heat pump frost up in winter
First of all, it’s completely normal for the out-door unit of your air-water heat pump to be covered by frost or light ice during cold winters. Before it becoming too heavy, your heat pump will go into the defrost mode to remove the coating of frost or ice.
When the defrost function does not work accurately any more, your air-water heat pump could be frosted/iced/freeze up abnormally and can not defrost well. Your heat pump will lost its heating capacity. The performance, why and what-to-do for abnormal frosting/icing/freezing are listed below:
Performance | Why | What to do |
|---|---|---|
| out-door unit bottom iced up | water outlet of drip pan blocked. icing up. | dredge drip pan |
| evaporator partly iced up | location of defrost sensor not right | defrost manually; move defrost sensor to the right place |
| evaporator covered by frost/ice, no defrosting | 1. defrost sensor error or ambient air temp sensor error | defrost manually; change sensor |
| 2. lack of refrigerant | add refrigerant | |
| 3. 4-way reversing valve failed or electromagnetic valve failed | check valve | |
| defrost not completely | 1. quit-defrosting-coil-temp set too low | change the parameter. set quit-defrosting temp higher |
| 2. coil defrost sensor put at wrong place, where frosting not the most seriously | put the sensor at the place where frosting is the most serious | |
| frost up too frequently | 1. evaporator not clean | clean evaporator |
| 2. fan motor broke or fan not powerful enough | repair fan motor or change or change a bigger fan | |
| 3. refrigerant not enough | add refrigerant | |
| 4. throttle expansion valve small opening | make the opening bigger | |
| 5. evaporator not big enough | change a bigger evaporator | |
| frost up badly, fins all covered by heavy frost | 1. start-defrosting-coil-temp set too low, or defrost interval time set too long. Can't start defrost in time | change parameters |
| 2. location of defrost sensor not right, not where frost is the most serious | put the sensor at the place where frosting is the most serious | |
| frost not evenly distributed. somewhere heavy, somewhere thick | 1. refrigerant not evenly distributed | adjust refrigerant distributor. refrigerant flow should match evaporating capacity |
| 2. structure of fin-coil evaporator not good | change evaporator or use a bigger fan | |
| low-pressure protect when defrosting | 1. defrosting low-pressure test not delayed not delayed not enough | delay and delay for enough time |
| 2. throttle expansion valve blocked or opening too small | change the valve or make the opening bigger | |
| high-pressure protect when defrosting | quit-defrosting-coil-temp set too high. not quit defrosting when high-pressure protecting | change the parameter |
| start defrosting while no frost on evaporator | start-defrosting-coil-temp set too high | change the parameter |