HVACopediaTrane · Furnace · Heating
Heating call sequence of operation
What happens, in order
- On a thermostat call for heat, R and W close and the control runs its self-check.
- The control confirms the pressure switch is open and the limit switch(es) are closed, then starts the draft blower.
- When the draft blower reaches speed, the pressure switch closes and the ignitor warm-up begins.
- The ignitor heats, then the gas valve opens to feed gas to the burners.
- The flame sensor must prove ignition within the 4 second trial period.
- After ignition is proven, the indoor blower starts after the fan-on delay.
- When the thermostat is satisfied, the gas valve closes, flames go out and the draft blower stops.
- The indoor blower keeps running for the fan-off period, then the control shuts it off.
Timings and thresholds
| Item | Value |
|---|---|
| Ignitor warm-up before gas valve opens | about 20 seconds |
| Flame sensor ignition trial period | 4 seconds |
| Indoor blower on delay, upflow | about 45 seconds after ignition |
| Indoor blower on delay, downflow | 10 seconds after ignition |
| Fan-off period (dip switch selectable) | 60, 100, 140 or 180 seconds; factory 100 seconds |
Applies to: UH1 and DH1 gas furnaces
Models
More Trane furnace sequences
- First-stage gas heating · Heating
- Heating sequence of operation · Heating
- Second-stage gas heating (S8X2 only) · Heating
- Cooling and heat pump calls on S8 furnace control · Cooling
- Cooling fan-off delay · Cooling
Related
Trane error codes · Trane tips · Trane parts · All Trane sequences
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Source: Trane 18-CD29D1-11 installer's guide, p. 40. 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.