KDHV/KCHV intermittent communication fault is often due to an earth loop issue within the electrical communication wiring.


⚠️ Safety Notice – Reverse Cycle Air Conditioners

This equipment must only be installed, commissioned, serviced and repaired by suitably qualified and licensed personnel.


Before commencing work, complete a task-specific risk assessment and ensure electrical isolation procedures, safe access, adequate service clearances and appropriate PPE have been considered. All work must comply with applicable regulations, standards and manufacturer requirements.


Particular care must be taken when working around electrical systems, refrigerant circuits, moving parts, roof spaces, ceiling spaces, confined spaces and working-at-heights hazards where applicable.


Do not proceed if safe access, required clearances, confined space risks or appropriate safety controls cannot be achieved and maintained. 


Safety takes priority over diagnosis, repairs, installation schedules and customer expectations. If the task cannot be completed safely, it must not proceed until the risks have been adequately controlled.


KCHV / KDHV Communication Issues and Earth Loop in Electrical Wiring

Symptoms:

  • No obvious errors.
  • Compressor runs for 10 seconds to 5 minutes, then stops unexpectedly.
  • Error log shows a brief communication fault.

Causes:

  1. Communication Signal Interference:
    • Communication wires are bundled with mains voltage power wires, causing interference.
  2. Earth Loop:
    • Power supply uses a 2-core + earth wire, earthed at both ends.
    • The interconnecting wire only requires a 2-core wire or figure-8.
    • If a wire with additional conductors is used, connecting a second parallel earth wire creates an earth loop.

Solution:

  • Disconnect the extra earth wire at one end to eliminate the earth loop and reduce interference.





What is an Earth Loop?

Definition: An earth loop happens when parallel earth conductors are joined between the same two points, such as the earth between outdoor and indoor units. This can create a loop that picks up unwanted electrical noise, causing interference.

Why It’s a Problem:

  • Interference: The loop can act like an antenna, picking up electromagnetic interference (EMI) that disrupts communication signals.
  • Unreliable Operation: This interference can cause intermittent faults and make the system unreliable.

Example:

  • When a cable exceeding manufacturer specification is used for communication.
  • The extra earth wire in this cable is connected to the ground at both ends, creating an earth loop.
  • This loop picks up interference, causing communication faults.

Solution:

  • Disconnect One End: To break the loop, disconnect the extra earth wire at one end. This stops the unwanted current flow and reduces interference.

Key Points:

  • Primary Earth Connection: Always keep the main grounding wire connected at both ends for safety.
  • Additional Earth Wires: Do not connect any extra grounding wires to avoid creating an earth loop.



Example diagram of an earth loop that requires to be disconnected at one end to reduce interference





IMPORTANT REMINDER: Data/Comms and 240 Volt cable routing

According to the Australian wiring Standard and Seeley International, a minimum spacing of 50mm is required between low voltage data/communication cables and 240 Volt cables when routing them. It is not permissible by Australian standards to route data/communication cables and 240 Volt cables together in conduit, or to bind or tape them together, as this can lead to induced EMF interference. Such interference may cause intermittent communication errors and erratic appliance operation.


The examples provided below are solely for the purpose of illustrating communication cable routing and do not represent KDHV/KCHV communication cables.