Picture of Austin Caldwell

Austin Caldwell

Technical Services Manager North Georgia District

Circuit B Has No Run Hours

This was a call we got through our Tech Service line. This was on a 48A series unit that was about a year old.
We worked through a few items and ended up concluding making a site visit this is what we found on site.

Troubleshooting Process

On our 48/50 A and P machines they are more than just a standard package unit. In this machine, in particular, When the B circuit Started the compressor fired up but you heard an audible groan from the condenser motors. This started the troubleshooting processes

  • dropped a side panel on the V side of the coil to access the motors.
  • Used lockout Tag out process before unhooking fan motor wiring.
  • Verified the ohms on both fans and made sure there wasn’t a ground issue or locked-up motor.
  • Then worked our way to the VFD. After reinstating power, verified the VFD was getting all three legs of power in.
  • We tested the fans using the service test mode on the Comfort link.

This is where we found the issue two legs on the VFD were sending power. We had one leg with no power. On this job, after tacking the wiring on a 48/50 the VFD is in the cabinet behind the Condenser but the wiring then goes to the control cabinet where it splits. This is where a loose wire was the problem.

This is a great look into breaking down a problem. This issue we broken down into 3 parts: high voltage, control voltage, and mechanical. This is always a great thing to do when you’re looking at a problem. This allows you to not get overwhelmed. Breaking down the problem into these distinct sections helped in isolating and resolving the issue efficiently, demonstrating the effectiveness of a structured approach to problem-solving.

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