DEFROST CONTROL (A108) CALIBRATION MODE SEQUENCE
Occurs after power up and cooling operation, or if the coil temperature exceeds
the termination temperature while in Heat Mode.
Demand defrost control defaults to 30 minute ime / Temperature Mode
Reset Compressor Runtime / Reset Three / Five Strike Counter
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| DEMAND MODE |
| THIRTY (30) MINUTE TIME / |
| 45 MINUTE |
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| Accumulate compressor runtime of |
| TEMPERATURE MODE |
| TIME/TEMPERATURE MODE |
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| more than 30 minutes while coil |
| Accumulate compressor runtime |
| Accumulate compressor runtime |
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| temperature is below 35° F (2°C). |
| while coil temperature is below 35° F |
| while coil temperature is below 35° |
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| When the accumulated compressor |
| (2°C). When the accumulated |
| F (2°C). When the accumulated |
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| time exceeds six (6) hours or if the |
| compressor time exceeds 30 minutes |
| compressor time exceeds 45 |
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| coil sensor indicates frost is present |
| go to Defrost. |
| minutes go to Defrost. |
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| on coil, go to Defrost. |
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DEFROST
SOutdoor Fan OFF
SReversing Valve ON
SW1 line ON
Monitor coil temperature and
time in defrost mode.
HOW DID DEFROST TERMINATE?
Coil temperature was above 35°F (2°C) for four (4) minutes. of the 14−minute defrost OR reached defrost termination temperature.
DEFROST TERMINATION
SCompressor runtime counter RESET
SOutdoor Fan ON
SReversing Valve OFF
SW1 line OFF
Defrosted for 14−minute without the coil temperature going above 35°F (2°C) for four (4) minutes and coil did not reach termination temperature.
DEFROST TERMINATION
SCompressor runtime counter RESET
SOutdoor Fan ON
S Reversing Valve OFF
SW1 line OFF
Attempt to Calibration emperature measurements are not taken for the first few minutes of each heat demand. This is
to allow coil temperatures to stabilize. demand defrost control has a maximum of 20 minutes of accumulated compressor runtime in heat mode to calibrate demand defrost control This may involve more than one heating demand.
YES
Was stable coil temperature attained within 20 minutes?
NO Demand defrost control reverts to 45 minute time / temperature.
Figure 26. Defrost Calibration
Page 36
