Snap Disc Thermostat Temperature Testing

Snap disc thermostat temperature testing is something we take very seriously here at Senasys. This is why Senasys thermostat switches stand out from other manufacturer’s with our testing and inspection of each switch. for example, our epoxy sealed thermostat switches have been tested down to -70°F and reacted to a temperature change of -50°F. They are excellent for dirty environments, as the epoxy completely protects the disc from moisture or debris. Epoxied sealed switches are slightly more expensive, but the cost is well worth it in some applications. Give us a call for for more information or visit our online store to purchase.

A thermostat switch should be temperature compensated to adjust the switch’s performance for when changes in temperature occur. For instance, a temperature switch may be set for the contacts to close at -30°F, but air temperature may reach -50°F. If the  switch wasn’t temperature compensated, the switch may have a poor reaction to the low temperature within the equipment and cause failure.

Air Chamber Test

The first test that you are going to see is the Air Chamber test. To perform this test, we use a sealed chamber. The air is then heated and mixed below the insulated surface, it is then brought into the chamber with the fan. The switches are then clipped into the brass tabs and connected to a computer program that monitors the chamber temperature at the moment that the switch opens or closes (depending on if it is an L or F switch). The temperature change in the chamber is not to exceed 1°F per minute.Snap Disc Air Chamber Test

Fluid Bath Test

Now we are moving onto the Fluid Bath test. When all of our discs are made, prior to being assembled in a switch every disc is tested above the designed range and below the designed range for both the open temperature and closed temperature.Snap Disc Fluid Bath Test

Hot Plate Test

Next, we are looking at the Hot Plate test, we like to call this the “creep test”. The hot plate is set at a temperature slightly past the switch temperature. The switch is then placed on a hot plate and the operator uses the toner to listen for a crisp snap and watches the gauge for rapid and complete open or closing of the contacts. We also have a booth that is monitored by a computer for the audio and the amperage, but this method is much more flexible for smaller run temperatures.Snap Disc Hot Plate Test

Additional Tests

There are two more tests that are done on the switches as they are made. The first measures the force of the arm that the contacts are mounted on. The second is a micrometer that measures the distance between the contact point on the arm and assigns a pin length in increments of .001”. These tests cannot be done once the switch is fully assembled.

Senasys designs and manufactures snap disc thermostat switches. Senasys switches are UL and CUL Recognized. The majority of our switches are made in the United States and our direct customer service would be happy to help you find the right switch for your application. Senasys snap disc thermostats are single pole, single throw, fixed thermostat which may be used in applications such as industrial and HVAC equipment.

If you have any other questions about how we test our snap disc thermostats please contact us! 

Contact our technical support today!


The superior controls manufactured by Senasys have a history of solid performance in many industries. From 22.5 mm selectors, to the four quadrant lighted feedback CMC controls, almost any switching need can be, and has been utilized in a variety of applications. Select a group below for more information. When you have found a switch that fits your needs, simply fax or email your specs to us and let our highly trained engineers find the most efficient configuration for your applications.

Custom Soltutions

Senasys products are designed & manufactured to meet the needs of original equipment manufacturers worldwide.

Made in U.S.A.

Senasys products are designed & manufactured in Eau Claire, Wisconsin, U.S.A.