Radiators and convectors — Methods and rating for determining the heat output

This document defines procedures for determining the standard thermal outputs and other characteristics of radiators and convectors installed in a permanent manner in construction works, fed with water or steam at temperatures below 120 °C, supplied by a remote energy source. This document specifies the laboratory arrangements and testing methods to be adopted, the admissible tolerances, the criteria for selecting the samples to be tested and for verifying the conformity of the current production with the samples tested at the initial test. This document also defines the additional common data that the manufacturer shall provide with the product in order to ensure the correct application of the products. This document does not apply to fan-assisted radiators, fan-assisted convectors and trench convectors or to independent heating appliances.

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Status
Published
Publication Date
11-Aug-2022
Current Stage
6060 - International Standard published
Due Date
25-Sep-2023
Completion Date
12-Aug-2022
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INTERNATIONAL ISO
STANDARD 24365
First edition
2022-08
Radiators and convectors — Methods
and rating for determining the heat
output
Reference number
ISO 24365:2022(E)
© ISO 2022
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ISO 24365:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
© ISO 2022 – All rights reserved
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ISO 24365:2022(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction .............................................................................................................................................................................................................................. vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms, definitions, symbols and units ......................................................................................................................................... 1

3.1 Terms and definitions ...................................................................................................................................................................... 1

3.2 Symbols and units of measurement..................................................................................................................................... 4

4 Selection of heating appliances to be tested .......................................................................................................................... 5

4.1 Classification ............................................................................................................................................................................................ 5

4.2 Selection of models to be tested for determining the thermal outputs of a type ....................... 6

4.2.1 Selection of models to be tested when the variable characteristic dimension

is the overall height and the cross-section of the variable part is constant .................. 6

4.2.2 Selection of models to be tested when the variable characteristic dimension

for the type is other than the overall height .............................................................................................. 7

4.3 Testing samples submission and identification ........................................................................................................ 8

4.4 Supplementary test ......................................................................................................................................................................... 11

5 Laboratory equipment and test methods ...............................................................................................................................11

5.1 Principle .................................................................................................................................................................................................... 11

5.2 Apparatus ................................................................................................................................................................................................. 11

5.2.1 Test system ........................................................................................................................................................................... 11

5.2.2 Reference test installation ...................................................................................................................................... 11

5.2.3 Master radiators .............................................................................................................................................................. 14

5.2.4 Verification of test installation repeatability and reproducibility ..................................... 18

5.2.5 Accuracy of measuring instruments and devices ..............................................................................23

5.2.6 Calibration of measuring instruments ........................................................................................................ 24

5.3 Preparation for thermal output test................................................................................................................................. 24

5.4 Test methods ......................................................................................................................................................................................... 24

5.4.1 General ..................................................................................................................................................................................... 24

5.4.2 Weighing method ............................................................................................................................................................ 24

5.4.3 Electric method ................................................................................................................................................................ 25

5.4.4 Measurements and calculations ........................................................................................................................ 25

5.4.5 Determination of the characteristic equation ......................................................................................28

5.5 Presentation of results .................................................................................................................................................................29

5.5.1 Standard thermal output of a model..............................................................................................................29

5.5.2 Determination of the catalogue outputs of a type made at variable water

flow rate .................................................................................................................................................................................. 30

6 Test report ...............................................................................................................................................................................................................30

Annex A (normative) Master radiators dimensional verification .....................................................................................33

Annex B (informative) Determination of pressure drop ............................................................................................................38

Annex C (normative) Least squares regression for a model ....................................................................................................43

Annex D (normative) Analysis of test results by the method of least squares multiple

regression ............................................................................................................................................................................................................... 44

Annex E (normative) Specimen of the test report ..............................................................................................................................46

Annex F (informative) Apparatus and method for checking the bulk temperature

measuring devices ..........................................................................................................................................................................................49

Annex G (informative) Examples of typical appliances according to Table 4 .......................................................51

Annex H (normative) Determination of the Φ values of the master radiators primary set ..............61

Annex I (normative) Calculation method for determining the energy calculation parameters ......62

iii
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ISO 24365:2022(E)

Bibliography .............................................................................................................................................................................................................................64

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ISO 24365:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 205, Building environment design.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
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ISO 24365:2022(E)
Introduction

This document results from the recognition that the heating appliances falling into the field of

application hereinafter stated are traded on the basis of their thermal output.

To evaluate and compare different appliances it is therefore necessary to refer to a single stipulated

value, hereinafter called the standard rated thermal output.

In addition, for low temperature systems, a standard low temperature thermal output is given.

The standard thermal outputs (standard rated thermal output and standard low temperature thermal

output) are a defined value taken from the characteristic equation.

The pre-requisites of the standard thermal outputs, as defined by this document, are the following:

— to be representative of the actual output of the appliance in different operating conditions;

— to be reproducible within the tolerances defined by this document, taking into account the state of

measuring techniques;

— to be representative of the thermal outputs, obtainable under the same test conditions, of any

identical sample taken out of the current production (within the tolerances defined by this document,

taking into account the state of measuring techniques and methods of manufacture).

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INTERNATIONAL STANDARD ISO 24365:2022(E)
Radiators and convectors — Methods and rating for
determining the heat output
1 Scope

This document defines procedures for determining the standard thermal outputs and other

characteristics of radiators and convectors installed in a permanent manner in construction works, fed

with water or steam at temperatures below 120 °C, supplied by a remote energy source.

This document specifies the laboratory arrangements and testing methods to be adopted, the admissible

tolerances, the criteria for selecting the samples to be tested and for verifying the conformity of the

current production with the samples tested at the initial test.

This document also defines the additional common data that the manufacturer shall provide with the

product in order to ensure the correct application of the products.

This document does not apply to fan-assisted radiators, fan-assisted convectors and trench convectors

or to independent heating appliances.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
heating appliance

device having the purpose of transferring heat in order to provide specific temperature conditions

inside buildings
3.1.2
independent heating appliance

self-contained heating appliance (3.1.1) which does not need to be connected to a remote energy source

(e.g. a boiler) as it contains its own energy source (e.g. gas fired appliances, electric appliances, air to air

heat pump appliances)
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ISO 24365:2022(E)
3.1.3
radiator

heating appliance (3.1.1) produced with different materials (e.g. steel, aluminium, cast-iron) and with

different designs (e.g. plate type, column type, tube type, finned tube type), which emits heat by free

convection and radiation
3.1.4
sectional heating appliances

heating appliance (3.1.1) manufactured in sections of identical design and traded in this form, which

can be joined together into modular assemblies so that the desired output can be obtained

Note 1 to entry: Mainly applied to radiators (3.1.3).
3.1.5
convector
heating appliance (3.1.1) which emits heat almost entirely by free convection

Note 1 to entry: A convector comprising at least a heat emitter and a casing which provides an unheated

convective chimney of defined height.
3.1.6
skirting convector

special convector (3.1.5) of limited height running along the base of an interior wall

3.1.7
dry heating surface
secondary heating surface

portion of the heat emitting surface which is in contact with air only (e.g. fins projecting from the wet

surface)
3.1.8
family of heating appliances

group of heating appliances (3.1.1) of similar design and construction and of identical material, positions

of primary fluid connections and other related variables that particularly affect the conditions of flow

of the primary fluid within the heating appliance (3.1.1)
3.1.9
model
heating appliance (3.1.1) of defined height, length and depth within a type
3.1.10
range of heights

difference between the maximum and minimum height of the models (3.1.9) in a type

3.1.11
module

reference length of the useful portion of a heating appliance (3.1.1)
Note 1 to entry: The module coincides with:
— the section, in the case of sectional heating appliances (3.1.4);
— a length of 1 m, in the case of non-sectional heating appliances (3.1.1);
— a finned length of 1 m, in the case of finned tube convectors (3.1.5).
3.1.12
sample

representative heating appliance (3.1.1) used for the determination of one or more of the performance

characteristics
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ISO 24365:2022(E)
3.1.13
inlet water temperature
bulk temperature of the water entering the heating appliance (3.1.1)
3.1.14
outlet water temperature
bulk temperature of the water leaving the heating appliance (3.1.1)
3.1.15
temperature drop
difference between inlet (3.1.13) and outlet water temperature (3.1.14)
3.1.16
mean water temperature
arithmetical mean of inlet (3.1.13) and outlet water temperature (3.1.14)
3.1.17
reference air temperature

air temperature measured on the vertical line at the centre of the test booth, 0,75 m above the floor

level
3.1.18
excess temperature

difference between mean water temperature (3.1.16) and reference air temperature (3.1.17)

3.1.19
standard excess temperature
excess temperature (3.1.18) of 50 K as determined in the standard conditions

Note 1 to entry: Inlet water temperature (3.1.13) of 75 °C, outlet water temperature (3.1.14) of 65 °C and reference

air temperature (3.1.17) of 20 °C.
3.1.20
air pressure
measured value at the test site
3.1.21
water flow rate
amount of water flowing through the heating appliance (3.1.1) per unit of time
3.1.22
standard water flow rate
water flow rate (3.1.21) relating to standard test conditions
3.1.23
standard rated thermal output

thermal output of a heating appliance (3.1.1) defined at 50 K excess temperature (3.1.18)

3.1.24
standard low temperature thermal output

thermal output of a heating appliance (3.1.1) defined at 30 K excess temperature (3.1.18)

3.1.25
characteristic equation

power function with a specific characteristic exponent that gives the thermal output as a function of

the excess temperature (3.1.18) at constant water flow rate (3.1.21)
3.1.26
standard characteristic equation

characteristic equation (3.1.25) which is valid for standard water flow rate (3.1.22) and from which the

standard thermal output can be found for the standard excess temperature (3.1.19) of 50 K

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ISO 24365:2022(E)
3.1.27
test installation
combination of:
— test booth and other related parts, and
— measuring instruments and related equipment
3.1.28
test system
combination of:
— test installation (3.1.27), and
— master radiators (3.1.34)
3.1.29
pressure drop

difference of pressure between water inlet and water outlet of the heating appliance (3.1.1)

3.1.30
supplementary test

test for the purpose of establishing the effect of minor technical modifications on the thermal output of

radiators (3.1.3) that have already been tested
3.1.31
radiated heat output factor

assumed ratio between the radiation heat output and the overall heat output of the radiator (3.1.3),

which is only valid for air pressure (3.1.20) correction purposes
3.1.32
exponent n

exponent for the air pressure (3.1.20) correction of the measured heat output of the radiator (3.1.3)

3.1.33
emissivity

ratio of energy radiated by a particular material to energy radiated by a black body at the same

temperature
3.1.34
master radiator
sample (3.1.12) used for the calibration of test installations (3.1.27)

Note 1 to entry: Master radiators are used to determine repeatability and reproducibility of the results of the test

installations (3.1.27) (see 5.2.3).
3.2 Symbols and units of measurement
Table 1 — Symbols, quanties and units of measurement
Quantity Symbol Unit
Thermal output Φ W
Standard thermal output Φ W
Modular thermal output Φ W
Reference value of a master radiator Φ W

Reference value of a primary set of master radiators for interlaboratory comparisons Φ W

Electrical method heat losses Φ W
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ISO 24365:2022(E)
Table 1 (continued)
Quantity Symbol Unit
Electric power P W
Thermodynamic temperature T K
Temperature T °C
Inlet water temperature T °C
Outlet water temperature T °C
Temperature drop T -T K
1 2
Mean water temperature T °C
Reference room air temperature T °C
Excess temperature ΔT K
Specific heat capacity c J/kg∙K
Specific enthalpy h J/kg
Inlet water enthalpy h J/kg
Outlet water enthalpy h J/kg
Water flow rate q kg/s
Standard water flow rate q kg/s
Pressure p kPa
Maximum operating pressure/resistance to pressure p kPa
max
Pressure drop Δp kPa
Repeatability tolerance S -
Reproducibility tolerance S -
Overall height of the heating appliance H m
Range of heights H m
Overall length of the heating appliance L m
Length of a section L m
Number of sections N -
Thermal resistance R m∙K/W
Time interval τ s
Radiated heat output factor Sk -
Emissivity ε -
4 Selection of heating appliances to be tested
4.1 Classification

4.1.1 Heating appliances shall be grouped into families and types according to the definition in this

document. A family can include different types.

4.1.2 For the purposes of determining catalogue outputs, a family shall be divided into a number

of separate types (in a family of radiators there can, for example, be single or double panels, with or

without convector surfaces, using the same basic components).

4.1.3 The output of each model shall not be greater than 3 500 W and the minimum thermal output of

the selected model shall be not less than 200 W at standard excess temperature.

On request of the manufacturer, lower thermal output can be tested and the deviation from the previous

requirements shall be registered in the test report.
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ISO 24365:2022(E)

4.2 Selection of models to be tested for determining the thermal outputs of a type

4.2.1 Selection of models to be tested when the variable characteristic dimension is the overall

height and the cross-section of the variable part is constant

4.2.1.1 When a type includes only models of height 300 mm and greater, the models to be tested

within that type shall be selected in accordance with 4.2.1.2, 4.2.1.3, 4.2.1.4 and 4.2.1.5.

If the type also includes heights below 300 mm, the minimum height below 300 mm shall be tested in

addition to the above models.

For a type in which all heights are below 300 mm, only the minimum and the maximum height shall be

tested.

4.2.1.2 The minimum number of models to be tested within a type is determined by the range of

heights as shown in Table 2.
Table 2 — Minimum number of models to be tested
Range of heights (m) Number of models
to be tested
H = H − H
r max min
≤ 1 m 3
> 1 m 4

4.2.1.3 The minimum length of finned coil of the models to be tested shall be 1 m or the closest to 1 m.

For skirting convectors only, the finned coil length shall be the closest to 3 m. In the case of sectional

radiators, having height H ≤ 1 m, the minimum number of sections shall be 10 or the minimum length

0,8 m. For sectional radiator having height greater than 1 m, the minimum length shall be 0,45 m.

For towel radiators see 4.2.2.

4.2.1.4 In the case of H ≤ 1 m, the models to be tested shall be three; the minimum and maximum

height of the range and an intermediate height so that H is equal to or the closest value greater than:

int
HH=×- H
int max r
where H is the maximum height of the type.
max

4.2.1.5 In the case of 1 m < H ≤ 2,5 m, the models to be tested shall be four; the minimum and

maximum height of the range and two intermediate heights so that H and H are the closest values

int1 int2
respectively to:
HH=×- H
int1 max r
and
HH=×- H
int 2rmax
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ISO 24365:2022(E)

4.2.2 Selection of models to be tested when the variable characteristic dimension for the type

is other than the overall height
4.2.2.1 General principle

The minimum number of models to be tested is three, having the same overall height and respectively,

the minimum, intermediate and maximum value of the relevant characteristic dimension (see 4.2.1.4).

The measured values shall be used to determine the characteristic equation of the type.

For the equation to be valid, all the measured thermal outputs shall fall within ±2 % of the prediction of

the equation.

If any value falls outside this range, the type shall be divided and new equations derived for each subset

of the results.

4.2.2.2 Selection of models to be tested when a type includes horizontal parallel flow models

This procedure applies to tubular radiators classified as “towel or bathroom radiators”, according to

Figure G.3.

If a type includes horizontal parallel flow models, with different heights and lengths, the thermal

outputs of models having L and L respectively shall be tested. If there are more than three heights,

min max

the thermal output for all heating appliances having L and L respectively shall be established

min max

using the respective characteristic equation. For each height, the thermal output for models having

length included between L and L shall be linearly interpolated. The adopted procedure shall be

min max
noted in the test report.
4.2.2.3 Straight or curved towel or bathroom radiator

For “towels and bathroom radiators” having similar external size (height, length, external diameter of

the tubes) and different shape of horizontal tube (straight or curved):

If it is proved by at least two tests that the difference between the thermal outputs of the model having

straight tubes and the model having curved tubes, is within ±4,0 %, then the catalogue data of the

models having curved tubes can be assumed equal to the equivalent models having straight tubes.

If the difference exceeds ±4,0 % the models are classified as a different type and tested for any specific

geometry.
4.2.2.4 Towel and bathroom radiator water circulation

For “towel and bathroom radiators” having the same external size (height, length, depth and external

diameter of the tube), but different internal circulation of the hot water, if it is proved by at least two

tests that the difference between the thermal outputs of the models having different internal circulation

is within ±4,0 %, then the catalogue data of all the models can be assumed to be equal. If the difference

exceeds ±4,0 % the models are classified as different type and so tested for any specific internal water

circulation.
4.2.2.5 Different surface treatments (chromed, polished)

Models having the same external size (height, length, depth and external diameter of the tube), but

different surface treatment (i.e. painted, chromed or mechanically polished), shall be tested as follows:

a) Models painted and chromed shall be tested according to 4.2;
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ISO 24365:2022(E)

b) For models having other surface treatments (e.g. satinated or polished) the minimum number of

samples to be tested shall be defined as follows:

1) for each other type, two models, having the minimum and the maximum heat output as

measured on painted model, shall be tested only to determine the less favourable reduction

coefficient;

2) the thermal output of all the models shall be calculated using the reduction coefficient

determined according to 1).
4.2.2.6 Influence of water flow rate on thermal output

On request of manufacturers, the influence of water flow rate on thermal output shall be verified.

In this case, additional characteristics shall be tested, setting half and double standard mass flow.

4.3 Testing samples submission and identification

4.3.1 On initial application for the testing of a family of heating appliances, or of a type within a

family, heating appliance samples and product drawings shall be submitted to the testing laboratory.

Product drawings shall be submitted by the manufacturer.
4.3.2 The product drawings shall:

— show all dimensions and features having an influence on the heat emission, including the detail of

welds or other assembly methods used;

— state the type of material and the nominal material thicknesses of wet or dry surfaces, with the

thickness tolerances, and type of paint;
— be identified by the drawing number and the date of revision.

4.3.3 Before proceeding with the thermal output testing, the laboratory shall identify the appliance

against the drawing and shall note conformity of the sample with the drawing in respect of:

— dimensional tolerances given in Table 3;

— material thickness tolerances of convective surfaces, shown on the product drawings.

The laboratory shall also measure the mass and the water content of the sample model

...

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