hvac temperature controlSenasys manufacturers a large variety of temperature switches for HVAC systems:

Bi-metal temperature switches

Bulb and capillary thermostats

Mechanical line voltage thermostats

Temperature switches found in HVAC systems are typically mechanical controls that are based on physics. More times than none, most HVAC systems have a requirement for these controls rather than an electronic type controller because failure modes are limited versus an electronic control. Rather than an electronic controller using inputs/outputs to communicate with the HVAC equipment, our temperature switches react to change in the environment causing the equipment mode to change as a reaction.

For more information about the temperature switches Senasys offers to the HVAC industry, continue reading below.

Temperature Sensing Switches

358W-136 Capillary Thermostat

Senasys manufactures a wide array of temperature switches for HVAC systems including bi-metal snap disc and duct limit temperature switches, bulb and capillary thermostats. The temperature switches for HVAC systems typically are used as a fan or limit when a pre-defined temperature is reached.


Quality-engineered thermal sensors specifically designed for a variety of major HVAC appliances, including room unit and space heaters, air conditioning systems and wood stoves. Commonly used as a limit, when temperature within the system exceeds the defined set point, the contacts open to shut the appliance off. For more information about our bi-metal snap disc switches, click here.


Our bi-metal duct limit switches are used to shut down HVAC equipment as well. Mounted to the outside of an air duct, the switch senses an increase of temperature within the duct system shutting down the equipment to avoid the possible travel of fire, smoke, or other harmful environments. Visit our website to learn more!


Our bulb and capillary thermostat line are found to be used as limit or control in HVAC equipment. Similar to our bi-metal temperature switches, the bulb and capillary style uses a liquid filled sensing element which expands/contracts when temperature changes opening or closing the micro switch contacts.


The line voltage thermostats function like a bulb and capillary style thermostat, but are commonly used among end users to control industrial heaters, barn fans and other HVAC equipment. When temperature within the system changes, the thermostat will either turn on an industrial heater, a fan, or shut a system down. Visit our website to learn more!

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Bulb & Capillary Thermostats

Original equipment manufacturers worldwide use thermostat switches designed and manufactured by STEMCO, a Division of Senasys. No matter which style or model you choose, all of the capillary thermostat switches operate using the same physics. A fluid is encapsulated in a metal and when the temperature changes the fluid either expands or contracts. This fluid change moves a diaphragm which is in touch with a snap action switch and either opens or closes a circuit.

Ambient Compensation

Our capillary thermostats can be ambient compensated to offset the differential in temperature which keeps our thermostat controls more accurate as it’s environment changes.

Custom Options

Capillary thermostat switches built by Senasys can also be built to customer specifications. This insures you get the exact control you want without paying for features you don’t need.