Refrigeration troubleshooting: A high discharge-side pressure gauge reading on a refrigerant compressor most likely indicates which of the following?

Introduction / Context:
Discharge pressure reflects condenser conditions. Elevated discharge pressure often signals poor heat rejection at the condenser, which can arise from several root causes.

Given Data / Assumptions:

• Vapour compression system with water- or air-cooled condenser.
• Pressure measured at compressor discharge port.
• Steady operating load.

Concept / Approach:
High condensing pressure occurs when the condenser cannot reject heat effectively. Causes include insufficient cooling medium flow, high inlet cooling medium temperature, and fouling or scaling that increases thermal resistance. Each increases condensing temperature/pressure, raising discharge pressure.

Step-by-Step Solution:
Check condenser water flow; low flow → reduced heat transfer coefficient → higher condensing pressure.Check water inlet temperature; higher temperature → reduced temperature difference → higher condensing pressure.Inspect for fouling; dirty tubes/fins → higher resistance → higher condensing pressure.

Verification / Alternative check:
Compare approach temperature (condensing temperature minus cooling medium outlet temperature). Large approaches point toward condenser-side problems.

Why Other Options Are Wrong:

• Any single item alone may be the cause, but the question asks for likely reasons collectively; therefore, all listed causes are valid contributors.
• Evaporator starved of refrigerant primarily affects suction pressure and superheat, not discharge pressure directly.

Common Pitfalls:
Adjusting expansion valve to “fix” high head pressure; this treats symptoms and can worsen system balance.

Final Answer:
All of these