IEC 63159-2-1:2021

Household electric instantaneous water heaters - Methods for measuring the performance - Part 2-1: Multifunctional electric instantaneous water heaters

IEC 63159-2-1:2021 applies to electric instantaneous water heaters designed to operate as multifunctional appliances with an electric rated power > 2 kW.
This document specifies tests for the assessment of the performance.
This International Standard is to be used in conjunction with IEC 63159-1:2021.

Chauffe-eau instantanés électrodomestiques - Méthodes de mesure de l’aptitude à la fonction - Partie 2-1: Chauffe-eau instantanés électriques multifonctions

L'IEC 63159-2-1:2021 s'applique aux chauffe-eau instantanés électriques conçus pour fonctionner comme des appareils multifonctions de puissance électrique assignée > 2 kW.
Le présent document spécifie les essais pour l'évaluation de l'aptitude à la fonction.
La présente Norme internationale doit être utilisée conjointement avec l'IEC 63159-1:2021.

General Information

• Status: Published
• Publication Date: 20-Oct-2021
• ICS: 91.140.65 - Water heating equipment
• Technical Committee: SC 59C - Electrical heating appliances for household and similar purposes
• Drafting Committee: WG 3 - TC 59/SC 59C/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 21-Oct-2021
• Completion Date: 19-Nov-2021

Standards Content (Sample)

IEC 63159-2-1 ®
Edition 1.0 2021-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Household electric instantaneous water heaters – Methods for measuring the
performance –
Part 2-1: Multifunctional electric instantaneous water heaters

Chauffe-eau instantanés électrodomestiques – Méthodes de mesure de
l'aptitude à la fonction –
Partie 2-1: Chauffe-eau instantanés électriques multifonctions

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IEC 63159-2-1 ®
Edition 1.0 2021-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Household electric instantaneous water heaters – Methods for measuring the

performance –
Part 2-1: Multifunctional electric instantaneous water heaters

Chauffe-eau instantanés électrodomestiques – Méthodes de mesure de

l'aptitude à la fonction –
Partie 2-1: Chauffe-eau instantanés électriques multifonctions

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 91.140.65 ISBN 978-2-8322-1040-6

– 2 – IEC 63159-2-1:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 General test conditions . 8
4.3 General conditions . 8
4.4 Test setup . 8
4.101 Symbols and units . 8
4.102 Time constants (measuring time) . 9
4.103 Test setup . 9
4.103.1 Measurement setup . 9
4.103.2 Setpoints . 9
4.103.3 Measurement of flow pressure and flow rate . 9
4.103.4 Temperature measurement . 9
5 Energy efficiency . 10
6 Performance tests . 10
6.1 Determination of classification factor CF . 10
6.1.1 General . 10
6.1.2 Definition of a reference instantaneous water heater . 10
6.1.3 Calculation method of nominal energy consumption . 11
6.1.4 Determination of energy demand of the sample . 11
6.1.5 Definition of classes H and E . 11
6.2 Determination of flow rates . 11
6.2.1 General . 11
6.2.2 E class water heater . 11
6.2.3 H class water heater . 12
6.2.4 Determination of the flow rate as a function of the pressure difference . 13
6.3 Pressure difference on activation of the heating capacity . 13
6.3.1 General . 13
6.3.2 E class water heater . 13
6.3.3 H class water heater . 13
6.4 Behaviour at switch-on of the appliance . 14
6.4.1 General . 14
6.4.2 E class water heater . 14
6.4.3 H class water heater . 15
6.5 Behaviour following the change of the flow rate . 15
6.5.1 General . 15
6.5.2 E class water heater . 15
6.5.3 H class water heater . 16
6.6 Behaviour following interruption of the flow . 17
6.6.1 General . 17
6.6.2 E class water heater . 17
6.6.3 H class water heater . 18
6.7 Behaviour at constant temperature setting . 19
6.7.1 General . 19
6.7.2 E class water heater . 19

6.7.3 H class water heater . 19
6.8 Behaviour following the change of the temperature selector setting . 19
6.8.1 General . 19
6.8.2 Electronically controlled appliances . 19
6.8.3 H class water heater . 20
6.9 Behaviour at voltage limits . 20
6.10 Additional tests for electronic instantaneous water heaters . 21
6.10.1 General . 21
6.10.2 Behaviour of the outlet temperature at decreasing water inlet
temperature . 21
6.10.3 Behaviour of the outlet temperature at changing water inlet temperature . 22
Annex A (normative) Load pattern . 23
Annex B (normative) Test setup . 24
Bibliography . 29

Figure B.101 – Single point (vented) . 24
Figure B.102 – Multi point (unvented) . 25
Figure B.103 – Test setup . 26
Figure B.104 – Damping device (Detail 4) . 27
Figure B.105 – Water connection part (Detail 5) . 27
Figure B.106 – Water connection part (Detail 6) . 28

Table 101 – Symbols and units . 8
Table 102 – Nominal values for E class water heater . 12
Table 103 – Nominal values for H class water heater . 12
Table 104 – Flow pressure and flow rate for multi point appliances . 13
Table 105 – Flow pressure and flow rate for single point appliances . 13
Table 106 – Pressure difference and flow rate . 13
Table 107 – Pressure difference and flow rate . 14
Table 108 – Behaviour at switch on of the appliance at different temperature selector
settings . 15
Table 109 – Behaviour at switch on of the appliance at different settings . 15
Table 110 – Behaviour following the change of the flow rate at different temperature
selector settings . 16
Table 111 – Behaviour following the change of the flow rate at different settings . 17
Table 112 – Behaviour following interruption of the flow . 18
Table 113 – Behaviour following interruption of the flow . 18
Table 114 – Behaviour at constant temperature setting . 19
Table 115 – Behaviour following the change of the temperature selector setting at a
flow rate of 50% . 20
Table 116 – Behaviour following the change of the temperature selector setting at a
flow rate of 100% . 20
Table 117 – Behaviour at voltage limits . 21
Table 118 – Behaviour of the outlet temperature at decreasing water inlet temperature . 22
Table 119 – Behaviour of the outlet temperature following the increase of the water
inlet temperature . 22

– 4 – IEC 63159-2-1:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HOUSEHOLD ELECTRIC INSTANTANEOUS WATER HEATERS –
METHODS FOR MEASURING THE PERFORMANCE –

Part 2-1: Multifunctional electric instantaneous water heaters

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 63159-2-1 has been prepared by subcommittee 59C: Electrical
heating appliances for household and similar purposes, of IEC technical committee 59:
Performance of household and similar electrical appliances.
The text of this International Standard is based on the following documents:
Draft Report on voting
59C/268/FDIS 59C/272/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
This International Standard is to be used in conjunction with IEC 63159-1:2021.
This standard supplements or modifies the corresponding clauses in IEC 63159-1. When a
particular subclause of IEC 63159-1 is not mentioned in this standard, that subclause is
applicable as far as reasonable. Where this standard states "addition", "modification" or
"replacement", the relevant requirements, test specifications or explanatory matter in
IEC 63159-1 should be adapted accordingly.
Subclauses or figures that are additional to those in IEC 63159-1 are numbered starting from
101. Additional annexes are lettered AA, BB, etc.
A list of all the parts in the IEC 63159 series, published under the general title Household
electric instantaneous water heaters – Methods for measuring the performance, can be found
on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 63159-2-1:2021 © IEC 2021
HOUSEHOLD ELECTRIC INSTANTANEOUS WATER HEATERS –
METHODS FOR MEASURING THE PERFORMANCE –

Part 2-1: Multifunctional electric instantaneous water heaters

1 Scope
This clause of IEC 63159-1:2021 is applicable with the following exception:
Addition:
This document applies to electrical instantaneous water heaters designed to operate as
multifunctional appliances with an electric rated power > 2 kW.
This document specifies tests for the assessment of the performance.
2 Normative references
This clause of IEC 63159-1:2021 is applicable with the following exception:
Addition:
IEC 63159-1:2021, Household electric instantaneous water heaters – Methods for measuring
the performance – Part 1: General aspects
3 Terms and definitions
This clause of IEC 63159-1 is applicable with the following exceptions:
Addition:
3.101
setpoint value
changeable value that is allocated to the appliance or the individual components thereof
3.102
pressure drop on activation of the heating capacity
pressure drop in the instantaneous water heater, at which the heating capacity is, and remains,
activated
3.103
90 % method
stop point of the measurement when 90% of value is reached
Note 1 to entry: Usually, a physical value reaches a final (average) value in an asymptotic manner. To reach a valid
measurement result, a stop point of the measurement has to be defined. The measurement is stopped when the
value finally reaches 90 % of the difference between the (average) starting value and the (average) final value.
3.104
10 %/90 % method
range between the start and stop points

Note 1 to entry: Usually, a physical value changes with a time delay in an asymptotic manner between the start
value and the final value. To reach a valid measurement result, a start point and a stop point have to be defined for
the measurement. The measurement is started when the physical value first reaches 10 % of the difference between
the (average) starting value and the (average) final value. The measurement is stopped when the value finally
reaches 90 % of the difference.

3.105
response time
time interval between the beginning of the changing of a value or parameter and the moment a
steady-state condition is obtained
Note 1 to entry: The 90 % method shall be used.
3.106
flow rate
rate at which water flows, expressed in l/min
3.107
heating-up duration
time interval between the opening of the withdrawal device and the obtainment of the final outlet
temperature
Note 1 to entry: The 90 % method shall be used.
3.108
pressure difference
difference between the pressure at the water inlet and the water outlet of the appliance at a
defined flow rate
– 8 – IEC 63159-2-1:2021 © IEC 2021
3.109
multifunctional appliances
instantaneous water heater that shall supply one or more outlets suitable for several functions,
for instance kitchen sinks, hand-washing sinks, showers and bathtubs
4 General test conditions
This clause of IEC 63159-1:2021 is applicable with the following exceptions:
4.3 General conditions
Modification:
The cold water temperature T shall be 15 °C ± 5 °C for the performance tests.
cold
4.4 Test setup
This subclause of IEC 63159-1:2021 is not applicable.
Addition:
4.101 Symbols and units
For the purposes of this document, the symbols and units of Table 101 apply.
Table 101 – Symbols and units
Symbol Unit Description
T °C The minimum setting of the temperature setting mechanism settable by user at which
min
the appliance heats.
If no user-accessible temperature selector is available, the relevant measurements
with T are not performed.
min
T °C Standard hot water temperature setpoint for various tests: 38 °C. If the temperature
setting mechanism settable by user does not permit an outlet temperature setting of
38 °C, a temperature as close as possible above 38 °C as possible shall be chosen.
This temperature shall be stated in the test report and shall be used for any further
measurements, instead of 38 °C.
The positions of the temperature setting mechanism shall be marked for reproducible
settings, taking into consideration the fact that T settings may depend on the
direction of the rotation of a knob.
If no user-accessible temperature selector is available, the temperature factory
setting is defined to be the T setting.
T °C The maximum setting of the temperature setting mechanism settable by the user.
max
If no user accessible temperature selector is available, the relevant measurements
with T are not performed.
max
T °C Temperature at the minimum permanent setting of the power selector settable by user
Pmin
at which the appliance heats.
If no user-accessible power selector is available, the relevant measurements with
T are not performed.
Pmin
T
°C Temperature at the maximum permanent setting of the power selector settable by
Pmax
user.
If no user-accessible power selector is available, the temperature factory setting is
defined to be the T setting.
Pmax
l/min The flow rate where the power consumption is 90 % of rated power at T and an inlet

V 38
90 % P
temperature of 15 °C.
Factor 
K The correction value for V if the inlet temperature differs by more than 1 K from

V 90 % P
15 °C.
Symbol Unit Description
l/min The flow rate related to the outlet temperature of 38 °C.

V
T °C Temperature from which counting of useful energy content starts.
m
T
°C Minimum (peak) temperature to be achieved during tapping.
p
T °C Cold water inlet temperature.
cold
F l/min Minimum flow rate to be reached during tapping.
P kW Minimum required instantaneous heating power to fulfil tapping.
min
T S Tapping duration.
d
P kW Minimum requited heating power of the appliance.
real
P
kW Nominal heating power of the appliance.
nom
Q kWh Nominal daily energy consumption of the appliance.
nom
Q kWh Real daily energy consumption of the appliance.
r
4.102 Time constants (measuring time)
Time constants shall be determined by means of the 10 %/90 % method.
4.103 Test setup
4.103.1 Measurement setup
The appliance shall be fixed in accordance with the installation instructions.
The measurement setup shall correspond to Figure B.101 for open-outlet appliances (single
point) and to Figure B.102 for closed-outlet (multi point) appliances.
4.103.2 Setpoints
Unless no specific setpoints for the individual test are defined, all non-user adjustable set-points
shall be adjusted in accordance with the manufacturer's instructions for a standard setup.
User adjustable selectors have to be set as follows:
– If the appliance has a power selector, the selector shall be adjusted to the highest value.
– If the appliance has a temperature-independent flow selector, it shall be adjusted to the
highest value.
– If the appliance has a flow-independent temperature selector, it shall be adjusted to the
highest value.
– All other selectors shall be set in accordance with the manufacturer's instructions.
4.103.3 Measurement of flow pressure and flow rate
Flow pressure and flow rate shall be measured in accordance with Annex B. Flow pressure shall
be determined by measuring the pressure difference.
4.103.4 Temperature measurement
The inlet and outlet temperatures of the water shall be measured using the setup shown in
Figure B.103.
– 10 – IEC 63159-2-1:2021 © IEC 2021
5 Energy efficiency
This clause of IEC 63159-1:2021 is applicable.
Replacement:
6 Performance tests
6.1 Determination of classification factor CF
6.1.1 General
To test the performance of instantaneous water heaters, it is necessary to specify classes:
"H class" (e.g. hydraulic instantaneous water heaters) and "E class" (e.g. smart electronic
instantaneous water heaters).
The following procedure shall be used to determine the classification. For that, it is necessary
to define a reference instantaneous water heater.
6.1.2 Definition of a reference instantaneous water heater
For each single tapping, the minimum required instantaneous heating power P is calculated
ref,i
as:
P ΔT× f/ 14,3
ref ,i i i
Where
14,3 is the conversion factor between units;
f is the flowrate, in accordance with Annex A
i
ΔTT−T ;
iip, cold
T is the cold water temperature;
cold
T is the temperature, in accordance with Annex A. If not given, T shall be used.
p,i m,i
Every single tapping results in a tapping duration. The time t [s] is calculated as:
d
t 3 600×Q /P
d,i tap,i ref,i
Where
Q is in accordance with Annex A.
tap,i
The reference instantaneous water heater is defined as a typical hydraulic instantaneous water
heater with two power levels of 50 % and 100 % of the nominal power P of the sample.
nom
The assumed power control of the reference instantaneous water heater is defined as follows:
– P = P , if P of a single tapping is larger than 0,5 × P ;
real,i nom ref,i nom
– otherwise P = 0,5 × P .
real,i nom
where
is the maximum rated device power of the sample;
P
nom
=
=
=
P is the defined device power for the reference unit depending on the respective tapping;
real,i
P is the minimum device power for the reference unit needed to fulfill the respective
ref,i
tapping.
6.1.3 Calculation method of nominal energy consumption
For every single daily tapping, a nominal energy consumption Q [kWh] is calculated as
nom,i
follows:
tP×
d,iireal,
Q =
nom,i
3 600
where
P is the defined device power for the reference unit depending on the respective tapping
real,i
6.1.4 Determination of energy demand of the sample
The measuring is carried out in accordance with Annex A for every different single tapping event
of a daily pattern. The flow rate is increased from zero to at least f until the appliance switches
on. If the sample has a user-accessible temperature setpoint, the temperature setpoint of the
appliance is adjusted to reach at least T or T , whichever is higher. The energy consumption
p,i m,i
P [kWh] of the unit is measured at steady-state conditions.
Calculation of real energy demand Q :
r,i
tP×
d,i i
Q =
r,i
3 600
Calculation of classification factor (CF):
The CF is based on the sum of the energy demand of every single tapping during a day, defined
in the load profiles, in comparison with the sum of the energy demand of the nominal unit.
∑Q
r,i
CF 1−
∑Q
nom,i
6.1.5 Definition of classes H and E
The classification of the instantaneous water heater is
– Class H: CF < 5 %;
– Class E: CF ≥ 5 %.
6.2 Determination of flow rates
6.2.1 General
The purpose of this test is to determine reference values for further measurements.
6.2.2 E class water heater
The appliance is operated under the boundary conditions of IEC 63159-1:2021, 4.3.

Set flow rate to V
90 % P
=
– 12 – IEC 63159-2-1:2021 © IEC 2021
– Closed outlet appliances: the water pressure difference shall be increased up to the half of

V
the nominal pressure of the appliance, if necessary. If the flow rate cannot be
90 % P
obtained, the flow rate at pressure difference of half nominal pressure of the appliance is
defined to be 100 %.

– Open outlet appliances: 0,1 MPa is the maximum useable pressure. If the flow rate V
90 % P
cannot be obtained, the flow rate at a pressure difference of 0,1 MPa is defined to be 100 %
If the inlet temperature deviates by more than 1 K from 15 °C, a correction factor K has to be

V
included:
ϑ −T
in,real 38
K = .

V
15 °C−T

The V value will be corrected to
90 % P

V × K ≙ 100 %

90 % P
V

V
Both, the outlet-temperature T and shall be stated in the test report and shall be used
90 % P
for any further measurements.
Table 102 – Nominal values for E class water heater
Rated 90 % Τ T  
VK× ≙ 100 %
in,real 38 V . K . 
90 % P V 90 % PV
power rated
power
nominal pressure pressure Flow rate ≙ 100 % [l/min]
difference
6.2.3 H class water heater
The flow rate shall be increased until the outlet temperature reaches the value of 38 °C. If a
high enough flow rate cannot be obtained, the water pressure shall be increased until the
pressure difference has reached half the nominal pressure of the appliance. For single-point
appliances, 0,1 Mpa is the maximum by which the pressure can be increased.
Nominal values shall be determined and recorded in the manner shown in Table 103.
The value of the flow rate is taken to be 100 %.
Table 103 – Nominal values for H class water heater
P T T 
nom out in V
nominal pressure pressure difference  Flow rate ≙ 100% [l/min]

6.2.4 Determination of the flow rate as a function of the pressure difference
The flow rates shall be determined at pressure differences given in Table 104 and in Table 105.
All flow limiting devices shall be fully opened. The measurement shall be carried out without
the supply voltage.
Table 104 – Flow pressure and flow rate for multi point appliances
Pressure difference Flow rate
MPa l/min
0,1
0,2
0,3
Table 105 – Flow pressure and flow rate for single point appliances
Pressure difference Flow rate
MPa l/min
0,025
0,05
0,1
6.3 Pressure difference on activation of the heating capacity
6.3.1 General
The purpose of this test is to measure the minimum pressure difference at the installation site,
to ensure a failure-free continuous operation of the appliance.
6.3.2 E class water heater
The temperature selector shall be set to the temperature setting T .
The flow rate shall be steadily increased until the heating capacity is activated. The required
pressure difference and the associated flow rate shall be given in Table 106.
Table 106 – Pressure difference and flow rate
Outlet temperature Pressure difference Flow rate Power
°C MPa l/min kW
6.3.3 H class water heater
The pressure difference shall be steadily increased until the heating capacity is activated or
switched over and remains permanently activated. The necessary flow pressure and the
corresponding flow rate shall be determined.
These measurements shall be carried out with the minimum (T ) and the maximum (T )
Pmin Pmax
permanent settings of the power and temperature selector which can be set by the user.
The pressure difference and the flow rate shall be given in Table 107.

– 14 – IEC 63159-2-1:2021 © IEC 2021
Table 107 – Pressure difference and flow rate
Outlet temperature Pressure difference Flow rate Power
°C MPa l/min kW
T
Pmin
T
Pmax
6.4 Behaviour at switch-on of the appliance
6.4.1 General
The purpose of this test is to determine the behaviour of the appliance following the opening of
the withdrawal device until stationary temperature values are obtained.
The withdrawal device has to be opened within 0,5 s.
6.4.2 E class water heater
Prior to and between the measurements, a flow rate shall be set at which the appliance does
not switch on. The flow rate shall be maintained until the inlet and the outlet temperatures no
longer differ by more than 2 K. Following this, the flow shall be interrupted.
The hydraulic conditions for a flow rate setting of 50 %, 75 % and 100 % shall be determined
for the temperature selector setting T . These hydraulic conditions shall be also used for
measurements applying T and T . The functioning of devices that automatically limit the
min max
flow rate shall not be interfered with. The actual determined flow rate values are entered into
Table 108.
The heating-up duration starts as soon as the withdrawal device is opened.
If the steady-state condition has been reached, the measurement is continued for at least one
additional minute to determine the respective temperature mean value.
The heating-up duration is considered as complete once the water outlet temperature has
reached the mean value − 1 K.
The values shall be entered into Table 108.

Table 108 – Behaviour at switch on of the appliance at different temperature selector
settings
Temperature Flow rate setting Flow rate Heating-up duration Outlet temperature,
selector setting actual value
% l/min s °C
T
min
T
T
max
6.4.3 H class water heater
Prior to, and between the measurements, a flow rate shall be set at which the appliance does
not switch on. The flow rate shall be maintained until the inlet and the outlet temperatures no
longer differ by more than 2 K. Following this, the flow shall be interrupted.
The heating-up duration starts as soon as the withdrawal device is opened. First of all wait until
the temperature reaches steady state, then measure for at least another minute in order to
determine the mean value.
The response time is determined by using the 10 %/90 % method.
The missing data shall be entered into Table 109.
Table 109 – Behaviour at switch on of the appliance at different settings
Temperature selector Flow rate setting Heating-up duration Outlet temperature,
setting (according to 6.4.2) actual value
l/min s °C
T
Pmin
T
Pmax
6.5 Behaviour following the change of the flow rate
6.5.1 General
The purpose of this test is to determine the behaviour of the appliance at varying flow rates.
The changeover of the flow rates shall be done in less than 0,5 s.
6.5.2 E class water heater
Following the increase or the decrease of the flow rate, the response time and the temperature
deviation of the water outlet temperature shall be determined as a function of the temperature
selector setting.
– 16 – IEC 63159-2-1:2021 © IEC 2021
Both before and after the flow rate is changed, wait until the temperature reaches steady state,
then measure for at least another minute in order to create a mean value of the temperature
before and after changing the flow rate. From the temperature profile occurring after steady
state has been reached, the respective mean value of the outlet temperature shall be
determined. If these mean values of the temperature at both different flow rates differ by more
than 1 K, then no value shall be indicated for the response time. For the maximum temperature
selector setting, the admissible deviation is 2 K.
The hydraulic conditions for a flow rate setting of 50 %, 75 % and 100 % shall be determined
for the temperature selector setting T (automatically operating flow-rate limiting devices
should be in position "fully open"). These hydraulic conditions shall also be used for
measurements applying T . The functioning of automatic flow-rate limiting devices shall not
max
be affected. The actual determined flow rate values are entered into Table 110.
The response time starts if the water outlet temperature leaves the mean value by more than
±1 K (±2 K at maximum temperature selector setting) and ends when this temperature enters
the new mean value with 1 K deviation (±2 K at maximum temperature selector setting).
The temperature deviation shall be given in the form of both the maximum positive and the
maximum negative deviations of the water outlet temperature from the mean value after having
changed the flow rate, occurring during response time.
The data shall be entered into Table 110.
Table 110 – Behaviour following the change of the flow rate
at different temperature selector settings
Temperature Temperature deviation Response time Outlet
Flow rate
selector setting during response time temperature at
K steady state
steady
state
l/min
+ − s °C
100 %  - - -
75 %
T
100 %
50 %
100 %
100 %  - - -
75 %
T
100 %
max
50 %
100 %
6.5.3 H class water heater
Following the increase or the decrease of the difference in pressure, the response time and the
temperature deviation of the water outlet temperature shall be determined.
Starting at a difference in pressure of half of the nominal pressure (0,1 MPa for open outlet
appliances) of the device (set to 100 %), reduce the flow rate until the difference pressure is
0,375 × nominal pressure (defined to be 75 %), and then 0,25 × nominal pressure (defined to
be 50 %). These values shall be entered into Table 111 to carry out the following tests.

Both before and after the flow rate is changed, wait until the temperature reaches steady state,
then measure for at least another minute in order to create a mean value of the temperature
before and after changing the flow-rate. From the temperature profile occurring after steady
state has been reached, the respective mean value of the outlet temperature shall be
determined.
The temperature deviation shall be given in the form of both the maximum positive and the
maximum negative deviations of the water outlet temperature from the mean value, which occur
during the response time, after having changed the flow rate.
The 10 %/90 % method is used to measure the response time.
The missing data shall be entered into Table 111.
Table 111 – Behaviour following the change of the flow rate at different settings
Power Nominal Difference  Temperature Response At steady state
pressure deviation time
selector pressure
during
response time
setting MPa
K
Actual Outlet Flow Power
value temperature rate
l/min + − s °C l/min kW
100 %  - - -
75 %
T
100 %
Pmax
...