Air System Problems
The primary problem that can occur in an air system is the reduction in airflow.
1- Air-handling systems do not suddenly increase in capacity.
2- On the other hand, the refrigeration system does not suddenly increase in heat-transfer ability.
To troubleshoot, first remove the panel to access the direct expansion (DX) coil in the air handler.
1- Take the temperature of the return air as it enters and then the supply air as it leaves the coil.
2- The difference between these two temperatures is referred to as the temperature drop or temperature difference of the air across the DX coil.
A sling psychrometer is used to measure the return-air dry-bulb and wet-bulb temperatures needed to determine the relative humidity. Next, determine the expected temperature drop.
This measurement will help to determine if the problem is a result of improper airflow or a refrigeration system error.
If the actual air temperature drop is greater than the required temperature drop, then the air quantity has been reduced.
Look for problems in the air-handling system:
1- Dirty air filters
2- A dirty evaporator coil
3- A problem with the blower
4- An unusual restriction in the duct system
Split-System Electrical Problems:
Since the greatest numbers of malfunction problems are electrical, it is common practice to perform electrical troubleshooting (including controls) before mechanical troubleshooting.
If the system will not operate at all, it is probably an electrical problem that must be found and corrected.
Electrical Operating Sequence
The operating sequence may be supplied by the manufacturer in the service instructions.
The technician can also determine the operating sequence by studying the schematic wiring diagram.
1- Necessary test instruments include:
2- Volt ohm meter
3- Clamp-on ammeter
4- Capacitor tester
5- Temperature analyzer
In Part 2 we will continue on HVACR troubleshooting Articles.