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  • From: Allan Balliett <allan.balliett AT gmail.com>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] Heating seedling trays
  • Date: Tue, 20 Dec 2011 10:33:06 -0500

Here's a question:

I'm using one of those 'plastic film' heating mats, probably 2x4 ft.

I'm having trouble with 'hot spots' in it. I have a good thermostat,
which I set of 70degrees. I have umpteen small soil thermometers stuck
in the trays but, of course, the thermostat sensor can only be in one
spot, so, until it reads 70 there, it keeps the juice on throughout
the mat. (I've read up to 100degrees in the soil at one point. Weird,
100 degrees BAKES seeds, which doesn't seem right) Anyway, I've
decided to sandwich the heat mat between a 1inch thick sheet of rigid
insulation (which I've had there all along) and a half inch thick
sheet of sheathing rigid (foam) insulation in the hopes that the
temperature will even out across the board and the thermostat sensor
will pick up more accurately. My question is: have you ever tried a
heat mat sandwiched between insulation boards? Is there a danger of
over heating the heat pad while trying to get 70degrees through the
top insulation? Other than buy a new heat mat, how would you approach
this problem. (Yes, mostly working with wheatgrass, peas and
sunflowers)

Thanks

-Allan in WV



On Mon, Dec 19, 2011 at 8:35 AM, MAsteveINE <MAsteveINE AT 207me.com> wrote:
>
> The system you discribe is available from suppliers under several names but
> commonly referred to as spaghetti tube, another alternative puts fin pipe
> (as is inside hot water baseboard) suspended under the bench. For a
> DIY system on the cheap use common black 1/2 inch plastic pipe in runs a few
> inches apart; running warm water,
> with a Taco 007 pump, from some type of water heater. ( longer pump runs of
> warm water is better than hot water which can overheat your crop, get your
> system together early and make a check run for a few days to see what is
> what; I like having the probe of an indoor/outdoor recording thermometer
> burried in the soil)
> My small system ran a Katz engine heater which is available at auto parts
> store; that was at the house (residence) where heat requirement was minimal
>
> For late season we needed something for lots of  vine crops direct seeded in
> 804 cell packs so we
>  put a 4' x 16' bench at about waist height, covered and skirted with 6 mil
> poly, a 1500 watt electric heater
> under there on a bulb type line voltage thermostat  Worked very well, and
> even better when we had
> the time and remembered to water with warm water!
>
> MAsteveINE
>
> 000000000000000000000000000000000000000000000000000000000000000000000000
>
> I’m looking for people’s experience heating seedling trays.  I’ve used heat
> pads in the past but I saw a system recently on a farm near Olympia,
> Washington.  This system consisted of a hot water tank used to heat water
> which was circulated through small diameter tubes under seedling trays.  The
> farmer indicated that it was a less expensive system to run than resistance
> heat pads.  I’m wondering what the experience is of people on this site and
> what their recommendations would be for efficiently heating seedling trays.
> Any and all thoughts would be much appreciated.
>
>
>
> Regards,
>
> Roy
>
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