running cable in screed

[rob999]

Hi Guys,
I want to put some sockets in a conservatory that i,ve just put up. Is it ok to run the cable from a seperate mcb in the c u , 32a rcd side as it is split load, and through 20mm flexible conduit layed in the screed floor, that i,ve yet to pour, which will be 50-60mm thick.
Appreciate any answers.

 

[Lectrician]

You will get conflickting answers to this.

Lots of people use 20mm plastic conduit to do the job (terminate the conduit with an adaptor into the boxes, and bend the tube up and down the walls with a bending spring, and use couplers to ensure the conduit is a single, easily pullable run.

It is considered better to use galanised steel conduit.

Another way being adopted recently is to use SWA. To terminate the swa into the socket box, terminate the gland into a coupler first, and the coupler to the box with a brass bush and serrated washer. Use 35mm boxes, as this ensures the coupler and gland are well below the surface.

 

[plugwash]

would go for a 16A or 20A mcb with 2.5mm cable

 

[rob999]

Thanks for the reply.
Two more questions, 1st what is swa ?. 2nd Any reason for using a lower rated mcb ?

 

[breezer]

steel wire armoured cable.

lower rating becsue its only for the conservatory

 

[plugwash]

SWA as breezer pointed out is steel wire armoured cable
http://www.tlc-direct.co.uk/Products/SW2dot5slash3.html

2.5mm cable can only be put on a 32A breaker if its a ring

so your choices are to go down to a smaller breaker or use a larger cable

and i really don't think you will need 32A in your conservatry

 

[rob999]

Thanks guys.
Appreciate your help.
Like the idea of using the swa.
Wan,t to put in 4 sockets so Just to make sure i,ve got this right.
use 2.5 armoured, 20a breaker on radial circuit.
35mm boxes fit with glands.
What's the best way to connect to cu ?

 

[plugwash]

gland SWA to metal adaptable box

either join to T&E in there or bring out the packing layer and cores along with a seperate earth wire for the box and armour

 

[dw3101]

I wouldnt go to the effort of swa.. I would just use the conduit.. pull the cable before screeding, and coil it up in each patress..

I would allways go for a ring, that way if the room next to it needs rewiring altering etc, it can encompass the conservatory ring iyswim.

Incidently, to bend plastic, I assume heat is needed?

David

 

[rob999]

You might be right there dave cost alone makes the steel or plastic conduit method a better option. Also i think i will be happier working with it now i,ve looked into it a bit more.
As long as plastic complies with current regs.
Rob.

 

[dw3101]

it does comply, its the burried in concrete bit that might not, but as its indoor, I see no difference to burried in plaster.. if you dont put wire in first, put some nylon rope in..

 

[Damocles]

Issue is someone driving nails into the floor. Does happen, even concrete. Cable should be 2 in below surface unless armoured, same as walls.