ISO 24365:2022

Overview

ISO 24365:2022 - "Radiators and convectors - Methods and rating for determining the heat output" is an international standard that defines laboratory procedures, test arrangements and rating methods to determine the thermal output of permanently installed radiators and convectors fed with water or steam (temperatures below 120 °C) supplied by a remote energy source. The standard establishes how to derive the standard rated thermal output (50 K excess temperature) and the standard low temperature thermal output (30 K excess temperature), including the characteristic equation used to represent heat output as a function of excess temperature.

Key topics and requirements

• Scope & applicability: Applies to fixed radiators and convectors (not fan‑assisted units, trench convectors, or independent heating appliances).
• Sample selection: Criteria for selecting representative models, sectional appliances and families of appliances for initial and supplementary tests.
• Laboratory arrangements: Test booth, reference installation and master radiators concepts; verification of repeatability and reproducibility.
• Test methods: Weighing method, electric method and measurement/calculation routines to determine heat output and pressure drop.
• Characteristic equation: Determination of the power function (characteristic exponent) that relates thermal output to excess temperature at constant water flow.
• Standard outputs: Definition and calculation of standard rated thermal output (50 K excess) and standard low temperature thermal output (30 K excess).
• Tolerances & conformity: Admissible tolerances, procedures for verifying current production against initial tested samples.
• Reporting & data: Required test report content and additional common product data manufacturers must supply (catalogue outputs, pressure drop, flow rates).
• Normative reference: ISO/IEC 17025 for laboratory competence is referenced.

Applications and users

ISO 24365 is used to:

• Provide comparable and reproducible heat-output ratings for radiators and convectors in product catalogues and technical data sheets.
• Support product type testing, factory conformity checks and regulatory compliance for building HVAC specifications.
• Inform HVAC designers, specifiers and energy assessors when selecting heating appliances for projects, especially low‑temperature systems.
• Guide accredited testing laboratories and manufacturers in test setup, measurement accuracy and reporting.

Primary users: radiator and convector manufacturers, test laboratories, certification bodies, HVAC designers, building engineers and regulatory authorities.

Related standards

• ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories (normative reference cited by ISO 24365).