Pam, I would just watch out with trying to make a home made heat system. A lot of times things like that don't work as well or wind up costing as much or more in the long run and are certainly not going to be nearly as convenient. As far as heat mats per thermostat, I think it can be quite a few. Probably only limited to total wattage of the heat mats. My thermostat says max 1000W which would be over 20 of my 10x20" mats. They are only 45 watts each. The only problem with running a whole lot of mats off one thermostat is that you can only monitor the one heat mat at a time. If one heat mat goes berzerk and over heats or dies altogether, it won't be regulated by the thermostat unless your temp probe happens to be in a plant on the specific mat.
Bruce

I have been using a homemade chicken incubator for germination and it works great with a total cost of only $20.

I use one 100w light bulb with a wafer thermostat and I could heat 10 flats the way its set up right now with room for more. Not only does it heat all the trays evenly with no drafts but it also holds the humidity in without putting a dome over each tray.

Just something to think about for those of you who are cheap like me . Google "fridge incubator" it is made from a scrap fridge I had already had but they can be found for free anywhere ,just look on craigslist. The wafer thermostat you can get online or at your local farm store (Got mine at co-op) and that is what cost $20.

Plus you never know you might end up with a chicken egg someday and then you will have a incubator for it lol.

Cheez2002 is right. However, I prefer in this instance to buy a product that is designed for precisely what I intend to use it for. When the germination stage is over, I can simply roll up the heat mats, cords and thermostat and put them all away. I dont have a fridge left and I dont plan on raising chickens any time soon. But hey, if that set up works for you, then great. If you use a working fridge, you could store night crawlers in there in the summer (:
If I didn't think I would be using my heat mats and accessories for many years to come, I would have gone on the cheap like I did last year (my first year starting peppers). I do use cheap shop lights for my grow lights if that is worth anything.

Bruce

Thanks guys. I have to admit, I have used nothing for the couple of decades that I've been growing, I didn't start using mats until last year. It would be easy to set up a chicken type incubator with plywood and lights. Although with the government deciding what lights we can and can't use, how do you find lights that give off heat?

I think they repealed the ban on incandescent bulbs. But never the less, the money (energy) you save by using CFL's or tube type shop lights can be spent on a small electric heater. It is probably a wash on the electric bill except that you have the option to more easily regulate the amount of heat and you won't have to worry about positioning the lights so that they will give the best light to the plants while ensuring they will not burn them.
Bruce

Not that I know of... I know some senators were trying to repeal it but it didn't succeed. I'm not too concerned with light for the plants, I have a greenhouse. What I'm trying to figure out is a way to have a cheap germination mat. ;-) talk about heaters, you should see the greenhouse right now, 2 baseboard heaters, and 3 electric heaters trying to keep it warm at night... talk about burning up money. I think it might be easiest to just bite the bullet and buy more mats. When I brought up the cables husband said I was going to end up burning the house down. haha, not too worried about that, just don't want to burn up all the animals in the process. ;-)

Can you block part of the greenhouse off and only try to heat a small part of it? could be helpful in more ways than one!

For what it is worth, the ban in incandescent bulbs has been overturned:
Check the link below.

Bruce

Here is a link that might be useful: The Washington Times, Dec 16, 2011

You can still buy normal bulbs where I am from but if you can't where you are they make small ceramic heating elements that screw into a light socket anyway. Trust me if you try an incubator style box you will love it,mine is cruising along at 89 degrees and 75% humidity without me having to monitor it .I did build mine for hatching eggs but I think I would still build one for just germination .

Quick and cheap. Ziplock bag, paper towel, water, DVR. I take 1/2 sheet paper towel, wet it, place seeds on 1/2 of the sheet, then fold it over and place into ziplock bag unzipped, place on top of the DVR. 6-10 days seeds sprouted. Bhuts, 7pot, red Hab, cayenne, billy goat, Peppadew, paprika. All did well using this method except 7pot did not do so well. Once I saw roots moved to pots (yougart cups and baby food cups poked holes for drainage) once seedling broke the soil placed under lights. Dont have a DVR, ive also used an aluminum food tray with plastic lid and set it next to the heat vent. Hope out of all the methods suggested one works for you.

Thanks Bruce. Last I heard they had tried to repeal but failed. Although I did hear that it wouldn't have an effect because all the companies had already switched over.... I guess time will tell.

tsheets, nope, I have 4 shelves/side, 26ft long of flats. I possibly could, but probably couldn't walk through without falling on something. ;-)

Hey cheeze2002 how about some pictures.

hahah habjolokia... for ~3000 plants? I thought about doing it that way and experimented with it this year... not sure, the results were ok, but I think since you need to pot them up once they sprout, it would be unfeasible for all the plants I have to start.

Incandescent light bulb ban put on hold
By Chris Isidore @CNNMoney December 16, 2011: 2:28 PM ET

Ban on old fashioned light bulbs that had been set to take effect in January is blocked by Congressional spending deal.

Ban on old fashioned light bulbs that had been set to take effect in January is blocked by Congressional spending deal.

NEW YORK (CNNMoney) -- The traditional incandescent light bulb won a nine-month reprieve late Thursday from new federal rules that would have led to its demise.

I suppose the ultimate fate of the incandescent bulb will be determined by the outcome of the elections this November.
Bruce

I could have sworn it was after Christmas that I heard on the news that it failed. They did say though, that it wouldn't matter if they remained legal or not, because the companies have already switched their manufacturing away from incandescent bulbs so no matter what, they won't be produced any longer.

ps... I believed you Bruce, you didn't have to go to all that trouble. :-)

Copy and paste....no trouble at all.

List has been quiet last couple days...guess this isn't aphid or spider mite season and damping off must be on a holiday.
Bruce

Controllers are best to be used with only one mat. Variations in the resistance of the mats can cause different temperatures in different mats. If you have several trays, you might want to consider 20x48 mats with a controller on each one. I find that larger mats give a more consistent even heat then several small ones. It is also cheaper to buy one large mat and controller then several small mats. For some reason which I don't understand, one large mat also uses less power per flat then small ones (I've measured it).

Capoman, I used two 20x20 mats this year on one controller. I also used a refrig/freezer thermometer to monitor the temps on both mats. They varied by a degree or two is all. Of course I may have been lucky to get two mats that heat very consistently. I am sure it is possible to have two identical mats to have varied heating capabilities. Also, I am sure there would be a significant difference if you used two different sized mats or ones from different manufacturers.

I was concerned about a variance in the heating between the two also. That is why I purchased the dual temp thermometer as well. It gives me good peace of mind.
Bruce

Capoman, I'm using the same setup as Bruce except that I'm running three individual tray mats. Yep, one larger would have been cheaper than three small but I accumulated them over a few seasons as needed.

Anyhow, I'm using the same dual fridge & freezer thermometer as Bruce and I'm not too concerned about mat temp variations, my mats are all within a few acceptable degrees of each other (I'm happy in the 82 - 86 zone). I'm also not concerned about a mat not monitored by the thermostat going crazy and frying my seeds/seedlings because the fridge/freezer thermometer allows you to set alarms for below and above temps. If a mat gets too hot I get an alarm. A bonus is that if the thermostat goes wonky then I'll get the alarm via one of the other mats getting too hot.

Prior to my current digital model thermostat, I had an analog one that failed in the always on position. I was lucky to catch it before baking my seeds.

Yep, Ottawpepper was the one I modeled my setup after. Thanks. Also, with two separate mats, you dont have to run one huge one if all you want to keep warm is a few plants.

Bruce