Standards Reading List

Familiarize yourself with these essential sections from the key standards.

AS/NZS 5125.1:2014 — Heat Pump Water Heater Performance Testing

• Section 2.2 — Test chamber conditions (test conditions 1–4)
• Section 3.2 — Test conditions and maximum temperature requirements
• Section 4.5 — Data correlation equations: selection of Tw (average tank) vs. Twi (inlet)
• Section 5.2 — Low temperature classification (Class A, Class B)
• Section 5.3 — Low temperature performance test and frosting penalty calculation
• Appendix B — Regression methodology

AS/NZS 4234:2021 — Annual Energy Performance Calculation

System Design

• Section 2.2.3 — Air-source heat pump systems
• Section 2.3 — Storage tank types

Compliance

• Section 3.6.2 — Legionella control strategies
• Section 3.6.3 — Minimum delivery temperature (MDT) requirements

Modelling

• Section 4.2 — Thermal stratification and mixing in hot water storage tanks
• Section 4.3 — Modelling thermal stratification in storage tanks
• Section 4.8 — Modelling heat pump water heaters:
  • Flow control for separate (stand-alone) heat pumps
  • Integral heat pump model setup
  • DTHX calibration
  • Stand-alone heat pump model setup
  • Variable flow modelling
  • Low temperature operation penalty calculation (frosting penalty)
• Section 7.3 — Annual energy savings calculation relative to reference systems

Reference Data

• Appendix A:
  • Climate zone weather data
  • Hot water demand loads (daily and seasonal profiles)
  • Cold water inlet temperature
  • Displaced energy calculation (STC)

AS/NZS 3498:2009 — Legionella Control

Section 7.1(j) defines two main legionella control methods. Choose based on test results and client preference.

Option 1: Weekly 90% Boost to 60°C + Daily Lower Setpoint

Requirements:

• AS/NZS 5125.1 test data must show bottom sensor (T6) reaching ≥ 60°C at test end
• HP must heat the entire tank to 60°C in one cycle
• Identify the mid-tank temperature (T3) when T6 = 60°C — typically 61–63°C
• Use this mid-tank temperature as the weekly setpoint

Typical settings:

• Daily: 55°C / 5 K deadband
• Weekly: 61°C / 1 K deadband (or based on observed T3)
• Weekly boost: Monday ~2am–7am (once per week)

Notes: More efficient than daily-only methods, but requires careful calibration. Risk: if T3 falls short of 60°C, system does not meet compliance.

Option 2: Daily 45% Boost to 60°C (Safer Default)

Requirements:

• HP sensor must have ≥ 45% tank volume above it
• Setpoint: 60°C (fixed)
• Maximize deadband while ensuring minimum delivery temperature ≥ 45°C

Typical settings:

• Daily: 60°C / 10 K deadband

Notes: Simpler and safer. Less efficient than weekly/daily combined, but more forgiving of model variations.

Decision Framework

Use Option 2 (45% daily) when: In doubt, or for conservative approach. Safer compliance margin.

Use Option 1 (weekly + daily) when: Client prefers efficiency and test data clearly supports higher stratification. Requires full validation against test results.

Consult with the client on their preference balancing efficiency and compliance risk.