Trane 4TXK6512G1000AA Service Manual page 171

Te≤C×TA-α OR TC≤C×TA-α and lasts for 5 minuts
Note: C:
TA<0°C, C=0.8
TA≥0°C, C=0.6
a. Entering temp. limit of defrosting 1: -15°C≤C×TA-α≤-2°C
b. Entering temp limit of defrosting 2: C×TA-α<-15°C & Te≤-15°C for continuous 5 minutes &
accumulated running time reaching 90 minutes.
c. Defrosting entering limit condition: indoor coil temp lower than 40 degree
d. Heating mode compressor running accumulated time stop/pause condition:
Detecting stop (end) : shifting from heating to cooling mode
Detecting pause: thermostat OFF, unit off.
2. Defrosting end contition:
After defrosting condition starts, it will last no more than 10 minutes (E) . Using Te to test outdoor heat exchanger
frosting condition, if it lasts over accumulative 60 seconds of 7°C (E) or over accumulative 30 seconds of 12°C (E)
or over 15°C (E) , defrosting will stop.
3. Forced defrosting control
Starting condition of forced defrosting: in heating operation (including standby state) , unit will start forced
defrosting after receiving forced defrosting signal by indoor.
Stopping condition of forced defrosting: refer to 7.3
Indoor manual defrosting signal will keep until outdoor enters defrosting.
Note: It can enter manual defrosting when compressor in OFF state, but it needs to follow 3-minute protection
rule.
4. Timing defrosting mode condition:
Starting condition: after setting outdoor function dip switch, it will execute timing defrosting in heating mode.
A. If outdoor ambient temp is over 10 degree (E) , even if timing defrosting is set, it will follow the auto
defrosting condition, meaning auto entering and auto quitting.
B. When outdoor ambient temp is lower than 10 degree (E) (including 10 degree ) , it will follow the
defrosting operation as below:
When compressor runs for continuous 10 minutes (E) and runs for accumulative 50 minutes (E) , it will enter
defrosting operation.
C. Timing defrosting operation and quit condition is the same as auto defrosting.
9.4.8 Four way valve control:
1. When powering on, four way valve is in OFF state.
2. In other modes except heating, the four way valve is powered off.
3. In heating mode, when thermostat is off, the four way valve will keep ON, but in heating mode, under the
following conditions, four way valve should be OFF.
1) in heating mode, in initial starting time of compressor to ensure the pressure difference ;
1) in defrosting operation:
a, if there is no compressor stopping, power four way valve off;
4. When shifting from heating to other modes, four way valve will power off after a while. Besides,
four way valve will keep powering on when from other mode changing to heating mode.
5. Protection of fault operation of four way valve.
In heating mode, after continuous running of compressor for 10 minutes, if Tm (indoor sensor) < indoor ambient
temp -2°C (E) and Te (outdoor sensor) >15°C (E) for continuous 1 minute, four way valve will be powered off,
reporting four way valve error. But if start after 3 minutes, and it happens 3 times continuously in 1 hour, it will
report four way valve switching error. It will not detect in heating defrosting and within 10 minutes after quitting
defrosting; It will not detect in heating oil return and within 10 minutes after quitting oil return;
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