What could cause increased discharge vapour superheat in an air conditioning system?

Increased discharge vapour superheat in an air conditioning system indicates that the refrigerant is absorbing heat from the system before it reaches the evaporator, leading to a higher temperature of the refrigerant gas returning to the compressor. This condition is often linked to insufficient refrigerant in the system.

When the refrigerant charge is low, it results in inadequate heat absorption in the evaporator. Consequently, the remaining refrigerant that does circulate will be subject to increased heat, causing it to superheat more than it normally would. This can lead to efficiency losses, compressor overheating, and potential system failure if not addressed.

The other factors, while they can influence air conditioning performance, do not directly cause increased discharge vapour superheat in the same way. For example, a faulty thermostat may lead to improper cycling of the system but doesn't inherently alter the refrigerant charge. Undersized ductwork can restrict airflow but typically results in poor cooling rather than affecting the refrigerant superheat directly. Excessive indoor temperatures can push a system’s limits but don’t directly cause the refrigerant to superheat unless compounded by low refrigerant levels.