Unit Sequence of Operation

Cooling Mode:

The units are factory set for the highest airflow for each model. Adjustments can be made to the cooling airflow by repositioning the jumper plug marked COOL - A, B, C, D (see AirFlow Adjustment Table on page 4) based on the information found in the table.

By moving the ADJUST jumper plug (see Table on page 4) from the NORM position to the (+) or (-) position will also cause the cooling airflow setting to be raised or lowered by 15%.

The TEST position on the ADJUST tap is not used.

To determine what CFM the motor is delivering at any time, count the number of times the amber LED on the control board flashes. Each flash signifies 100 CFM; count the flashes and multiply by 100 to determine the actual CFM delivered (for example: 10 flashes x 100 = 1000 CFM).

Here's How Your Heating System Works:

Standby Mode

When the control is in standby mode, it continually monitors thermostat input, rollout switch, and flame sense.

Call For Heat

On a call for 1st stage heat (W1) from the room thermostat, the ignition control performs a 1-second self- check. The control verifies the limit switch is closed and both low and high pressure switches are open. The control always starts on low-fire and ignores 2nd stage call for heat until low heat is established and heat blower on delay is complete. The induced draft blower is energized to high speed and waits for the low pressure switch to close before starting a 15-second pre-purge period. Upon completion of the pre-purge the hot surface igniter is energized for a period of 7 seconds (15 seconds on retries) before the gas valve is energized on 1st stage and main burners ignite. The induced draft blower remains on high speed with the gas on low fire for the first 15 seconds of steady heat and ignores any 2nd stage demand. After the 15 second period the control switches the inducer to low speed. After a 30 seconds blower "on" delay, the control energizes the low heat circulating air blower. The blower runs at reduced CFM (approximately 400 CFM) for 30 seconds then ramps up to 1st stage heat speed.

If 1st stage heating operation is not sufficient to satisfy the heating demand, the room thermostat initiates a call for 2nd stage heat (W1 and W2). The control changes the inducer from low to high speed and confirms the high-fire pressure switch contacts are closed and the gas valve energizes on 2nd stage heat. The circulating air blower then ramps up to 2nd stage heat speed.

When the 2nd stage call for heat is satisfied, the control shuts off the gas valve and runs the combustion air blower for a post purge period of 5 seconds. The circulating air blower continues to run for approximately 3 minutes before ramping down. If the thermostat W2 call ends and W1 remains, the control de-energizes the high gas output, changes the inducer speed from high to low and the gas valve drops back to 1st stage heat. After approximately 2 minutes the circulating air blower ramps down to 1st stage heat speed.

In the event the unit loses ignition, the control will attempt to recycle up to five times before it goes into a 1- hour lockout. Lockout may be manually reset by removing power from the control for more than 1 second or removing the thermostat call for heat for more than 3 seconds.

If during a heating cycle the limit control senses an abnormally high temperature and opens, the ignition control de-energizes the gas valve and the combustion blower while the circulating blower ramps up to 2nd stage heat speed. The circulating blower remains energized until the limits are closed.

Should overheating occur, or the gas supply fail to shut OFF, turn OFF the manual gas valve to the appliance BEFORE turning OFF the electrical supply. A failure to adhere to this warning can result in a fire or explosion and bodily harm.

Fan "ON"

A call for continuous fan from the thermostat closes R to G on the control board. The control waits for a 1- second debounce delay before responding by energizing the circulating air blower at 50% of the cooling speed. When the call for fan is turned off, the control de- energizes the circulating blower.

Cooling

A call for cooling from the thermostat closes R to Y and R to G on the blower control board. The control waits for a 1-second thermostat debounce delay before energizing the circulating air blower to 82% of the cooling

speed. After 7.5 minutes, the circulating blower automatically ramps up to 100% of the cooling speed. When a call for cooling is satisfied, the circulating blower ramps back down to 82% of the cooling speed for 60 seconds then shuts off.

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