power to kitchen island

Hi,

newly registered on the forum though I've browsed it regularly - extremely useful!

I have got to run power in the floor to a kitchen island. Currently the concrete slab is down, the rest of the floor is going to be made up of kingspan insulation directly on the slab followed by a vapour barrier and moisture resistant chipboard. I know there are issues with burying cables in insulation (Thermal correction factors and the like) Can I bury some form of conduit in the kingspan that will allow a small amount of circulation around the cables? Or should I try and channel it in the slab??

I also have a related question, there is a small amount of pitched roof in the kitchen, this has 70mm of kingspan between the rafters and will have another 60mm placed across underneath the rafters leaving a 5mm max cavity (seems excessive to me but it's on the drawings), the plasterboard will then be fixed either through the kingspan to the joists or I'll fix battens of some kind through the kingspan to the joists and then fix the plasterboard to these - I might want to put spots in this sloped ceiling but am concerned about cabling and heat from the lights...? is this possible or should I just find another way?

sorry for the long post - should I have split it in two?

thanks for any help

Trev

Alright Trev,

This is what I would do. Instead of burying the cable in the insulation, channel the slab out, and use some conduit so you can replace any cable later. Also you won't have to take into account thermal correction factors. Although you will have to bear in mind grouping factors and space factors in conduit. (use a big one.)

As for the roof you will just have to make sure there is enough clearance from the roof, and from the insulation for the fittings you intend to install. Check manufactures guidance. Bear in mind thermal correction factors for this cable and possible fire hoods.

Hope this helps. Some of the pro's will probably add to this.

I assume 2 inch insulation to the floor?

I would simply lay a duct on the slab, and allow the insulation to pretty much touch each side of the duct. Use some 2 inch duct if you can! If not, then 25mm round conduit is a minimum for for 2 x 2.5 T+E.

If the thermal insulation is not in contact with the duct, I wouldn't take thermal correction factors into play.

Also, C+G boy, Conduit Factors are only used and availble when using conduit with single insualted single core cable T+E doesn't come into play with the factors. Basically, if you struggle to pull the 2 x 2.5mm in, the duct is to small.

Notice the word 'duct' rather than conduit - this is because I assume the duct will simply stop/start beneath the two units, and will not be terminated into any accessory, back box, trunking etc.....it it therefore a duct, and not conduit

Hi guys,

thanks for your help , the insulation is actually going to be pretty deep (>70mm) so I can easily loose some trunking in it, so if I were to use something like the below resting on the concrete ensuring there was a gap either side and above?

http://www.tlc-direct.co.uk/Main_Index/Trunking_Pvc_Index/Maxi_2/index.html
(or do I need galvanised trunking?)

run my 2x2.5mm T&E through it with maybe a right angle at either end to bring it up (as you say Lectrician) under the cabinets with the trunk left open..?

C&G, thanks for the pointers on the roof.

crafty, I've been looking at those but really want something that dims and don't think they do? (have replied to another thread asking about comercial flourescent downlighters, digital dimming etc. so won't cross post)

Trev

Trunking would be OK, but duct would be better - I don't like seeing it, but using some waste pipe would allow pulling in/out easier in the future. Only thing with waste pipe is it looks like waste pipe when excavated

2 inch poly duct / civil pipe / electrical duct would be best.

Lectrician said:

Also, C+G boy, Conduit Factors are only used and availble when using conduit with single insualted single core cable T+E doesn't come into play with the factors.

Click to expand...

Point taken Lectrician.
Makes me wonder why though. Surely in some trunking/conduit, you could stuff loadsa T+E in, with almost no space to dissipate heat?

How is this different to the need of singles to dissipate heat?

There is your fatal mistake

The conduit factors are not there to ensure heat disipation.....sooo many people think they are! We have the grouping correction factor for that!

There is only one reason we use conduit/trunking factors, and that is to ensure no damage is done to cables when you pull then in! Hence why the factors altar depending on how many bends, length of run etc.

It's all a learning curve

All has become clear!

Lectrician = Legend.

Hi,

have been looking around for 2"/50mm poly duct / civil pipe / electrical duct / conduit but can't find any anywhere... any ideas?

thanks again

Trev