I have the Lux Smart Temp TX500 thermostat installed. I have programmed the thermostat throughout the week and at no time is it set to heat above 69. However, I find that the heat will often continue to flow well beyond the set temperature when in Auto Mode. I will come home from work to find the residence 85 degrees, the screen showing it was set at 69 degrees, the dial set to Run, and the switches are on Heat and Auto. Sometimes I also turn thermostat to Off and the heat still continues to flow into the residence.

I need help diagnosing the problem. Is it the batteries, the wiring (loose or improper), on the thermostat itself. To aid in the diagnosis I have attached pictures of the thermostat and it's wiring. I did notice the small black wire does not seem to be screwed down like the others. This can be seen in some of the pictures I have attached. The wiring diagrams in the manual were not helpful in showing how it should be wired.

Thank you in advance for your time and assistance in this matter.

Sounds like the Lux Smart Temp TX500 ,is not so smart after all. You might recall the tstat installer ,but 1st ask about the warranty and if they stand behind their install. Not knowing what kind of heat you have, it just might be the fought of your heating system,, more info needed to tell you where to look.

My heating system is a hydroheat system that feeds off the hot water heater. It is not under warranty anymore. I thought I had attached pictures but for some reason I do not see them here,

I have the same issue too... Anyone find any solution to this problem?