Improper Piping Design

Probable cause: Remedy:
Excessive vertical lift of the liquid line.Generally, for every foot of vertical list using R-22, there is approximately Yz psi drop.
If a system has excessive vertical lift, then flash gas will form.
Make sure that before the refrigerant starts up the riser, it is subcooled enough so that it will not change to a gas when its pressure decreases to that which exists at the top riser.In practice, subcooling 10°F is generally sufficient for elevations up to 25 ft. To be safe, check the manufacturer’s specifications.
Liquid line too long, liquid line too small, or too many fittings. All three will cause excessive liquid line pressure drop. Replace piping sections with correct line size.
In sizing refrigerant lines, the piping designer must resolve two problems: pressure drop and velocity. This means that the piping system must be large enough to minimize the pressure drop.
On multi-case lineups or hot gas defrost systems, watch for the incorrect piping practice in every case. A full liquid line may be at the first case’s TEV, but not at the others on the same lineup.
On remote condensers, the liquid outlet from the condenser should drop below the condenser block.