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RoyJ RoyJ is offline
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Default Heating Elements for the soil

Do a google search on "greenhouse soil heater" brings up several
suppliers. "driveway heat cables" will get you some more. ditto on
"gutter heat cables"

Around here we use a lot of heating cables for ice control in the
winter. While not exactly UL approved for your application, they are
certainly some tough cable. These are 2 wire plus a ground sheath.
Normally run 3 watts per foot and about $.50 per foot in 40' to 120'
lengths.
http://www.warmzone.com/otherproducts.asp

Just how much you would need to run these would depend on what soil temp
you need, how much heat loss through the bottom, what spacing you decide
on, etc etc. I looked at some of the suppliers for some watts per square
foot info, didn't find too much. But a 60' cable would give you about 3"
max distance to a heat source, run 180 watts, cost around $30 to $40. I
would put it on either a timer or a thermostat.

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.