SIST EN 15316-5:2025

SLOVENSKI STANDARD
01-november-2025
Nadomešča:
SIST EN 15316-5:2018
Energijske lastnosti stavb - Metoda za izračun energijskih zahtev in učinkovitosti
sistema - 5. del: Sistemi za ogrevanje prostora in shranjevanje tople sanitarne
vode (brez hlajenja) - Modula M3-7 in M8-7
Energy performance of buildings - Method for calculation of system energy requirements
and system efficiencies - Part 5: Space heating and DHW storage systems (not cooling),
Module M3-7, M8-7
Energetische Bewertung von Gebäuden - Verfahren zur Berechnung der
Energieanforderungen und Nutzungsgrade der Anlagen -Teil 5: Raumheizung und
Speichersysteme für erwärmtes Trinkwasser (keine Kühlung), Modul M3-7, M8-7
Performance énergétique des bâtiments - Méthode de calcul des besoins énergétiques
et des rendements des systèmes - Partie 5 : Systèmes de stockage pour le chauffage et
l'eau chaude sanitaire (sans refroidissement), Module M3-7, M8-7
Ta slovenski standard je istoveten z: EN 15316-5:2025
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.65 Oprema za ogrevanje vode Water heating equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 15316-5
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2025
EUROPÄISCHE NORM
ICS 91.140.65 Supersedes EN 15316-5:2017
English Version
Energy performance of buildings - Method for calculation
of system energy requirements and system efficiencies -
Part 5: Space heating and DHW storage systems (not
cooling), Module M3-7, M8-7
Performance énergétique des bâtiments - Méthode de Energetische Bewertung von Gebäuden - Verfahren zur
calcul des besoins énergétiques et des rendements des Berechnung der Energieanforderungen und
systèmes - Partie 5 : Systèmes de stockage pour le Nutzungsgrade der Anlagen - Teil 5: Raumheizung und
chauffage et l'eau chaude sanitaire (sans Speichersysteme für erwärmtes Trinkwasser (keine
refroidissement), Module M3-7, M8-7 Kühlung), Modul M3-7, M8-7
This European Standard was approved by CEN on 6 July 2025.

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, 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, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 15316-5:2025 E
worldwide for CEN national Members.

Contents Page
Introduction . 5
1 Scope . 6
2 Normative references . 8
3 Terms and definitions . 8
4 Symbols and abbreviations . 9
4.1 Symbols . 9
4.2 Subscripts . 9
5 Description of the methods . 10
5.1 Output of the method . 10
5.2 Extension of the method . 10
5.3 Technologies covered and schematic of the hot water storage system . 11
5.4 Principles of the calculation of hot water storage systems by layers . 12
6 Calculation method . 14
6.1 Output data . 14
6.2 Selection of method and adaptation of calculation interval . 15
6.3 Input data . 15
6.3.1 Product data . 15
6.3.2 Source of data . 17
6.3.3 System design data . 18
6.3.4 Control . 19
6.3.5 Operating conditions . 19
6.3.6 Constants and physical data . 21
6.4 Calculation procedure . 21
6.4.1 Applicable time-step . 21
6.4.2 Operating conditions calculation . 21
6.4.3 Energy calculation (storage modelled with multi volumes – Method A) . 21
6.4.4 Energy calculation for a storage modelled with a single volume – Method B . 30
6.4.5 Calculation of the auxiliary energy . 34
6.4.6 Recoverable thermal losses . 34
7 Quality control . 34
8 Compliance check. 34
Annex A (normative) Template for input data and choices . 36
A.1 General . 36
A.2 References . 36
A.3 Model information . 37
A.4 Product description data . 37
A.4.1 Type of use (services) . 37
A.4.2 Product technical data . 38
A.4.3 Priority of heaters . 39
A.4.4 Factors for energy recovery . 39
A.5 Design data . 39
A.5.1 Storage localization . 39
A.5.2 Multiple storage units connection. 40
A.6 Operative conditions . 40
Annex B (informative) Default values . 41
B.1 General . 41
B.2 References . 41
B.3 Model information . 42
B.4 Product description data . 43
B.4.1 Type of use (services) . 43
B.4.2 Product technical data . 43
B.4.3 Priority of heaters operation . 44
B.4.4 Factors for energy recovery . 45
B.5 Design data . 45
B.5.1 Storage localization . 45
B.5.2 Multiple storage units connection. 46
B.6 Operative conditions . 46
Annex C (normative) Calculation procedure for step 7 (Method A) . 47
Bibliography . 50

European foreword
This document (EN 15316-5:2025) 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 March 2026, and conflicting national standards shall be withdrawn
at the latest by March 2026.
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 15316-5:2017.
The main changes compared to EN 15316-5:2017 are:
1) inclusion of simultaneous heating of the storage;
2) inclusion of arbitrary layer volume selection;
3) inclusion of additional heat losses due to the pipe internal circulation in storage connections;
4) calculation procedure for method A and B have been reviewed and several changes implemented;
5) Annex A contains a template for the data and parameters used in the standards and Annex B a set of
default values. Default values given in Annex B may be overridden by a national annex;
6) the previous Annexes C and D have been withdrawn;
7) inclusion of calculation approach for solving the re-arranging the layer temperatures in method A in
determined number of steps.
Any feedback and questions on this document should be directed to the users’ national standards body. A
complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: 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, Türkiye and the United Kingdom.

Introduction
This document 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.
EPB standards deal with energy performance calculation and other related aspects (like system sizing) to
provide the building services considered in the EPBD.
CEN/TC 228 deals with water based heating and cooling systems in buildings. Subjects covered by
CEN/TC 228 are:
— energy performance calculation for heating and cooling systems;
— inspection of heating systems;
— design of heating systems and water based cooling systems;
— installation and commissioning of heating systems.
This document specifies two methods to take into account the energy performance of storage systems for
heating of domestic hot water and/or space heating coupled to generation system(s) producing hot water
or using independent energy input to the storage unit. This document presents two methods applicable to
the different types of water based storage system and related controls systems:
— method A applies when the hot water is thermally stratified;
— method B applies when the hot water contained in the storage unit(s) is thermally homogeneous.
For the correct use of this document, Annex A specifies the required choices and input data. Default choices
and input data are presented in Annex B. 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, in particular for the application within the context of EU Directives transposed into national
legal requirements. These choices can be made available as National Annex or as separate (e.g. legal)
document. If the default values and choices in Annex A are not followed due to national regulations, policy
or traditions, it is expected that:
— either the national standardization body will consider the possibility to add or include a National Annex
in agreement with the template of Annex A;
— or the national or regional authorities will, in the building regulations, reference the standard and
prepare data sheets containing the national or regional choices and values, in agreement with the
template of Annex A.
This updated standard covers hourly calculation intervals (or shorter).

1 Scope
This document specifies energy performance calculation of water based storage sub-systems used for
heating, for domestic hot water or for combination of these.
This document does not apply to sizing or inspection of such storage systems.
Table 1 shows the relative position of this document 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 — Position of this document within the modular structure of the set of EPB standards
Building
Overarching Technical building systems
(as such)
sub sub sub
M1 M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
1 1 1
1 General  1 General 1 General
Common
terms and
definitions; Building
2 — 2 2 Needs — — — — — — —
symbols, energy needs
units and
subscripts
(Free) Indoor
Maximum
conditions
3 Applications — 3 3 load and — — — — — — —

without
power
systems
Ways to Ways to Ways to
express express express
4 — 4 4 — — — — — — — — —
energy energy energy
performance performance performance
Building
Heat transfer
functions and Emission and
5 — 5 by 5 — — — — — — — —
building control
transmission
boundaries
Building Heat transfer
occupancy by
Distribution
6 and — 6 infiltration 6 — — — — — — — — —
and control
operating and
conditions ventilation
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic
hot water
Lighting
Building automation and
control
Electricity production
Building
Overarching Technical building systems
(as such)
sub sub sub
M1 M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
1 1 1
Aggregation
of energy
Internal Storage and 15316- 15316-
7 services and — 7 7 — —  — —
heat gains control 5 5
energy
carriers
Building Solar
8 — 8 8 Generation — — — — — — — — —
partitioning heat gains
Combustion
8–1 — — — — — — — — —
boilers
8–2 Heat pumps — — — — — — — — —
Thermal
8–3 solar — — — — — — — — —
photovoltaics
On-site
8–4 — — — — — — — — —
cogeneration
District
8–5 heating and — — — — — — — — —
cooling
Direct
8–6 electrical — — — — — — — — —
heater
Wind
8–7 — — — — — — — — —
turbines
Radiant
8–8 heating, — — — — — — — — —
stoves
Load
Building
Calculated dispatching
dynamics
9 Energy — 9 9 and — — —  — —
(thermal
Performance operating
mass)
conditions
Measured Measured Measured
15378-
10 energy — 10 energy 10 energy — — — — 15378-3 — — —
performance performance performance
15378-
11 Inspection — 11 Inspection 11 Inspection — — — — 15378-1 — — —
Ways to
express
12 — 12 – 12 BMS        —
indoor
comfort
External
13 environment —
conditions
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic
hot water
Lighting
Building automation and
control
Electricity production
Building
Overarching Technical building systems
(as such)
sub sub sub
M1 M2  M3 M4 M5 M6 M7 M8 M9 M10 M11
1 1 1
Economic 1545
calculation 9-1
NOTE The shaded modules are not applicable.

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 ISO 7345:2018, Thermal performance of buildings and building components — Physical quantities and
definitions (ISO 7345:2018)
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 7345:2018 and
EN ISO 52000-1:2017 and the following apply.
3.1
layer
part of the volume of the whole storage which is considered having homogeneous temperature
3.2
minimum temperature of domestic hot water
minimum temperature required to state that it is usable (same as draw off temperature if neglecting thermal
losses along the pipe during draw off)
3.3
required storage output for domestic hot water
energy output from the storage to be delivered to the domestic hot water distribution system (without the
circulation loop thermal losses)
3.4
required storage output for domestic hot water circulation system
energy output from the storage to cover domestic hot water circulation loop thermal losses
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic
hot water
Lighting
Building automation and
control
Electricity production
3.5
required storage output for space heating
energy output from the storage to be delivered to space heating distribution system
3.6
usable energy
accumulated energy in the storage/layer available at the temperature above or equal to the min. required
value for domestic hot water or space heating service
3.7
energy input to the storage from the generation system
energy delivered to the storage by external/internal heater and/or solar loop
3.8
energy deficiency to be supplied by other systems
amount of energy that cannot be provided by heater(s) plus accumulated energy to cover the demand
3.9
pipe internal circulation in storage connection
natural convection induced circulation flow in connecting pipes due to temperature difference between
storage and fluid in pipes in time steps without draw-off and/or when pump in DHW circulation loop is
turned off
3.10
additional heat loss for connections with account of thermosyphon circulation
additional storage thermal loss that takes into account the presence of pipe internal circulation in storage
connections
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the symbols given in EN ISO 52000-1:2017 apply.
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 2 apply.
Table 2 —Subscripts
Subscript Term Subscript Term
bu heater ls losses
stby standby amb ambient
ref reference mn mean
vol,i layer index RT return temperature
cold cold water Hc heating circuit
ubl usable sol solar
nsup supplied by other exh heat exchanger
systems (if available)
use used sh space heating
nd needed ch consecutive hours
ncons no consumption avb available

5 Description of the methods
5.1 Output of the method
This method covers the calculation of temperature distribution within the storage unit, energy input to the
storage systems from generation systems, energy supplied by the storage systems to the domestic hot water
and space heating distribution system and thermal losses (recoverable or not) of storage systems.
5.2 Extension of the method
The method which is presented in the standard can be extended to storage systems with multiple storage
units.
The adaptation depends on the hydraulic schema used for the design of the storage system:
— serial connection – the storage units are hydraulically linked as the output of the storage unit 'n' become
the input of the storage unit 'n+1'. By default, hot water is delivered to the distribution system from
output of the last storage unit in series. The control system sets the priority of energy input to the
particular unit (e.g. based on the achieved storage units water content temperature in the previous time
step). The simplified approach involves casting series of storages into a single fictive storage with
superimposed layers (e.g. the second storage unit layers are positioned above the first storage unit
ones). The layers with energy inputs can be regarded as being supplied by the same source (generator
system). The standby heat loss coefficient of each layer should be accordingly calculated. The thermal
loss of transfer circuits between storages can be calculated according to the method for calculation of
the additional thermal loss for distribution pipes with open circuited stubs described in EN 15316-3
(M3-6, M4-6, M8-6) by using the storage units water content temperature of the preceding storage from
the previous time step. This thermal loss should then be accounted for in the subsequent storage. In
time step with no flow through the transfer circuits no thermal loss occurs. In case of insulated circuits,
the thermal loss of transfer circuits between storages can be neglected;
— parallel connection – the control system sets the priority (hot water/energy output/energy input) for
the storage units that are considered independently. The thermal loss of connecting pipes can be
accounted for in the overall thermal loss of distribution pipes according to EN 15316-3 (M3-6, M4-6,
M8-6) by adding the extra length to the distribution pipes.
NOTE 1 Parallel connection is for hygienic reasons normally used only for storage units with technical water.
NOTE 2 It is assumed that each storage unit is connected to the same incoming and outgoing distribution line.
5.3 Technologies covered and schematic of the hot water storage system
The following storage units and control systems are covered:
— type of heating source and withdraw connection: direct connection, heat exchanger;
— type of heat withdraw: domestic hot water or heating energy;
— position of heating source(s) and heat withdrawal(s) within the storage unit (Method A);
— control strategy of the storage temperature:
— based on availability of energy delivered to the storage unit(s);
— priority given to domestic hot water, then space heating (by default);
— priority to solar heating, then additional heater(s).
5.4 Principles of the calculation of hot water storage systems by layers
General model of layered storage unit is shown on Figure 1.

Key
1 layer 1 i+1 layer i+1
2 energy input n-1 layer n-1
3 energy input n layer n – number of layers
i layer i 4 mixing valve
Figure 1 — General model of the layered storage unit
Key
1 layer i
2 energy exchange due to thermal conduction with the upper layer
3 energy exchange with ambient – contribution of layer i to thermal losses
4 energy exchange due to thermal conduction with the lower layer i-1
5 energy input into layer i
6 energy exchange due to mass transfer
7 energy output from layer i
Figure 2 — Energy balance for layer i
The energy balance for layer i (Figure 2) is described by Formula (1):
.
m c (ϑ - ϑ ) = Q + Δm c (ϑ - ϑ ) + H (ϑ - ϑ ) - Q (i) - H (ϑ - ϑ
i p t+1,i t,i in,i t w,p t,i-1 i TR, i+1 t,i+1 t,i sto,ls TR, i t,i t,i-
) – Q (1)
1 out,i
where
Key 1 m c (ϑ - ϑ ) is the variation of the enthalpy of the layer i;
i p;w t+1,i ,i
Key 5 Q : is the energy input to the layer i;
t+1,i
Key 6 . is the variation of enthalpy due to mass transfer with temperature
Δm c (ϑ - ϑ )
t p t,i-1 t;i
of the underlying layer;
Key 2 H (ϑ - ϑ ) is the energy exchange due to conduction with the lower layer;
TR, i ,i t,i-1
Key 4 H (ϑ - ϑ ) is the energy exchange due to conduction with the upper layer;
TR, i+1 t,i+1 t,i
Key 3 Q (i) is the contribution of the layer i to the thermal losses of the
sto,ls
storage unit;
Key 7 Q is the energy output from the layer i.
out,i
NOTE 1 Formula (1) is only illustrative and is not directly used in the calculation.
NOTE 2 H is not determined in the standardized tests and is neglected in the calculation. Consequence of
TR
neglecting conduction heat transfer between layers in the Method A is reduced thermal stratification. The energy
balance at the storage level is respected.
6 Calculation method
6.1 Output data
The output data of this method are listed in Tables 3 and 4.
Table 3 — Output data of method A
Name Symbol Computed Unit Intended
symbol destination
Energy supplied by storage to the Q Q_X_sto_out kWh M3–1
X;sto;out
distribution system (expressed per service
M8–1
X)
Energy input to the storage from the Q Q_H_sto_X_in kWh M3–1
H;sto;X;in
generation system
M8–1
Heat losses Q Q_H_sto_ls kWh M2–2
H;sto;ls
Heat losses location (thermal zone Z Z_th ID M2-2
th
identifier)
Energy deficiency to be supplied by other Q Q_X_sto_nsup kWh M3–1
X;sto;nsup
systems (if available)
M8-1
Temperature (s) of the layer(s) within the ϑ theta_sto_vol_i °C M3-7
sto;vol,i
storage unit
M8–7
Temperature at the output of the solar loop ϑ Theta_sol_loop_i °C M3–8-3
sol;loop;in
heat exchanger (inlet to the solar loop) n
M8–8-3
Temperature at the output of the heater heat ϑ Theta_Hc_RT °C M3–1
Hc;RT
exchanger (return to generator)
M8–1
Mean temperature in the heater heat ϑ Theta_Hc_mn °C M3–1
Hc;mn
exchanger
M8–1
Table 4 — Output data of method B
Name Symbol Computed Unit Intended
symbol destination
Energy supplied by storage to the Q Q_X_sto_out kWh M3–1
X;sto;out
distribution system (expressed per service
M8–1
X)
Energy input to the storage from the Q Q_H_sto_X_in kWh M3–1
H;sto;X;in
generation system
M8–1
Heat losses location (thermal zone Z Z_th ID M2-2
th
identifier)
Heat losses Q Q_H_sto_ls kWh M2–2
H;sto;ls
Energy deficiency to be supplied by other Q Q_X_sto_nsup kWh M3–1
X;sto;nsup
systems (if available)
M8-1
Temperature of the storage unit ϑ theta_sto °C M3-7
sto
M8–7
Temperature at the output of the heater ϑ Theta_Hc_RT °C M3–1
Hc;RT
heat exchanger (return to generator)
M8–1
Mean temperature in the heater heat ϑ Theta_Hc_mn °C M3–1
Hc;mn
exchanger
M8–1
If the generators cannot provide the requested energy, the missing energy is reported in the output data (as
the energy deficiency to be supplied by other systems).
Energy output Q and Q are the thermal energies provided by the storage to the heating
H;sto;out W;sto;out
or domestic hot water distribution system in the calculation interval.
6.2 Selection of method and adaptation of calculation interval
Tables A.2 and B.2 give precise guidance for selection of the suitable method (Method A or Method B).
The methods described in Clause 6 are suitable for hourly time interval (or shorter). For the most cases, the
volume of domestic water extracted from the storage in any time step should be lower than the volume of
the storage unit affected by the heater/back-up heater. In other cases, shorter calculation time step should
be used. More details are given in the accompanying Technical Report.
6.3 Input data
6.3.1 Product data
6.3.1.1 Product description data (qualitative)
The product description data of the storage unit are described in Table 5.
Table 5 — Product description data list
Description Identifier Validity interval Varying
Type of use (services) STO_USE See Tables A.3 and B.3 NO

6.3.1.2 Product technical data
Required technical data for this calculation procedure are listed in the Table 6.
Table 6 — Product technical input data list
Characteristics Symbol Catalogue Validity Ref. Varying
unit interval
Total volume V L [0:+∞] Local NO
sto;tot
Layer volume fraction f - [0:1] Local NO
vol,i
Standby losses coefficient H W/K [0:+∞] Local NO
sto;ls
Energy input
- - - - -
(e.g. solar loop)
Position in the storage unit i Integer [1:N ] Local NO
vol
(layer)
Heat exchange coefficient of H W/K [0:+∞] Local NO
exh;sol
solar loop heat exchanger
Energy input
(e.g. external/internal heater)
- - - - -
(Storage can be equipped with
more than one heater)
Set point temperature (heater ϑ °C 0…110 Local YES/NO
sto;set;on
OFF temperature)
Heater ON temperature ϑ °C 0…110 Local YES/NO
sto;,set;on;bu
Position in the storage unit i Integer [1:N ] Local NO
vol
(layer)
Power of heater P kW [0:+∞] Local NO
sto,H,bu,i
Heat exchange coefficient of H W/K [0:+∞] Local NO
exh;bu
heater heat exchanger
Energy output
- - - - -
(e.g. heating distribution
system)
Position of the output (layer) i Integer [1:N ] Local NO
vol
NOTE Solar loop is by default connected to the lowest layer (layer 1).
Typical storage can be equipped with solar loop heat exchanger and additional heaters (e.g. heat exchanger
connected to the heating system and electrical back-up heater). Default priorities are given in Tables A.7 and
B.7.
Default values for layer volume fraction are given in Tables A.4 and B.4.
Default data on the positioning of energy input(s)/output(s) are given in Tables A.5 and B.5.
6.3.2 Source of data
The input data corresponding to the physical characteristic (volume(s), type of energy input, power of the
heater(s), and properties of the heat exchanger(s)) of the storage unit are obtained from the product data
description of the manufacturer.
The total volume V corresponds to the declared value by the manufacturer.
sto;tot
If not known, each layer volume in Method A is calculated according to Formula (2) based on data expressed
in Tables A.4 and B.4.
V fV⋅ (2)
sto;,vol i vol,i sto;tot
where
[-] is the layer volume fraction;
f
vol,i
[L] is the total volume of the storage.
V
sto;tot
The standby heat losses coefficient is expressed commonly in this document in W/K. Stand-by heat losses
are usually determined in terms of energy losses during a 24h period. Formula (3) allows the calculation of
H based on a reference value of the daily heat losses
sto;ls
1000⋅ Q
stby;;ls ref
H = (3)
sto;ls
24⋅−ϑ ϑ
( )
sto;;set ref amb;ref
where
[kWh/24h] is the standby heat losses at the standardized conditions;
Q
stby;;ls ref
[°C] is the temperature of the water in the storage for the standardized
ϑ
sto;;set ref
conditions;
[°C] is the ambient temperature for the standardized conditions.
ϑ
amb;ref
If not known, Formula (4) gives provision to calculate the corresponding value of H according to
sto;ls
different type of storage, based on data expressed in Tables A.6 and B.6.
1000 C

H ⋅ C+⋅C V (4)

sto;;ls 1 2 sto tot

C ⋅ C
Then for each layer H can be calculated by two approaches depending on the available input data.
sto;,ls i
H can be calculated according to Formula (5) based on data expressed in Table B.4.
sto;,ls i
=
=

D
+⋅f H

vol,i

⋅ H  in case of the highest and lowest layers
sto;ls
D

+ H
H = (5)

sto;,ls i
f ⋅ H

vol,i
⋅ H                  in case of all other layers

sto;ls
D

+ H

2
where
D [m] is the diameter of the storage unit (including insulation);
H [m] is the height of storage unit (including insulation).
NOTE Formula (5) assumes cylindrical shape of the storage placed vertically.
In another approach, Formula (6) allows calculation of H based in the average transmittance of storage
sto;ls,i
U
insulation .
sto
H U⋅ A (6)
sto;;ls i sto i
where
[W/m K] is the average transmittance of storage insulation;
U
sto
[m] is the layers external surface area (including insulation).
A
i
Average transmittance of storage insulation U can be estimated using Formula (7).
sto
U = (7)
sto
dd
aa
⋅ ln +
2⋅λ d − 2⋅ s h
Da a
where
[m] is the outside diameter of storage unit (including insulation);
d
a
s
[m] is the thickness of insulation;
[W/mK] is the thermal conductivity of insulation;
λ
D
[W/m K] is the total outer surface heat transfer coefficient (convection and
h
a
radiation) (see B.4.2).
6.3.3 System design data
The process design data are given in Table 7.
=
Table 7 — Process design data
Description Identifier Validity interval Varying
Location of the storage unit(s) STO_LOC See Tables A.11 and YES
(heating space, boiler room, external) B.11
Multiple storage units connection STO_MCONN See Tables A.12 and NO
B.12
Number of storage units STO_N [1:+∞] NO

6.3.4 Control
The process control options are given in Table 8.
Table 8 — Process control option
Description Identifier Validity interval Varying
Order of priority for multiple storage GEN_CTRL_PRIO [1…STO_N] NO
units
Authorization to operate the internal GEN_CRTL YES/NO YES
heating element considered from an
external signal
6.3.5 Operating conditions
Required operating conditions data for this calculation procedure are listed in Table 9.
Table 9 — Operating conditions data list
Name Symbol Unit Range Origin Varying
Module
Operating conditions data
Energy use (storage, use for heating - List - M3–1 YES
/DHW)
M8-1
Calculation interval t h 0.8760 M1–9 NO
ci
Required storage output for space Q kWh 0.∞ M3–6 YES
H;sto;out;req
heating
Temperature required for heating ϑ °C 0…100 M3–1 Yes
H;out;min
Required storage output for domestic Q kWh 0.∞ M8-1 YES
W;sto;out;req
hot water (without circulation system
M8–6
losses)
Required storage output for domestic Q kWh 0.∞ M8-1 YES
W;dis;ncons
hot water circulation system
M8–6
Minimum temperature of domestic hot ϑ °C 0–100 M8-1 NO
W;out;min
water
Name Symbol Unit Range Origin Varying
Module
Storage unit ambient temperature ϑ °C 0–100 M2-1 NO
sto;amb
Local
Solar loop energy output (input to Q kWh 0.∞ M3-8-3 YES
sol;loop;out
storage)
M8-8-3
Temperature of incoming domestic ϑ °C 0–100 M8–2 NO
W;enter
water
Local
(This can be the cold domestic water
temperature ϑ when it is the only one
Ν
or the first storage in series, or it is the
output of previous storage when
connected in series)
Number of layers N - 1-10 Local NO
vol
Temperature of layer i ϑ °C 0–110 Local YES
sto;vol,i
Part of the thermal losses transmitted to f - [0–1] Local NO
sto;m
the room
Thermal losses correction factor for f - [1–5] Local NO
sto;conn;ls,i
connecting pipes
Additional heat loss for connections H W/K [0:+∞] Local NO
sto;add;ls,i
with account of thermosyphon
circulation
NOTE 1 Q represents the energy required for domestic hot water without the thermal losses of the
W;sto;out;req
domestic hot water circulation system. Domestic hot water circulation system thermal losses are taken into account by
Q .
W;dis;nocons
Default data on the factors for energy recovery are given in Tables A.10 and B.10.
Default data on the thermal loss correction factor for connecting pipes that accounts the pipe internal
circulation in storage connections f is given in Tables A.8 and B.8. In case of detailed approach
sto;conn;ls,i
f equals 1.
sto;conn;ls,i
In the detailed approach, additional heat loss coefficient due to the pipe internal circulation in storage
connections is calculated according to Formula (8) based on the data expressed in Tables A.9 and B.9.
HLψ ⋅ (8)
sto;add;ls sto;add;ls
where
[W/mK] is the pipes linear transmittance coefficient;
ψ
sto;;add ls
L [m] is the total length of the pipes to the heat trap.

Additional heat losses due to the pipe internal circulation in storage connections is calculated only in time
steps when there is no hot water draw-off and/or when pump in DHW circulation loop is turned OFF.
=
The internal pipe circulation flow shall be distinguished from the flow in the circulation loops of DHW
systems. The heat losses in DHW circulation loops (due to fluid circulation) are calculated in the separate
standard dealing with distribution subsystem (EN 15316-3).
This detailed approach is an alternative to the use f .
sto;dis;ls
NOTE 2 In case of detailed approach f equals 1.
sto;conn;ls,I
6.3.6 Constants and physical data
Constants and physical data used in calculation is given in Table 10.
Table 10 — Constants and physical data
Name Symbol Unit Value
Water specific heat C Wh/(kg·K) 1,16
p;w
6.4 Calculation procedure
6.4.1 Applicable time-step
This procedure shall be used with the hourly time step (or shorter). Shorter time steps can be used for
adaptation to the tapping patterns and to adjust the volume of extracted domestic hot water in a calculation
time step to the calculation requirements described in 6.2.
6.4.2 Operating conditions calculation
Heat output to the domestic hot water and space heating distribution system is provided by EN 15316-1
(M3-1, M8-1).
The information obtained from the control system will set the priority given for energy storage, energy
delivery or combination of both.
The calculation is solely based on the thermal transfers due to identified inputs and outputs of energy in the
storage as well as the energy losses through storage thermal insulation considering also additional losses of
the connecting pipes that account for pipe internal circulation in storage connections.
6.4.3 Energy calculation (storage modelled with multi volumes – Method A)
...