On Dec 28, 6:34 pm, trg-s338 wrote:
I'm building a 4 x 8 foot greenhouse planter and would like to embed
an electrical heating system, some kind of grid/mesh in the soil.
Just need to keep the soil around 70 degrees. Accomplishing this with
the least use of electricity is a plus if possible. Is this something
I can build or salvage off of an existing system? I would appreciate
any suggestions or direction where I can research further. Thanks.

A system I saw years ago at a friends workshop was:-

he ran a continuous length of galvanized fencing wire in a snake
pattern , suspended about half the thickness of the slab above ground
- he used bits of garden hose for this. He then poured the slab. (He
had brought the 2 ends of the wire out of the slab before he poured
it). He then connected the wire ends to a 30v transformer, from fading
memory it was supplying approx 3 amps. 90 watts doesn't sound much,
but it kept the place warm (and dry) throughout winter. Cost to
install was minimal.

No idea where you live, Melbourne gets to perhaps 3 dgrees C on a cold
night, 13 degrees C is a cold day.

Just an idea - you would need to do the maths for your location....

And if anyone on the side remembers Roy Hartkopf VK3AOH now SK and
has more data of his shack heating, please post it here...

Andrew VK3BFA.