Ecb40‐25Cb - 208/230V Single-Phase Sequence Of Operation - Lennox CBX40UHV Series Installation And Service Procedure

First-Stage Heat
1. W1 of the thermostat provides a W1 demand to the AHC. The AHC outputs a 22VDC signal to the K32 and K34 relays.
K32-1 and K34-1 closes.
2. Assuming the N.C. primary (S15) and secondary (S20) limit switches are closed, electric heat elements HE1 and HE2 are
energized.
Second-Stage Heat (remove jumper between W2 and R)
3. When K34 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 K35 relays. When K33-1 and K35-1 closes and assuming
the N.C. primary (S15) and secondary (S20) limit switches are closed, electric heat elements HE3 and HE4 are
energized.
Third-Stage Heat (remove jumper between W3 and R, if using third stage)
4. When K35 closes, the unit is ready for a third stage heat demand. W3 of the thermostat, if available, provides a W3 demand
to the AHC. The AHC outputs a 22VDC signal to the K36 relay. When K36-1 and K36-2 closes and assuming the N.C.
primary (S15) and secondary (S20) limit switches are closed, electric heat elements HE5 and HE6 are energized.
CBX40UHV
ECB40‐25CB - 208/230V Single-Phase Sequence of Operation
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