Overview
ISO 9459-2:1995 - "Solar heating - Domestic water heating systems - Part 2" defines outdoor test methods for characterizing the performance of solar-only domestic water heating systems and for predicting their yearly performance. This Part 2 uses a black-box approach (no assumptions about system architecture) and is suitable for many system types - e.g., forced circulation, thermosiphon, freon-charged, and integrated collector-storage systems. The standard targets systems without integral auxiliary heating and limits applicability to systems with solar storage capacity of 0.6 m3 or less. It is not generally applicable to concentrating collectors and does not determine freeze-protection energy losses.
Key topics and requirements
- Scope and applicability
- Outdoor performance testing for solar-only domestic hot water systems.
- Applicable only for an evening draw-off pattern and storage ≤ 0.6 m3.
- Excludes systems with integral auxiliary heaters and concentrating systems.
- Black-box test procedure
- Produces input–output characteristics that can be combined with local meteorological daily-mean data (solar irradiation, ambient temperature, cold-water temperature) for annual performance prediction.
- Measurement and instrumentation
- Uses field radiometry (pyranometers, pyrheliometers) and calibrated instruments per referenced standards (e.g., ISO 9060, ISO 9846, ISO 9847).
- Test execution and analysis
- Defines system classifications, test conditions, required measurements, data analysis and presentation of results.
- Includes procedures for predicting long-term (annual) performance from outdoor test data.
- Annexes and tools
- Annex A: format sheets for test and annual performance prediction.
- Annex B: example computer programs for long-term prediction.
- Annex C: optional test for midday draw-off (informative).
- Annex D: bibliography.
Practical applications and users
ISO 9459-2 is useful for:
- Solar hot water manufacturers validating product performance claims.
- Independent test laboratories conducting outdoor system characterization.
- HVAC and solar consultants performing system sizing and annual yield predictions.
- Certification bodies and standards organizations comparing system performance internationally.
- Researchers and universities studying real-world solar domestic water heating performance.
Keywords: ISO 9459-2:1995, solar heating, domestic water heating systems, outdoor test methods, performance characterization, yearly performance prediction, solar-only systems, pyranometer, irradiance, black-box testing.
Related standards
- ISO 9459 (other parts): Part 1 (indoor rating), Part 3 (solar plus supplementary), Part 4 and 5 (component tests and dynamic simulation).
- ISO 9060, ISO 9846, ISO 9847 (radiometer calibration and measurement guidance).
- ISO 11924 (reliability and safety testing for solar domestic water heating systems).
Open preview (PDF)Solar heating — Domestic water heating systems — Part 2: Outdoor test methods for system performance characterization and yearly performance prediction of solar-only systems
