Sequence
- Ignition control (IGN) runs self-check (including verification that the gas valve is de-energized).
- IGN checks the high limit switch (TCO1 and TCO2) for closed contacts, the pressure switch (PS) for open contacts, and flame rollout (FR) for closed contacts.
- IGN energizes the inducer draft blower motor or (CFB).
- When PS closes, 20-second pre-purge begins.
- After 20 seconds, the IGN energizes the spark, gas valve, and the pre-mix blower at the same time.
- The spark will stay energized for at least 4 seconds attempting to establish flame.
- If a flame is not established, the unit will attempt 3 IGN trials before lockout.
- Once a flame is established, the spark is de-energized and indoor blower motor (IBM) timing begins.
- 45 seconds later, the RTRM energizes the indoor blower motor (IBM).
- When the zone sensor or thermostat is satisfied, the gas valve and pre-mix blower are de-energized, the inducer runs for 20 seconds then stops (post-purge), and the IBM runs for 60 seconds and then stops unless being requested to run continuously.
- NOTE: The gas valve and pre-mix blower come on at the same time
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.