SLUGGING is the result of trying to compress liquid refrigerant and/or oil in the compressor cylinders.

Common ways to identify a slugging issue:

• Broken reeds, rods, or crankshaft
• Loose or broken backer bolts
• Blown head gaskets

Corrections for a slugging issue:

• Maintain proper evaporator and compressor superheat
• Correct abnormally low load conditions
• Install accumulators to stop uncontrolled liquid return
• Locate compressor in a warm ambient or install a continuous pump down.

LATENT HEAT is heat that produces a change of state (e.g. liquid to gas) without a change in temperature.

SENSIBLE HEAT is heat that causes a temperature change and can be sensed by a thermometer or by touch.

HOT PULL DOWN Refrigeration equipment mostly runs in a very stable environment with very little change in box temperature. However, on occasion it will see a major change in load such as a door being left open or a large amount of warm product being placed inside. In this case it will need to "pull down" the temperature. When the equipment is in this hot pull down it cannot be expected to follow DTD (design temp difference) or superheat rules. The unit needs to get close to the DTD before any fine adjustments are made.

EVAPORATOR TD (temperature difference) is the measured difference between the suction saturation temperature (SST) and the box temperature. DTD (design temp difference) is just the expected or designed TD.

SUPERHEAT is the increase in temperature between the suction saturation temperature (SST) and the suction line temperature leaving the evaporator. Superheat is the sensible heat (measurable) gained between the point that all of the liquid boils off in the evaporator coil and the suction line (at the outlet of the coil). 

SUCTION SATURATION TEMPERATURE (SST) is the temperature a refrigerant will be at a given pressure if it is currently changing state. This change of state being from liquid to vapor (boiling) in the case of the low side (evap/suction line). When using SST instead of pressures we can use similar rules. We will also see a similar SST across all refrigerants when being applied the same.