I needed a heat pad to start peppers and cane up with this idea.
Took a heat pad, wrapped it in plastic wrap, put into a cookie sheet, placed a sheet of foam, wrapped that in plastic, turned the cookie sheet (with heating pad inside) over and wrapped all of it in foil (to protect from water).
Orange = Heat pad
Silver = foam
On high soil temp runs about 90
Med about 80
Low about 70
That's with the GH temp at 65
The cookie sheet is turned upside down, the heating pad is inside the cookie sheet and the foam is now on the bottom. Then everything wrapped with foil.
Even with the precautions you've taken, I'm just not a fan of using home heating pads in this way. Newer heating pads come with auto shut-offs, partly because they're not designed for constant use. I use a lot of things in ways they're not originally intended -- but I heed the warnings on electrical stuff.
I know a lot of folks have heard me get on this soap box before! :-)
I did suggest some alternatives to buying "official" seedling heat mats in this article, if you want to check it out: http://davesgarden.com/guides/articles/view/556/
I'm surprised there haven't been more post as yours, Critter, and I respect your opinion.
I have read your pages and received lots of great info, but a lot of people would never go
sky diving...that's why I tittled it 'Don't do this' ^_^
Many caution's on products are a bit much, 'Don't use this Hair Dryer in the Shower'
My GH is constructed of metal and glass and the bench the heat pad is on is metal,
so I may have cooked seeds, blown fuse or some nice peppers.
As I said, you've taken some precautions, and I figured you were using it out in your GH... but despite the title of the thread, I didn't want somebody to think this might be an ideal way to use a heating pad to start some seeds on a table by their living room window, next to the drapes, using an ungrounded outlet...
I think I'd rather take my chances some other way than by courting electrical fires. But I don't think I'll try using my hair dryer in the shower any time soon, either! LOL
Thanks for reassuring me that if anything goes wrong with your arrangement, your house, life, etc. aren't endangered.
My own "don't try this at home!" thread involved trying to sterilize too-dry potting mix in the microwave.. Fire in the hole! :-)
Your idea got me thinking, around 2AM this morning. I have a waterbed heater I am not using and was thinking of how to concoct a heating pad setup. It has a thermostat already in place and is designed to stay on.
What are your thoughts?
My thought is that the waterbed heater is designed to heat a much bigger volume of water than the tray of sand or water reservoir or whatever you're thinking of putting it in under your seedlings... Unless you're really comfortable with home wiring projects (some people are completely competent electricians even if they're not certified professionals), I wouldn't suggest "concocting" something of that nature. If you want to concoct, try making a light box or using Christmas rope lights... even those heating cables that growers use are cheaper than the official seedling heat mats... but please be careful. :-)
I used a back heating pad for years as a propagation mat, but I don't think it's a good idea to wrap them in anything. I have cats, and sometimes they would decide that the mat where I was warming seeds was a good place to hatch an egg. I would notice often that the seeds underneath them would get cooked. This year I finally graduated to real propagation mats. I went to throw out the old "propagation mat" and saw that it was discolored in a pattern tracing the wires inside. Scary.
Yes you must be careful with anything you do.
Sonoita if I had a water bed heater and thermostat I would try it , with caution , as Critter says.
I lay a Thermometer on top of the soil to check the temp...nothing is perfect and a DIY can save you lots of $$$$$
I know someone that used the whole waterbed as a seed starting mat and it worked in their gh very well but then they were the only ones using it. However I doubt that it would be energy efficient for a small grower. It is designed to turn on and off with the built in thermostat.
Using a whole waterbed is different from taking the heater and thermostat out of a waterbed and putting it to a use it wasn't really designed for. If you don't quite know what you're doing, you can get yourself into trouble trying to re-purpose electrical equipment. It's just not worth the risk, IMO. Buy a seedling heat mat, or opt for another inexpensive alternative, or just let your peppers take longer to germinate. :-)
Thanks for the fedback. I may try the heater, I may not...I've worked with electricity, though I am not an electrician and the notion of experimenting with the waterbed heater is less scary than the heating pad to me.