Working principle

Thermostatic valves are actuated by chemical composition of the wax/copper material to expand or contract.

The composition material is sensing for temperature change of fluid media. The temperature increases to cause expand of composition material-slide the sleeve of valve goes up. and the temperature decreases to cause contract of composition material -slide the sleeve of valve goes down.

The flow rate of fluid media would be controlled by valve's open or down, allow how much volume to go to cooler, the purpose is keeping temperature of fluid media at set point.

The diagram on the right shows the valve actuation in diverting mode at start and cooling positions

Work Curve

The curve shows the precise piston position over the operating temperature range of the thermostat. The curve is plotted in two sections; one with the temperature increasing and the wax expanding, the second with the temperature decreasing and the wax contracting. The dfference between the two curves is called the hysteresis; it is caused by the compression and friction of the internal components and thermal inertia.

The shape of the curve and its gradient a (mm/℃ or inch/F) depend on the composition of the wax.