General Assist Technical Reference

Error Code 15.4

Incompatible indoor unit / indoor unit data acquisition / primary-secondary setting error
Error 15.4 indicates that the remote controller has detected an issue relating to the connected indoor unit. The source information identifies three possible causes: an incompatible indoor unit, an indoor unit data acquisition error, or an incorrect primary/secondary unit setting.

1. What does Error Code 15.4 mean?

When an error occurs on the applicable remote controller, the controller displays an error screen containing the remote controller code and the applicable error code.

Error codeMeaning
Er 15.4 / EE 1d
  • Incompatible indoor unit is connected
  • Indoor unit data acquisition error
  • Primary unit / Secondary unit setting error

2. Possible causes

Incompatible indoor unit
The indoor unit connected to the controller is not compatible with the HVAC system or with the specific controller being used.
Indoor unit data acquisition error
The controller has been unable to collect or process the required data from the indoor unit. The source information notes that this may occur where communication between the controller and indoor unit is interrupted.
Primary / Secondary unit setting error
The primary and secondary units have not been configured correctly, resulting in a configuration or communication issue between the units.

3. Recommended checks

Service personnel: Confirm the applicable model documentation and controller configuration before changing any settings. The source information identifies the possible causes but does not provide model-specific setting values or wiring instructions.
  1. Confirm indoor unit compatibility. Verify that the connected indoor unit is supported by the controller/system.
  2. Check indoor unit data acquisition. Confirm that communication between the controller and indoor unit is available and has not been interrupted.
  3. Check Primary / Secondary configuration. Confirm that the units are assigned correctly and that there is no duplicated or incorrect role setting.
  4. Recheck the displayed fault. After correcting the identified issue, confirm whether Error 15.4 returns.

4. Frequently asked questions

Q: What is Error Code 15.4?

A: Error 15.4 is an error message relating to the connected indoor unit. It may indicate an incompatible indoor unit, an indoor unit data acquisition error, or a primary/secondary unit setting error.

Q: What does an incompatible indoor unit mean?

A: The indoor unit connected to the controller is not compatible with the HVAC system or the specific controller.

Q: What is an indoor unit data acquisition error?

A: It is a failure to collect or process data from the indoor unit. This may occur if communication between the controller and indoor unit is interrupted.

Q: What is a Primary / Secondary unit setting error?

A: It is a configuration issue where the primary and secondary units have not been set correctly, which can lead to communication problems between the units.

Note: The fault table shown in the source applies to systems without zone control. Use the relevant service documentation where a different system configuration is installed.