Evaporators should never exceed a pressure drop of:

Evaporators should never exceed a pressure drop of:

• A. 0 psig
• B. 1 psig
• C. 2 psig
• D. 4 psig

Answer: (C)

The main idea is keeping the pressure drop across the evaporator small so the compressor sees the right suction pressure and the refrigerant flows evenly through the coil. As refrigerant passes through the evaporator, friction and flow resistance create a drop from the inlet side (after the expansion device) to the outlet side (toward the compressor). If this drop is too large, the suction pressure entering the compressor falls, which can reduce the evaporating temperature, lower cooling capacity, and raise the risk of liquid refrigerant reaching the compressor and poor oil return. A practical limit that balances these factors is about 2 psig. Staying under this helps maintain adequate suction pressure, stable operation, and better heat transfer across the coil. Choosing 0 psig isn’t realistic in normal operation because some drop is always present due to flow, and 1 psig is acceptable but not the standard maximum. 4 psig would exceed the typical recommended limit and can lead to the problems described above.

The main idea is keeping the pressure drop across the evaporator small so the compressor sees the right suction pressure and the refrigerant flows evenly through the coil. As refrigerant passes through the evaporator, friction and flow resistance create a drop from the inlet side (after the expansion device) to the outlet side (toward the compressor). If this drop is too large, the suction pressure entering the compressor falls, which can reduce the evaporating temperature, lower cooling capacity, and raise the risk of liquid refrigerant reaching the compressor and poor oil return.

A practical limit that balances these factors is about 2 psig. Staying under this helps maintain adequate suction pressure, stable operation, and better heat transfer across the coil.

Choosing 0 psig isn’t realistic in normal operation because some drop is always present due to flow, and 1 psig is acceptable but not the standard maximum. 4 psig would exceed the typical recommended limit and can lead to the problems described above.