Lennox CHA16 - A15 diagram with B9 diagram ECH16-185 15 kW 208;230 V Operating Sequence; Operation Sequence: A15 Section and B9 Sections (15 kW 208;230 V electric heat wired to CHA16-1853); 1- 1 st stage heating demand closes W1...; 2- When K77-1 closes, heating pilot relay K77...

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A15 diagram
with B9 diagram
ECH16-185 15kW 208/230V Operating Sequence
Operation Sequence: A15 Section and B9 Sections (15kW 208/230V electric heat wired
to CHA16-1853)
1- 1st stage heating demand closes W1. W1 energizes pilot relay K77. K771 closes.
2- When K771 closes, heating pilot relay K9 is energized. K91 switches and K93 closes.
3- When K91 switches, indoor blower contactor K3 is energized (and optional power exhaust fan
relay K65 is enabled when K32 contacts close).
4- When K93 closes, electric heat contactor K15 is energized. K151 closes.
5- When K151 closes, the heating elements are energized. The elements are arranged in a
Delta" configuration for 208/230V operation.
6- Additional heating demand W2 energizes pilot relay K49. K49-1 closes.
7- When K491 closes, nothing happens; ECH1618515Y is a single stage electric heater.