HVACopediaTrane · Heat pump · Defrost
Heat pump demand defrost
What happens, in order
- Demand defrost is enabled when the outdoor ambient sensor reads 50 F or below and heating demand has run for the required time
- The control reads the outdoor ambient sensor and the coil sensor and works out Delta T between them
- Defrost starts when the current Delta T goes above the Delta T initiate value (adaptive, so it works across outdoor temperatures)
- With communicating Trane thermostats, defrost is reported through the O signal and high stage heat is called automatically during defrost; X2 is not wired
- The coil sensor is also used to end the defrost; termination temperature can be raised by clipping the defrost termination jumper pin
- Forced defrost system must be running a heat call; hold the forced defrost button for more than 5 seconds; the display shows 7 as the first digit
Timings and thresholds
| Item | Value |
|---|---|
| Defrost enabled | outdoor temp at or below 50 F |
| Forced defrost button hold | over 5 s |
Codes you may see during this
7 (defrosting) on the LED display
Applies to: 5TTR7 and 5TWR7 heat pumps
Models
Related
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Source: Trane 5TTR7/5TWR7 installation ODR-SVN002E-EN, Defrost Control p.33 and wiring notes. 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.