Dumb heat mat thermostat question

I've read all the info I could find here about heat mats and appreciate all the links as well as the cautions about using items not intended for this purpose. The "pet bed" clearance mat looks interesting, despite needing to have a plug put on it, but is 200 watts, while most of the commercial plant mats are more like 17-25 watts, something to consider if someone is planning to control multiples of these with a single thermostat, since most of the thermostats are limited to 500 watts or so.

I was hoping you could help me understand better how the thermostats operate. It looks like for the starting hobby grower, there are two main options -- The Hydrofarm http://shop.horticultureguy.com/heat-mat-thermostat-464.html and the Supersprouter http://www.horticulturesource.com/product_info.php/products_id/1081

So I'm gathering the way these work is that there is a soil probe attached to the thermostat. My question is that if you control more than one mat with a single thermostat, are you just assuming that the temperature for the flats associated with the other mats are more or less the same as the one you're probing? Does that work out okay? I'm working with one of the "hardware store metal shelving on wheels" type of "greenhouses", so trays are stacked and I don't know whether higher trays would be warmer since heat rises, or cooler, since heat might dissipate before it gets to the upper trays... But I surely can't afford a thermostat AND mat for every tray!

Thanks!

I have those pet heat mats...and of course no thermostat, they are hot too. I got around the thermostat by using 48 setting timer switch I ironically had purchased during Christmas. I have the timer plugged directly into the wall to a power strip, where the heat mat is plugged into. I have the timer on for 30 minutes, off for an hour. I do have towels under and over the heat mat. Personally I don't know how a dog would ever tolerate that under it's bed, but oh well. Probably has a thermostat eh?
I have to say I'm delighted with the way it all worked out so well, as I was having issues about the safety, the timer direction advise not to plug into heating devices- but power strips are fine. The timer is off before the mat is heated to the 200 watt hot, and has an hour to cool. The MG seeds I planted came up in 2 days, so it was pure happenstance that all of it worked so well in the first round. I also have a light plugged into the strip, just as a visual for me to see that things are working. I still unplugged it when I went to work, and after some observation felt good enough to leave it on, and it's been abover my expectations.

There are also heavy duty power strip timers that you can control the same way. They are wonderful! I bought them at Gardeners Supply Magazine..Now I think they're available at home depot and all those places.

Rj

Thanks, RJ!

oh...my.....I hadn't realized the exact name/person I was talking too...but I have to tell you I was cruising throught the thread menu earlier today, and saw the name MysteryPoodle..and I nearly spit my coffee all over the computer I was laughing so hard.!...I sure enjoyed that handle!! ..great one!

This message was edited Jan 28, 2008 7:34 PM