An equalizer line should be used if the pressure drop between the inlet and outlet of the evaporator exceeds 4 psi.

• A. True
• B. False
• C. Not Determined
• D. Not Applicable

Answer: (A)

When the evaporator coil has a noticeable pressure drop from inlet to outlet, the pressure at the evaporator outlet is much lower than at the inlet. If the expansion device (like a TXV) only senses pressure from the inlet side, it misses the actual evaporating pressure along the rest of the coil. An equalizer line bridges the valve’s sensing point to the evaporator outlet, so the valve meters refrigerant based on the pressure at the far end of the coil. This keeps superheat correct and prevents overfeeding early in the coil or liquid return problems later on. When the evaporator’s pressure drop is around 4 psi or more, using an equalizer line helps the system respond properly, which is why this statement is true.