Daikin Chiller

Daikin Chiller Error Code UC

Troubleshooting guide for the Daikin Chiller system fault UC.

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What It Means

Indicates two or more centralized control devices — such as central remote controllers, schedule timers, or centralized monitoring units — share the same address on the chiller's control network, which the system cannot resolve automatically.

Possible Causes

  • Duplicate address set on two or more centralized control devices.
  • Address rotary switch left at the default/factory setting on multiple controllers.
  • Address never set after installation.
  • Defective indoor unit PCB address recognition circuit.
  • Centralized control equipment replaced without re-setting its address.

Not sure which one it is — or if it's none of these? Try ACLogics today.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis

Indicates two or more centralized control devices — such as central remote controllers, schedule timers, or centralized monitoring units — share the same address on the chiller's control network, which the system cannot resolve automatically. This is an address-configuration fault rather than a wiring or transmission failure, distinguishing it from UE, which reports an actual communication breakdown between the indoor unit and centralized control equipment once addressing is correct, and from MC, which covers address duplication among central remote controllers specifically rather than centralized control equipment broadly. Reassigning a unique address to each centralized control device typically clears the fault.

All Recorded Causes

Duplicate address set on two or more centralized control devices. Address rotary switch left at the default/factory setting on multiple controllers. Address never set after installation. Defective indoor unit PCB address recognition circuit. Centralized control equipment replaced without re-setting its address.

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and chiller context before acting on a generic code description.
  2. Confirm board LEDs, wiring polarity, and model compatibility before replacing control boards — this Daikin fault points at duplicate address set on two or more centralized control devices.
  3. Check for intermittent communication faults caused by connectors, moisture, or damaged harnesses, and rule out address rotary switch left at the default/factory setting on multiple controllers.
  4. After the correction, run the system long enough to confirm the chiller fault does not return under normal load.

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