An overcharge of refrigerant will cause:

• A. Decreased head pressure
• B. Increased head pressure
• C. No change in head pressure
• D. Increased suction pressure

Answer: (B)

Overcharging increases the amount of refrigerant circulating in the system, especially on the high-pressure side. The condenser must reject heat to condense this larger mass from vapor to liquid. With more refrigerant in the condenser, more work is required to push it through, and the condenser pressure (head pressure) rises as a result. The compressor then has to operate against a higher high-side pressure, so head pressure goes up.

This is why the option indicating increased head pressure is correct. The other possibilities don’t fit the effect of adding extra refrigerant: head pressure isn’t typically reduced or unchanged, and while low-side (suction) pressure can vary with conditions, the most noticeable and direct change from overcharging is the rise in high-side pressure.