The equipment in this month’s troubleshooting situation is a split system that has only been in service for two years, but there is a lot of history: several service calls since the equipment was installed, and an on-going complaint from the customer that the system just doesn’t keep their manufactured home comfortable.

Several technicians have reported that they checked the refrigerant charge. One technician reported adjusting the OBD (Opposed Blade Damper) supply registers in an effort to achieve a better balance of airflow throughout the three bedrooms, living room, dining room, and kitchen. Another technician replaced the indoor blower motor with an exact OEM replacement motor and capacitor. None of the previous service calls solved the problem and the customer complaint that the house often seems “sticky”.

After considering the previous work performed, you elect to do a series of temperature tests on the duct system. Figure One shows the test points at which you measured both the dry bulb and wet bulb temperatures in both the return and supply duct assemblies. When you calculate your results with a psychrometric chart, you note that there is a significant specific humidity change in the return duct system.

Your troubleshooting question: What is the next step you need to take in servicing this equipment?

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