If a low temperature Ammonia booster has a discharge temperature drop from 120°F to 80°F, what is indicated?

When a low temperature ammonia booster experiences a discharge temperature drop from 120°F to 80°F, it can indicate that there is possibly liquid in the suction line. This is because the presence of liquid refrigerant in the suction line can lead to a decrease in temperature as the liquid refrigerant absorbs heat from the system. As it mixes with the vapor refrigerant, the overall temperature of the discharge can drop significantly, reflecting an issue with the phase of the refrigerant present in the suction line.

In this scenario, the other options can be examined to understand their relevance. A higher BTU load in refrigerated areas would typically cause the discharge temperature to increase due to a greater demand for cooling, not a drop. If suction superheat were too high, it would normally indicate that the refrigerant is fully vaporized before entering the compressor, again leading to a corresponding rise in discharge temperature. Lastly, if a hand expansion valve were closed off too much, it would restrict the flow of refrigerant and potentially cause a rise in temperature due to insufficient cooling, which counters the situation described in the question. Therefore, the observed drop in discharge temperature is most consistent with the possibility of liquid in the suction line.