I'm knocking holes through walls to put wires through, mains electric and ethernet. I've been concreting in offcuts of round plastic drainpipe. How would I seal these against smoke and fire? Is there a better way to do it? Someone said using metal would cause induction.
[g]
Only if you have a brain te size of a peanut encased in a tinfoil hat.
Where IS dennis today?
This might give you some ideas!
Keywords: intumescent, fireproof, silicone, firestop, foam, penetration.
e.g.
You may not need to. Per the regulations, a conduit up to 32mm diameter is acceptable without.
Above that, you need a barrier that achieves the same degree of fire protection as the wall already achieved. This doesn't mean the same construction, merely that if the wall was already required to have 1/2 hour resistance, the duct should do so too.
You probably need a draught barrier anyway.
An intumescent barrier is one that's not necessarily a barrier when cold, but will expand to form one during the heat of a fire. Intumescent mastics (Screwfix etc., cheap) are convenient for small ducts, especially if the cabling is permanent. For large ducts, pre- made collares are usually used, but these can get expensive.
A cheap and simple barrier that's useful when cables might come and go is just to use a lid of plasterboard or Viroc Versapanel, according to the usual fire regs. This can be split around the cables.
But will it leach the plastic surrounding the electric wires?
perhaps put them ins maller conduit then foam around them inside the plastic drainpipe?
[g]
How much of a seal do you need? These no good?
Maybe, but it's a problem easily prevented by wrapping polythene around any PVC cables before applying the foam, or indeed by oversheathing the cables with heatshrink.
You would still need to seal the smaller conduit against smoke.
Unless you're talking meter tails, in which case I've seen it said you shouldn't put phase and neutral through *separate* metal conduits.
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