How does a digital thermostat determine when to bring on second stage?
Digital thermostats constantly monitor the performance of 1st stage. When the system is within 1 degree of set point for an extended period (good system performance) the second stage will take longer to come on even if you increase the set point. If you are more than 1 degree from set point the calculation in the thermostat starts counting down until it brings the second stage on. With second stage the system usually satisfies for heat or cool and turns off. On the next cycle the second stage will come on sooner because the memory in the thermostat remembers it’s previous performance. Most models have a way to bring second stage on quickly to test second stage. This can also be used to bring on the second stage quickly whenever a customer wants.
