Lennox CHA16 Service Manual page 59

NOTE-In order to understand how optional controls affect the operation of the CHA16, you
must first read and understand how all the CHA16 components work.
NOTE-In this operation sequence the unit diagram has been omitted in order to concen
trate on the interaction between thermostat and economizer.
NOTE-Relay K9 is part of the ECH16 electric heater used with the CHA16 unit for heating.
NOTE-K11 relay is part of the REMD16M 185 economizer.