Capillary Switch Senses Liquid Temperature
Most commercial style dishwashers, and even a number of household type dishwashing appliances, use one or two capillary switches to heat the water.
The capillary switch’s bulb will be immersed directly into the water or contained within a thermowell, which controls a series of heating elements in either a fixed temperature style or an adjustable range style. When the water heater is turned on the capillary, bulb or probe, senses the temperature and turns on the elements. When the calibrated temperature of the capillary switch is reached it turns off the heater until the water temperature is cooled to a pre-set or calibrated temperature; and then the process starts all over.
A second capillary would be used as a limit to prevent the heaters from going into a runaway condition and overheating the system. This second limit capillary could be a manual reset, which requires human intervention to restart, or automatic allowing the system to operate under normal conditions once the temperature has dropped.
This same design is used to heat or cool many other fluids such as food grade oils, lubricants, chemicals and solvents. The better quality capillary thermostat switches, such as ours, can be ambient temperature compensated. The less expensive ones are not.
Capillary Switches Product Details
No matter which style or model you choose, all of the thermostats with capillary tube 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. Our capillary thermostats also offer the option of being ambient compensated to offset the differential in temperature which keeps our thermostat controls more accurate as it’s environment changes.
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