What effect does a 5 psig pressure drop in a suction line due to a long run have on system capacity?

A 5 psig pressure drop in a suction line can significantly impact system capacity by leading to a decrease in the capacity of the refrigeration or air conditioning system. When the pressure in the suction line drops, the compressor has to work harder to draw in the refrigerant. Lower suction pressure means that the refrigerant will have a lower boiling point, which can result in a reduction in the overall flow of refrigerant through the system.

As the suction pressure decreases, the saturation temperature of the refrigerant also decreases, potentially leading to inefficient evaporation and less effective heat absorption. This inefficiency means that the system cannot effectively transfer heat from the environment to the refrigerant, thereby reducing the system's cooling capacity.

In summary, the pressure drop in the suction line creates a disadvantage for the efficiency of the system, ultimately leading to a decrease in system capacity as the compressor struggles to maintain the necessary performance level.