How is an evaporator typically defrosted?

The correct method for defrosting an evaporator is by using hot gas from the discharge line. This process is known as hot gas defrosting. When the hot gas is introduced into the evaporator, it warms the coils and helps to melt any accumulated frost or ice. This ensures that the system continues to operate efficiently, as excess ice can hinder heat exchange and reduce the overall performance of the refrigeration system.

Cold refrigerant from the evaporator is less effective at absorbing heat, so introducing hot gas effectively reverses the cooling effect temporarily, allowing for the defrosting process to take place without significantly disrupting the operation of the system. This method is preferred because it is efficient and minimizes downtime for the system.

Other options, while they might influence system operation, are generally ineffective for defrosting. Shutting off the compressor would stop the refrigerant circulation, potentially allowing ice to continue forming. Increasing the refrigerant flow would not directly lead to defrosting and could exacerbate frost buildup. Lowering the system pressure might lead to a drop in refrigerant temperature, which would worsen freezing conditions, rather than help with defrosting.