If the screen on the CTH-291 is completely blank upon startup, it most likely means that either there is no power connected to the thermostat, or the thermostat is defective. To function, 24VAC needs to be supplied to terminals R & C in the CTH-291.
If the screen on the CTH-291 is completely blank upon startup, it most likely means that either there is no power connected to the thermostat, or the thermostat is defective. To function, 24VAC needs to be supplied to terminals R & C in the CTH-291.