Lennox International Inc G32Q4-125, G32Q3-100 On call for heat from a single-stagethermostat

4- After the prepurge is complete and the pressure switch is closed, a 20-second initial ignitor warm-up period begins.

5 - After warm-up period, gas valve is energized on sec- ond stage (high heat).

6 - Gas valve opens and gas is ignited. When flame is established, flame sensor sends signal to control module to de-energize the ignitor.

NOTE - If the flame is not detected after the first igni- tion attempt, the control module de-energizes the gas valve and the prepurge / ignition sequence is re- peated. After five ignition trials without proof of flame, the unit will go into a Watchguard / Flame Fail- ure mode. In Watchguard mode, control will repeat the prepurge and ignition trial sequence after 60 min- utes of unsatisfied thermostat demand.

7 - After flame is sensed, 45-second FAN ON delay be-

gins. Indoor blower is energized on high heating speed after delay. ACC and HTG ACC terminals are energized.

8 - When heat demand is satisfied, gas valve is de-ener- gized, combustion air inducer goes to 5-second postpurge and adjustable FAN OFF delay begins.

B - Heating Sequence - Mode of Operation Jumper in "W2 TIMED" Position

NOTE - To operate in this mode, the mode of operation jumper on the two-stage control board must be in the "W2 TIMED" position. See figure 31.

1 - On call for heat from a single-stage thermostat,

operation sequence followssteps 1 through4 as out-

lined above in single-stageheating sequence.

2- Gas valveisenergizedon low heat(firststage). Ignition occursand signal is sentfrom control moduleto two-

stage controlboard to begin "W2 ON" delay (factory set at 8 minutes).See figure 31 for delay settings.

3 - "FAN ON" delay begins. When delay ends, indoor blower motor is energized on low speed.

4- If the selected "W2 ON" delay ends and the demand

for heat is still not satisfied, the two-stage control switches the furnace to secondstage operation(high heat). In second stage operation, the following oc- cur: combustion air inducer motor is energized at high speed; indoorblowermotoris energizedon high

heating speed; and gas valve is energized on high heat after an 8-second delay.

5 - When the demand for heat is satisfied, the high- and low-heat gas valves are de-energized, the combus- tion air inducer goes into the 5-second post purge op oration on low speed and the indoor blower motor goes into the FAN OFF delay on low speed.

Applications Using A Two-Stage Thermostat

C - Heating Sequence - Mode of Operation Jumper in

"13NO-STAGE" Position (Factory Setting)

The sequence of operation is the same as outlined above

(in section B), except that low-heatand high-heat opera- tion is controlled from the room thermostat.

1 - When the thermostat is set to "FAN ON," the indoor blower will run on continuous fan speed when there is no cooling or heating demand.

2 - When the G32 is running in the low heat (first stage) mode, the indoor blower wilt run on continuous fan

speed.

3 - When the G32Q is running in the high heat (second stage) mode, the indoor blower will run on the heat- ing speed.

4 - When there is a cooling demand, the indoor blower will run on the cooling speed.

Gas Flow

To checkfor propergas flowto the combustionchamber. determine the Btu (kW) inputfrom theunitratingplate.Di- vide this inputrating by the Btu (kW) per cubicfoot (cubic meter) of availablegas. The resultis the requirednumber of cubicfeet (cubicmeter) per hour.Determinethe flow of gas throughthe gas meterfor two minutesand multiplyby

30to get the houdy flow of gas. Gas Pressure

1 - Check gas line pressurewith unitfiringat maximum rate. A minimumof 4.5 in. w.c. (1.12 kPa) for natural gas should be maintained.

2- After line pressure has been checked and adjusted, check high heat regulatorpressure.See figure34 for gas pressure adjustment screw location. High heat manifoldpressure is given in table 6.

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