GardenBanter.co.uk - View Single Post - convert a soil warming cable into a heating mat

Granity · 22-03-2009, 10:42 PM

Quote:

Originally Posted by Martin[_2_]

On Sun, 22 Mar 2009 18:45:21 -0000, "Jeff Layman" lid
wrote:

Jenny wrote:
Hi I have a soil warming cable and thermostat that I used to have in a
sand box on a bench in my greenhouse. However it was very heavy and my
bench collapsed. So I thought I would update my bench and propagator and
use the soil warming cable to make a pad similar to this.

http://www.keengardener.co.uk/produc...cm-(42w).rails

So what type of material should I use to make the pad from? And how would
I fix the cable to the material? I suppose I could put it in the middle
of two layers and sew it in place with nylon fishing line but would that
melt with the heat?

I did try using a sheet of expanded polystyrene but the cable is melting
into it plus I used cable clips and they keep coming out of the
polystyrene and I am worried it might catch fire.

So any suggestions?
Thanks, Jenny

Why not use perlite or vermiculite instead of sand?

I'm surprised these things all run at mains voltage and that the word green
makes them cost twice as much as ordinary heaters.
--

Martin

Do NOT put electrical cable near polystyrene, it can, due to chemical reaction, seriously damage the insulation depending on the plastic used for cable covering.

The reason the cable is melting is that it needs to be able to loose heat uniformly which it can't do if one side is on a heat insulator.

A stronger bench and go back to sand is the best way forward imho.