Tips for properly installing these mixing valves in radiant heating systems.
One of the best known temperature control devices in hydronic radiant heating systems is the three-way thermostatic mixing valve. It's available from several manufacturers with either an internal thermostatic element or an external actuator. The latter uses capillary tube sensing bulbs for temperature measurement.
Because these valves have been around for decades, many installers feel they fully understand how such valves work and how to install them in a radiant heating system. Unfortunately, the number of problem jobs that I see or hear about suggests otherwise.