A condenser pump circulates water at 85F in, 88F out. If the condenser pressure is high while tubes are clean, which is a likely cause?

• A. Low ambient temperature
• B. Over charge of refrigerant
• C. Insufficient water flow
• D. Faulty thermostat

Answer: (B)

Condenser head pressure is largely controlled by how much refrigerant is circulating and how effectively the condenser can reject heat. If the condenser tubes are clean and the water flow is adequate (as shown by only a small rise from 85°F to 88°F), a high condenser pressure points to too much refrigerant in the system. An overcharged refrigerant charge means more vapor or liquid must be condensed at the same condenser temperature, which raises the pressure on the high side. The other options don’t fit as well: low ambient temperature would tend to reduce head pressure, insufficient water flow would typically show a larger rise in the cooling water temperature and can raise pressure too—but the clean tubes and only a small water rise argue against that, and a faulty thermostat wouldn’t directly cause high condenser pressure.