Portable method and apparatus for monitoring refrigerant-cycle systems

A monitoring system for monitoring the operation of a refrigerant-cycle system, the monitoring system comprising:

• a monitoring unit including a processing system, a display, and one or more user input devices;
• an airflow sensor provided to the monitoring unit and configured to generate airflow data;
• a power sensor provided to the monitoring unit and configured to generate power data;
• an ambient temperature sensor provided to the monitoring unit and configured to generate ambient air temperature data for air provided to an evaporator of the refrigerant-cycle system;
• and
• a network interface provided to the monitoring unit,
• the monitoring unit using the network interface to query and receive performance information regarding an HVAC unit identified by a model number,
• the performance information comprising efficiency data specifying, for an input present ambient air temperature, a maximum expected efficiency of the HVAC unit according to the input present ambient air temperature,
• the monitoring unit determining a present maximum expected efficiency of the HVAC unit, wherein the present maximum expected efficiency of the HVAC unit is determined using the input present ambient air temperature and using an input present ambient humidity,
• the monitoring unit using the airflow data, the power data, output air temperature data for air flowing from the evaporator, and the ambient air temperature data to compute a present efficiency of the HVAC unit, and
• the monitoring unit using the display to display a relationship between the present efficiency and the present maximum expected efficiency.