Snap Disc Thermostat Switch - Circuit On at 35°F and Off at 45°F - Large Flange, Part Number 2511L002-2132

Snap disk. Seems to work. You can hear these things "snap" on and off when they get to temperature limits.

If a heating zone with circulating hot water is not being used, and the pipes pass through an unheated crawl space, they will eventually freeze in sub-freezing temperatures regardless of how well insulated they are. An inexpensive fix is to put the head of this thermostatic switch in close contact with the pipe in the unheated area (holding them together tightly with duct tape is just fine), cover the switch/pipe pair with some fiberglass insulation (you want the switch to sense the pipe temperature, not the air temperature), and connect the switch contacts in parallel with your thermostat.The switch then acts as a theromostat the runs the circulator when the pipe temperature falls below 35 deg (plus or minus 3 degrees according to the manufacturer) and releases the circular when the pipe heats the switch to 45 degrees (again +/-3 degrees). The circulator will run for very short intervals, keeping the pipe above freezing with very little heat escaping to the unoccupied rooms. (I installed two switches on two places along the pipe, all wired in parallel. Works just fine.)

i have outdoor chiller for my dry cleaning machine and in winter we allways have problem with freezing, after installing this it work great, but the only problem is if the disc is little bit curve than it help to install properly on pipes. it run the pump autometically when its too cold and warm up the pipe.

Used this to replace the thermostat on my farm innovators heater chicken waterer. WORKS PERFECT. Keeps water warm to drink, never hot. Had to modify by laying the leads flat but it works and I dont have to buy a whole new unit since the company refuses to sell the thermostats as a replacement part.

Same issue. I have mine inline with the low voltage timer for swimming pool pump piping! I installed it about a month ago, and check to make sure worked by putting a plastic bag with ice cubes touching the switch, it worked fine. It's 45 degrees and I just heard my pump come on, and a few minutes later went off. So, the part that bothers me: "I decided to check the weather proof box that all my electronics are housed in, to make sure it wasn't one of the timers incorrectly set. As I touched the thermal switch, the pool pump started, then turned off. I only paid $13 for it, I'm thinking I got a bad switch. Since I drilled a hole specifically to fit this switch, I'll try another one theirs. Thanks for sharing. Selby Goss

Use this as a safety switch to prevent radiator pipes from freezing in the garage, I put this in the cold spot of the radiator pipes and wire it in parallel with the thermostat, even when the thermostat is off it will send a quick burst of hot water through the pipes when it gets around 35 degrees. Won't warm the room, just keeps the pipes from freezing.

Use this device to control small electric heater in basement. Heater has only on/off control - this makes up for lack of thermostat.

I tried testing this several times and could not get the circut to shut off (open) once it had closed until it was well over 60F.The circut also did not close when temp reached 34 degrees F. I had to get the temp to 32 before the circut would close.