Installation Examples of Thermostatic Valves
Figure 1 illustrates a cooling water diverting system using a radiator. Figure 2 is a cooling water mixing system using a heat exchanger. Please note the difference between a diverting system and a mixing system. In the diverting system the three-way thermostatic control valve diverts part of the fluid out of the C port into the cooler, and part of the fluid out of the B port to bypass the cooler. In a mixing situation part of the flow comes from the cooler or heat exchanger into the C port, the other part of the fluid comes from the B port or by-pass, mixes in the valve and comes out the A port at the desired temperature. In comparing these two systems, diverting and mixing, it has been found that the diverting system will provide a better and more even temperature control than the mixing system. This is because the diverting system has introduced a more temperature-even homogeneous fluid to the sensing element. On the other hand a mixing system requires two different fluid temperatures to mix in a small volume of the valve in order to exit through the temperature-sensing unit. You will note that in all of the piping diagrams, a mixing system controls the temperature of the fluid going into the engine or the compressor. The diverting system controls the temperature coming out of the engine or compressor.
Diverting System (Fig 1):
The liquid bypasses the cooler when cold so the system reaches the desired operating temperature quickly.
Mixing System (Fig 2):
Hot water from the heat source and cold water from the cooler are mixed in the valve.
Boiler Return:
Hot water from the boiler and cooler water from the heating system are mixed in the valve.
Water Saving:
Valve maintains a minimum flow through the cooler to conserve water. It requires an internal leak hole to permit a small flow for sensing temperature.