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Cables under concrete floor
I need to do some rewiring in my kitchen. It has a concrete floor, and
the easiest way to route the twin & earth would in places be under the floor. Once everything is done I'm intending to put Wickes electric floor heating on top followed by ceramic tiles. So, what I'd like to do is to put my SDS drill to good use to gun up some channels in the floor, lay the cables and fill in the channels with mortar. Is it OK to do this? Must I use conduit (in which case I'd go for http://www.screwfix.com/app/sfd/cat/...81966&id=12389 )? Are there rules about the course the cables must take (no diagonals, etc)? While I'm at it I intend to put some cat5 and coaxial cables in as well (although not to close to the electrics), anyone foresee any problems with that idea? I'm a bit worried that the underfloor heating might bugger it up. Thanks for any ideas, Martin |
#3
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Cables under concrete floor
1: PVC cable is unsuitable for embedding directly in concrete according to the On Site Guide, table 3A (p94) so some sort of conduit is called for. If PVC cable is unsuitable for this - why is it suitable for direct bury in roughging when used on blockwork walls ?? it's the same material in contact ? Rick |
#4
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Cables under concrete floor
In message ,
"Rick Hughes" wrote: Martin Angove wrote: 1: PVC cable is unsuitable for embedding directly in concrete according to the On Site Guide, table 3A (p94) so some sort of conduit is called for. If PVC cable is unsuitable for this - why is it suitable for direct bury in roughging when used on blockwork walls ?? it's the same material in contact ? Hmmm... come to think of it, what the OSG probably means is not to lay cable and then pour concrete all over it. It is possible that something in the unset/setting mix will react with the PVC. I really don't know, and someone else here can probably advise better. When putting cable in channel, the stuff is already set and so presumably more-or-less inert? They're not worried about wet plaster - good job too! Hwyl! M. -- Martin Angove: http://www.tridwr.demon.co.uk/ Don't fight technology, live with it: http://www.livtech.co.uk/ .... Dammit Bones, I'm a captain, not a doctor! |
#5
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Cables under concrete floor
"Martin Angove" wrote in message
... Hmmm... come to think of it, what the OSG probably means is not to lay cable and then pour concrete all over it. It is possible that something in the unset/setting mix will react with the PVC. I really don't know, and someone else here can probably advise better. When putting cable in channel, the stuff is already set and so presumably more-or-less inert? I suspect it's more physical than chemical. Concrete (as opposed to sand & cement screeds or plaster undercoats) contains stone chippings with sharp edges. You wouldn't want to put a relatively fragile cable through mass concrete which is going to be poured by the barrow load (or more) then tamped or settled with a vibrating poker. The (un)delicacy of the concreting operations just isn't compatible with the cable - even 10 mm^2 T&E starts to seem small and fragile in those circumstances... In the floor screed I'd still use PVC conduit though - it's cheap and saves an awful lot of hassle if you need to replace the cable. -- Andy |
#6
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Cables under concrete floor
Interesting. THE Boat Safety Scheme (Inland waterways) does not permit
PVC cable layed in polystyrene insulation foam as conatact makes the PVC brittle and a fire hazard. On Mon, 13 Oct 2003 00:19:24 +0100, "Andy Wade" wrote: "Martin Angove" wrote in message ... Hmmm... come to think of it, what the OSG probably means is not to lay cable and then pour concrete all over it. It is possible that something in the unset/setting mix will react with the PVC. I really don't know, and someone else here can probably advise better. When putting cable in channel, the stuff is already set and so presumably more-or-less inert? I suspect it's more physical than chemical. Concrete (as opposed to sand & cement screeds or plaster undercoats) contains stone chippings with sharp edges. You wouldn't want to put a relatively fragile cable through mass concrete which is going to be poured by the barrow load (or more) then tamped or settled with a vibrating poker. The (un)delicacy of the concreting operations just isn't compatible with the cable - even 10 mm^2 T&E starts to seem small and fragile in those circumstances... In the floor screed I'd still use PVC conduit though - it's cheap and saves an awful lot of hassle if you need to replace the cable. Lawrence usenet at lklyne dt co dt uk |
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