Thermal shutoff
In the event of a failure of the hot supply port, the piston closes the cold supply port. Similarly, if
the cold water supply fails, the piston closes the hot supply port. The Caleffi
521201A thermostatic
mixing
valve requires a minimum temperature differential from hot inlet to mixed water outlet of
18°F (10°C) to ensure the correct operation of the thermal shutoff feature.
4
Operating principle
The thermostatic mixing valve mixes hot and cold water in such a way as to maintain constant
set temperature of the mixed water at the outlet. A thermostatic element is fully immersed into the
mixed water. This element then contracts or expands causing movement of the piston, closing
either the hot or cold inlets, regulating the flow rates entering the valve. If there are variations of
temperature or pressure at the inlets, the internal element automatically reacts to restore the original
temperature setting. In the event of a failure of either the hot or cold supply, the piston will shut off,
stopping water discharging from the mixed water outlet.
COLD INLET
HOT INLET
MIX OUTLET
COLD OUTLET
