The air is then sprayed out through a small nozzle to the evaporator. At this point, the air is rapidly cool and is of lower pressure. It flows through the evaporator coils where it's warmed up. In instances where the condenser changes to evaporator or vice versa, a single heat pulp will be enough to provide the warmth during the cold seasons and cooling during the hot season. However, the main problem with the heat pumps is that the coils on the outside are likely to collect ice which reduces their efficiency. But the heat pump ensures that the ice is melted periodically.