During cold start up, total flow is through the by-pass port. Once the fluid temperature reaches the opening point, the valve begins to open and flow to the heat exchanger supply port begins. As the temperature rises the valve shifts further allowing more flow through the heat exchanger supply port and less to the by-pass port. When the fully shifted temperature is reached the valve is fully stroked and all flow is directed to the heat exchanger port.
Three way Oil Thermostatic Valves