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Modular blower heat pump heating call (single and two-stage)
What happens, in order
- Thermostat closes R-Y1-G, sending 24 V to Y1 and G on the blower control
- The Y1-O jumper must be removed on heat pump systems for correct display; if left in, the display reads CL1
- 24 V goes to the outdoor unit and starts first-stage compressor operation
- Indoor blower ramps to first-stage heat pump airflow; the display alternates HP1 and ARF
- Second stage R-Y2 closes, the outdoor unit goes to second stage, blower ramps to second-stage airflow (display HP2)
- Satisfied contacts open, the outdoor unit and the blower stop (display IDL)
- W1 and W2 are disabled on this control; 24 V on either one creates an error
- The HUM relay closes about 1 second after the blower starts on any heat pump heating call and opens when the call ends
Timings and thresholds
| Item | Value |
|---|---|
| HUM relay delay | about 1 s after blower starts |
| Calculated airflow settle time | about 1 to 2 min |
Codes you may see during this
HP1, HP2, IDL; blower faults e01, e6.1, e6.2, e12 to e18 on the display
Applies to: P0V0 modular blowers on heat pumps
Models
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Source: Trane P0V0 modular blower installation 18-GE20D1-1E-EN (Nov 2021), Sequence of Operation pp.30-33. 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.