The amount of refrigerant flowing through economizer orifices is determined by

• A. Evaporating temperature
• B. Condenser temperature
• C. Difference between the high side and low side pressure
• D. Subcooling level

Answer: (C)

The amount of refrigerant flowing through economizer orifices is driven by the pressure drop across the orifice—the difference between the high-side (condenser) pressure and the low-side (evaporator) pressure. In an economized system, liquid is throttled to an intermediate pressure, and the flow rate through that throttling path is governed by how large that pressure difference is. If the driving ΔP increases, more refrigerant can pass; if it decreases, less passes. Evaporating temperature and condenser temperature set those pressures but do not directly determine the flow through the orifices themselves. Subcooling is more a result of how the refrigerant is distributed and condensed, not the direct control for the economizer flow.