This standard outlines the general requirements and test methods for solar water heating systems that use evacuated tube collectors (ETC). It covers specifications for materials, construction, safety, thermal performance, and durability to ensure system quality and efficiency. The standard is applicable to both thermosyphon and forced circulation type systems.
Specifies general requirements and methods of test for solar water heating systems utilizing evacuated tube collectors.
Quick Reference Values
Minimum borosilicate glass thickness for tubes1.6 mm
Maximum heat loss for storage tank (up to 200L)1.8 kWh/24h
Hydrostatic pressure test for unpressurized tankTested to a head of 3 m of water
Hydrostatic pressure test for pressurized tank1.5 times the maximum operating pressure (min. 3 bar)
Hail resistance test requirement withstand impact of 25 mm dia ice ball at 20 m/s
Minimum thermal insulation thickness (PUF)50 mm
Key Formulas
η = F'(τα)e - F'UL * (Ti - Ta) / G — Collector thermal efficiency formula used in performance testing.
Practical Notes
The performance of ETC systems is highly dependent on the vacuum integrity of the glass tubes. Check for a 'silvered' or milky appearance at the bottom of the tube, which indicates a loss of vacuum and a faulty tube.
In hard water areas, scaling inside the tubes can severely degrade performance. Regular cleaning or the use of a water softener is crucial for long-term efficiency.
Ensure the mounting structure is robust and complies with local wind load requirements (e.g., as per IS 875 Part 3), as this standard focuses on the thermal system, not its structural mounting.