In this troubleshooting situation, the customer, who can’t provide you with any helpful information about the history of this comfort cooling system since they just recently purchased the business, is complaining that the temperature inside their small convenience store won’t get comfortable in the warmer part of the day.

One piece of information they can provide is that they recently renovated, removing a wall, expanding what was formerly warehouse area into retail space.

The equipment is old, a three-phase, five-ton rooftop unit that is charged with R-22 (see Figure One, top), and when you evaluate the operation of the system, you find the following:

• A visual inspection of the filters and coils proves that they are clean, and there is water in the condensate drain pan.
• An accurate check of the supply air shows it to be 65°F dry bulb.
• The liquid line sight glass is clear, and the oil level in the compressor is at ½ the sight glass.
• Both the condenser and evaporator fan motors are operating normally.

You also note that after several hours of continuous operation, all system components remained relatively unchanged. All continued to operate, and none shut down on any safeties.

Your troubleshooting question: What is your diagnosis of this situation?

Compare your answer with ours here.