HVACopediaCarrier · Furnace · Heating
Single-stage 80% furnace: heating cycle, blower delays and shutdown
What happens, in order
- After flame is proven, blower starts on heat speed 25 s after the gas valve opens; the electronic air cleaner terminal comes on with the blower
- Burners run until the thermostat is satisfied
- R-W opens gas valve closes and the 24 V humidifier terminal drops out
- Inducer runs for a short post-purge, then stops
- Blower keeps running for the heat-off delay (90, 120, 150 or 180 s), then stops
- If power is lost during a call for heat, on return the control runs the blower alone for 90 s starting 2 s after power is back (display code 12), then answers the thermostat normally
Timings and thresholds
| Item | Value |
|---|---|
| Blower-on delay | 25 s |
| Inducer post-purge | 5 s |
| Blower-off delay options | 90 / 120 / 150 / 180 s |
| Blower-off delay factory | 120 s |
| Blower-only run after power-up | 90 s |
Codes you may see during this
Applies to: Carrier 58SB0A / 58SB1A 80% single-stage gas furnace
Models
58SB0A58SB1A
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Source: Carrier 58SB0A/58SB1A installation manual, Sequence of Operation. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.