Diagnosing and Repairing a Carrier RTU on a No-Cooling Service Call

October 29, 2024

Diagnosing and Repairing a Carrier RTU on a No-Cooling Service Call

In commercial HVAC systems, a well-maintained rooftop unit (RTU) is essential for comfortable indoor temperatures and efficient energy use, especially in high-demand environments. Recently, we responded to a service call from a client in Palm Desert, CA, whose new Carrier RTU wasn’t cooling. Here’s a look into our troubleshooting and repair process that restored the unit to optimal performance.

Initial Assessment and Troubleshooting

Upon arrival, we found the thermostat calling for heat, yet the system remained unresponsive. Since the unit was a 2019 model, we suspected an electrical or mechanical issue. A quick inspection revealed an error code displaying four consecutive flashes, indicating a limit switch fault. This fault could point to multiple issues, such as a broken belt or a blower motor problem.

Digging Deeper: Checking Voltage and Internal Components

After verifying the line voltage at 208-230 volts, we inspected the blower compartment. Opening the panel revealed the issue: a broken belt jammed against a pulley, which had been spinning and overheating due to the increased friction. The blower motor had also sustained damage, with signs of overheating—blackened windings and a distinct burnt odor.

Addressing the Overheating and the Blower Motor Issue

Given the wear on the blower motor, we recommended a motor replacement. Though technically still functioning under amp draw limits, the motor exhibited significant heat damage and loud bearing noise, indicators of potential failure. Ensuring equipment reliability is critical in commercial environments, where even short downtimes can impact operations and comfort.

Belt Replacement and System Adjustments

To restore functionality, we replaced the broken belt with an alternate size (an A48 instead of the recommended A49) and adjusted the motor for proper alignment and tension. While this served as a temporary solution, we advised returning to fit the correct belt and make any necessary readjustments, ensuring the system’s long-term reliability.

Final Testing and System Check

After reassembling the unit and powering it on, we confirmed both the heating and cooling functions were operational. We also inspected the air filters, which were due for a replacement, and cleaned the drain trap to prevent clogs. Performing these additional maintenance steps ensures peak efficiency and reduces the likelihood of future breakdowns.

Conclusion

Commercial HVAC systems require regular inspection and maintenance to avoid costly repairs and unexpected downtime. This service call highlighted the importance of a comprehensive, step-by-step approach to HVAC maintenance, ensuring every component functions optimally.

Don’t Let HVAC Problems Slow You Down – Contact Us Today!

If your business needs reliable commercial HVAC service, whether for routine maintenance or urgent repairs, Contact us. We’re here to keep your systems running smoothly, no matter the season.

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No Commercial HVAC or Refrigeration job is too small or too far for us. While our primary branches are located in Palm Desert and Rancho Cucamonga, California, we’re dedicated to reaching customers wherever they are in need.

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