In low pressure refrigeration systems, a high head pressure is typically caused by what?

In low pressure refrigeration systems, high head pressure is often caused by air accumulation within the system. When air enters the refrigeration cycle, it doesn't condense like refrigerant does. Instead, it occupies space within the system and can lead to an increase in pressure in the condenser or discharge side of the system. This excessive pressure can hinder the proper function of the system, leading to inefficient cooling and potential equipment damage.

In contrast, excess refrigerant can cause problems, but it's typically associated with other symptoms rather than a specific high head pressure. Similarly, evaporator blockages would lead to low pressure scenarios as the refrigerant cannot adequately absorb heat. Dirty filters, while they can impair airflow and efficiency, are more likely to cause low performance issues than a direct increase in head pressure. Thus, air accumulation is the primary culprit behind high head pressure in these systems.