Trane ReliaTel - Independent Circuit Defrost Operation

RT-SVD03G-EN 95
Heat Pump Demand Defrost
Independent Circuit Defrost Operation
For Odyssey and EMEIA Independent Circuit Heat Pump units with two outdoor coil temperature
sensors, the unit will perform defrost per circuit based on its own coil temperature sensor value,
the outdoor ambient temperature, and the accumulated circuit run time. At least one stage of
auxiliary heat will be energized anytime either circuit is in defrost mode. All other defrost
functionality, including the diagnostic conditions, will perform as described above independently
per circuit.
Table 37. Demand Defrost Fault Designation
Symptom Diagnostic Response
Coil temperature Sensor Failure Sensor is shorted or open Activate Defrost Fault
Outdoor Temperature Sensor Failure Sensor is shorted or open Activate Defrost Fault
D
T
is below Minimum Value 12 minutes after defrost is
terminated
Low D
T
If> 2 hours, activate Defrost Fault Reset timer if D
T
returns within bounds.
Defrost Terminated on time requirement Time Termination
If defrost is terminated on time requirement (vs.
differential temperature) After 10 consecutive Time
Terminations, activate Defrost Fault.
D
T
is above Maximum Value 12 minutes after defrost is
terminated
High D
T
Initiate Defrost
After 16 consecutive High D
T
Initiations activate
Defrost Fault.
D
T
does not change by 2 degrees in an hour’s time
starting 12 minutes after defrost is terminated and D
T
is
less than or equal to 4 degrees 12 minutes after defrost
is terminated
Unchanging D
T
Initiate Defrost and activate Defrost Activate Defrost
Fault
Defrost Termination Temperature (DTT) = Outdoor Air Temperature (OAT) + 47ºF
57ºF <= DDT <= 72ºF
DT = Outdoor Air Temperature (OAT) – Outdoor Coil Temperature (OCT)
Defrost Initiate Temperature= 1.8 * (DT) 12 Minutes After Defrost Mode is terminated)