Thermostat for Seedling Mat

Item No. PR-HMT-500
This Thermostat for Seedling Mat allows growers to select and maintain optimal temperatures when germinating seeds or rooting cuttings for fastest growth. In addition to its horticultural uses, it is also a great tool for homebrewing (maintenance of optimal fermentation temperature) and
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This Thermostat for Seedling Mat allows growers to select and maintain optimal temperatures when germinating seeds or rooting cuttings for fastest growth. In addition to its horticultural uses, it is also a great tool for homebrewing (maintenance of optimal fermentation temperature) and environmental control in reptile terrariums. This UL-listed digital thermostat provides constant, uniform temperature control for germination, propagation and fermentation environments between 68°F-108°F (20°C-42°C). Will control up to 1000 watts of propagating mats. Works with the Seedling Propagation Mat (SUNPAD Lite Heat Mat) or most other 120V mats.

  • Temperature Display Range: 32°F-140°F
  • Celsius or Fahrenheit display
  • Includes temperature probe with 6' cord with 3-prong ground plug
  • Simple push-button operation with LED indicator lights
  • 120 Volts / 8.3 Amps / 60 Hz
  • 1-year warranty
  • Easy plug-in operation

Additional Information

SunPack Heat Mat Temperature Controller Instructions (PDF)

LTL Freight Type GROUND
Replenishment System Purchase
Available for Drop Shipment Yes
Reviews (41)
  • Loose Outlet
    I finally dug deep and bought a real seedling heat pad and controller. Unfortunately, the model I bought had a loose outlet, which is a serious fire danger. It also had one LED in the display blink out after a week or so. It did work, but I never trust a loose outlet. GMS was good enough to send me a new controller, which unfortunately also had a loose outlet, so they refunded my money. GMS has always given great service; I have no beef with them and will continue to use their great website, but I will have to find another controller elsewhere.
  • Poor Quality
    It seems to work OK. One of the LEDs on the display quit working after a few days. Worst of all, the socket that the heat mat plugs in to is loose. It draws 8 amps, so a loose socket is dangerous. I frankly don't trust the UL certification mark, as the Chinese have learned to put false UL or Intertek mark on electrical products. Returned for different brand.
  • thermostat
    I have beed using it for 2 weeks, seems to work well
  • Love It
    First time to use a heating mat as i never thought it would make a difference, but I was wrong. The night time temps were to cold for this time of year and seeds were not germinating, so i broke down and ordered a mat. I am so happy I did. I replanted seeds and put on the mat and had great results with germination
  • Thermostat for Seedling Mat
    Seemed to easy to set and worked fine. But, only used for a couple of weeks so far. Hope it has a good life expectancy which will tell the tale. Check back in a couple of years!!The temp sensor was a bit large and the wire just a bit too stiff for my fragile 4x6 seed starting containers but with proper set up, stayed in place and worked.
  • Accuracy
    It does work well with the heating mat, however, I've had to set the thermostat several degrees higher to obtain the actual temperature I'm wanting to obtain. I'm not sure if this is an issue with the thermostat or the heating mat.
  • Works great
    Works perfectly with my seedling mat. Great results with germinating this year.
  • thermostat control
    works well
  • seeding mat
    work well
  • hobby gardner
    This product works well with my existing heating mat. It is easy to use and holds the temperature at a consistent temperature.
  • Thermostat for Seedling Mat
    Love the convenience!
  • Works Good
    Keeps temp of my seed starter kit where I want it. That's all I can ask for.
  • helpful
    This is the second one of these I've purchased. Went from using an old heat mat with no thermostat to using newer mats with these thermostats. They are easy to set, and keep the medium in the starting trays within a few degrees of the set temperatures, with a significant improvement in speed and rate of germination.
  • Seedling Mat Thermostat
    This thermostat has worked great this season. A little hard to read on a bright day but has helped me fill a 20x50 greenhouse full of plants.
  • Questionable
    The thermostat says it will control up to 2 heating mats, and i do have it controlling 2 through a plug strip, but the temperature still seems to be running hot. set for 73 degree and running at 85 degrees??? i am worried it has killed all of my seeds prior to them even germenating. 10 % growth
  • Thermostat
    Seemed to work ok but only has one outlet right next to the cord so hard to plug in a multiplug adapter for several maps. Had they turned the outlet just 90 degrees... Red led hard to see in daytime. Winters here are mild so don't know how it would work back east. Fed two mats adequately after monkeying up a cord adapter.
  • Thermostat
    The thermostat works very well. The temperature control drops a few degrees at times, but it holds it within acceptable levels. I have started asparagus, artichokes, peppers, tomatoes, strawberries, celery, cabbage, and many more seeds. They have all germinated well and much faster than without it. I am pleased with this purchase and would like to get another heating pad with the thermostat, I am running out of space.
  • Seed Starting Heat Mat Thermostat
    This is a very good tool from starting your seeds from scratch. I highly recommend it.
  • Seedling Mat Thermostat
    Used the thermostat to control 3 Mats. It worked great.
  • Good product
    So far, so good. I bought this thermostat to drive two mats, it includes some really helpful documentation. It performs as advertised, seems well built. This is my first season with it. I had to hook up a twofer cable to drive the two mats, and I've used thermometers to ensure that the sensor placement represents average conditions of the starts. There is only one sensor, so you need to place it carefully for best results.
  • Thermostat
    I plugged the thermostat in, set it for 68 degrees and it is working beautifully. My only suggestion would be if they could lower the range down to 50 degrees.
  • Seedling mat
    I like this product because of the ease of seeing the temp and the lights that let me know if heating or not. Unfortunately, now that my seedlings are a few inches high, I would like to turn the temp of the mat down but unable to. I have tried what the instructions says to do to change temp but it won't let me. Need suggestions on what to do.
  • Rugged, foolproof, set and forget
    I now have two of these and they are just perfect. I use one in my basement for propagating and one in a cold frame outside. Set the temp, add your heat mats, and leave it alone. Never feeling the mat to see if it is warm and working, just look at the temperature on the thermostat at a glance.Make sure you buy full size heat mats because this thermostat will shut down if power to the mats runs continuously for more than 4 hours.
  • Good Product and Works Well
    Does a good job of keeping the soil at the appropriate temperature for near 100% germination. Haven't gotten my first electric bill since using it and wonder how much it will affect my bill.
  • Accurate, Works great
    I have been running for 3 weeks now and it's great. Temperature regulation is excellent. Using a digital probe to check both were within one degree.I am running two mats, one 18 watt which is actually a small dog heating mat. The other is the 15 watt mat that comes with the Jiffy seed starting set. I get 100% coverage under the standard 10x20 tray.The basement is in the low sixty's this time of year and with the two mats I get only 73 to 74 degrees. The probe is buried in the seed tray. The seedlings are lit with 4 old style fluorescent tubes. So if you want warmth for your seedlings you need a 30 watt mat minimum under a 10x20 tray in those conditions.I use a short extension cord from the control with 3 outlets to plug my mats into.I reviewed the number 1 (worst) reviews before purchasing the control, but my experience has been great.
  • you need this
    great product, great price
  • Thermostat for Seedling Mat
    This Thermostat for Seedling Mat is working perfectly with my heating mats. Keeps a temperature between 10 deg of the setpoint.
  • Hydrogrow Thermostat
    The thermostat works great for germinating seeds that require higher temperatures like peppers and tomatoes.
  • Great product and price!
    I have looked at the price of this item on other websites and Greenhouse Megastore is always cheaper on its prices. This product works very well and I don't know how I did without for so long. Thank you again!
  • dial it in
    It would be nice if the heat matt came with this thermostat but its worth the extra expense to get the results your looking for.
  • like
    i really do like it. set it an that it nice.
  • Well made
    I like the temperature feedback. My mats typically run at 75 degrees, which is the maximum temperature on a countertop in my basement. I suppose the thermostat is optional, but I do like to monitor the temperature.
  • Works great with heat mats
    Keeps mats at desired temp and prevents them from baking seedlings. Excellent product!
  • Thermostat for Seedling Mat
    Very easy to set up and program.Well worth the investment.I am getting a couple of more to expand my operation.
  • Great Unit
    If your are going to use a Seedling Propagation Mat, your going to want one of these. Great unit.
  • What a partner!
    For a effortless seed starting operation, you just gotta have this to go with the propagation mat (s). Set it and forget it! (Sound familiar?) I love it and highly recommend it!
  • Working well
    We're using this with the seedling mat. It holds the temperature well. The user interface is non-intuitive, so I needed to use the instructions to program the temperature.
  • Nice but one little thing missing
    Everything is very good about the thermostat but it should have multiple plug-ins to make it easier to use with multiple mats.
  • Great Asset!
    I am very pleased with this purchase. I wasn't sure if I really needed it but it gives you such accuracy with soil temperature. I like the fact that I can just look at the display in passing and know if I am giving the plants just what they need for heat.
  • Nice Controller
    This controller has been working perfectly since I installed it. I'm using it with two propagation mats. It's really needed down south because the daytime temps in the greenhouse can cook the young seedlings and I feel better being able to see the temp of the trays at a glance. The programming is easy and the display is large enough to see without glasses. The only real drawback is that in order to use more than one mat, I had to buy a pigtail with 3 a/c outlets from Lowe's. It will set you back another $10 or $15 if you get one built with 12 gauge wire.