ESCO Air Conditioning Practice Exam

What can cause a partially iced over evaporator in an air conditioning system?

1. An undercharge

2. Excessive airflow

3. Overcharging the system

4. High ambient temperature

The correct answer is: An undercharge

An undercharge can cause a partially iced over evaporator in an air conditioning system because it indicates that the air conditioning system does not have enough refrigerant. When there is not enough refrigerant, the evaporator coil cannot absorb enough heat from the surrounding air, causing it to freeze and limit the system's ability to cool the air. Excessive airflow is incorrect because, while it may cause the evaporator to become dirty and reduce the efficiency of the system, it does not directly result in the evaporator becoming iced over. Overcharging the system is also incorrect because it would result in the opposite problem - too much refrigerant and not enough liquid to absorb heat, leading to poor cooling. High ambient temperature is not the direct cause of a partially iced over evaporator, although it can exacerbate the problem by causing the system to work harder and potentially freeze up if not maintained properly.