SIST EN 12831-3:2018

Energy performance of buildings - Method for calculation of the design heat load - Part 3: Domestic hot water systems heat load and characterisation of needs, Module M8-2, M8-3

This standard describes a method to calculate the power and the storage volume required for the dimensioning of domestic hot water systems (DHW). The applicability ranges from direct water heaters (no storage volume and a comparatively large effective heating power) to long term storage systems (e.g. seasonal storage with a comparatively small heating power and large storage volume).
This standard is applicable to the following water storage systems
-   storage charging systems characterized by a minimised mixing zone, e.g. layer-charging storage tanks or storage tanks with external heat exchangers, and
-   hot water tanks and storage systems characterized by a distinct mixing zone, e.g. storage systems with internal heat exchangers,
and for different uses.
The scope of the second part is to standardise the methods for determining the energy need for domestic hot water. This standard covers the domestic hot water needs in buildings.
The calculation of the energy needs for domestic hot water applies to a dwelling, a building or a zone of a building.
This standard also provides energy needs for different application cases of DHW-systems in hourly, monthly, and seasonal time steps, based on national default values.

Energetische Bewertung von Gebäuden - Verfahren zur Berechnung der Norm-Heizlast - Teil 3: Trinkwassererwärmungsanlagen, Heizlast und Bedarfsbestimmung, Module M8-2, M8-3

Diese Europäische Norm beschreibt ein Verfahren zur Berechnung der Leistung und des Speichervolumens, die zur Bemessung von Anlagen zur Trinkwassererwärmung erforderlich sind. Die Anwendbarkeit erstreckt sich von direkten Trinkwassererwärmern (kein Speichervolumen und eine vergleichsweise große effektive Wärmeleistung) bis hin zu größeren Speicheranlagen mit einer vergleichsweise geringen Wärmeleistung und großen Speichervolumina).
Diese Europäische Norm gilt für die folgenden Speicheranlagen für Trinkwasser:
   Speichersysteme, die durch einen minimalen Mischbereich gekennzeichnet sind (wie Schichtlade-Trinkwasserspeicher oder Trinkwasserspeicher mit externen Wärmeüberträgern). Diese Systeme werden in dieser Norm als „Speicherladesysteme“ bezeichnet;
   Speicher-Wassererwärmer und Warmwasserspeicher mit einem ausgeprägten Mischbereich (wie Trinkwarmwasser-Speicher mit internen Wärmeüberträgern) werden in dieser Norm als „gemischte Speichersysteme“ bezeichnet;
und für andere Zwecke.
Der Anwendungsbereich umfasst auch Standardisierungsverfahren zur Bestimmung des Energiebedarfs für die Trinkwassererwärmung. Diese Norm behandelt den Bedarf an erwärmtem Trinkwasser in Gebäuden.
Die Berechnung des Energiebedarfs für Anlagen zur Trinkwassererwärmung gilt für Wohn  und Nichtwohngebäude, ein sonstiges Gebäude oder für einen Bereich eines Gebäudes.
Bild 1 zeigt die relative Position dieser Norm innerhalb des EPB Normenpakets im Kontext der modularen Struktur wie in EN ISO 52000 1 dargelegt.
ANMERKUNG 1   In CEN ISO/TR 52000 2 findet sich die gleiche Tabelle mit den Nummern (für jedes Modul) der jeweiligen EPB-Normen und den dazugehörigen technischen Berichten, die bereits veröffentlicht wurden oder sich in der Erstellung befinden.
ANMERKUNG 2   Die Module repräsentieren EPB Normen, auch wenn eine EPB-Norm mehr als ein Modul abdecken kann und ein Modul von mehr als einer EPB-Norm abgedeckt werden kann, zum Beispiel jeweils ein vereinfachtes und ein detailliertes Verfahren. Siehe auch  2 und Tabellen A.1 und B.1.
Tabelle 1 zeigt die relative Position der vorliegenden Norm innerhalb des EPBD-Normenpakets

Performance énergétique des bâtiments - Méthode de calcul de la charge thermique nominale - Partie 3 : Charge thermique des systèmes de production d’eau chaude sanitaire et caractérisation des besoins, Module M8-2, M8-3

La présente Norme européenne décrit une méthode pour calculer la puissance et le volume de stockage requis pour le dimensionnement des systèmes de production d’eau chaude sanitaire. Son applicabilité s’étend des appareils de chauffage direct de l’eau (sans volume de stockage et avec une puissance efficace de chauffage comparativement importante) aux systèmes de stockage plus importants avec, comparativement, une puissance de chauffage faible et des volumes de stockage importants.
La présente Norme européenne s’applique aux systèmes de stockage de l’eau suivants :
   systèmes de stockage caractérisés par une zone de mélange minimale (comme les réservoirs de stockage à charge stratifiée ou les réservoirs de stockage avec échangeurs de chaleur externes) : ces systèmes sont dénommés dans la présente norme « systèmes de stockage à charge » ;
   appareils de chauffage de l’eau à réservoir de stockage et réservoirs de stockage d’eau chaude avec une zone de mélange prononcée (comme les réservoirs de stockage des systèmes de production d’eau chaude sanitaire avec échangeurs de chaleur internes), dénommés dans la présente norme « systèmes de stockage mélangé » ;
et pour différents usages.
Le domaine d’application inclut également des méthodes de normalisation pour déterminer le besoin énergétique pour la production d’eau chaude sanitaire. La présente Norme européenne traite des besoins d’eau chaude sanitaire dans les bâtiments.
Le calcul des besoins énergétiques des systèmes de production d’eau chaude sanitaire s’applique à des bâtiments résidentiels et non résidentiels, un bâtiment ou une zone d’un bâtiment.
La Figure 1 indique la position relative de la présente norme dans l’ensemble de normes PEB, dans le contexte de la structure modulaire définie dans l'EN ISO 52000 1.
NOTE 1   Le CEN ISO/TR 52000 2 contient le même tableau avec, pour chaque module, les numéros des normes PEB pertinentes et les rapports techniques associés qui ont été publiés ou qui sont en cours de préparation.
NOTE 2   Les modules représentent les normes PEB ; toutefois une même norme PEB peut couvrir plus d’un module et un module peut être couvert par plus d’une norme PEB, comme dans le cas d’une procédure simplifiée et d’une procédure détaillée, respectivement. Voir également l’Article 2 et les Tableaux A.1 et B.1

Energijske lastnosti stavb - Metoda za izračun projektnih toplotnih obremenitev - 3. del: Sistemi za pripravo tople sanitarne vode, toplotna obremenitev in opredelitev potreb - Modula M8-2 in M8-3

Ta standard opisuje metodo za izračun moči in potrebnega shranjevalnega prostora za dimenzioniranje sistemov vroče vode za domačo uporabo (DHW). Uporaba zajema vse od neposrednih grelnikov vode (brez shranjevalnega prostora in s primerljivo veliko efektivno močjo gretja) do sistemov za dolgotrajno shranjevanje (npr. sezonsko shranjevanje s primerljivo nizko močjo gretja in veliko shranjevalnega prostora).
Ta standard se uporablja za naslednje sisteme za shranjevanje vode:
– sistemi za polnjenje shranjevanja, za katere je značilno zmanjšano območje mešanja, npr. rezervoarji za shranjevanje s plastnim polnjenjem ali rezervoarji za shranjevanje z zunanjimi izmenjevalniki toplote in
– rezervoarji za vročo vodo in sistemi za shranjevanje, za katere je značilno posebno območje mešanja, to je sistemi shranjevanja z notranjimi izmenjevalniki toplote
ter druge uporabe.
Cilj drugega dela je standardizirati metode za določanje energijskih potreb po gospodinjski topli vodi. Ta standard pokriva potrebe po gospodinjski topli vodi v stavbah.
Izračun energijskih potreb po gospodinjski topli vodi velja za stanovanje, stavbo ali predel stavbe.
Ta standard vključuje tudi energijske potrebe za različne primere uporabe sistemov gospodinjske tople vode (DHW) v urnih, mesečnih in sezonskih korakih, glede na nacionalno privzete vrednosti.

General Information

• Status: Published
• Public Enquiry End Date: 08-Feb-2015
• Publication Date: 17-Apr-2018
• ICS: 91.140.65 - Water heating equipment
• Technical Committee: OGS - Heating for buildings
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 13-Feb-2018
• Due Date: 20-Apr-2018
• Completion Date: 18-Apr-2018
• Directive: 2010/31/EU - Directive 2010/31/eu of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast)
• Directive: TRRTP021 - Pravilnik o načinu delitve in obračunu stroškov za toploto v stanovanjskih in drugih stavbah z več odjemalci
• Directive: TRRTP126 - Tehnična smernica TSG-01-004:2010 - Učinkovita raba energije v stavbah
• Mandate: M/480 - Mandate to CEN, CENELEC and ETSI for the elaboration and adoption of standards for a methodology calculating the integrated energy performance of buildings and promoting the energy efficiency of buildings, in accordance with the terms set in the recast of the Directive on the energy performance buildings (2010/31/EU)
• Ref Project: EN 12831-3:2017 - Energy performance of buildings - Method for calculation of the design heat load - Part 3: Domestic hot water systems heat load and characterisation of needs, Module M8-2, M8-3

Relations

• Replaces: SIST EN 15316-3-1:2007 - Heating systems in buildings - Method for calculation of system energy requirements and system efficiencies - Part 3.1 Domestic hot water systems, characterisation of needs (tapping requirements)
• Effective Date: 01-May-2018
• Amended By: SIST EN 12831-3:2018/oprA1:2021 - Energy performance of buildings - Method for calculation of the design heat load - Part 3: Domestic hot water systems heat load and characterisation of needs, Module M8-2, M8-3
• Effective Date: 01-Apr-2021

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 12831-3:2018
01-maj-2018
1DGRPHãþD
SIST EN 15316-3-1:2007
(QHUJLMVNHODVWQRVWLVWDYE0HWRGD]DL]UDþXQSURMHNWQLKWRSORWQLKREUHPHQLWHY
GHO6LVWHPL]DSULSUDYRWRSOHVDQLWDUQHYRGHWRSORWQDREUHPHQLWHYLQ
RSUHGHOLWHYSRWUHE0RGXOD0LQ0
Energy performance of buildings - Method for calculation of the design heat load - Part 3:
Domestic hot water systems heat load and characterisation of needs, Module M8-2, M8-
3
Energetische Bewertung von Gebäuden - Verfahren zur Berechnung der Norm-Heizlast -
Teil 3: Trinkwassererwärmungsanlagen, Heizlast und Bedarfsbestimmung, Module M8-2,
M8-3
Performance énergétique des bâtiments - Méthode de calcul de la charge thermique
nominale - Partie 3 : Charge thermique des systèmes de production d’eau chaude
sanitaire et caractérisation des besoins, Module M8-2, M8-3
Ta slovenski standard je istoveten z: EN 12831-3:2017
ICS:
91.140.65 Oprema za ogrevanje vode Water heating equipment
SIST EN 12831-3:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 12831-3:2018

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SIST EN 12831-3:2018


EN 12831-3
EUROPEAN STANDARD

NORME EUROPÉENNE

July 2017
EUROPÄISCHE NORM
ICS 91.140.10; 91.140.65 Supersedes EN 15316-3-1:2007
English Version

Energy performance of buildings - Method for calculation
of the design heat load - Part 3: Domestic hot water
systems heat load and characterisation of needs, Module
M8-2, M8-3
Performance énergétique des bâtiments - Méthode de Energetische Bewertung von Gebäuden - Verfahren zur
calcul des déperditions calorifiques de base - Partie 3 : Berechnung der Energieanforderungen und
Charge thermique des systèmes de production d'eau Nutzungsgrade der Anlagen - Teil 3: Dimensionierung
chaude sanitaire et caractérisation des besoins, Module von Trinkwassererwärmungsanlagen und
M8-2, M8-3 Bedarfsbestimmung, Modul M8-2, M8-3
This European Standard was approved by CEN on 27 February 2017.

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. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12831-3:2017 E
worldwide for CEN national Members.

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 7
2 Normative references . 11
3 Terms and definitions . 11
4 Symbols and abbreviations . 13
4.1 Symbols . 13
4.2 Subscripts . 14
5 Description of the methods . 16
5.1 General description of the method for sizing domestic hot water systems . 16
5.2 General description of the methods for calculating the energy needs for domestic
hot water . 17
6 Calculation procedures . 17
6.1 Output data . 17
6.2 Calculation time steps . 17
6.3 Input data . 18
6.3.1 General . 18
6.3.2 Product data . 18
6.3.3 System design data . 19
6.3.4 Operating data and boundary. 19
6.3.5 Other data . 19
6.4 Calculation procedure for sizing domestic hot water systems . 19
6.4.1 Calculation of the energy needs curve for DHW . 19
6.4.2 Energy supply . 22
6.4.3 Procedure for dimensioning the DHW system . 35
6.5 Calculation procedure for determining the energy needs for domestic hot water. 38
6.5.1 Energy need for domestic hot water based on draw-off or load profiles . 38
6.5.2 Energy need for domestic hot water based on volume required . 38
6.5.3 Energy need for domestic hot water based directly on floor area . 40
6.5.4 Tabulated energy need for domestic hot water . 41
7 Quality control . 41
8 Compliance check. 41
Annex A (normative) Template for input data . 42
A.1 Load profiles . 42
A.2 Parameters to calculate energy needs . 42
A.3 Parameters for sizing DHW systems . 43
A.4 General values . 45
Annex B (informative) Default input data . 46
B.1 Load profiles . 46
B.2 Parameters to calculate energy needs . 48
B.3 Parameters for sizing DHW systems . 51
B.4 General values . 56
2

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Bibliography . 57

3

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
European foreword
This document (EN 12831-3:2017) has been prepared by Technical Committee CEN/TC 228 “Heating
systems and water based cooling systems in buildings”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by January 2018, and conflicting national standards shall
be withdrawn at the latest by January 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 15316-3-1:2007.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
The changes made to the previous edition are minor editorial corrections:
a) minor improvement readability of Figure 4;
b) correction of an incorrect term in Formula (14);
c) correction of an incorrect symbol in Figure 14.
EN 12831, Energy performance of buildings — Method for the calculation of the design heat load, is
composed with the following parts:
— Part 1: Space heating load, Module M3-3;
— Part 2: Explanation and justification of EN 12831-1, Module M3-3 [CEN/TR];
— Part 3: Domestic hot water systems heat load and characterisation of needs, Module M8-2, M8-3;
— Part 4: Explanation and justification of EN 12831-3, Module M8-2, M8-3 [CEN/TR].
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
4

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Introduction
CEN/TC 228 deals with heating systems in buildings. Subjects covered by CEN/TC 228 are:
— energy performance calculation for heating systems;
— inspection of heating systems;
— design of heating systems;
— installation and commissioning of heating systems.
This European Standard was developed to cover hourly and minutely time-steps.
This European Standard is part of a series of standards aiming at international harmonization of the
methodology for the assessment of the energy performance of buildings, called “set of EPB standards”.
All EPB standards follow specific rules to ensure overall consistency, unambiguity and transparency.
All EPB standards provide a certain flexibility with regard to the methods, the required input data and
references to other EPB standards, by the introduction of a normative template in Annex A and Annex B
with informative default choices.
For the correct use of this standard a normative template is given in Annex A to specify these choices.
Informative default choices are provided in Annex B.
Use by or for regulators: In case the standard is used in the context of national or regional legal
requirements, mandatory choices may be given at national or regional level for such specific
applications. These choices (either the informative default choices from Annex B or choices adapted to
national / regional needs, but in any case following the template of this Annex A) can be made available
as national annex or as separate (e.g. legal) document (national data sheet).
NOTE So in this case:
— the regulators will specify the choices;
— the individual user will apply the standard to assess the energy performance of a building, and thereby use
the choices made by the regulators.
Topics addressed in this standard can be subject to public regulation. Public regulation on the same
topics can override the default values in Annex B of this standard. Public regulation on the same topics
can even, for certain applications, override the use of this standard. Legal requirements and choices are
in general not published in standards but in legal documents. In order to avoid double publications and
difficult updating of double documents, a national annex may refer to the legal texts where national
choices have been made by public authorities. Different national annexes or national data sheets are
possible, for different applications.
It is expected, if the default values, choices and references to other EPB standards in Annex B are not
followed due to national regulations, policy or traditions, that:
— national or regional authorities prepare data sheets containing the choices and national or regional
values, according to the model in Annex A. In this case the national annex (e.g. NA) refers to this
text;
— or, by default, the national standards body will consider the possibility to add or include a national
annex in agreement with the template of Annex A, in accordance to the legal documents that give
national or regional values and choices.
5

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Further target groups are parties wanting to motivate their assumptions by classifying the building
energy performance for a dedicated building stock.
More information is provided in the Technical Report accompanying this standard (EN 12831-4).
6

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
1 Scope
This European Standard describes a method to calculate the power and the storage volume required for
the dimensioning of domestic hot water systems (DHW). The applicability ranges from direct water
heaters (no storage volume and a comparatively large effective heating power) to larger storage
systems with a comparatively small heating power and large storage volumes.
This European Standard is applicable to the following water storage systems:
— storage systems characterized by a minimal mixing zone, (such as stratified charging storage tanks
or storage tanks with external heat exchangers): these systems are nominated in this standard as
“charging storage systems”;
— storage tank water heaters and warm water storage tanks with a pronounced mixing zone (such as
DHW storage tanks with internal heat exchangers), nominated in this standard as “mixed storage
systems”;
and for different uses.
The Scope also includes standardization methods for determining the energy need for domestic hot
water. This European Standard covers the domestic hot water needs in buildings.
The calculation of the energy needs for DHW-Systems applies to residential and non-residential
buildings, a building or a zone of a building.
Figure 1 shows the relative position of this standard within the set of EPB standards in the context of
the modular structure as set out in EN ISO 52000-1.
NOTE 1 In CEN ISO/TR 52000-2 the same table can be found, with, for each module, the numbers of the
relevant EPB standards and accompanying technical reports that are published or in preparation.
NOTE 2 The modules represent EPB standards, although one EPB standard may cover more than one module
and one module may be covered by more than one EPB standard, for instance a simplified and a detailed method
respectively. See also Clause 2 and Tables A.1 and B.1.
Table 1 shows the relative position of this standard within the EPB package of standards.
7

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Table 1 — Position of this standard, within the modular structure of the set of EPB standards
Building
Overarching Technical Building Systems
(as such)
Building
Sub Humidif Dehumidifi Domestic Electricity
Descriptions  Descriptions  Descriptions Heating Cooling Ventilation Lighting automation
module ication cation Hot water production
and control
sub1  M1  M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
1 General  General  General 15316–1     15316–1
Common
terms and
definitions; Building Energy
2   Needs      12831–3
symbols, Needs
units and
subscripts
(Free) Indoor
Maximum
Conditions
3 Applications   Load and 12831–1     12831–3
without
Power
Systems
Ways to Ways to
Ways to
Express Express
4  Express Energy  15316–1     15316–1
Energy Energy
Performance
Performance Performance
Building
Heat Transfer
categories Emission and
5  by  15316–2 15316–2
and Building control
Transmission
Boundaries
Building
Occupancy Heat Transfer
Distribution
6 and  by Infiltration  15316–3 15316–3    15316–3
and control
Operating and Ventilation
Conditions
Aggregation
of Energy 15316–5
Internal Storage and
7 Services and   15316–5     15316–4–
Heat Gains control
Energy 3
Carriers
8

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Building
Overarching Technical Building Systems
(as such)
Building
Sub Humidif Dehumidifi Domestic Electricity
Descriptions  Descriptions  Descriptions Heating Cooling Ventilation Lighting automation
module ication cation Hot water production
and control
sub1  M1  M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
Building Solar
8   Generation
zoning Heat Gains
Combustion 15316– 15316–4–
8–1
boilers 4–1 1
15316– 15316– 15316–4–
8–2     Heat pumps
4–2 4–2 2
Thermal solar
15316– 15316–4–
8–3           15316–4–3
4–3 3
Photovoltaics
On-site 15316– 15316–4–
8–4           15316–4–4
cogeneration 4–4 4
District
15316– 15316–
8–5     heating and       15316–4–5
4–5 4–5
cooling
Direct
15316– 15316–4–
8–6     electrical
4–8 8
heater
15316–4–
8–7     Wind turbines
10
Radiant
15316–
8–8     heating,
4–8
stoves
Load
Calculated Building
dispatching
9 Energy  Dynamics
and operating
Performance (thermal mass)
conditions
Measured  Measured Measured
10 Energy Energy  Energy 15378–3     15378–3
Performance Performance Performance
9

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Building
Overarching Technical Building Systems
(as such)
Building
Sub Humidif Dehumidifi Domestic Electricity
Descriptions  Descriptions  Descriptions Heating Cooling Ventilation Lighting automation
module ication cation Hot water production
and control
sub1  M1  M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
11 Inspection  Inspection  Inspection 15378–1     15378–1
Ways to
Express
12  – BMS
Indoor
Comfort
External
13 Environment
Conditions
Economic 15459–
14
Calculation 1
NOTE The shaded modules are not applicable.
10

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 12897, Water supply — Specification for indirectly heated unvented (closed) storage water heaters
EN 50440, Efficiency of domestic electrical storage water heaters and testing methods
EN ISO 52000-1:2017, Energy performance of buildings — Overarching EPB assessment — Part 1:
General framework and procedures (ISO 52000-1:2017)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 52000-1:2017 and the
following apply.
3.1
energy storage tank
storage tank for providing thermal energy amongst others for use in domestic hot water systems
(DHW)
Note 1 to entry: The storage medium is not potable water.
3.2
centralized DHW system
DHW system where water for several building units is heated centrally and then distributed to each
building unit
3.3
potable water, cold (PWC)
water that has not been heated by the DHW system
3.4
decentralized, individual DHW system
DHW System in which PWC is distributed to each draw-off point, dwelling or building unit and then
individually heated (e.g. via a separate DHW module), in which case hot water is only distributed within
individual building units)
Note 1 to entry: In this case, hot water is only distributed within individual building units.
3.5
domestic hot water
DHW
potable water, the temperature of which has been increased by means of heat transfer
Note 1 to entry: In this standard, the term domestic hot water (DHW) is equivalent to the term potable water
hot (PWH). The usage of the term DHW also applies to non-domestic buildings and their systems.
3.6
DHW storage tank
tank for storage of domestic hot water (DHW)
11

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
3.7
mixed storage system
tank (energy storage or DHW storage tank) which is characterized by a pronounced mixing zone during
the charging phase and a minimal mixing zone during the exclusive discharging phase
Note 1 to entry: E.g. storage systems with internal heat exchangers.
Note 2 to entry: As an example see Figure 1:


a) Charging phase of a mixed storage system b) Discharging phase of a mixed storage system
Figure 1 — Phases of a mixed storage system
3.8
charging storage system
tank (energy storage or DHW storage tank) which is characterized by a minimal mixing zone during
charging and discharging phases
Note 1 to entry: Examples are: stratified charging tanks and tanks with external heat exchangers.
Note 2 to entry: As an example see Figure 2:

a) Charging phase of a charging storage b) Discharging phase of a charging storage
system system
Figure 2 — Phases of a charging storage system
3.9
summation curve
cumulated course of a time-dependent element over time
Note 1 to entry: The needs curve and the supply curve are summation curves.
12

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
3.10
needs curve
cumulated course of energy needs which is to be supplied by the DHW system
3.11
supply curve
cumulated course of energy supplied by the DHW system including the losses thereof
3.12
residual capacity curve
cumulated course of useful energy in the storage tank at the switch-ON point
3.13
distribution system
piping sections connecting the heat generator, storage system (energy- and DHW storage tanks) and
tapping points
3.14
draw-off temperature
temperature measured at the draw-off point (tapping point) of the DHW system
3.15
minimal useable draw-off temperature
minimal withdrawal temperature at a draw-off point which can still be seen as a fulfilment of the
specified temperature needs
Note 1 to entry: In systems with different temperature needs, the highest temperature needs to be applied.
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the symbols given in EN ISO 52000-1:2017 and the specific symbols
listed in Table 2 apply. Symbols and subscripts may have more than one denotation.
13

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Table 2 — Symbols and units
Symbol Name Unit
Φ Power/Wattage (Heat power) W
ϑ Temperature on the Celsius scale °C
6
Q Energy kWh or J/3,6x10 also
depending on context, absolute or time-specific kWh/[unit of time]
q´ heat loss per unit length of pipe W/m

volume flow rate (water) l/s
V
U (Linear) Thermal transmittance of the piping W/mK
l Length of the piping m
f Adjustment/correction factor or term -
ρ Density 3
kg/m or kg/l
c Specific heat capacity kJ/kgK
3
V Volume m
n number –
h Height m
x Relative amount of water drawn within a certain period of time -
t Depending on context, a period of time or a time step (e.g. 1 min) eg. min
S standing loss value [W]

4.2 Subscripts
For the purposes of this document, the subscripts given in EN ISO 52000-1:2017, and the specific
subscripts listed in Table 3 apply. Subscripts may have several denotations.
14

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
Table 3 — Subscripts
Index Meaning/Use
W Water
a Ambient
b Building needs
c Cold; referring to cold water
ch Charging
D Design
A Draw-off flow rate
sto Storage
sb Standby
dis Distribution
d, day Per day, daily
t Time; referring to a period of time or one time step within the calculation
draw Drawn; referring to properties of the water drawn-off at the tap
i General numbering index
i Loop cycle / calculation step (one cycle per each minute of the period under consideration); referring
to cumulated items
t Time step, one minute; referring to non-cumulated items
l Load, loading
h Hourly, per hour, over the time of an hour
sensor Temperature sensor of the storage tank
sup Supply
start Start; referring to (estimated) start values for iterative calculation approaches
ON Switch on point; setting, at which the temperature sensor turns on the heat generator (reheat)
OFF Switch off point; setting, at which the temperature sensor turns off the heat generator
eff Effective
HE Heat exchanger
HG Heat generator
min Minimum
max Maximum
m Mean
N Net floor area
N Nominal
lag (Time) lag

15

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SIST EN 12831-3:2018
EN 12831-3:2017 (E)
5 Description of the methods
5.1 General description of the method for sizing domestic hot water systems
This standard describes a method to determine the power and the storage volume required for
designing and dimensioning DHW systems. The method is based on a comparison of the curves of the
energy needs for domestic hot water and the energy supply from the hot water system as a function of
time.
The sizing of DHW systems can be depicted graphically. The graphical approach is called summation
curve method. Here, the energy need for DHW (needs curve) as well as the energy supply from the hot
water system (supply curve) are depicted in the form of cumulative curves for a certain time period
(usually 24 h). The hot water system is adequately designed as long as:
— the supply curve does not intersect with or fall below the needs curve in systems with a minimal
mixing zone (charging storage systems) or
— the supply curve always lies above the needs curve while maintaining a minimal distance in
systems with a distinct mixing zone (mixed storage systems).
Both curves are determined with a time step of 1 min. The input data for the needs curve can also be
given on a different time basis, such as an hourly basis. In this case, the data are broken down into equal
minutely values.
The design steps are as follows:
a) determination of the hot water needs:
1) by measuring the volume flow rate of hot water on a minutely basis and considering the hot
and cold water temperatures;
2) on the basis of statistical methods (characteristic needs);
3) on the basis of published and accepted characteristic load profiles (to be determined on a
national basis. In the absence of national values defaul
...

SLOVENSKI STANDARD
oSIST prEN 12831-3:2015
01-januar-2015
2JUHYDOQLVLVWHPLLQVLVWHPL]DKODMHQMH]YRGRYVWDYEDK0HWRGDL]UDþXQD
SURMHNWQLKWRSORWQLKREUHPHQLWHYGHO7RSORWQHREUHPHQLWYHKLãQLKWRSORYRGQLK
VLVWHPRYLQ]QDþLOQRVWLSRWUHE
Heating systems and water based cooling systems in buildings - Method for calculation
of the design heat load - Part 3: Domestic hot water systems heat load and
characterisation of needs
Heizungsanlagen und wassergeführte Kühlanlagen in Gebäuden - Verfahren zur
Berechnung der Energieanforderungen und Nutzungsgrade der Anlagen - Teil 3:
Trinkwassererwärmung, Heizlast und Bedarfsbestimmung
Systèmes de chauffage et systèmes de refroidissement à eau dans les bâtiments -
Méthode de calcul des déperditions calorifiques de base - Partie 3 : Charge thermique
des systèmes de production d’eau chaude sanitaire, caractérisation des besoins
Ta slovenski standard je istoveten z: prEN 12831-3
ICS:
91.140.65 Oprema za ogrevanje vode Water heating equipment
oSIST prEN 12831-3:2015 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 12831-3:2015

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oSIST prEN 12831-3:2015

EUROPEAN STANDARD
DRAFT
prEN 12831-3
NORME EUROPÉENNE

EUROPÄISCHE NORM

October 2014
ICS 91.140.65 Will supersede EN 15316-3-1:2007
English Version
Heating systems and water based cooling systems in buildings -
Method for calculation of the design heat load - Part 3: Domestic
hot water systems heat load and characterisation of needs
Systèmes de chauffage et systèmes de refroidissement à Heizungsanlagen und wassergeführte Kühlanlagen in
eau dans les bâtiments - Méthode de calcul des Gebäuden - Verfahren zur Berechnung der
déperditions calorifiques de base - Partie 3 : Charge Energieanforderungen und Nutzungsgrade der Anlagen -
thermique des systèmes de production d'eau chaude Teil 3: Trinkwassererwärmung, Heizlast und
sanitaire, caractérisation des besoins Bedarfsbestimmung
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 228.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12831-3:2014 E
worldwide for CEN national Members.

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
Contents
Page
Foreword .3
1 Scope .6
2 Normative references .7
3 Terms and definitions .8
4 Symbols and abbreviations . 10
4.1 Symbols . 10
4.2 Subscripts . 10
5 Sizing of domestic hot water systems. 12
5.1 General . 12
5.2 Output data . 12
5.3 Calculation time steps . 13
5.4 Input data . 13
5.5 Calculation procedure . 14
5.5.1 Energy need . 14
5.5.2 Energy supply . 16
5.5.3 Time lag of the heat generation system . 22
6 Method for calculation of energy need for domestic hot water for different installations . 24
6.1 General . 24
6.2 Energy need for domestic hot water based on tapping programs . 24
6.3 Energy need for domestic hot water based on volume required . 24
6.3.1 General . 24
6.3.2 Domestic hot water delivery temperature . 25
6.3.3 Cold water supply temperature . 25
6.3.4 Domestic hot water volume . 25
6.3.5 Single family dwellings . 25
6.3.6 Time periods . 26
6.4 Energy need for domestic hot water based directly on floor area . 26
6.5 Tabulated energy need for domestic hot water . 26
Annex A (normative) Input data . 28
A.1 Energy demand for water heating . 28
A.2 Parameters of DHW systems . 29
A.2.1 Charging factors f of hot water tanks . 29
ch
Annex B (informative) Default input data . 30
B.1 Energy demand for water heating . 30
B.2 Parameters of DHW systems . 31
B.2.1 Charging factors f of hot water tanks . 31
ch
Annex C (informative) Tapping programs for single family dwellings . 32
Annex D (informative) Informative values for calculation of the energy need for domestic hot
water in buildings . 36


2

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oSIST prEN 12831-3:2015
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Foreword
This document (prEN 12831-3:2014) has been prepared by Technical Committee CEN/TC 228 “Heating
systems and water based cooling systems in buildings”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 15316-3-1:2007.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
3

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Introduction
1)
This standard is part of a package developed to support EPBD implementation, hereafter called "EPB
standards".
CEN/TC 228 deals with heating systems in buildings. Subjects covered by CEN/TC 228 are:
 energy performance calculation for heating systems;
 inspection of heating systems;
 design of heating systems;
 installation and commissioning of heating systems.
This standard was developed to cover hourly/monthly/seasonal time-steps.
This standard includes and replaces the EN 15316-3-1:2007.
Figure 1 shows the relative position of this standard within the EPB package of standards.

1) Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of
buildings (recast)
4

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)

Building
Overarching Technical Building Systems
(as such)


sub M1
M1 sub1 M2 sub1 M3 M4 M5 M6 M7 M8 M9 M11
1  0
1 General 1 General 1 General 15316-1     15316-1
Common terms
and definitions; Building Energy
2 2 2 Needs      12831-3
symbols, units Needs
and subscripts
(Free) Indoor
Maximum Load and
3 Applications 3 Conditions without 3 12831-1     12831-3
Power
Systems
Ways to Ways to Express
Ways to Express
4 Express Energy 4 Energy 4 15316-1     15316-1
Energy Performance
Performance Performance
Building
Functions and Heat Transfer by
5 5 5 Emission & control 15316-2 15316-2
Building Transmission
Boundaries
Building
Heat Transfer by
Occupancy and
6 6 6
Infiltration and Distribution & control 15316-3 15316-3    15316-3
Operating
Ventilation
Conditions
Aggregation of
Energy Internal 15316-5
7 7 7 Storage & control 15316-5
Services and Heat Gains 15316-4-3
Energy Carriers
Building
8 8 Solar Heat Gains 8 Generation
Partitioning
   8-1 Combustion boilers 15316-4-1   15316-4-1
   8-2 Heat pumps 15316-4-2 15316-4-2  15316-4-2
Thermal solar
   8-3 15316-4-3   15316-4-3  15316-4-3
Photovoltaics
   8-4 On-site cogeneration 15316-4-4   15316-4-4  15316-4-4
District heating and
  8-5
 15316-4-5 15316-4-5    15316-4-5
cooling
Direct electrical
  8-6
 15316-4-6   15316-4-6
heater
  8-7
 Wind turbines     15316-4-7
Radiant heating,
   8-8 15316-4-8
stoves
Calculated Load dispatching
Building Dynamics
9 Energy 9 9 and operating
(thermal mass)
Performance conditions
Measured
Measured Energy Measured Energy
10 Energy 10 10 15378-3     15378-3
Performance Performance
Performance

11 Inspection 11 Inspection 11 Inspection 15378-1     15378-1
Ways to
12 Express Indoor 12 -- 12 BMS
Comfort
External
13 Environment

Conditions
Economic
14 15459-1
Calculation
Figure 1 — Position of EN 12831-3 within the modular structure

5
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic Hot water
Lighting
Building automation
& control
Electricity
production

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
1 Scope
This standard describes a method to calculate the power and the storage volume required for the
dimensioning of domestic hot water systems (DHW). The applicability ranges from direct water heaters (no
storage volume and a comparatively large effective heating power) to long term storage systems (e.g.
seasonal storage with a comparatively small heating power and large storage volume).
This standard is applicable to the following water storage systems
 storage charging systems characterized by a minimised mixing zone, e.g. layer-charging storage tanks or
storage tanks with external heat exchangers, and
 hot water tanks and storage systems characterized by a distinct mixing zone, e.g. storage systems with
internal heat exchangers,
and for different uses.
The scope of the second part is to standardise the methods for determining the energy need for domestic hot
water. This standard covers the domestic hot water needs in buildings.
The calculation of the energy needs for domestic hot water applies to a dwelling, a building or a zone of a
building.
This standard also provides energy needs for different application cases of DHW-systems in hourly, monthly,
and seasonal time steps, based on national default values.
6

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2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 15316-1, Heating and DHW systems in buildings — Part 1: General and Energy performance expression
prEN 15603, Energy performance of buildings — Overarching standard EPB
EN 12897, Water supply — Specification for indirectly heated unvented (closed) storage water heaters
7

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3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 7345:1995, prEN 15603:2013
and the following specific definitions apply.
3.1
buffer storage/tank
tank for heat storage/buffering (DHW).
3.2
centralised DHW system
DHW system where water for several building entities is heated centrally and then distributed to each building
entity.
3.3
cold water
water that has not been heated by the DHW system.
3.4
decentralised, individual DHW system
DHW system where water is distributed as cold water to each building entity and then individually heated
(e. g. separate DHW module in each apartment); here, usually, hot water is only distributed within each
building entity
3.5
energy need for domestic hot water
heat to be delivered to the needed amount of domestic hot water to raise its temperature from the cold
network temperature to the prefixed delivery temperature at the delivery point
3.6
DHW energy supply
amount of energy that the DHW system is able to deliver over the considered period of time (usually a day).
3.7
hot water
water heated by the DHW system to a specified temperature.
3.8
hot water tank
tank for heating and storage of domestic hot water (DHW).
3.9
hot water tank with distinct mixing zones
in hot water tank with distinct mixing zones, mixing of hot and cold water is not minimised by design; e. g.
tanks with internal heat exchanger.
3.10
needs curve
cumulated course of energy needs.
3.11
storage charging system
hot water or buffer tank characterised by a minimised mixing zone during the charging process (no mixing
between hot and cold water in the tank intended); e. g.
 Layer-charging tanks
8

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
 Tanks with external heat exchanger
Within this standard, storage charging always refers to hot water tanks (DHW).
3.12
summation curve
cumulated course of a time-dependent item over time; the needs curve and the supply curve are summation
curves.
3.13
supply curve
cumulated course of the energy supply that the DHW system can deliver.
9

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this European Standard, the symbols given in prEN15603:2013 and the specific symbols
listed in Table 1 apply.
Table 1 — Symbols and units
Symbol Name Unit
Φ Power/Wattage (Heat power) W
ϑ Temperature on the Celsius scale °C
Q Energy kWh or
depending on context, absolute or time-specific kWh/[unit of time]
U (Linear) Thermal transmittance of the piping W/mK
l Length of the piping m
q Specific energy, relating to a certain period of time kWh/d
f
Adjustment/correction factor or term -
ρw Density of water kg/l
cw Specific thermal capacity of (liquid) water kJ/kgK
V Volume m³
h Height
x
Relative amount of water drawn within a certain period of time -
t Depending on context, a period of time or a time step (1 minute) min

4.2 Subscripts
For the purposes of this European Standard, the subscripts given in prEN 15603:2013, and the specific
subscripts listed in Table 2 apply.
Table 2 — Subscripts
Index Meaning/Use
w Water
W Domestic hot water
c Cold; referring to cold water
sto
Storage
sb Standby
dis Distribution
d, day Per day, daily
t Time; referring to a period of time or one time step within the calculation
draw Drawn; referring to properties of the water drawn at the tap
heat-up Heating up; referring to the period of time that is required before the full power of the heat
10

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generator is available for the heating of (drinking-)water
i General numbering index
i Loop cycle / calculation step (one cycle per each minute of the period under consideration);
referring to cumulated items
t Time step, one minute; referring to non-cumulated items
ch Charging
h Hourly, per hour, over the time of an hour
sup
Supply
start Start; referring to (estimated) start values for iterative calculation approaches
r Rated, obtained from manufacturer data
pon Power on; referring to times the heat generator is on/heating
eff Effective
HG
Heat generator
min Minimum
max Maximum
m Mean
l (Time) Lag

11

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oSIST prEN 12831-3:2015
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5 Sizing of domestic hot water systems
5.1 General
This standard covers a method to determine the power and the storage volume required for domestic hot
water systems. The method is based on a comparison of the curves of the energy needs for hot water and the
energy supply from the DHW system as a function of time.
The results can be depicted graphically; the graphical approach is called summation curve method. Here, the
energy need for DHW (needs curve) as well as the energy supply from the DHW-system (supply curve) are
depicted in the form of cumulative curves for a certain time period (usually 24h). The DHW-system is not
undersized as long as
 the supply curve does not intersect with the needs in case tanks with minimised mixing zone or
 the supply curve always lies above the needs curve maintaining a minimal distance in case of tanks with
distinct mixing zone.
Both curves are determined with a time step of 1 minute.
The design steps are as follows:
 Determine the hot water needs for the building use in l/day or kWh/day along with the mean temperatures
of cold water and hot water when drawn.
 Determine the appropriate needs profile for DHW (e.g. according to a national annex to this standard,
flow measurements or values given on a statistical basis).
 Calculate the energy needs curve for DHW based on the needs profile (optional, graphic depiction in the
summation curve diagram).
 Determine the specific values of the DHW system, such as the effective heating power and the time lag of
the heat generator, buffer storage type and volume, the relative position of the temperature sensor in the
hot water tank and the specific heat losses of the storage tank and the distribution pipes.
 Calculate the energy supply curve of the DHW system (optional, graphic depiction in the summation
curve diagram).
 Compare both curves and, if required, modify/optimise the specific values of the DHW system.
5.2 Output data
This standard provides a method or (default) values to determine the following items. Note that the method
presented here may require first estimates (start values) of some items considered output data. Therefore,
some items may be both output and input data.
Table 3 — Output data
Description Symbol Unit Intended use Intended destination
module
Effective power Φ W Dimensioning of components M8-3
W
required for DHW for DHW, as
heat generators
3
Storage volume of the V M8-3
m
sto
hot water tanks
hot water tank
Daily energy needs Q kWh/d Energy demand calculation M8-2
W;b;day
for DHW
12

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5.3 Calculation time steps
The calculation time step for the purpose of sizing the DHW system is one minute. The determined energy
needs values can be converted to hourly / daily and monthly values.
5.4 Input data
The following data is required and shall be obtained from the sources named hereafter. In case of multiple
sources for one item, all sources are arranged in order of priority from highest to lowest.
Table 4 — Input data
Symbol Description Unit Source (from highest to lowest priority)
V Volume of water drawn at the time t l Building data / design

t
(minute)
National annex to this standard
Informative annex …
V Volume of water drawn per day; l Building data / design

day
optional: may be used to determine V

t National annex to this standard
Informative annex …
V
Effective size of the hot water tank l Depending on application case

sto
Manufacturer data or
Estimate (start value)
x Relative amount of water drawn each - Building data / design

h
hour of a day; optional: may be used to
National annex to this standard
determine V

t
Informative annex …
ρ Density of water kg/l National annex to this standard

w
Informative annex …
c Specific thermal capacity of water kJ/kgK National annex to this standard

w
Informative annex …
ϑ Water temperature at the tap (e. g. °C Building data / design

w;draw
45 °C)
National annex to this standard
Informative annex …
ϑ Cold-water temperature (e. g. 10 °C) °C Building data / design

w;c
National annex to this standard
Informative annex …
f Charging factor – Manufacturer data / design

ch
National annex to this standard
Informative annex …
q Standby heat loss of the hot water tank kWh/d Manufacturer data

B,sto
Estimation in accordance with EN 12897
t Heating-up time of the heat generator min Manufacturer data

heat-up
(from the perspective of water-heating)

13

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
5.5 Calculation procedure
5.5.1 Energy need
The cumulative energy need for each minute is calculated in accordance with Equation (1).The total energy
need for DHW Q is determined according to chapter 6. It can also be calculated from every-minute values
W;b
(Equation (2)).
i
Q = [Q ] with i = 1, 2, ., i
(1)
W;b;i ∑ W;b;t max
t=1
informative:
i
max
Q = max[Q ] = [Q ] (2)
W;b W;b;i ∑ W;b;t
t=1
Key
Q Cumulative energy need for water heating at the time t (one minute-value of the needs curve) [kWh]
W;b;i
Q Total energy need for water heating for one day [kWh]
W;b
Q Energy need for water heating at the time t (minute), either taken from a national annex to this
W;b;t
standard or calculated in accordance with Equation (3) [kWh]
t Time step, one minute [min]
i Loop cycle / calculation step [-]
i Maximum number of loops
max
 The method requires one loop per every-minute value of energy need. Thus, the evaluation over the
 period of one day requires 1440 loops. [-]


Figure 2 — Exemplary needs curve (summation curve diagram)
14

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
The energy need for DHW in time steps of one minute shall be calculated from the water volume drawn every
minute.
Q ⋅ x
1
W;b h

Q = V ⋅ρ ⋅ c ⋅ (ϑ −ϑ )⋅ =
W;b;t t w w w;draw w;c (3)
3600 60
Key
Q Energy demand for DHW at the time t (minute) [kWh]
W;b;t
V Volume of water drawn at the time t (minute) [l]
t
 Density of water [kg/l]
w
c Specific thermal capacity of water [kJ/kgK]

w
ϑ Temperature of the water drawn at the tap [°C]
w;draw
ϑ Cold-water temperature [°C]
w;c
x Relative amount of water drawn each hour -
h

Where no every-minute data on the drawn water-volume is available, it shall be calculated from hourly data.
x ⋅ V
h day
V =

t (4)
60
Key
V Volume of water drawn at the time t (minute) [l]
t
V Total volume of water drawn in a day [l]
day
x Relative amount of water drawn each hour -
h


Figure 3 — Exemplary needs profile, relative hot-water demand over the day given in hourly values
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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
5.5.2 Energy supply
5.5.2.1 General
The supply curve is determined by cumulating the energy supplied by the DHW system. The following DHW
systems shown in Figure 4 are covered by this standard.
Table 5 — DHW-systems covered by this standard
DHW-storage system
- central system
- directly or indirectly heated
- monovalent hot water tank
- with distinct mixing zone while
charging
- internal heat exchanger
- with or without circulation
- with or without room heating

Figure 2a — DHW storage system
- central system
- bivalent hot water tank
- with distinct mixing zone in the
stand-by volume of the tank
while charging
- internal heat exchanger
- with or without circulation
- with or without room heating

Figure 4b — DHW storage system
DHW-charging system
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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
- central system
- charging system (minimal
mixing zone during charging
and discharging of the water
tank)
- with or without circulation
- with or without room heating

Figure 4c — DHW charging system
DHW direct flow system with buffer storage
- central system
- DHW production in direct flow
- buffer storage as a charging
system (minimal mixing zone
during charging and
discharging)
- external or internal heat
exchangers
- with or without circulation

- with or without room heating
Figure 4d —DHW direct flow system with buffer
storage
- decentralised DHW system
- DHW production in direct flow
- buffer storage as a charging
system (minimal mixing zone
during charging and
discharging)
- external heat exchangers
- DHW without circulation
- circulation within the charging
system

- with or without room heating
Figure 4e — DHW direct flow system with buffer
storage

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oSIST prEN 12831-3:2015
prEN 12831-3:2014 (E)
5.5.2.2 Determination of the supply curve
The supply curve is calculated on an every-minute basis according to the following algorithms in Figure 5.
Start
i = 1 tpon = Qsup,i = Qstart i = i + 1

t
pon,start
i > 1440
Stop
Q → Memory/Table/Diagram
sup,i
i Qsup,i
1 …
2 …
3 …
… …
(Q - Q ) ≥ Q
sup,i w,b,i s,min
Power on Power off
Q = Q * min[(t /t ); 1]
eff N pon heat-up
Q = 0
eff
t = t + 1
pon pon
Q = Q – Q – Q + Q
sup,i sup,i w,sto w,dis eff

Figure 3 — Determination of the supply curve, calculation flow chart
If the difference between the supply curve and the needs curve is less than Q (Q = 0 for charging
sto;min sto;min
systems), the DHW system is not able to fulfil the needs set by the profile. In this case either the power of the
heat generator or the Volume of the hot water tank has
...