Lennox International Inc DAVE LENNOX SIGNATURE COLLECTION GAS FURNACE DOWNFLOW AIR DISCHARGE

Models: 090V60C 110V60C 090V36C 070V36B DAVE LENNOX SIGNATURE COLLECTION GAS FURNACE DOWNFLOW AIR DISCHARGE

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closed contacts and pressure switches for normally open contacts. The combustion air inducer is ener- gized at ignition speed, which is approximately the same as the inducer speed at 70 percent firing rate.

2 − Once the control receives a signal that the low−fire pressure switch has closed, the combustion air induc- er begins a 15−second pre−purge in low speed.

3 − After the pre−purge is complete, a 20−second initial ig- nitor warm−up period begins. The combustion air in- ducer continues to operate at the ignition speed.

4 − After the 20−second warm−up period has ended, the gas valve is energized and ignition occurs. At the same time, the control module begins an indoor blower 45−second ON delay. When the delay ends, the indoor blower mo- tor is energized at a speed that matches the firing rate. After the 10−second ignition stabilization delay ex- pires, the inducer speed is adjusted to the appropriate target rate. If the furnace is operating in the initial heat- ing cycle after power−up, the initial firing rate will be approximately 35 percent. The firing rate on subse- quent cycles will be automatically adjusted by the inte- grated control based on thermostat cycles. The firing rate will vary and will range from 35 percent to 90 per- cent. The furnace will continue this operation as long as the thermostat has a first−stage heating demand.

5 − If second−stage heat is required, the thermostat sec- ond−stage heat contacts close and send a signal to the integrated control. The integrated control either in- creases the firing rate to 70 percent (if the current rate is at or below 60 percent) or increases the firing rate by 10 percent (if the current rate is above 60 percent). If the call for heat continues 5 minutes beyond this ini- tial upstage, the rate will be increased by 10 percent every 5 minutes until the call for heat is satisfied or the furnace reaches 100 percent rate. As the firing rate in- creases, the indoor blower motor is adjusted to a speed which is appropriate for the target rate.

6 − If second−stage heat demand is satisfied, but first stage is still present, the furnace will continue to oper- ate at the present firing rate until the heat cycle ends.

7 − When the demand for first− and second−stage heat is satisfied, the gas valve is de−energized and the field− selected indoor blower off delay begins. The combus- tion air inducer begins a 20−second post−purge period.

8 − When the combustion air post−purge period is com- plete, the inducer is de−energized. The indoor blower is de−energized at the end of the off delay.

Applications Using A Single−Stage Thermostat

C − Heating Sequence −− Control Thermostat Selection DIP switch in tage" Position

1 − On a call for heat, thermostat first−stage contacts close sending a signal to the integrated control. The inte- grated control runs a self-diagnostic program and checks high temperature limit switches for normally closed contacts and pressure switches for normally open contacts. The combustion air inducer is ener- gized at the ignition speed, which is approximately the same as the inducer speed at 70 percent firing rate.

2 − Once the control receives a signal that the low−fire pressure switch has closed, the combustion air induc- er begins a 15−second pre−purge at the ignition speed.

3 − After the pre−purge is complete, a 20−second initial ig- nitor warm−up period begins. The combustion air in- ducer continues to operate at the ignition speed.

4 − After the 20−second warm−up period has ended, the gas valve is energized and ignition occurs, which initiates a 10−second ignition stabilization delay. At the same time, the control module sends a signal to begin an indoor blower 45−second ON delay. When the delay ends, the indoor blower motor is energized at a speed which is appropriate for the firing rate. After the 10−second igni- tion stabilization delay expires, the inducer speed is adjusted to 35 percent speed. The integrated control also initiates a second−stage on delay (factory−set at 7 minutes; adjustable to 12 minutes).

5 − If the heating demand continues beyond the second− stage on delay, the integrated control energizes the combustion air inducer at 70 percent speed. The in- door blower motor is adjusted to a speed which matches the target rate. A fixed, 10−minute third−stage on delay is initiated.

6 − If the heating demand continues beyond the third− stage on delay, the integrated control energizes the in- ducer at high speed. The indoor blower motor is ad- justed to a speed which is appropriate for the target rate.

7 − When the thermostat heating demand is satisfied, the gas valve is de−energized and the combustion air in- ducer begins a 20−second post−purge. The field−se- lected indoor blower off delay begins.

8 − When the combustion air post−purge period is com- plete, the inducer is de−energized. The indoor blower is de−energized at the end of the off delay.

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Lennox International Inc DAVE LENNOX SIGNATURE COLLECTION GAS FURNACE DOWNFLOW AIR DISCHARGE, 070V36B, 090V36C, 110V60C