Thermal Imaging (Case Six)

Case Six: Thermostatic Mixing Valve

Building Type: 200+ Room Hotel located in Boston

Complaint: Guests often complained of either very hot or lukewarm hot water.

Type: Guest comfort, scald risk.

Cause: There is one thermostatic mixing valve serving the domestic hot water to the guest rooms. The purpose of this valve is to take the 150 degree hot water made by a boiler and mix it with cold water to supply 120 degree water for guests. The operation of this thermostatic mixing valve is in question. Since there are no thermometers installed in the piping, it is difficult to tell if it is working. The only temperature sensor available, is the hot water temperature entering the valve. The owner placed a data logger on the piping to monitor and trend the water temperatures. The data recovered from the logger indicated that it varied in temperature slightly. The thermistors attached to the mixing valve did not react quickly enough to catch the rapidly changing water temperature. Using thermal imaging technology we were able to determine that the mixed water temperature leaving the valve was varying considerably. The threads of the piping connection of the valve have a high emissivity and were determined to be accurate by comparing the temperatures of the entering water temperature with the thermal images. See image Pair1.

Image Pair 1

Digital Image of mixing valve

Thermal image of mixing valve

Solutions: The valve was determined to be defective and was replaced.