HVAC D-2 License Practice Test 2026 - Free HVAC D-2 Practice Questions and Study Guide

The ability of a refrigerant compressor to move refrigerant is tied to its displacement. When part of the compressor is unloaded, the effective displacement drops, so the amount of refrigerant pumped per cycle decreases. This unloading mechanism reduces capacity to match the cooling load without stopping or restarting the compressor at full pressure. In practice, some cylinders or stages are kept from pumping, or a bypass/unloader valve prevents those sections from compressing, cutting the output in half or by the desired fraction depending on how many parts are unloaded. That’s why this option best explains how to reduce compressor capacity during lower cooling demands.

Condenser fan speed changes how effectively heat is rejected and can influence pressures and overall efficiency, but it doesn’t change the compressor’s pumping capacity. The receiver simply stores liquid refrigerant and doesn’t alter how much the compressor can move. A filter restricts flow, which can lower system performance, but it isn’t a built-in method to reduce the compressor’s capacity.