ISO 9459-1:1993

Overview

ISO 9459-1:1993 - "Solar heating - Domestic water heating systems - Part 1: Performance rating procedure using indoor test methods" defines a uniform indoor test method for rating solar domestic hot water systems under benchmark conditions. The standard applies to systems designed solely to heat potable water for domestic use and is intended to provide a reproducible, comparable one-day performance rating. Tests cover systems with solar storage capacity ≤ 0.6 m³ and use either solar irradiance simulators or thermal (non‑irradiated) simulation methods.

Key topics and requirements

• Scope and applicability
  • Applies only to solar water heating systems for potable domestic hot water.
  • Limits: storage capacity of 0.6 m³ or less; excludes many integral collector storage and thermosiphon systems for non‑irradiated array tests.
• Test methods
  • Indoor testing using irradiance simulators or non‑irradiated thermal simulation.
  • Procedures for solar‑only, solar‑preheat, and solar-plus‑supplementary systems.
  • Specific tests such as the hot water continuous‑draw test for solar energy only.
• Measurement and instrumentation
  • Measurement accuracy, precision, symbols and units are defined.
  • Requirements reference calibration and radiometric methods (e.g., ISO 9059, ISO 9060).
• System requirements and controls
  • System classification by attributes, requirements for collector-loop configuration, controls and instrumentation.
  • Use of a collector loop heater (annex B) for non‑irradiated array testing and equations to control thermal output.
• Data recording and reporting
  • Standardized recording and reporting formats to allow direct comparison of system ratings.
• Annexes
  • Annex A–D are integral (test day specs, collector loop heater equations, optical property calculations, equivalent irradiance calculation); Annex E is bibliography.

Practical applications and users

• Manufacturers: product development, factory testing and comparative performance claims.
• Test laboratories and certification bodies: standardized indoor test protocols for repeatable ratings.
• Architects, specifiers and HVAC engineers: performance data for system selection in building designs.
• Researchers and policy makers: standardized metrics for comparative studies, incentive programs and regulatory compliance.

Using ISO 9459-1:1993 helps stakeholders obtain consistent, comparable performance ratings for solar domestic water heating systems without field variability, enabling fair product comparison and informed specification.

Related standards

• ISO 9459 series (Parts 2–5) for outdoor tests, black‑box correlations and simulation methods.
• ISO 9806 (collector test methods), ISO 9059 (pyrheliometer calibration), ISO 9060 (solar instrument classification), ISO 9845/9846 (reference spectral irradiance and pyranometer calibration).