Re: waterbed heater for seed starting?

Yes, I've used them for several years for starting seeds.  There are a few things you would need to know.  Does yours have a thermostat with it?  If not, maybe the funny-looking plug is where it plugs into a thermostat.  I'm not sure if you could get a thermostat by itself for a reasonable cost -- maybe at the Goodwill or something? 

Anyway, if you do have a thermostat you'll see that it has a dial where you set the temperature, and then a wire leading to a little fat metal stick.  This is the temperature sensor.  You want to tape the sensor to the mat with masking tape or duct tape or something so it can provide feedback to the thermostat, and tell it when the mat has reached the target temperature.  If you don't do this then the mat will keep getting hotter and hotter and hotter, until the air in the room has gotten up to the target temperature (by which time your seedlings will be dead or on fire or who knows what!)  The lowest setting on the thermostat will still be too hot for your seedlings, so you want to put some little sticks of wood or something to create an air space between the mat and the seed trays -- don't set the trays directly on the mat.  At least this is all true for the mats I've used, YMMV :).

With all these little adjustments and caveats, I do find that these waterbed heaters make a great inexpensive seed tray warmer.  If yours doesn't have a thermostat, you might want to get a whole new heater and thermostat at your local Goodwill.  An electric blanket might work well too.  You could just throw it in the washer when it gets dirty :-).


At 09:39 AM 11/30/03 -0800, Diane Whitehead wrote:
I have a couple of old waterbed heating mats and decided to see if they could be used for bottom heat to start seeds in the greenhouse. Has anyone else used them for this purpose?

They have a strange little 3-pronged plug, though, with the prongs much shorter than normal plugs.  Are they meant to be attached to some sort of transformer which then gets plugged into the wall socket?


--
Diane Whitehead  Victoria, British Columbia, Canada
maritime zone 8
cool mediterranean climate (dry summer, rainy winter - 68 cm annually)
sandy soil
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