why in winter air condition condenser take ice and the inside heating is decrease?

Question

In winter air condition condenser take ice especial wen the temperature is coming under zero degree
and the heating is decrease inside.
why?

Answer 1

In cold weather, the heat pump is operating in reverse. The compressor compresses the refrigerant gas to a high pressure, and by the 3 way valve, this gas is directed inside the home to the evaporator coil. In this coil, the refrigerant gas gives up it's heat and becomes a liquid refrigerant. From the inside coil this liquid now goes outside to an already cold coil that now has to flash that liquid refrigerant into a gas. If it can, this further lowers the temperature of the coil. If there is moisture in the air, it will condense on the coil, and freeze there. This ice tends to insulate the coil from the air, and hinders the system from operating properly even more than the ambient temperature already has. Heat pumps, for this reason are not a good idea for areas that experience a lot of days where daily temperatures are at, or below freezing temperatures for most of the day.
During the summer, the outside coil changes the compressed refrigerant into a liquid, and the inside coil changes it back to a gas, thus absorbing heat from the inside air. As described, this is the direct opposite of winter time operation. If the heat pump can not give adequate heat, resistance strips turn on to heat the air to the desired temperature. Heating strips are also some times placed in the outside coils to get rid of the heat, unless the owner chooses to run the unit in the air conditioner cooling mode to get rid of the ice, which it would.

Answer 2

Note that when there is a wide temperature differential, e.g., when heating a house on a very cold winter day, it takes more work to move the same amount of heat indoors as on a mild day. Ultimately, due to Carnot efficiency limits, the heat pump's performance will approach 1.0 as the outdoor-to-indoor temperature difference increases. This typically occurs around −18 °C (0 °F) outdoor temperature. Also, as the heat pump takes heat out of the air, some moisture in the outdoor air may condense and possibly freeze on the outdoor heat exchanger. The system must periodically melt this ice. In other words, when it is extremely cold outside, it is simpler, and wears the machine less, to heat using an electric-resistance heater than to strain an air-coupled heat pump.