soil warming cable

some info here:

https://www.parasene.com/vshop/details.asp?prodID=221

smud6ie

Hi drythropple

I have just extended my heated bed over winter: -

A 150W cable will cover an area approximately 2Mts. square.
Build a wooden box with sides about 150mm high.
Place a layer of 25mm thick polystyrene on the bottom of the box.
Cover the polystyrene with a 50mm (ish) layer of sharp sand (builders concreting sand).
Lay the cable on top of that as shown on the Parasene web site.
Cover the cable with another 50mm layer of sharp sand.
Ensure the sand is kept damp at all times or the cables can overheat.

Its best to control the temperature with a rod stat which is inserted in the middle of the top layer of sand. A stat will also reduce costs which can mount up if the heater is used regularly. Without a stat a 150W cable would cost you about £2.50 a week to run.

I would also recommend using an RCD breaker somewhere in your power supply for safety reasons.

The bed will take a couple of hours or more to warm up.

Wouldn’t be without my heated bed as I get great germination rates and grow allsorts of early salad crops. In fact I am going to start sowing some this next week.

Hope that helps.

About 20 degrees C is about the right temp for most seeds.