| 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. |
