Reducing Outdoor Unit De-Ice Cycles in Reverse Cycle Inverter Systems During Heating Operation


Applies to:

All reverse cycle inverter air conditioning systems, including the Dominator series.




Overview

In colder climates, icing of the outdoor unit during heating mode is normal operation for inverter systems. While some icing is expected due to the nature of heat pump operation, excessive or prolonged icing can impact performance and efficiency.

This article outlines best practices to mitigate icing and improve system efficiency and reliability.




Key Factors Influencing Icing

Outdoor Ambient Temperature

  • Icing typically occurs when ambient temperatures fall below 10°C.
  • The condenser operates at approximately 10°C colder than the surrounding air.

Condenser Location

  • Most critical factor.
  • Poor placement can lead to recirculation of cold exhaust air, increasing icing frequency and duration.




Installation Best Practices

✅ Avoid Recirculation Zones

  • Install the outdoor unit in an open area with maximum clearance behind and around the unit.
  • Do not rely solely on minimum clearance specifications — more space is better.

✅ Elevation and Drainage

  • Elevate the unit to prevent ice buildup around the base.
  • Ensure proper drainage to allow melted ice to escape freely.
  • If drain lines used in below zero climates, ensure protection from freezing and ice blockages

✅ Sheltering Without Enclosure (Australian Installations)

  • Use open-sided pergolas, carports, or eaves for overhead protection.
  • Ensure at least two sides are open to allow unrestricted airflow and prevent cold air recirculation.

❌ Avoid Full Enclosures or Fencing ❌ 

  • Do not box in the unit with timber, metal, or composite fencing.

✅ Positioning Near Buildings

  • Maintain manufacturer’s clearances — the more, the better.
  • Avoid placing units in narrow alleyways or courtyards where cold air can pool.
  • The use of condenser Air Deflectors will assist in diverting air away from close obstacles.

✅ Elevated Mounting

  • Use wall brackets or raised plinths, especially in frost-prone areas like Adelaide Hills, Ballarat, Canberra and Riverina.

✅ Consider Local Climate

  • In colder regions (e.g., Canberra, Tasmania), consider installing a wind baffle or snow hood.

✅ Air Deflectors

  • Use air deflectors to redirect cold exhaust air away from the unit, especially when installed with minimal clearance.

Click below link to view - Air Deflector Grille Compatibility Guide

Reverse Cycle Outdoor Unit Air Deflector Selection Chart July 2025: Seeley International Pty Ltd




Operational Tips

      Defrost Cycles

  • Icing is normal and managed by automatic defrost cycles.
  • If defrosting seems excessive, review installation site and airflow conditions.
  • Ensure regular maintenance is conducted including cleaning of condenser coil and drains.

      Monitoring

  • Encourage users to monitor performance during cold spells.
  • Report any unusual behavior such as:
    • Loud noises
    • Prolonged defrosting
    • Reduced heating output




System and Product Maintenance Issues

Regular maintenance is essential to prevent excessive icing and ensure optimal performance. Technicians should check for:

1. Refrigerant Charge Problems

  • Low refrigerant levels due to leaks or insufficient charging can cause premature icing.
  • Verify refrigerant levels and ensure proper charging.

2. Dirty Outdoor Coil

  • A clogged coil restricts airflow and reduces heat exchange efficiency.
  • Clean regularly using appropriate coil cleaner and water pressure.

3. Undersized System

  • Undersized systems may run continuously, increasing icing risk.
  • Confirm correct size and review load calculations.

4. Multiple Outdoor Units Nearby

  • Clustering units can create a cold microclimate.
  • Ensure adequate spacing and consider air deflectors.

5. Faulty Outdoor Ambient Sensor

  • An out of calibration sensor may prevent defrost cycles.
  • Test and replace if readings are inaccurate.

6. Outdoor Fan Motor Issues

  • Malfunctioning or wind-affected fan motors may reduce airflow.
  • Inspect motor operation and check for obstructions.

7. Compressor Stuck On

  • Continuous compressor operation can lead to excessive icing.
  • Check control board and compressor relay functionality.




Consumer Communication

When discussing with consumers:

  • Reassure them that some icing is normal and expected.
  • Emphasize the importance of correct installation, site selection, and regular maintenance.