- Thermostat Operating Principle

1. The outer shell made of high expanding metal.
2.The strut assembly-made of low expanding metal.

A pair of electrical contacts is mounted on the strut assembly and installed in the shell under tension or compression. Because each end of the strut assembly is mechanically connected to the ends of the shell, a net change in force is produced on the low expansion strut assembly as the high-expanding shell expands or contracts with changing temperature. The temperature at which the contacts “make” or “break” can be regulated by a temperature adjusting sleeve. The advantage of this method of operation is that the accuracy is considerably better that that obtainable from other types of thermostat, such as the snap acting type. Low load switching differentials of less than 0.1 degree Celsius are achieved.

This adaptation of the differential expansion principle gives several important control advantages:
1. Withstand large temperature changes without damage
2. Resistance to vibration
3. Short reaction times
4. Simple and full adjustability over range
5. High Sensitivity
6. Inherent temperature anticipation
7. Wide operating range
8. Direct response to radiant heat
9. High switching capacity
10. Accessibility of adjusting sleeve and lead wires
11. Ease of installation
12. Low cost
12. Choice of mountings