Heat pump control monitors mode of | Defrost Calibration |
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operation through outdoor ambient | Coil sensor (RT21) detects temperature below 35°F {2°C} | ||||
temperature | (RT13), outdoor coil | during either initial power−up, after loss of power or after | |||
temperature (RT21) and compressor | cooling mode, a sacrificial defrost will be used to ensure there | ||||
run−time to determine when a defrost | is a clear coil before attempting calibration. |
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cycle is required. |
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NOTE |
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be active for defrost calibration to be |
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achieved. |
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| Coil sensor |
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| below 35°F {2°C} | NO | No attempt |
100 |
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| to calibrate. |
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DEGREE |
| E47 |
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TARGET |
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| YES |
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100 | *Heat Pump Control (A175) |
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| 90 70 50 | Defrost Termination (E47) |
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90 |
| Pins (Factory Default is 50ºF) |
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| Accumulate compressor run−time while outdoor |
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DEGREE |
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TARGET |
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| coil temperature sensor input (RT21) is below |
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100 90 70 50 |
| 35°F (2°C) |
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70 |
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DEGREE |
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TARGET |
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| Continue to |
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| 30−35 minutes |
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| 90 70 50 |
| NO | accumulate | |
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| run time. | |
*50 |
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| run−time |
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DEGREE | 100 |
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TARGET |
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| 90 70 50 |
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| YES |
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| Demand Mode | Defrost Mode |
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After the initial calibration, the heat pump control | Initiate a defrost and monitor coil | temperature |
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sensor input (RT21) and accumulate defrost time. |
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disables the defrost mode for 30−34 minutes in |
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order to avoid unnecessary defrosts. Beyond |
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this timing period, both the ambient (RT13) and |
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coil (RT21) sensors are continuously moni- |
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tored. If the coil temperature is below 35°F (2°C) |
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and the calibration delta is reached or accumu- |
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lated compressor run−time is more than six (6) |
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hours, a defrost is to be initiated. |
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| How did defrost |
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| terminate? |
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Coil temperature sensor input (RT21) reached specified de- frost termination temperature as set on heat pump control E47 pins*.
Defrosted for 14 minutes with- out the coil temperature sensor input (RT21) reaching defrost termination temperature as set on heat pump control E47 pins*.
Calibration Attempted
(Unit Running in Heat Mode)
YES Calibration NO
Figure 26. Defrost Calibration Sequence of Operations
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