A tempering valve may be used for cases where plant flow control is needed to make efficient use of thermal storage and is required in solar hot water loops to prevent the DHW loop thermal storage tank from becoming warmer than is necessary or allowable for safe use of the hot water. Although real installations of a tempering, or anti-scald valve, would more commonly mix a new stream of mains water with the hot water to achieve a desired outlet temperature, this is difficult to model directly within EnergyPlus because plant loops need to be closed circuits. For installations where the water entering the splitter is directly from the mains, such as make up water entering a water heater tank, the modelling provided with this object will be thermodynamically equivalent.
The Tempering valve models a temperature-controlled diversion valve on a bypass pipe that can open to divert flow around one or more plant components. It can only be used on one of two branches between a Splitter and a Mixer. The figure below shows the use of the tempering valve with a Water heater component on “Stream 2.” The tempering valve acts to divert flow through the branch it is on in order to adjust the temperature at the outlet of the mixer. If the temperature at Stream 2 Source Node is warmer than the setpoint and the inlet flow is cooler than the setpoint, then a controller determines how much flow should bypass the storage tank to achieve the desired setpoint.
No data entry is required for tempering valves.