Installation and Troubleshooting
What this domain tests
Installation and Troubleshooting tests whether you can install equipment to the manufacturer's instructions and code, commission it, and diagnose faults in a logical order. Expect line sizing, evacuation, charging, airflow measurement, electrical checks, and documentation.
Core rules and concepts
- Read the installation manual before setting equipment; it governs clearances, line sizes, venting, and charging.
- Pressure-test with dry nitrogen, evacuate with a vacuum pump to the specified micron level, and hold the vacuum to check for leaks.
- Charge by weight when the line set is known, or by the manufacturer's superheat/subcooling chart after airflow is verified.
- Measure external static pressure and compare it with the fan table; high static pressure means low airflow.
- Troubleshoot in order: verify the call at the thermostat, check power and control voltage, confirm airflow, then evaluate refrigerant measurements.
- Record readings and corrections; commissioning data supports warranty and future diagnosis.
Worked example
A residential air handler has a return static of -0.20 in. w.c. and a supply static of +0.40 in. w.c. External static pressure is 0.20 + 0.40 = 0.60 in. w.c. The manufacturer's table allows 0.50 in. w.c. at the required airflow. The system is over the limit, so airflow is low even if the blower is running. Check the filter, coil, duct sizing, and registers before adding refrigerant. The reasoning: excess static pressure shifts the fan to a lower airflow, which changes the refrigerant readings and can make a correctly charged system look undercharged.
Traps
Do not add refrigerant before verifying airflow. Do not use a vacuum pump without a micron gauge and assume evacuation is complete. Do not ignore the installation manual's line-size and clearance requirements. Do not leave a system without recording final charge, static pressure, and temperature difference.