Heating pipes in concrete

[regsmyth]

In our extension, I am trying to decide the best way to run the ch piping. Where I have to take the piping across the new doorway, I had originally planned to take it up in a stud wall, across inside the ceiling void and then back down the wall (surface mounted) to the radiator.
Now I'm wondering if it would be better/more efficient to cut a channel in the 100mm conc slab just inside the doorway - much less pipework.
Question is, how big to make the channel? Big enough for fully lagged pipes with say 15mm concrete back on top (ie about 70wide x 50 deep), or just big enough for some hairy lagging wrap (ie about 45wide x 35 deep). Will the heating/cooling cause problems with quarry tiles laid on the concrete?
Any thoughts?

 

[Agile]

Probably best in a convoluted plastic tube.

Felt wrap is fine but the pipe should ideally be wrapped in waterproof plastic tape or best in densotape to avoid any chance of corrosion.

The important thing is that the pipe can expand.

Its generally considered that 20 mm above a pipe is safer.

Tony

 

[regsmyth]

Do you mean like a flexible pvc conduit?
Not sure if it is much benefit - I'm a little concerned about making the channel too big and causing a weakness in the slab. But it's a toss up between insulating the pipes to prevent possible problems with the tiling, and keeping the channel small to maintain strength.
So how about lagging them in hairy wrap, then wrapping them in tin foil to prevent too much heat getting into the concrete? Or wouldn't this work?

 

[Agile]

Felt wrap is fine but the pipe should ideally be wrapped in waterproof plastic tape or best in densotape to avoid any chance of corrosion.

The important thing is that the pipe can expand.

Tony

The felt wrap is what you are calling "hairy" !

No need to wrap in kitchen foil.

You can buy convoluted plastic tube ducting made for the purpose.

Tony

 

[spacethegas]

"convoluted plastic tube ducting"

isn't that for 'going round the houses'

 

[regsmyth]

Do you mean flexible pvc tubing like this? http://www.davico-industrial.ltd.uk/img/products/DPC Conduit.png Or do you mean something specifically to insulate and protect heating pipes

 

[spacethegas]

yes, thats the sort of stuff he means.

 

[Agile]

Its rarely used on heating pipes as no one controls them much.

It is usually used for mains water plastic pipes as they must be fully accessable under the water regulations. The pipe can then be withdwawn from the duct.

Tony

 

[regsmyth]

Hi Agile,
I take it you don't mean the flexible pvc pipe I put a link to.
Can you post a link to whatever it is you're suggesting, although it might not be practical to get just a metre or two.
However if you DO mean the flexible pvc pipe, I dont really see the advantages of it over insulation felt wrap and a bit of polythene, as it doesn't insulate, and it needs a bigger slot in the concrete to recess it.
Thanks again.

 

[mogget]

This might seem a really silly question, as I have no real knowledge of this, but - why not bury plastic pushfit-type pipes in the concrete, and then feed through smaller plastic pipes for the CH?

so if the CH pipes need to be 15 mm then bury two 22mm plastic pipes in the concrete, then afterwards feed 15mm plastic through for actually carrying the water? That way there'd be no corrosion problem and the pipes would be replaceable.

Or am I being an eejit?

 

[spacethegas]

that is the idea behind the flexible conduit pipe discussed.

 

[uknokianut]

This is the stuff you need. http://www.hep2o.co.uk/v2Oconduit1.htm

 

[Agile]

so if the CH pipes need to be 15 mm then bury two 22mm plastic pipes in the concrete, then afterwards feed 15mm plastic through for actually carrying the water? That way there'd be no corrosion problem and the pipes would be replaceable.

Or am I being an eejit?

There is little chance of any corrosion on a plastic pipe!

 

[spacethegas]

Agile.

pedantic.

 

[regsmyth]

Thanks for all your thoughts, like I said the slab is only 100mm and I don't want to weaken it too much by making the channel too big.
And a nice gentle sweep of ducting in and out isn't really an option either in this case, so I guess I'll just be wrapping them in felt and polythene after all.