How does Coil Boss know when the Evaporator is ready to defrost?

It utilizes an array of sensors to determine when the evaporator is declining in performance due to frost build-up.

How does Coil Boss know when the Evaporator is clean?

Coil Boss monitors the temperature of the coil at multiple locations to ensure that you will have a clean coil when defrost is terminated. Varying the “hot gas” portion of the defrost cycle on each defrost allows for less heat being re-introduced to the space and longer run time.

Sometimes Coil Boss knows a defrost is needed but it won’t call for defrost- why?

If there are abnormal conditions, Coil Boss will alert and sometimes stop calling for defrost if it is determined that defrosting again would not be wise. For example, if the drain line heat fails defrosting could create a mess that has the potential to spill water from the drain pan to people or product below the evaporator.