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IS 12933 Part 2 : 2003Solar water heating systems - Part 2: Method of test for thermal performance

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EN 12976-1 · AS/NZS 2712 · ISO 9459-5
CurrentSpecializedTesting MethodBIMMEP · Solar and Renewable Energy Installations
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OverviewValues5InternationalTablesFAQ4

IS 12933:2003 Part 2 is the Indian Standard (BIS) for solar water heating systems - part 2: method of test for thermal performance. This standard specifies the method for testing the thermal performance of both thermosyphon and forced circulation solar water heating systems. It details the test setup, environmental conditions, measurement procedures, and calculations required to determine the system's instantaneous efficiency and overall performance characteristics.

Specifies methods for testing the thermal performance of solar water heating systems.

Overview

Status
Current
Usage level
Specialized
Domain
MEP — Solar and Renewable Energy Installations
Type
Testing Method
International equivalents
EN 12976-1:2017 · CEN (European Committee for Standardization), EuropeAS/NZS 2712:2007 · Standards Australia / Standards New Zealand, Australia/New ZealandISO 9459-5:2014 · ISO (International Organization for Standardization), InternationalICC 901/SRCC 300-2020 · ICC (International Code Council) / SRCC, USA
Also on InfraLens for IS 12933
5Key values4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! Test results are highly sensitive to weather conditions; ensure stable (quasi-steady) solar radiation and low wind for reliable and repeatable data.
! Accurate calibration of all instruments, especially the pyranometer, flow meter, and temperature sensors, is critical for test validity and minimizing measurement uncertainty.
! The standard helps generate a performance curve, which is more valuable than a single efficiency value, as it shows how the collector performs under different operating temperatures.
Frequently referenced clauses
Cl. 4Test ApparatusCl. 5Test MethodsCl. 6Test ProcedureCl. 7Calculation of Thermal PerformanceAnnex A - Recommendations for Achieving Quasi-Steady State
Pulled from IS 12933:2003. Browse the full clause & table index below in Tables & Referenced Sections.
solar collectorsglazingabsorber coatinginsulationstorage tanks

International Equivalents

Similar International Standards
EN 12976-1:2017CEN (European Committee for Standardization), Europe
HighCurrent
Thermal solar systems and components - Factory made systems - Part 1: General requirements
Covers general design, safety, and durability requirements for factory-made solar domestic water heating systems.
AS/NZS 2712:2007Standards Australia / Standards New Zealand, Australia/New Zealand
HighCurrent
Solar and heat pump water heaters — Design and construction
Specifies requirements for the design and construction of solar water heaters, including materials and safety devices.
ISO 9459-5:2014ISO (International Organization for Standardization), International
MediumCurrent
Solar heating — Domestic water heating systems — Part 5: System performance characterization by means of whole-system tests and computer simulation
Focuses on performance testing methods, but its requirements are foundational for system design and validation.
ICC 901/SRCC 300-2020ICC (International Code Council) / SRCC, USA
HighCurrent
Standard for Solar Thermal Water Heating System and Component Certification
Covers minimum requirements for materials, construction, and performance for certifying solar water heating systems in the US.
Key Differences
≠IS 12933 is tailored for Indian climatic conditions, with an emphasis on high ambient temperatures, UV resistance, and water hardness, while freeze protection is optional. European (EN) standards make freeze protection a mandatory requirement for most systems.
≠The Indian standard is more prescriptive about materials (e.g., specific grades of copper or stainless steel), whereas modern international standards like EN 12976-1 are more performance-based, allowing any material that passes specified durability and safety tests.
≠IS 12933:2003 is an older standard and is not fully harmonized with the latest ISO standards. Newer standards like EN 12976:2017 and ICC 901/SRCC 300:2020 are aligned with ISO 9806 and ISO 9459, reflecting current global testing and simulation methodologies.
≠IS 12933 has a strong implicit focus on natural circulation (thermosyphon) systems, which are prevalent in India. International standards tend to provide more detailed and distinct requirements for a wider variety of system types, including forced circulation, drain-back, and integrated collector-storage systems.
Key Similarities
≈All standards mandate fundamental safety requirements, including protection against excessive pressure (pressure relief valves) and excessive temperature (high-temperature cut-offs or tempering valves).
≈A core objective across all standards is ensuring long-term durability. This is addressed through requirements for corrosion resistance of materials, weatherproofing of external components, and mechanical strength of the support structure.
≈All standards define requirements for the same fundamental system components: solar collector, storage tank, and interconnecting pipework, ensuring they function as an integrated system.
≈The provision of comprehensive documentation is a common requirement. Manufacturers must supply clear instructions for installation, commissioning, user operation, and routine maintenance to ensure safety and performance.
Parameter Comparison
ParameterIS ValueInternationalSource
Tank Hydrostatic Pressure TestTest at twice the maximum working pressure, but not less than 0.2 MPa (2 bar).Test at 1.5 times the maximum allowable pressure of the hydraulic circuit.EN 12976-1:2017
Freeze Resistance RequirementOptional; required only if specified by the purchaser for cold climates.Mandatory for systems intended for use in climates where freezing occurs; must pass specific freeze resistance tests.EN 12976-1:2017
Tank Standby Heat LossMaximum 24h temperature drop of 7°C for tanks up to 200L, tested at a specific temperature differential.Performance-based; heat loss coefficient (W/K) is measured. Limits are set by certification schemes (e.g., Solar Keymark) based on tank volume.EN 12976-2:2017
Collector Glazing MaterialPrescribes 'toughened glass' with minimum 80% transmittance.Performance-based; material must pass impact resistance (hail test), thermal shock, and UV exposure tests without significant degradation.AS/NZS 2712:2007
High Temperature / Stagnation ProtectionSystem must withstand stagnation temperatures without failure. A pressure and temperature relief valve is mandatory.System must either limit hot water delivery temperature to safe levels (e.g., <95°C) or be designed to withstand stagnation without damage, verified by specific tests.EN 12976-1:2017
Absorber Selective Coating PropertiesSpecifies minimum solar absorptance (α ≥ 0.92) and maximum thermal emittance (ε ≤ 0.20) for selective surfaces.Does not prescribe values, but provides standardized test methods (via ISO 9806) to measure α and ε, which are then used for certification.EN 12975-1 / ISO 9806
⚠ Verify details from original standards before use

Key Values5

Quick Reference Values
Minimum quasi-steady solar radiation700 W/m²
Maximum mean wind speed during test3 m/s
Maximum incidence angle for test points40 degrees
Test fluid flow rate variation± 1 percent
Test fluid inlet temperature variation± 0.1 °C
Key Formulas
ηi = [ṁ * Cpf * (Tfe - Tfi)] / (Ac * G) — Instantaneous collector efficiency

Tables & Referenced Sections

Key Tables
No tables data
Key Clauses
Clause 4 - Test Apparatus
Clause 5 - Test Methods
Clause 6 - Test Procedure
Clause 7 - Calculation of Thermal Performance
Annex A - Recommendations for Achieving Quasi-Steady State

Frequently Asked Questions4

What is the main purpose of this test method?+
To determine the thermal performance characteristics of a solar water heater under standardized, quasi-steady state conditions (Clause 1.1).
What is the minimum solar radiation required for a valid test point?+
The global solar radiation on the collector plane must be above 700 W/m² during the test period (Clause 6.1.1).
Does this standard apply to evacuated tube collectors (ETC)?+
Yes, the standard is applicable to solar water heating systems using various collector types, including flat plate and evacuated tube collectors.
What is the primary output of this test?+
A thermal performance curve plotting collector efficiency against the parameter (Tfi - Ta)/G, as described in Clause 7.

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