I've got a 2 ft x 4 ft heat mat that gets too hot, so I connected a dimmer switch to it and I can raise and lower the temp, although it is pretty much a shotgun adjustment. I also place some plastic covers under my trays that provide about 1/2" space between the mat and the trays and that buffers the heat. I'm getting good, speedy germination with my peppers and tomatoes.

I have jumpstart seedling heat mat. It works just fine, and has no thermostat control.

I use one of the $12 seed heat mats from Amazon that does not have a thermostat. I find I do not need it to germinate tomatoes but must use it to germinate and start eggplants successfully. I will run it for two or three weeks straight.

I have heat mats...6 that are 4' long and a bunch of the single tray ones. I can't say that one brand is better than another. at their expense... the cheap ones are very economical. I have been using them for about 7 or 8 years and maybe have thrown one of them away. I have plug in ones and ones you need a thermostat with.a red rubber one, and thin black wire embedded ones that need a sheet of plastic on top of them ( I think these are my least favorite as they also have a layer of screen on top of the mat... I get my hair and my clothes snagged on the very nicely bound edge), ...I think I like the red rubber one he best though. it was the most expensive of the mats but it heats a bit better although I am not sure the difference in price is worth the "bit" nor does it scoot around when moving trays off and on the mat and the ones you linked to ALI.... heavy plastic "cheap" black ones that plug directly into the outlet. they could be plugged into a thermostat to control the heat like the other mats but they don't have to be. one temp is all you get if you plug it into the wall outlet. they work fine. I have single tray sized ones and a couple that are 48" long. they hold 4 trays.

[QUOTE=JerryHaskins;684162]

I have been trying to germinate hot pepper seeds. They need a really warm temperature.[/QUOTE]

This is probably somewhat obvious, but one can sprout seeds in wet paper towels or similar, you can put them on top of the other and place them in a thin walled container, which can be put on top of any heat source, like a radiator. you just need to 'water' them every day.
After 4-7 days the peppers started sprouting roots, I moved them to the final trays. There it takes about 4-5 days more to fully emerge from the soil. Space efficient and imo quite work efficient.

Do you have a supplier for the heating cables?

I had two 9 X 19 1/2 inch heating mats from Hydrofarm that quit working. After several emails to [email]support@hydrofarm.com[/email] they replaced the mats with their new improved versions.
I seriously doubt that Aliexpress would have any support.

[QUOTE=FourOaks;684052]Although it doesnt directly answer your question, I dont use heat mats myself.

I put my flats ON TOP of T8 lights. They produce ample heat. But if this is not an option... I guess it doesnt help.:?!?:[/QUOTE]

How do you do this? Do you turn the fixture upside down or just on top of the fixture?

[QUOTE=volare71;686291]I had two 9 X 19 1/2 inch heating mats from Hydrofarm that quit working. After several emails to [EMAIL="support@hydrofarm.com"]support@hydrofarm.com[/EMAIL] they replaced the mats with their new improved versions.
I seriously doubt that Aliexpress would have any support.[/QUOTE]


That is good to know. I try and buy from companies with good support. Third party sellers are hit and miss for me.

I would like to know what the new improvements are in the mats that were replaced. I only see same old on the websites. Mine are ancient but still kickin.

- Lisa

Quick review: I have the [URL="https://www.amazon.com/VIVOSUN-Waterproof-Seedling-Hydroponic-Standard/dp/B00P7U259C/ref=sr_1_4?s=lawn-garden&ie=UTF8&qid=1519975260&sr=1-4&keywords=vivosun+heat+mat"]VIVOSUN from Amazon[/URL] and it works well with no complaints. Don't know how hot it gets, but it does the job for me.

[QUOTE=shatbox;686552]Quick review: I have the [URL="https://www.amazon.com/VIVOSUN-Waterproof-Seedling-Hydroponic-Standard/dp/B00P7U259C/ref=sr_1_4?s=lawn-garden&ie=UTF8&qid=1519975260&sr=1-4&keywords=vivosun+heat+mat"]VIVOSUN from Amazon[/URL] and it works well with no complaints. Don't know how hot it gets, but it does the job for me.[/QUOTE]

I have this exact same one, and have been extremely pleased with its performance and quality.

I use an old waterbed heater mat for peppers. It has a thermostat and set on LOW it heats to about 95 F. It gets set on a plywood table top with 2"X2" spacers between the mat and the plastic trays. This stays on the entire time the pepper seedlings are growing.

Just bought three cheap mats without thermostats on e-bay for $10 each. These are for tomato seedlings until it is time for the first transplant. Then the mats are put away for the year. These happen to be Simplex but when comparing the new ones to the old ones, they all look the same with a different brand name.