oSIST prEN 15316-7-1:2026
(Main)Energy performance of buildings - Method for calculation of system energy requirements and system efficiencies - Part 7-1: DHW instantaneous heat recovery- Module M8-13
Energy performance of buildings - Method for calculation of system energy requirements and system efficiencies - Part 7-1: DHW instantaneous heat recovery- Module M8-13
This calculation module applies to instantaneous domestic hot water heat recovery using a counter-flow heat exchanger between the drain water and the incoming domestic cold water. This module calculates the recovered heat, to be taken into account in the overall calculation procedure of the energy performance of the building.
The scope of this document is to standardize the:
- required inputs;
- calculation methods;
- required outputs;
of the instantaneous heat recovery from domestic hot water drains.
This document provides a calculation method for one calculation interval.
This calculation is intended to be connected to the whole building calculation model and takes into account the external conditions and system controls that may influence the instantaneous heat recovery from domestic hot water drains.
This document does not apply to storage heat recovery or the use of drain water as a source for heat pumps.
This document does not apply to sizing or inspection of domestic hot water heat recovery devices.
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 The same Table is found in CEN ISO/TR 52000-2, 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 might cover more than one module and one module might be covered by more than one EPB standard, for instance a simplified and a detailed method respectively. See also Clause 2 and Table A.1 and Table B.1.
Energetische Bewertung von Gebäuden - Verfahren zur Berechnung der Energieanforderungen und Nutzungsgrade der Anlagen - Unmittelbare Wärmerückgewinnung für Trinkwarmwasser, Modul M8
Dieses Berechnungsmodul gilt für die Wärmerückgewinnung von Durchlauf-Brauchwarmwasser mit Hilfe eines Gegenstrom-Wärmetauschers zwischen dem Ablaufwasser und dem Zulauf-Brauchkaltwasser. Dieses Modul berechnet die zurückgewonnene Wärme, die in dem allgemeinen Berechnungsverfahren der Energieleistung des Gebäudes zu berücksichtigen ist.
Der Anwendungsbereich dieses Dokuments besteht in der Normung der:
- notwendigen Eingabedaten;
- Berechnungsverfahren;
- notwendigen Ausgabedaten;
der Durchlauf-Wärmerückgewinnung aus Brauchwarmwasser-Abläufen.
Dieses Dokument bietet ein Berechnungsverfahren für ein Berechnungsintervall.
Diese Berechnung soll in das Berechnungsmodell für das gesamte Gebäude einbezogen werden und berücksichtigt die äußeren Bedingungen und die Systemsteuerungen, die unter Umständen die Durchlauf- Wärmerückgewinnung aus Brauchwarmwasser-Abläufen beeinflussen.
Dieses Dokument gilt nicht für die Speicher-Wärmerückgewinnung oder Verwendung von Ablaufwasser als Quelle für Wärmepumpen.
Dieses Dokument gilt nicht für die Bemaßung oder Inspektion von Wärmerückgewinnungseinrichtungen für Brauchwarmwasser.
Tabelle1 zeigt die relative Position dieses Dokuments innerhalb des EPB-Normenpakets im Kontext der in ENISO52000-1 dargelegten modularen Struktur.
ANMERKUNG1 Die gleiche Tabelle findet sich in CENISO/TR52000-2 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.
ANMERKUNG2 Die Module stellen EPB-Normen dar, auch wenn eine EPB-Norm mehr als ein Modul abdecken könnte und ein Modul von mehr als einer EPB-Norm abgedeckt sein könnte, wie es sich zum Beispiel bei einem vereinfachten und einem detaillierteren Verfahren verhält. Siehe auch Abschnitt2 und TabelleA.1 undTabelleB.1.
Performance énergétique des bâtiments - Méthode de calcul des besoins énergétiques et des rendements des systèmes - Récupération de chaleur instantanée DHW - Module M8
Energijske lastnosti stavb - Metoda za izračun energijskih zahtev in učinkovitosti sistema - 7-1. del: Takojšnja rekuperacija toplote za sanitarno vode - Modul M8-13
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2026
Energijske lastnosti stavb - Metoda za izračun energijskih zahtev in učinkovitosti
sistema - 7-1. del: Takojšnja rekuperacija toplote za sanitarno vode - Modul M8-13
Energy performance of buildings - Method for calculation of system energy requirements
and system efficiencies - Part 7-1: DHW instantaneous heat recovery- Module M8-13
Energetische Bewertung von Gebäuden - Verfahren zur Berechnung der
Energieanforderungen und Nutzungsgrade der Anlagen - Unmittelbare
Wärmerückgewinnung für Trinkwarmwasser, Modul M8
Performance énergétique des bâtiments - Méthode de calcul des besoins énergétiques
et des rendements des systèmes - Récupération de chaleur instantanée DHW - Module
M8
Ta slovenski standard je istoveten z: prEN 15316-7-1
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.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2025
ICS 91.120.10
English Version
Energy performance of buildings - Method for calculation
of system energy requirements and system efficiencies -
Part 7-1: DHW instantaneous heat recovery- Module M8-
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 - Récupération de chaleur instantanée DHW - Nutzungsgrade der Anlagen - Unmittelbare
Module M8 Wärmerückgewinnung für Trinkwarmwasser, Modul
M8
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, 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15316-7-1:2025 E
worldwide for CEN national Members.
Contents Page
Introduction . 5
1 Scope . 6
2 Normative references . 9
3 Terms and definitions . 9
4 Symbols and abbreviations . 10
4.1 Symbols . 10
4.2 Subscripts . 10
5 Description of the methods . 11
5.1 Output of the method . 11
5.2 Alternative methods . 11
5.3 System boundary . 11
5.4 Auxiliary energy . 11
6 Calculation method . 11
6.1 Output data . 11
6.2 Input data. 12
6.2.1 Product data . 12
Figure 1 — Temperatures involved in the definition of η . 13
dwhr
6.2.2 Process design description and data . 14
Figure 2 — Example of connection type A . 16
Figure 3 — Example of connection type B . 17
Figure 4 — Example of connection type C . 18
6.2.3 Operating conditions data . 19
6.2.4 Control options . 20
6.2.5 Constants and physical data . 20
6.3 Calculation time intervals . 20
6.4 Calculation procedure flow chart . 20
6.5 Calculation procedure . 20
6.5.1 General. 20
6.5.2 Domestic hot water needs related to DWHRD . 21
6.5.3 Efficiency of the DWHRD with balanced flow rate . 22
6.5.4 Recoverable heat and DWHRD heat exchanger actual efficiency . 23
6.5.5 Correction factor for transient operation . 25
6.5.6 Recovered heat . 26
6.5.7 Auxiliary energy . 27
6.5.8 Recoverable heat losses . 27
7 Quality control . 28
7.1 Calculation report . 28
7.2 Error reporting . 28
8 Compliance check . 28
Annex A (normative) Template for input data . 29
Annex B (informative) Default values . 33
Annex C (informative) Calculation flow chart . 37
Figure — A.1 . 37
Bibliography . 38
European foreword
This document (prEN 15316-7-1:2025) 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 document is currently submitted to the CEN Enquiry.
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
informative default choices in Annex B.
EPB standards deal with energy performance calculation and other related aspects (like system sizing)
to provide the building services considered in the EU EPBD Directive.
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 how to calculate the energy performance of instantaneous domestic hot water
heat recovery for domestic hot water preparation.
This document covers only instantaneous heat recovery. Storage heat recovery is not included.
For the correct use of this document, Annex A specifies the required choices and input data. Default
choices and input data are proposed 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, e.g. for the application within the context of the transposition of EU Directives into
national legal requirements. These national or regional choices can be made available as National Annex
or as separate (e.g. legal) document that override partly or entirely informative Annex B.
If the default values and choices proposed in the Annex B of this document are not followed due to
national regulations, policy or traditions, it is therefore 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 and/or application documents containing the national or regional choices and
values, in agreement with the normative template given in Annex A to this document.
1 Scope
This calculation module applies to instantaneous domestic hot water heat recovery using a counter-flow
heat exchanger between the drain water and the incoming domestic cold water. This module calculates
the recovered heat, to be taken into account in the overall calculation procedure of the energy
performance of the building.
The scope of this document is to standardize the:
— required inputs;
— calculation methods;
— required outputs;
of the instantaneous heat recovery from domestic hot water drains.
This document provides a calculation method for one calculation interval.
This calculation is intended to be connected to the whole building calculation model and takes into
account the external conditions and system controls that may influence the instantaneous heat recovery
from domestic hot water drains.
This document does not apply to storage heat recovery or the use of drain water as a source for heat
pumps.
This document does not apply to sizing or inspection of domestic hot water heat recovery devices.
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 The same Table is found in CEN ISO/TR 52000-2, 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 might cover more than one module
and one module might be covered by more than one EPB standard, for instance a simplified and a detailed method
respectively. See also Clause 2 and Table A.1 and Table B.1.
Table 1 — Position of this document, within the modular structure of the set of EPB standards
Overarching Building (as such) Technical Building Systems
sub M1 sub M2 sub M3 M4 M5 M6 M7 M8 M9 M10 M11
1 General 1 General 1 General
Common terms and
2 definitions; symbols, units 2 Building Energy Needs 2 Needs
and subscripts
(Free) Indoor Conditions
3 Applications 3 3 Maximum Load and Power
without Systems
Ways to Express Energy Ways to Express Energy Ways to Express Energy
4 4 4
Performance Performance Performance
Building Functions and Heat Transfer by
5 5 5 Emission and control
Building Boundaries Transmission
Building Occupancy and Heat Transfer by
6 6 6 Distribution and control
Operating Conditions Infiltration and Ventilation
Aggregation of Energy
7 Services and Energy 7 Internal Heat Gains 7 Storage and control
Carriers
8 Building Partitioning 8 Solar Heat Gains 8 Generation
8–1 Combustion boilers
8–2 Heat pumps
Thermal solar
8–3
Photovoltaics
8–4 On-site cogeneration
8–5 District heating and cooling
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic Hot
water
Lighting
Building
automation and
Electricity
production
Overarching Building (as such) Technical Building Systems
sub M1 sub M2 sub M3 M4 M5 M6 M7 M8 M9 M10 M11
8–7 Wind turbines
8–8 Radiant heating, stoves
Calculated Energy Building Dynamics Load dispatching and
9 9 9
Performance (thermal mass) operating conditions
Measured
Measured Energy Measured Energy
10 Energy 10 10
Performance Performance
Performance
11 Inspection 11 Inspection 11 Inspection
Ways to Express Indoor
12 12 — 12 BMS
Comfort
External Environment
13 13 Heat recovery EN XXX
Conditions
14 Economic Calculation
NOTE The shaded modules are not applicable.
Descriptions
Descriptions
Descriptions
Heating
Cooling
Ventilation
Humidification
Dehumidification
Domestic Hot
water
Lighting
Building
automation and
Electricity
production
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE Additional references are identified by the EPB module code number and the default references are
specified in Table B.1 (informative default references) according to the template given in Table A.1 (normative
template with the list of required references).
EN ISO 52000-1:2017, Energy performance of buildings — Overarching EPB assessment — Part 1: General
framework and procedures (ISO 52000-1:2017)
EN ISO 7345:2018, Thermal performance of buildings and building components - Physical quantities and
definitions (ISO 7345:2018)
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.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
Instantaneous domestic hot water heat recovery device
DWHRD
heat exchanger and related optional auxiliary devices intended to instantaneously recover heat from
drain water to preheat incoming cold domestic water
Note 1 to entry: An auxiliary device may be e.g. a pump used to lift drain water.
3.2
drain water
water flowing out from the shower device
3.3
preheated water
domestic water flowing out from the DWHR device heat exchanger after heat recovery
3.4
primary of the DWHR device
the high temperature side of the DWHR device, where drain water is flowing
3.5
secondary of the DWHR device
the low temperature side of the DWHR device, where the incoming cold domestic water is flowing
3.6
shower device
fixture where one can take a shower
Note 1 to entry: A shower device can be a shower cabin or a bathtub equipped with a shower.
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this document, the symbols given in EN ISO 52000-1, and the specific terms listed in
Table 2 apply.
Table 2 — Symbols
Symbol Units Description
V′ m /h Volumetric flow rate
V′ m /h Volume flow rate
NTU — Number of thermal units of the heat exchanger
C* — Ration of heat capacities of primary and secondary side of a heat exchanger
Δθ °C Temperature difference
4.2 Subscripts
For the purposes of this document, the subscripts given in EN ISO 52000-1, and the specific subscripts
listed in Table 3 apply.
Table 3 — Subscripts
A for type A connection – at condition A eq equivalent sec secondary
B for type B connection – at condition B exc heat exchanger shw shower
btub bath-tub hyb hybrid trans transient
C for type C connection – at condition C in input ut utilization
drain shower drain p at constant pressure wh water heater
dwhr domestic hot water heat recovery pre preheated X Any one of A, B or C
The abbreviation and acronyms used in this document are listed in Table 4.
Table 4 — Acronyms
Acronym Meaning
DWHR Drain water heat recovery
DWHRD Drain water heat recovery device
EPB Energy performance of buildings
EPBD EU directive on energy performance of buildings
5 Description of the methods
5.1 Output of the method
The method described in this module covers the calculation of:
— Recovered heat Q
W;dwhr;rvd;ci
— Recovered heat to the shower mixer Q
W;dwhr;rvd;shw,ci
— Recovered heat to the water heater Q
W;dwhr;rvd,wh,ci
— Preheated water temperature θ
W;pre,ci
— Energy for auxiliaries W
dwhr;aux,ci
— Recoverable heat losses to the heated space Q
W;dwhr;ls;rbl
This method is intended to be used for monthly and hourly calculation intervals.
5.2 Alternative methods
There is only one method. The calculation path depends on the type of connection. The considered types
of connections are identified by the identifier DWHR_CONN with values given in Table 9.
5.3 System boundary
The system boundary defines the components of the domestic hot water systems that are considered in
this module.
For the domestic water recovery subsystem, the system boundary includes:
— the domestic hot water heat recovery device;
— the preheated water pipes;
— the shower device;
— the drain water connection from the shower to the DWHRD, including any pump to raise drain water.
5.4 Auxiliary energy
The auxiliary energy of an optional drain water lifting pump is considered, if installed.
6 Calculation method
6.1 Output data
The output data are listed in Table 5.
Table 5 — Output data of this method
Intended destination
Description Symbol Unit
module
Recovered heat Q kWh M8–1
W;dwhr;rvd;ci
Recovered heat through the shower mixer Q kWh M8–1
W;dwhr;rvd;shw,ci
Recovered heat through the water heater Q kWh M8–1 to M8–7
W;dwhr;rvd,wh,ci
Preheated water temperature θ °C M8–1 to M8–7
W;pre,ci
Auxiliary energy W kWh M8–1
W;dwhr;aux,ci
Recoverable heat losses to the heated space Q kWh M2–2
W;dwhr;ls;rbl
a
Location of recoverable heat losses ZT ID M2–2
W;dwhr;pre
a
Identifier
6.2 Input data
6.2.1 Product data
6.2.1.1 Product description data (qualitative)
There is no applicable product description data.
6.2.1.2 Product technical data
6.2.1.2.1 List of product technical data
The required technical data for this calculation procedure are listed in Table 6.
Table 6 — Input product technical data list
Catalogue Validity
Characteristics Symbol Ref. Varying
unit interval
Steady-state efficiency of the DWHRD at
η % 0…100 Local NO
dwhr;X
balanced test condition X
Primary and secondary flow rate at balanced
V′ l/min 0…1 000 Local NO
dwhr;X
test condition X
Volume of water in the DWHRD Vdwhr;W l 0…100 Local NO
Mass of the heat exchanger m kg 0…1 000 Local NO
dwhr;exc
Specific heat of the heat exchanger material cdwhr;exc kWh/kg K 0…0,01 Local NO
Rated power of auxiliaries P kW 0…1 Local NO
dwhr;aux
Fraction of actual operating time of the pump k — 0…1 Local NO
dwhr;aux
6.2.1.2.2 Steady-state efficiency of the heat exchanger with balanced flow rates
The efficiency of the DWHRD η in condition X is defined as the following ratio of temperatures:
dwhr,X
θθw;pre, xx− w;cold,
(1)
η =
wwhr;x
θθw;drain,xx− w;cold,
where
θ is the preheated water temperature (outlet of the secondary of the DWHRD);
W;pre;X
θ is the cold domestic water temperature (inlet to the secondary of the DWHRD);
W;cold;X
θ is the drain water temperature (inlet to the primary of the DWHRD).
W;drain;X
NOTE Formula (1) is always true (also for unbalanced operation) because the flow rate on the secondary side
is always less than or equal to the flow on the primary side of the DWHRD and there is the same fluid (water) on
both sides.
Figure 2 identifies the above listed temperatures.
Key
1 DWHR device
Figure 1 — Temperatures involved in the definition of η
dwhr
The efficiency of the DWHRD η is declared by the manufacturer:
dwhr
— for steady-state, balanced operating conditions (temperatures are measured after they have reached
steady-state conditions given the testing flow rates);
— for at least two flow rates (conditions A and B), that should encompass the foreseen actual domestic
hot water secondary flow rate.
Testing can be performed according to EN DWHRD. The steady-state efficiency can also be based on data
collected during tests performed before the publication of EN DWHRD according to relevant national
standards, if the collected data include the required temperatures after steady-state condition is reached.
EXAMPLE Test according to NEN 8801:2022 – Annex U
6.2.1.2.3 Primary and secondary flow rate at balanced test condition X
The flow rate V′ is the value of the primary and secondary flow rate when measuring η at
dwhr;X dwhr;X
balanced test condition X. Default values for the testing flow rate are given in Table B.2.
The value of V′ is declared by the manufacturer together with the corresponding value of η .
dwhr;X dwhr;X
6.2.1.2.4 Volume of water in the DWHRD
The volume of water in the DWHRD V is the total volume of cold domestic water and drain water
dwhr;w
accumulated in the primary and secondary side of the DWHRD during steady-state operation.
The value of V is declared by the manufacturer.
dwhr;w
NOTE 1 The volume of water in the secondary side is the geometrical internal volume because domestic cold
water is pressurized. The volume of water in the primary side is usually less than the geometrical internal volume
because of open channel and gravity flow in the drain pipes.
NOTE 2 The total volume is required. It will be multiplied by 0,5 in Formula (25) of this document to take into
account the effect of the temperature profile along the DWHRD.
6.2.1.2.5 Mass of the DWHRD heat exchanger
The mass of the heat exchanger of the DWHRD m is the value declared by the manufacturer.
dwhr;exc
The mass m shall include all the materials that are in contact with cold water and drain water. If
dwhr;exc
this value is not known, the total mass of the device is used.
NOTE The total mass is required. It will be multiplied by 0,5 in Formula (25) of this document to take into
account the effect of the temperature profile along the DWHRD.
6.2.1.2.6 Specific heat of the DWHRD heat exchanger material
The specific heat of the materials of the DWHRD heat exchanger c is the value declared by the
dwhr;exc
manufacturer.
If no data is available, default values for selected materials are given in Table B.3.
6.2.1.2.7 Rated power of auxiliaries
For DWHRDs that require auxiliary energy, the power of auxiliaries P during DWHRD operation
dwhr;aux
(e.g. the pump to lift drain water) is the value declared by the manufacturer for the same test conditions
as for the efficiency measurement.
If no auxiliary energy is required, then P = 0.
dwhr;aux,X
The factor k is the fraction of time that the auxiliary is on during showering. If not declared by the
dwhr;aux
manufacturer, a default value is given in Table B.4.
6.2.2 Process design description and data
6.2.2.1 List of process design data
The process design data are given by the identifiers listed in Table 7.
Table 7 — Process design identifiers
Description Identifier Validity interval Varying
Type of hydraulic connection of the DWHRD DWHR_CONN A, B and C NO
Location of preheated water pipes ZT_W_PRE Valid thermal zone ID NO
and by the following values
Table 8 — Process design data
Characteristics Symbol Unit Validity interval Varying
Volume of water in the shower and drain V l 0…100 NO
shw;drain
Length of the pipes for preheated water Lpre,i m 0…1 000 NO
Inner diameter of the pipes for preheated water D m 0,00…1,00 NO
in;pre,i
Characteristics Symbol Unit Validity interval Varying
Recoverable fraction of preheated water pipes
k — 0…1 NO
pre;rbl
losses
Number of fixtures connected to the DWHRD Nshw;dwhrd — 0…10 NO
Number of showering fixtures Nshw — 0…10 NO
Number of bathing fixtures N — 0…10 NO
btub
Number of hybrid fixtures Nhyb — 0…10 NO
6.2.2.2 Connection type DWHR_CONN
The DWHRD can be connected in the domestic hot water system so that the preheated water is feeding:
— both the domestic hot water heater and the cold water tap, which is called connection type A, see
Figure 2;
— only the cold water tap, which is called connection type B, see Figure 3;
— only the domestic hot water heater, which is called connection type C, see Figure 4.
The connection types are indicated by the identifier DWHR_CONN. The possible values of DWHR_CONN
are listed in Table 9.
Table 9 — Values for the identifier DWHR_CONN
Description Identifier
Connection type A DWHR_CONN_A
Connection type B DWHR_CONN_B
Connection type C DWHR_CONN_C
Key
DH Domestic hot water heater
OTH To other fixtures
SEW To sewer
Figure 2 — Example of connection type A
Key
DH Domestic hot water heater
OTH To other fixtures
SEW To sewer
Figure 3 — Example of connection type B
Key
DH Domestic hot water heater
OTH To other fixtures
SEW To sewer
Figure 4 — Example of connection type C
6.2.2.3 Volume of water in the shower and drain V
shw;drain
The volume of water in the shower and drain V is the total volume of water which is accumulated
shw;drain
during steady-state operation of the shower in:
— the shower floor and walls;
— the shower drain and syphon;
— the drain pipe from the shower drain up to the DWHRD primary inlet.
If this value is not known, default values are given in Table B.5.
The value can be less than the geometrical volume of the siphon and drain pipe due to open channel,
gravity flow.
6.2.2.4 Length and inner diameter of the preheated water pipes
These are the lengths L and corresponding inner diameters D of all the preheated water pipes
pre,i in;pre,i
connecting the DWHRD secondary outlet to:
— the domestic hot water heater;
— and/or the cold water tap of the shower mixer.
NOTE The domestic hot water pipes from the domestic hot water heater outlet up to the hot water tap of the
shower mixer will not be considered here. They are already taken into account in the distribution losses, module 8–
5.
6.2.2.5 Location of preheated water pipes
The identifier ZT_W_PRE specifies in which thermal zone the pre
...
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