Capillary thermostats and thermowells are commonly used in various HVAC (Heating, Ventilation, and Air Conditioning) applications due to their simplicity and cost-effectiveness. These thermostats consist of a sensing bulb connected to the main unit via a capillary tube, which allows them to sense temperature at a remote location and control the HVAC system accordingly. Refrigeration temperature controlTo view our catalog of STEMCO Capillary Thermostats, click here.

When the temperature changes in the controlled area, the fluid within the capillary tube expands or contracts accordingly. This movement causes pressure changes, which are transmitted to a diaphragm within the thermostat. The diaphragm, in turn, operates a set of contacts that control the HVAC system’s heating or cooling equipment.

When the desired temperature is reached, the capillary thermostat maintains the setpoint by modulating the heating or cooling system. For example, if the temperature falls below the set point, the thermostat will activate the heating system until the desired temperature is achieved. Contrarily, if the temperature exceeds the set point, the cooling system will be engaged until the temperature is brought back within the desired range.

HVAC Applications where you might find Capillary Thermostats
  • Air Conditioners: Capillary thermostats are used in air conditioners to control the cooling cycle and maintain the set temperature in the conditioned space.
  • Water Heaters: Capillary thermostats are used in water heaters to regulate the heating element and maintain the desired water temperature.
  • Dehumidifiers: Capillary thermostats are used in dehumidifiers to control the humidity levels and turn the unit on or off as needed.
  • Cold Storage Units: Capillary thermostats are used in commercial cold storage units to regulate the temperature and ensure proper storage conditions for perishable goods.

As you can see, bulb and capillary thermostats play a vital role in enhancing HVAC systems’ performance by providing precise and reliable temperature control. With their accuracy, versatility, and energy efficiency, they contribute significantly to creating a comfortable and sustainable environment within buildings. As technology continues to evolve, capillary thermostats are expected to remain an integral component in the quest for better HVAC solutions that benefit both occupants and the environment alike.


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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.