Two-stage heat call, high-fire light-off and staging

What happens, in order

1. R and W close; control runs a self-check and verifies the pressure switch contacts are open
2. Inducer starts on high until the low pressure switch closes (60 s maximum)
3. After a 30 s pre-purge the spark igniter energizes and the high fire valve opens
4. Remote flame sensor must prove the flame
5. If no flame the valve closes, igniter goes off and the process repeats, up to 4 times
6. After the 4th failure the furnace goes into a 1 hour soft lockout; reset by breaking power 5 to 10 s at the thermostat or unit disconnect
7. Once flame is proven the inducer and gas valve drop to low fire right away
8. Main blower starts 20 s after flame on low heat speed
9. A single-stage thermostat moves the furnace to high heat after the timer set by jumper P7 (5 or 12 minutes)
10. If flame is lost the valve closes, the inducer finishes its post-purge and the cycle restarts; 5 flame losses in one call for heat lead to lockout

Timings and thresholds

Codes you may see during this

Status LED: 1, 2, 3, 4, 6 blinks

Models

More Rheem furnace sequences

• Initial startup and lighting (communicating furnace) · Startup
• Gas heat call, direct spark ignition and retry · Ignition
• Gas heat call, hot surface ignition and retry · Ignition
• Gas heat call, ignition and retry (direct spark) · Ignition
• Heating ignition and blower sequence · Ignition
• Retry sequence when burners do not light or flame is not sensed · Ignition
• Two-stage gas heat call, ignition on high fire and retry · Ignition
• Heating call sequence of operation (Honeywell integrated control, direct spark ignition) · Heating