oSIST prEN 1434-6:2020

Thermal energy meters - Part 6: Installation, commissioning, operational monitoring and maintenance

This document specifies commissioning, operational monitoring and maintenance and applies to thermal energy meters. Thermal energy meters are instruments intended for measuring the energy which in a heat-exchange circuit is absorbed (cooling) or given up (heating) by a liquid called the heat-conveying liquid. The thermal energy meter indicates the quantity of thermal energy in legal units.
Electrical safety requirements are not covered by this document.
Pressure safety requirements are not covered by this document.
Surface mounted temperature sensors are not covered by this document.
This document covers meters for closed systems only, where the differential pressure over the thermal load is limited.

Thermische Energiemessgeräte - Teil 6: Einbau, Inbetriebnahme, Überwachung und Wartung

Dieses Dokument legt die Inbetriebnahme, Betriebsüberwachung und Wartung fest und gilt für thermische Energiemessgeräte. Thermische Energiemessgeräte sind Messgeräte, die dazu bestimmt sind, die Energie zu messen, die in einem Wärmetauschkreislauf von einer als Wärmeträgerflüssigkeit bezeichneten Flüssigkeit aufgenommen (Kühlung) oder abgegeben (Heizung) wird. Das thermische Energiemessgerät zeigt die Menge der thermischen Energie in gesetzlichen Einheiten an.
Anforderungen an die elektrische Sicherheit sind nicht Gegenstand dieses Dokuments.
Anforderungen an die Drucksicherheit sind nicht Gegenstand dieses Dokuments.
Oberflächenmontierte Temperaturfühlern sind nicht Gegenstand dieses Dokuments.
Dieses Dokument behandelt nur Messgeräte für geschlossene Systeme, bei denen der Differenzdruck über die thermische Last begrenzt ist.

Compteurs d'énergie thermique - Partie 6 : Installation, mise en service, surveillance et maintenance

Le présent document spécifie l’installation, la mise en service, la surveillance de fonctionnement et la maintenance et s’applique aux compteurs d’énergie thermique. Les compteurs d’énergie thermique sont des instruments destinés à mesurer l’énergie thermique qui, dans un circuit d’échange thermique, est absorbée (refroidissement) ou cédée (chauffage) par un liquide appelé « liquide caloporteur ». Le compteur d’énergie thermique fournit la quantité d’énergie thermique en unités de mesure légales.
Le présent document ne traite pas des prescriptions de sécurité électrique.
Le présent document ne traite pas des prescriptions de sécurité relative à la pression.
Le présent document ne traite pas des sondes de température montées en surface.
Le présent document couvre les compteurs pour les systèmes fermés uniquement, où la pression différentielle dans la charge thermique est limitée.

Merilniki toplote - 6. del: Vgradnja, zagon, nadzor in vzdrževanje

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Nov-2020
• ICS: 17.200.20 - Temperature-measuring instruments
• Technical Committee: OGS - Heating for buildings
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 02-Oct-2020
• Due Date: 19-Feb-2021
• Completion Date: 15-Jan-2021
• Directive: 2014/32/EU - Directive 2014/32/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of measuring instruments
• Mandate: M/541 - [C(2015)8558] Standardization request in support of the implementation of Directive 2014/32/EU on measuring instruments
• Ref Project: prEN 1434-6 - Thermal energy meters - Part 6: Installation, commissioning, operational monitoring and maintenance

RELATIONS

• Revised: SIST EN 1434-6:2016+A1:2019 - Thermal energy meters - Part 6: Installation, commissioning, operational monitoring and maintenance
• Effective Date: 01-Nov-2020

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 1434-6:2020
01-november-2020
Merilniki toplote - 6. del: Vgradnja, zagon, nadzor in vzdrževanje

Thermal energy meters - Part 6: Installation, commissioning, operational monitoring and

maintenance
Thermische Energiemessgeräte - Teil 6: Einbau, Inbetriebnahme, Überwachung und
Wartung

Compteurs d'énergie thermique - Partie 6 : Installation, mise en service, surveillance et

maintenance
Ta slovenski standard je istoveten z: prEN 1434-6
ICS:
17.200.20 Instrumenti za merjenje Temperature-measuring
temperature instruments
oSIST prEN 1434-6:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 1434-6:2020
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oSIST prEN 1434-6:2020
DRAFT
EUROPEAN STANDARD
prEN 1434-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2020
ICS 17.200.20 Will supersede EN 1434-6:2015+A1:2019
English Version
Thermal energy meters - Part 6: Installation,
commissioning, operational monitoring and maintenance

Compteurs d'énergie thermique - Partie 6 : Installation, Thermische Energiemessgeräte - Teil 6: Einbau,

mise en service, surveillance et maintenance Inbetriebnahme, Überwachung und Wartung

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 176.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1434-6:2020 E

worldwide for CEN national Members.
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oSIST prEN 1434-6:2020
prEN 1434-6:2020 (E)
Contents Page

European foreword ...................................................................................................................................................... 3

1 Scope .................................................................................................................................................................... 4

2 Normative references .................................................................................................................................... 4

3 Terms and definitions ................................................................................................................................... 4

4 Requirements ................................................................................................................................................... 5

4.1 Design requirements ..................................................................................................................................... 5

4.2 Installation requirements............................................................................................................................ 7

4.3 Thermal energy meter commissioning ................................................................................................... 7

4.3.1 General ................................................................................................................................................................ 7

4.3.2 Certification check .......................................................................................................................................... 8

4.3.3 Installation check ............................................................................................................................................ 8

4.3.4 Thermal energy meter security ................................................................................................................. 8

4.4 Operating requirements with heat-conveying liquids other than water ................................... 8

Annex A (informative) Thermal energy meter installation .......................................................................... 10

A.1 General .............................................................................................................................................................. 10

A.2 Criteria for the selection of a thermal energy meter ....................................................................... 10

A.3 Quality of the heat conveying liquid ...................................................................................................... 10

A.3.1 General .............................................................................................................................................................. 10

A.3.2 Primary water quality ................................................................................................................................. 11

A.3.3 Secondary water quality............................................................................................................................. 11

A.3.4 Monitoring heat conveying liquids other than water ...................................................................... 11

A.4 Thermal energy meter flow circuit design .......................................................................................... 12

A.5 Additional recommendations for cooling application .................................................................... 13

A.6 Examples for the installation of thermal energy meters ................................................................ 14

A.7 Additional recommendations for large pipes > DN 250 ................................................................. 21

Annex B (informative) Thermal energy meter operational monitoring and maintenance .............. 22

B.1 Introduction .................................................................................................................................................... 22

B.2 Thermal energy meter service life ......................................................................................................... 22

B.3 Thermal energy meter monitoring procedures ................................................................................ 22

B.4 Maintenance check list ................................................................................................................................ 23

B.5 Replacement of failed thermal energy meters ................................................................................... 23

Annex C (informative) Suggested gauge for checking the dimensions of installed temperature

sensor pockets ............................................................................................................................................... 25

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/32/EU aimed to be covered ...................................................... 26

Bibliography.................................................................................................................................................................. 27

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European foreword

This document (prEN 1434-6:2020) has been prepared by Technical Committee CEN/TC 176 “Thermal

energy meters”, the secretariat of which is held by SIS.
This document is currently submitted to the CEN Enquiry.
This document supersedes EN 1434-6:2015+A1:2019.
EN 1434, Thermal energy meters consists of the following parts:
— Part 1: General requirements
— Part 2: Constructional requirements
— Part 3: Data exchange and interfaces
— Part 4: Pattern approval tests
— Part 5: Initial verification tests
— Part 6: Installation, commissioning, operational monitoring and maintenance
In comparison to EN 1434-6:2015+A1:2019, the following changes have been made:
— the title of this standard was changed into “Thermal energy meters”;
— Annex ZA was adjusted to the new Directive 2014/32/EU (MID);

— wording “heat meter” was partly and where applicable changed into “thermal energy meter” within

the whole document.

This document has been prepared under a standardization request given to CEN by the European

Commission and the European Free Trade Association, and supports essential requirements of

EU Directive(s).

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this

document.
EN 1434-3 is maintained by CEN/TC 294.
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1 Scope

This document specifies commissioning, operational monitoring and maintenance and applies to thermal

energy meters. Thermal energy meters are instruments intended for measuring the energy which in a

heat-exchange circuit is absorbed (cooling) or given up (heating) by a liquid called the heat-conveying

liquid. The thermal energy meter indicates the quantity of thermal energy in legal units.

Electrical safety requirements are not covered by this document.
Pressure safety requirements are not covered by this document.
Surface mounted temperature sensors are not covered by this document.

This document covers meters for closed systems only, where the differential pressure over the thermal

load is limited.
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.

prEN 1434-1:2020, Thermal energy meters — Part 1: General requirements
3 Terms and definitions

For the purposes of this document, the terms and definitions given in prEN 1434-1:2020 and the

following apply.

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

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
thermal energy system

heating or cooling installations of the dwelling or premises, including the exchange circuit, the thermal

energy meter, the associated fittings and the electrical equipment

Note 1 to entry: The heating or cooling systems typically commences and finishes at the two connections to the

heat or cooling mains.
3.2
thermal energy mains

heat or cooling suppliers distribution pipes to which the consumer's installation is connected

3.3
inlet and outlet limbs
pipes connecting the heating or cooling system to the thermal energy mains
3.4
primary circuit
circuit hydraulically connected to the thermal energy mains
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oSIST prEN 1434-6:2020
prEN 1434-6:2020 (E)
3.5
secondary circuit
circuit hydraulically separated from the primary circuit
3.6
competent authority

persons or organizations charged with the responsibility for the thermal energy meter and/or its

installation
3.7
cooling system

cooling installation of an apartment or building, including cooling exchanger circuit, cooling meter,

accessories and electrical equipment

Note 1 to entry: The cooling system usually starts and ends at the two connections to the cooling distribution

network.
4 Requirements
4.1 Design requirements

4.1.1 When designing the heating and cooling system, the thermal energy meter's manufacturer

specification and installation instructions shall be followed.

For q 6 m /h and less, it is recommended to use direct short sensors. To achieve good temperature

sensitivity, direct sensors should be installed without temperature pockets. Temperature pockets should

only be used when required for safety reasons.

These installation points shall be insulated in accordance with the applicable legal regulations or other

technical measures shall be taken to reduce dissipation errors.

4.1.2 To avoid systematic measurement errors, the temperature sensors in the supply and return pipes

shall be used at almost identical pressure conditions.

For typical systematic negative error as a function of differential pressure and temperature difference,

see Table 1. Table 1 is only applicable to the medium water.
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Table 1 — Typical systematic negative error as a function of differential pressure and

temperature difference
Diff pressure Temperature difference in K
in bar
3 5 10 20 30 40 50 60
0,5 0,2 0,2 0,1 0,1 0,1 0 0 0
1 0,5 0,4 0,3 0,2 0,1 0,1 0,1 0,1
2 0,9 0,7 0,5 0,3 0,2 0,2 0,1 0,1
3 1,4 1,1 0,8 0,5 0,3 0,2 0,2 0,2
4 1,8 1,5 1,0 0,6 0,4 0,3 0,3 0,2
5 2,3 1,9 1,3 0,8 0,5 0,4 0,3 0,3
6 2,7 2,2 1,5 0,9 0,6 0,5 0,4 0,3
7 3,2 2,6 1,9 1,1 0,7 0,6 0,5 0,4
8 3,6 3,0 2,0 1,2 0,9 0,7 0,5 0,4
9 4,1 3,3 2,3 1,4 1,0 0,7 0,6 0,5
10 4,5 4,0 2,5 1,5 1,1 0,8 0,7 0,5

The values are shown as fraction of the maximum permissible error for the calculator. The values below

the marked line are higher than 1/3 of the maximum permissible error for the thermal energy

calculator. If the resulting error is higher than 1/3 of the maximum permissible error, it is

recommended to change the installation to have smaller differential pressure.

NOTE In cases where flows from two different loads with different temperatures (e.g. for space heating and

domestic warm water) are merged together just before the temperature sensor, the optimum position for the sensor

is after the flow sensor.

4.1.3 For bifunctional meters for change-over systems between heating and cooling additional

requirements are necessary to ensure the correct switching over function between the heating and

cooling register. These requirements are:

— the lowest operating temperature in the inlet pipe at heating conditions shall be at least 3 °C higher

than any specified optional switching over temperature θ ;

— the highest operating temperature in the inlet pipe at cooling conditions shall be at least 3 °C lower

than any specified optional switching over temperature θ ;

— the minimum temperature difference in heating and cooling application shall be more than 3 K.

NOTE The above mentioned temperature range of at least 3 °C covers the maximum accepted uncertainty in

measured temperature and the cable resistance.

A temperature sensor with smaller tolerances than 2 °C for measuring of the measured temperature is

recommended.

4.1.4 In the heating or cooling system there shall be at least one tapping point for the check according

to 4.4 “Operating requirements”.
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4.1.5 Temperature sensors for fast response meters shall be direct mounted probes, type DS or type

DL. Pocket mounted probes are not suitable for fast response meters.
4.2 Installation requirements

The thermal energy meter shall be installed in accordance with the manufacturer's instructions.

Before installation, the circuit into which the flow sensor is to be installed shall be thoroughly flushed to

remove debris. The strainer, where fitted, shall be cleaned.

The thermal energy meter shall be protected from the risk of damage by shock and vibration induced by

the surroundings at the place of installation.

The thermal energy meter shall not be subjected to undue stresses caused by pipes and fittings.

The pipelines of the heating system up and downstream of the thermal energy meter shall be adequately

anchored.

Thermal energy meters designed to operate from an AC mains supply shall be wired in accordance with

wiring regulations applicable.

The AC mains power supply shall be secured against accidental interruption. However, circuit protection

shall be incorporated according to the state of the art, to safely disconnect the device when electrical

problems occur.

Measurement signal leads shall not be laid directly alongside other leads such as mains supply cables,

low voltage supply cables and data communication cables and shall be independently supported. The

separation between those groups shall not be less than 50 mm. Unless the calculator under installation

was type tested according to the latest version of prEN 1434-4, it is recommended to install cables and

calculators with a distance of at least 60 cm to strong electromagnetic fields, e.g. frequency controlled

pumps and similar high energy mains cables.

Mains and external signal cables longer than 10 m shall in areas where lightning is frequent be protected

with an external lightning surge protection at the cable entrance to the building.

Each signal lead between temperature sensors and calculator shall be one continuous length without

joints except 4-wire connection solutions which are approved.

Signal circuits between parts of a thermal energy meter shall be so installed as to deter unauthorized

interference and disconnection.

Precautions shall be taken to prevent damage to the thermal energy meter by unfavourable hydraulic

conditions (cavitation, surging, water hammer).

When the installation of the thermal energy meters is complete, it shall be inspected and approved by

representatives of the competent authority in accordance with established procedures and the inspection

shall be documented.
Installation shall be done according to national legislation on legal metrology.
4.3 Thermal energy meter commissioning
4.3.1 General

The responsibility for the carrying out of each of the inspection phases is not necessarily restricted to one

person or one authority depending on the national legislation on legal metrology, but however arranged,

the following points shall be addressed and responsibilities defined.
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4.3.2 Certification check

Before commissioning commences it shall be ascertained firstly, that the correct thermal energy meter

has been installed by comparing the thermal energy meter manufacturer's type and size designation

against the system specification. Secondly, it shall be checked that the thermal energy meter, if a complete

instrument, bears the correct pattern approval mark and, if a combined instrument, that each of the

meters sub-assemblies bear the pattern approval marks stipulated in the pattern approval document for

the thermal energy meter installed.
4.3.3 Installation check
At least the following points shall be checked:

— Is the flow sensor mounted in the correct position and with the correct flow direction?

— Does the temperature sensor fit correctly into the pocket (pockets shall be marked “EN 1434” or

dimensions checked)?
— Are the temperature sensors correctly installed?

— Is the thermal energy meter installed at a safe distance from sources of electromagnetic interference

(switchgear, electric motors, fluorescent lights)?
Where called for, has the thermal energy meter been correctly earthed?

— The specified protection class (IP) has to be ensured: Is every cable diameter within the minimum

and maximum diameter as specified by the manufacturer?

— Are the gaskets dedicated to the application (e.g. temperature range, pressure, durability, medium)?

— Are the accessories correctly installed according to the installation instructions of the manufacturer

and operator?

— Is the thermal energy meter seen to be functioning when the heating or cooling system starts

operating?
4.3.4 Thermal energy meter security

At the completion of commissioning, the thermal energy meter's protective devices shall be sealed by

representatives of the competent authority. For any further adjustment of the meter or for replacement

of sub-assemblies, batteries, etc., it will thus be necessary to break one or more seals.

If a seal has to be broken, then the renewal shall be conducted in conformity with the national legislation

of legal metrology.
4.4 Operating requirements with heat-conveying liquids other than water

Damage to the liquid due to overheating and oxygen influence shall be prevented by suitable design and

operational management of the system. If the liquid has been damaged, the liquid in the system shall be

exchanged.

The concentration of the heat conveying liquid other than water shall be monitored. Tapping should be

performed through the filling/draining point. Any dead volumes of stagnant liquid shall be drained before

sampling. The concentration shall be determined and documented based on a density measurement or

the refractive index (see Annex A, A.3.4) when the system is initiated. If it can be demonstrated that the

same accuracy can be achieved by another method, this method may also be used. In addition, the

determined concentration of the filled mixture shall be compared with the initial concentration of the

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liquid. If the concentration deviates by more than ± 1,0 % compared to the initial concentration, it shall

be brought to the initial concentration of the system filling (e.g. initiated by dilution or segregation).

When refilling, the concentration of the initial fluid shall be maintained. Another option is that the meter

has the functionality to self-adapt to the new physical properties of the liquid.

It shall then be checked at least every 12 months. The results of the test shall be officially documented

including following information: name of investigator, date of investigation, instrumentation used, result.

If the concentration deviates by more than ± 1,0 % compared to the initial concentration, it shall be

brought to the initial concentration of the system filling or the meter needs the functionality to self-adapt

to the physical properties of the liquid. The concentration shall be determined at a reference temperature.

This is particularly necessary because the density is highly temperature dependent.

The meter shall only be approved for liquids that have been traceably tested for their thermophysical

properties, considering a permissible density fluctuation of ± 0,001 g/cm .

The composition of the heat conveying liquid and its concentration shall be indicated on the type plate of

the heating or cooling system.
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Annex A
(informative)
Thermal energy meter installation
A.1 General

This annex gives recommendations for the installation of thermal energy meters into the heating or

cooling system of which they form a component.

It includes reference to the quality of the heat conveying liquid and contains recommendations of direct

concern to the distributor of thermal energy, the building owner and the final consumer.

A.2 Criteria for the selection of a thermal energy meter

The type, size, accuracy and environmental class of a thermal energy meter is determined according to

the operating and environmental conditions of the installation, taking into account in particular the

following:
a) pressure of the thermal energy conveying liquid;
b) physical and chemical characteristics of the thermal energy conveying liquid;
c) acceptable pressure loss across the thermal energy meter;
d) accuracy requirements;

e) temperature ranges in inlet and outlet limbs to the heating and/or cooling system and the system

temperature difference;
f) expected maximum and minimum flow rate of the heat conveying liquid;
g) required thermal power of the heating or cooling system;

h) nature of the flow rate through the thermal energy meter, whether constant, variable or intermittent;

i) requirements concerning the electrical supply to the thermal energy meter;

j) special requirements of the space around the thermal energy meter for ease of reading, security

installation and servicing of the meter;
k) requirements for connections, i.e. flanges, fittings and meter dimensions.
A.3 Quality of the heat conveying liquid
A.3.1 General

Thermal energy meters in general are constructed to withstand variations in the chemical constituents

and the acidity or alkalinity of the heat conveying liquid. However, the presence of solids in suspension

and their deposition onto the surfaces of the passages of the thermal energy meter or their effect on the

moving parts of a mechanical flow sensor causes degradation of the performance with time.

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Solids may be present as products of corrosion from the materials of which the heating system and the

supply mains are constructed. They may also be created, in the case of hot water systems, within the

circuit by the action of heat on the chemicals contained in the water.
A.3.2 Primary water quality

The quality of the water in primary circuits is in general high and closely controlled because of its boiler

origin. Hence thermal energy meters in primary circuits tend to function in a satisfactory environment.

Water quality should be according to CEN/TR 16911.
A.3.3 Secondary water quality

Thermal energy meters functioning in secondary circuits, experience shows, are more prone to problems

arising from the water quality. Water quality should be according to CEN/TR 16911.

When purchasing or specifying thermal energy meters the owner of the meter should consult with the

meter manufacturer to determine any particular water requirements.
A.3.4 Monitoring heat conveying liquids other than water

The specific heat capacity of e.g. glycol-like fluids can be measured with high effort with a relative

measurement uncertainty of 1,5 % (k = 2) while the density can be measured with high effort with an

uncertainty of 0,005 %. Combined, these values form the basis for the calculation of the enthalpy

coefficients k. The concentration of the liquid is decisive for the calculation of the change in enthalpy of

the measuring liquid between flow and return.

Knowledge of the concentration is therefore important for the accuracy of the heat output measurement,

since for a typical propylene glycol-based fluid, for example, a segregation of 1 % results in a change in

the specific heat capacity of 0,4 %, which results in a deviation of the enthalpy coefficient of 0,4 %.

Two illustrating examples (see Table 1 below): The following example shows that a typical liquid based

on propylene glycol at 20 °C with a change in concentration by 5 % (from 40 % to 35 %). The specific heat

capacity increases by approx. 3 %, while the density decreases by approx. 0,5 % and the refractive index

is reduced by approx. 0,4 %. For a typical liquid based on ethylene glycol at 20 °C, a change in the volume

fraction by 5 % (from 40 % to 35 %) leads to an increase of the specific heat capacity by approx. 2,5 %,

while the density is reduced by approx. 0,7 % and the refractive index is reduced by approx. 0,4 %.

Thus, changes in density and refractive index of the respective mixtures based on propylene or ethylene

glycol are less pronounced than their effects on the respective specific heat capacities.

Table 1— Example of fluid properties of heat transfer concentrates based on propylene and

ethylene glycol depending on the volume fraction at 20 °C
NOTE Data according to liquid manufacturer's specifications.
Refractive specific heat
volume fraction density
index capacity
Fluid base
in Vol.-% in g/cm
in nD in kJ/kg·K
30 1,029 1,3677 3,91
Propylene glycol 35 1,034 1,3734 3,83
40 1,039 1,3792 3,72
30 1,044 1,3653 3,85
Ethylene glycol 35 1,052 1,3707 3,77
40 1,059 1,3762 3,68
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Due to the thermodynamic properties of the heat conveying liquid and the expected process-related

variability of the mixture, the concentration shall be measured annually with a suitable measuring

instrument demanding high requirements (e.g. hydrometer or refractometer). The density and the

refractive index as material properties are suitable for operational control of the volume fraction of a

glycol-water mixture.

For the density and refractive index measurements, high requirements shall be demanded regarding

their measurement uncertainties
...