HVACopediaSkymark · Air conditioner · Heating
Gas heating cycle
What happens, in order
- Thermostat calls for heat (R to W on the fan timer control module)
- Ventor motor starts and the vacuum switch contacts close
- Pilot gas valve and hot surface igniter are energized
- When a flame signal is seen at the pilot, the main gas valve opens and the main burners light; the igniter is turned off
- Burners normally light within 5 seconds of the heat call
- Circulating fan starts 30 seconds after the main burners light
- Thermostat is satisfied W de-energizes, main and pilot valves close
- Ventor motor runs 5 seconds post-purge, then stops
- Circulating fan runs on for the off delay (60 s factory setting)
Timings and thresholds
| Item | Value |
|---|---|
| Main burner light-off | Within 5 s of heat call |
| Fan on delay | 30 s after burners light |
| Post-purge | 5 s |
| Fan off delay | 60 s (adjustable 60-180 s) |
Applies to: Skymark RGAC / SGAC self-contained gas heat / electric cool wall units
Models
More Skymark air conditioner sequences
- Cooling cycle · Cooling
Related
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Source: Skymark RGAC/SGAC installation and operation instructions FORM 145.24-IOM1, 17 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.