Lennox CBX40UHV Series Installation And Service Procedure page 60

G-ECB40-8, 10 and ECB40‐15CB - 208/230V Single-Phase Sequence of Operation
First-Stage Heat
1. W1 of the thermostat provides a W1 demand to the AHC. The AHC outputs a 22VDC signal to the K32 relay. K32-1 closes.
2. Assuming the N.C. primary (S15) and secondary (S20) limit switches are closed, electric heat element HE1 is energized.
Second-Stage (remove jumper between W2 and R)
3. When K32‐1 closes, the unit is ready for a second stage heat demand. W2 of the thermostat provides a W2 demand
to the AHC. The AHC outputs a 22VDC signal to the K33 and K34 relays.
4. When K33‐1 and K34-1 close, assuming the N.C. primary (S15) and secondary (S20) limit switches are closed,
electric heat elements HE2 and HE3 are energized.
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CBX40UHV