths, I am intending to run 4 or 5 radials at first floor level and dropping down to the ground floor sockets, in safe zones. Splitting the house into three sections and a further two for the kitchen / utility circuits. Is this a reasonable idea?

Thanks for any advice

Mouseman

---------- AUTO MERGE Post added at 22:33 ---------- Previous post was at 22:07 ----------

Ah, I just found this

http://www.talk.electricianforum.co.uk/showthread.php?t=1700&highlight=workshop+supply

It now has me thinking. What if I run the outhouse lights and boiler thru a FCU off a radial in that part of the house and run SWA direct to a sub unit in the Shed then I do not need to go under the concrete floor with UFH?

Cheers

Mouseman

 

[Riggy]

1. SWA every time for me

2. Either split before CU or non-RCD way in CU, then RCD at local board

3. Sounds sensible to me.

 

[kme]

More info needed!

What earthing system?

KME

 

[Lurch]

Why would the cable to the outhouses need to go under the floor?

 

[Mouseman]

What is the earth?

I do not know yet? Please do not shout at me! The old system was a TT but the house has been seriously rebuilt and the disruptor disconnected the supply before the property because it was dangerous. I am guessing they will re-instate the supply as a TN-S as that is what I have three doors up. They have not confirmed yet and the build is still ongoing.

Why under the floor.

Picture the house as a 10m by 10 m square. The mains enter in the bottom right, the out house is half way up the left side and the sheds are about 10 m directly up from the top left corner, ie diagonally opposite the entry point and up 10 meters. My original plan was to go under the internal floor to the outhouse and then up to the sheds. Giving all the outside stuff a Sub Unit in the outhouse. Now I am thinking of coming back out through the entry point and going up the right side, across the top and up to the shed only, then take the outhouse off a radial in that part of the house (through an outside wall)

Hope that make some sense.

Mouseman