Ingersoll-Rand ReliaTel, Manual, Page: 125 / 176

RT-SVD03L-EN 125
Emergency Heat Operation
When the system selection switch is in the ’EM HEAT’
Mode, and the zone temperature falls below the
heating setpoint controlband, the RTRM bypasses
compressor and outdoor fan operation and energizes
the K1 relay located on the RTRM. When K1 relay
contacts close, the first stage auxiliary electric heat
contactor (AH) is energized. If the first stage of auxiliary
electric heat cannot satisfy the heating requirement,
the RTRM energizes the K2 relay located on the RTRM.
Diagnostic Information
Demand defrost also tracks failures and operating
problems as follows:
When the K2 relay contacts close, the second stage
auxiliary electric heat contactor (BH) is energized. The
RTRM cycles both the first and second stages of heat
’On’ and ’Off’ as required to maintain the zone
temperature setpoint.
Correct defrost operation relies on accurate
temperature information from the outside air sensor
(OAS) and the coil temperature sensors (CTS).
If either of these sensors fail, the unit will revert to the
default mode any time the unit is in the active heat
mode with compressors running.
When any Defrost Fault is active, or if any sensor has
failed, a 5-minute defrost cycle will be initiated after
each 30 minutes of cumulative compressor heating
operation.
Table 91. 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
DT is below Minimum
Value 12 minutes after
defrost is terminated
Low DT
If> 2 hours, activate
Defrost Fault Reset
timer if DT returns
within bounds.
Table 91. Demand defrost fault designation
(continued)
Symptom Diagnostic Response
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.
DT is above Maximum
Value 12 minutes after
defrost is terminated
High DT
Initiate Defrost. After
16 consecutive High
DT Initiations activate
Defrost Fault.
DT does not change by
2 degrees in an hour’s
time starting 12
minutes after defrost
is terminated and DT is
less than or equal to 4
degrees 12 minutes
after defrost is
terminated
Unchanging DT
Initiate Defrost and
activate Defrost
Activate Defrost Fault
Notes:
1 . Defrost Termination Temperature (DTT) = Outdoor Air Temperature
(OAT) + 47ºF
2 . 57ºF <= DTT <= 72ºF
3 . Defrost Temperature (DT) = Outdoor Air Temperature (OAT) –
Outdoor Coil Temperature (OCT)
4 . Defrost Initiate Temperature = 1.8 x DT (only initiates after a
minimum of at least 12 minutes after the previous defrost mode
has ended)
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.
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