Which of the following can cause high discharge pressure in the system?

High discharge pressure in a refrigeration system can result from several factors that impede the efficient operation of the condenser and overall system. Each factor mentioned contributes to the elevation of discharge pressure in a unique way.

When the condenser is undersized, it cannot adequately dissipate heat from the refrigerant, which leads to a buildup of pressure as the refrigerant struggles to release the heat. Similarly, insufficient cooling water can cause the condenser to become less effective at transferring heat away from the refrigerant, leading to increased temperatures and pressures in the system. Lastly, a fouled condenser—where debris, mineral deposits, or other contaminants obstruct proper airflow or heat exchange—also impedes the condenser's ability to cool the refrigerant effectively, raising the discharge pressure.

Since all these factors contribute variously to the inability of the system to maintain proper condensation and hence result in elevated discharge pressures, the correct answer encompasses all these potential causes. Understanding how each factor influences system performance is crucial for identifying and addressing issues in refrigeration systems.