Direct Spark Ignition Control
1-Stage Units
Ignition control (IGN) runs a self-check (including verification that the gas valve is de-energized). IGN checks the high limit switch (TCO1) for closed contacts, the pressure switch (PS) for open contacts, and flame rollout (FR) for closed contacts.
IGN energizes the inducer blower. When PS closes, a 20-second pre-purge begins. After 20 seconds, the IGN energizes the spark and gas valve at the same time. The spark will stay energized for at least 2 seconds attempting to establish flame. If a flame is not established, the spark will continue up to 7 seconds. Once a flame is established, the spark is de-energized and indoor blower motor (IBM) timing begins. 45 seconds later, the RTRM energizes the IBM. When the zone sensor or thermostat is satisfied, the gas valve is de-energized, the inducer runs for 5 seconds then stops (post purge), and the IBM runs for 60 seconds and then stops unless being requested to run continuously.
2-Stage Units
Ignition control (IGN) runs a self-check (including verification that the gas valve is de-energized). IGN checks the high limit switches (TCO1 & TCO2) for closed contacts, the pressure switch (PS) for open contacts, and flame rollout (FR) for closed contacts. IGN energizes the inducer blower at high speed. When PS closes, 20 seconds (15 seconds on high, 5 seconds on low)pre-purge begins. After 20 seconds, the IGN energizes the spark and gas valve at the same time. The spark will stay energized for at least 2 seconds attempting to establish flame. If a flame is not established, the spark will continue for up to 7 seconds. Once a flame is established, the spark is de-energized and indoor blower motor (IBM) timing begins. 45 seconds later, the RTRM energizes the IBM. If a deviation from the setpoint is great enough, there is no minimum delay before 2nd stage is energized. When the zone sensor or thermostat is satisfied, the gas valve is de-energized, the inducer runs for 5 seconds then stops (post-purge), and the IBM runs for 60 seconds and then stops unless being requested to run continuously. If the burner fails to ignite, the ignition module will attempt two more ignition cycles before locking out. The green LED will indicate a lockout with two fast flashes. An ignition lockout can be reset by:
• Open for 3 seconds and close the main power
disconnect switch.
• Switching the mode switch on the zone sensor to off
and then to the desired position.
• Allow the ignition control module to reset automatically
after one hour.
If the burner trips due to a high-temperature limit, the unit will shut down and initiate a four-flash diagnostic. After the limit cools down and closes, the burner will again restart. There is no limit to the number of high-limit trips that can occur.
Direct spark ignition control sequence of operation
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.