ISO 19967-1:2019

Heat pump water heaters - Testing and rating for performance - Part 1: Heat pump water heater for hot water supply

This document specifies test conditions and test procedures for determining the performance characteristics of air source heat pump water heaters for hot water supply with electrically driven compressors with or without supplementary electric heater and connected to or including only one hot water storage tank. Hot water storage tanks that are connected in series or parallel and behave hydronically as one single tank are considered as one hot water storage tank. In the case of heat pump water heaters consisting of several parts with refrigerant or water connections, this document applies only to those designed and supplied as a complete package. NOTE This document is not applicable to testing procedures for simultaneous operation for hot water supply and space heating. "Simultaneous" means that hot water supply and space heating generation occur at the same time and may interact.

Chauffe-eau à pompe à chaleur — Essais et classification des performances — Partie 1: Chauffe-eau à pompe à chaleur pour l'alimentation en eau chaude

General Information

• Status: Published
• Publication Date: 18-Mar-2019
• ICS: 27.080 - Heat pumps
• Technical Committee: ISO/TC 86/SC 6 - Testing and rating of air-conditioners and heat pumps
• Drafting Committee: ISO/TC 86/SC 6/WG 12 - Heat pump water heaters
• Current Stage: 9093 - International Standard confirmed
• Start Date: 26-Jul-2024
• Completion Date: 13-Dec-2025

Overview

ISO 19967-1:2019 specifies standardized test conditions and procedures for determining the performance of air‑source heat pump water heaters for hot water supply. It applies to units with electrically driven compressors, with or without a supplementary electric heater, and connected to (or including) a single hot water storage tank. The standard covers installation requirements, climatic and test‑room conditions, measurement methods and reporting - but it is not applicable to combined or simultaneous hot water and space‑heating tests.

Key topics and technical requirements

• Scope and definitions: clear definitions for terms such as storage volume, reference hot water temperature, volume of mixed water at 40 °C, off‑peak products, and smart control.
• Installation and test setup: requirements for test apparatus, uncertainties of measurement, test room for the outdoor heat exchanger (air‑source units), and procedures for multi‑part packaged units.
• Settings and test conditions: prescribed settings for non‑ducted and ducted units (including external static pressure), plus general and additional test conditions.
• Performance test sequence: staged test procedure covering stabilization (stage A), filling/storage (B), filling and heating up (C), standby power (D), water draw‑offs and COP calculation (E), and reference temperature/volume at 40 °C (F).
• Energy metrics and corrections: determination of useful energy content, total energy consumption, Coefficient of Performance (COPHW), standby power input, fan/pump power corrections, and handling of off‑peak and smart control products (including the Smart Control Factor, SCF).
• Load profiles and annexes: normative and informative annexes provide standard load profiles (Annex A), SCF determination (Annex B) and operating temperature range guidance (Annex C).
• Reporting and marking: required test data to record and content for the test report, plus marking requirements for units.

Applications and who uses this standard

ISO 19967-1:2019 is designed for practical use by:

• Manufacturers and product designers for product development and warranty claims.
• Independent test laboratories and certification bodies to perform repeatable performance tests and generate comparable ratings.
• Regulators and energy labeling programs that need consistent test data for efficiency claims and compliance.
• Specifiers, procurement teams and installers who compare performance, COP and standby losses when selecting equipment for residential and light‑commercial hot water supply projects.
• R&D teams assessing smart control benefits and off‑peak operation strategies.

Related standards

• Part of the ISO 19967 series (other parts cover different heat pump water heater types and test aspects).
• Developed by ISO/TC 86 (Refrigeration and air‑conditioning), in alignment with ISO/IEC directives for standardization.

Keywords: ISO 19967-1:2019, heat pump water heaters, testing and rating, performance testing, air source heat pump, COP, smart control, load profiles, standby power, hot water storage tank.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 19967-1
First edition
2019-03
Heat pump water heaters — Testing
and rating for performance —
Part 1:
Heat pump water heater for hot
water supply
Chauffe-eau à pompe à chaleur — Essais et classification des
performances —
Partie 1: Chauffe-eau à pompe à chaleur pour l'alimentation en
eau chaude
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Installation requirements. 5
5.1 Test apparatus and uncertainties of measurement . 5
5.2 Test room for the outdoor heat exchanger of air source heat pump water heaters . 5
5.3 Installation and connection of the heat pump water heaters. 6
5.4 Installation of heat pump water heater consisting of several parts . 6
6 Settings and test conditions . 6
6.1 General . 6
6.2 Settings for non-ducted air source units . 6
6.3 Setting the external static pressure difference for ducted air source units . 7
6.4 Test conditions . 7
6.4.1 General test conditions . 7
6.4.2 Additional test conditions . 7
7 Performance test and determination of the energy consumption . 9
7.1 General . 9
7.2 Basic principles. 9
7.3 Off-peak products .10
7.4 Power input corrections .11
7.4.1 Power input of fans for heat pump water heater with duct connection .11
7.5 Stabilization [stage A] .12
7.6 Filling and storage [stage B] .12
7.7 Filling and heating up period [stage C] .12
7.8 Standby power input [stage D] .13
7.9 Water draw-offs and COP calculation [stage E] .13
7.9.1 Determination of the useful energy content .13
7.9.2 Determination of the energy consumption .15
7.9.3 Coefficient of performance (COP ) .16
HW
7.10 Reference hot water temperature and volume of mixed water at 40 °C [stage F] .16
7.11 Units with smart control . .17
7.12 Temperature operating range .17
8 Test results and test report .17
8.1 Data to be recorded .17
8.2 Test report .18
8.2.1 General information .18
8.2.2 Main results .19
9 Marking .19
Annex A (normative) Load profiles .20
Annex B (informative) Determination of the smart control factor SCF .22
Annex C (informative) Temperature operating range .28
Bibliography .30
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 86, Refrigeration and air-conditioning,
Subcommittee SC 6, Testing and rating of air-conditioners and heat pumps.
A list of all parts in the ISO 19967 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 19967-1:2019(E)
Heat pump water heaters — Testing and rating for
performance —
Part 1:
Heat pump water heater for hot water supply
1 Scope
This document specifies test conditions and test procedures for determining the performance
characteristics of air source heat pump water heaters for hot water supply with electrically driven
compressors with or without supplementary electric heater and connected to or including only one
hot water storage tank. Hot water storage tanks that are connected in series or parallel and behave
hydronically as one single tank are considered as one hot water storage tank. In the case of heat pump
water heaters consisting of several parts with refrigerant or water connections, this document applies
only to those designed and supplied as a complete package.
NOTE This document is not applicable to testing procedures for simultaneous operation for hot water supply
and space heating. “Simultaneous” means that hot water supply and space heating generation occur at the same
time and may interact.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:/ /www. iso. org/obp
— IEC Electropedia: available at http:/ /www.e lectropedia. org/
3.1
heat pump water heater for hot water supply
air source heat pump water heater with electrically driven compressors with or without
supplementary electrical heater and connected to or including a hot water storage tank for hot water
supply for human use
3.2
hot water supply
water heated for human use or household or similar purposes
3.3
storage volume
V
m
measured volume of hot water that can be contained in the storage tank
3.4
non heated space air
heat source for a heat pump which absorbs heat by an air heat exchanger in direct contact with the air
inside a space in a building which is not heated
3.5
coefficient of performance for hot water supply
COP
HW
coefficient of performance which is determined by the use of reference load profiles and which includes
the heat losses of the storage tank
3.6
reference hot water temperature
θ'
WH
temperature determined as the mean temperature value of the average temperatures during one single
draw-off which ends when the hot water temperature is below 40 °C
3.7
volume of mixed water at 40 °C
V
volume of water at 40 °C, which has the same heat content (enthalpy as the hot water which is delivered
above 40 °C at the output of the heat pump water heater
3.8
off-peak product
heat pump water heater that is energised for a maximum period of eight consecutive hours between
22:00 and 07:00 of the 24-h tapping pattern
3.9
load profile
given sequence of water draw-offs
Note 1 to entry: See Annex A.
3.10
water draw-off
given combination of useful water flow rate, useful water temperature, useful energy content and
target temperature
3.11
useful water flow rate
f(t)
minimum flow rate for the draw-off of the load profile
3.12
useful water temperature
T
m
minimum hot water temperature for the draw-off of the load profile
3.13
useful energy content
Q
tap
energy content of hot water provided at a temperature equal to, or above, the useful water temperature,
and at water flow rates equal to, or above, the useful water flow rate
3.14
target temperature
T
p
minimum water temperature to be achieved during water draw-off calculated as the mean value over
the water draw off
3.15
reference energy of the load profile
Q
ref
sum of the useful energy content of water draw-offs in a particular load profile
2 © ISO 2019 – All rights reserved

3.16
smart control
device that automatically adapts the water heating process to individual usage conditions with the aim
of reducing energy consumption
3.17
smart control factor
SCF
water heating energy efficiency gain due to smart control
3.18
standby power input
P
es
total power input of the unit during the standby test, including the power input of the unit to overcome
heat losses of the tank and the power input of any auxiliary device
3.19
coefficient of performance of smart control products
COP
smart
coefficient of performance of unit that can take benefit from a smart control
3.20
nominal volume
V
n
volume of water that is assigned to the storage tank by the manufacturer and that is marked on the tank
3.21
operating range
working range for the heat pump water heater as specified by the manufacturer
4 Symbols and abbreviated terms
Symbol Description Units
SCF smart control factor —
COP coefficient of performance for a given reference load profile —
HW
COP coefficient of performance of smart control products —
smart
C specific heat capacity of water kJ/(kg·K)
p
Δp measured external static pressure difference Pa
e
Δp measured internal static pressure difference Pa
i
f minimum flow rate for which hot water is contributing to the reference energy l/min
f maximum flow rate of considered load profile l/min
max
f (t) flow rate of hot water during draw-off l/min
max
f(t) useful water flow rate l/min
i index for the draw-off —
m difference of the two weights (filled / empty) of the hot water storage tank kg
act
η efficiency of the fan is 0.3 -
n number of draw-offs during the load profile —
tap
P standby power input kW
es
P measured average power consumption for off-peak products kW
s
Q calculated heat energy produced by electrical resistance heater during the whole load profile kWh
EL-LP
Calculated heat energy produced by electrical resistance heater to reach the required
Q kWh
EL-tap
tapping temperature
Q useful energy during one single draw-off kWh
HP-tap
Symbol Description Units
Q total useful energy content during the whole load profile kWh
LP
total useful energy consumption during the smart period of the smart cycle
smart
kWh
Q
elec
total useful energy content during the smart period of the smart cycle
smart
kWh
Q
LP
Total electricity consumption during the reference period of the smart cycle
ref
kWh
Q
elec
total useful energy content during the reference period of the smart cycle
ref
kWh
Q
LP
Total electricity consumption of the WHL control cycle
WHL,C
kWh
Q
elec
Q reference energy of the considered load profile kWh
ref
energy content of hot water provided at a temperature equal to, or above, the useful
Q kWh
tap
water temperature, and at water flow rates equal to, or above, the useful water flow rate
ρ(T) density of water at temperature T kg/m
t test phase duration s
d
t duration of the last on-off-cycle of the heat pump water heater s
es
t heating up time s
h
t time from starting the draw-off until θ is less than 40 °C s
40 WH
t duration of a draw-off of useful water s
tap
t load profile time / duration h
TTC
T dry bulb temperature °C
DB
T useful water temperature at which hot water starts contributing to the reference energy °C
m
T target water temperature to be achieved during water draw-off °C
p
T Wet bulb temperature °C
WB
θ incoming cold water temperature °C
WC
θ (t) incoming cold water temperature during draw-off °C
WC
θ outgoing hot water temperature °C
WH
θ (t) hot water temperature during draw-off °C
WH
θ' reference hot water temperature °C
WH
V nominal air volume flow rate m /s
air
V measured liquid volume flow rate m /s
Fluid
V measured volume of a hot water storage tank l
m
V mixed volume of mixed water at 40 °C l
V volume of water that is assigned to the storage tank by the manufacturer and marked on it l
n
W total electricity consumption during the test duration t kWh
eh-HP h
W measured electricity consumption during the test duration t kWh
eh-M h
W correction due to electricity consumption of fan/liquid pump kWh
EL-Corr
W total electrical energy consumption during the whole load profile kWh
EL-LP
W total measured electrical energy input kWh
EL-M-LP
W calculated energy consumption for off-peak products kWh
EL-OFF
W total energy input during the last on-off-cycle kWh
es-HP
W measured energy consumption during the last on-off cycle kWh
es-M
4 © ISO 2019 – All rights reserved

5 Installation requirements
5.1 Test apparatus and uncertainties of measurement
The test apparatus shall be designed in such a way that all requirements for adjustment of set values,
stability criteria and uncertainties of measurement according to this document can be fulfilled.
Water systems or other heat transfer liquid systems shall be sufficiently free of entrained gas as to
ensure that the measured results are not significantly influenced.
The inlet and outlet temperatures of the hot water supply are measured in the centre of the flow and
as close as possible to the appliance. The response time of the temperature sensor and the sampling
interval shall be chosen to maintain the uncertainties in Table 1. Ducted air systems shall be sufficiently
airtight to ensure that the measured results are not significantly influenced by exchange of air with the
surroundings.
For inverter type control units, the setting of the frequency shall be done for each rating condition. The
manufacturer shall provide in the documentation information instructions on obtaining the necessary
data to set the required frequencies. If skilled personnel with knowledge of control software are
required for the start of the system, the manufacturer or the nominated agent should be in attendance
when the system is being installed and prepared for tests.
The uncertainties of measurement shall not exceed the values specified in Table 1.
Table 1 — Uncertainties of measurement
Measured quantity Unit Uncertainty
Hot water supply
Temperature °C 0,15 K
Temperature difference K 0,15 K
Volume L 2 %
Volume flow l/min 2 %
Thermal energy kWh 5 %
Air (heat source)
Dry bulb temperature °C 0,2 K
Wet bulb temperature °C 0,4 K
Volume flow m /h 5 %
5 Pa (∆P ≤ 100 Pa)
Static pressure difference Pa
5 % (∆P ≥ 100 Pa)
Electrical quantities
For ≥10 W, 1 %
Electric power W
For <10 W, 0.1 W
Electrical energy kWh 1 %
Voltage V 0,5 %
current A 0,5 %
Ambient
Ambient temperature indoors °C 0,5 K
5.2 Test room for the outdoor heat exchanger of air source heat pump water heaters
The size of the test room shall be selected to avoid any resistance to air flow at the air inlet and air
outlet orifices of the test object. The air flow through the room shall not be capable of initiating any
short circuit between the two orifices, and therefore the velocity of air flow at these two locations shall
not exceed 1,5 m/s when the test object is switched off.
Unless otherwise stated by the manufacturer, the air inlet and air outlet orifices shall not be less than
1 m from the surfaces of the test room; this also applies to any measuring ducts.
Any direct heat radiation (e.g. solar radiation) onto heating units in the test room onto the heat pump
water heater or onto the temperature measuring points shall be avoided.
5.3 Installation and connection of the heat pump water heaters
The heat pump water heater shall be installed and connected for the test as recommended by the
manufacturer’s installation and operation manual. The accessories provided by option (for example
heating element) are not included in the test. Temperature and pressure measuring points shall be
arranged in order to obtain representative mean values.
5.4 Installation of heat pump water heater consisting of several parts
In the case of heat pump water heaters consisting of several refrigeration parts (split heat pump water
heater) the following installation conditions shall be complied with for the tests:
a) each refrigerant line shall be installed in accordance with the manufacturer's instructions; the
length of each line shall be between 5 m and 7,5 m;
b) the lines shall be installed so that the difference in elevation does not exceed 2,5 m;
c) thermal insulation shall be applied to the lines in accordance with the manufacturer's instructions;
d) unless constrained by the design, at least half of the interconnecting lines shall be exposed to the
outdoor conditions with the rest of the lines exposed to the indoor conditions.
For indirect systems where the heat pump water heater is separated from the tank, water or brine
connections to the tank shall be installed in accordance with the manufacturer’s instructions to the
maximum stated length or 5 m whichever is shorter. Piping shall be well insulated and made as short as
possible and with as few bends as possible.
6 Settings and test conditions
6.1 General
Set points for internal control equipment of the unit such as thermostats, pressure switches or mixing
valves shall be set to the values as stated in the installation and operating instructions. If several set
points or a range are stated, the manufacturer shall indicate the one to be used for the tests.
Thermostat settings and settings for supplementary electrical heaters shall be done according to the
installations and operating instructions and shall remain in the same position for the duration of the
test. If the heat pump water heater is equipped with a mixing valve for the hot water, this valve shall be
set at the manufacturer's recommended setting throughout the test.
6.2 Settings for non-ducted air source units
For non-ducted units, the adjustable settings such as louvers and fan speed shall be set according to the
installation and operating instructions. Without information from the manufacturer, louvers and fan
speed shall be set for maximum air flow rate.
6 © ISO 2019 – All rights reserved

6.3 Setting the external static pressure difference for ducted air source units
The volume flow and the pressure difference shall be related to standard air and with a dry heat
exchanger. If the air flow rate is given by the manufacturer with no atmospheric pressure, temperature,
and humidity conditions, it shall be considered as given for standard air conditions.
The air flow rate as stated in the installation and operating instructions shall be converted into
standard air conditions. The air flow rate setting shall be made when the fan only is operating.
The rated air flow rate as stated in the installation and operating instructions shall be set and the
resulting external static pressure (ESP) measured.
If the ESP is lower than 30 Pa, the air flow rate is decreased to reach this minimum value. The apparatus
used for setting the ESP shall be maintained in the same position during all the tests.
If the installation and operating instructions state that the maximum allowable duct length is for inlet
and outlet together less than 2 m, then the unit shall be tested with the duct length and the ESP is
considered to be 0.
6.4 Test conditions
6.4.1 General test conditions
The tests shall be carried out at the test conditions specified in Table 3 and Table 4 as appropriate.
Permissible deviations shall not exceed the values specified in Table 2. In addition, the maximal
permissible deviation of thermal energy for the complete load profile shall be less than 5 %.
6.4.2 Additional test conditions
Table 2 — Variations allowed for the test conditions when the heat pump water heater is running
Variations of arithmetical mean values Variation of individual readings from speci-
Readings
from specified test conditions fied test conditions
Interval Interval Interval Interval Interval Interval
a b c a b c
H D S H D S
Air temperature
d
dry-bulb ±0,6 K ±1,5 K ±1,0 K ±5,0 K ±2,5 K
— wet-bulb ±0,3 K ±1,0 K ±0,6 K —
— volume
±5 % ±10 %
flow
— static
pressure — ±10 %
difference
— ambient
temperature
of the tank
±1 K ±2 K
(if not used as
heat source)
a
Interval H applies when the heat pump water heater is in the heating mode, except for the first 10 min after termination
of a defrost cycle, and the first 10 min after a restart of the heat pump water heater.
b
Interval D applies during a defrost cycle and during the first 10 min after the termination of a defrost cycle when the
heat pump water heater is operating in the heating mode.
c
Interval S applies when the compressor is stopped and during the first 10 min after the hot water thermostat has
started the heat pump water heater again.
d 2
For units with outdoor heat exchanger surfaces greater than 5 m , the deviation on the air inlet dry bulb temperature
is doubled.
Table 2 (continued)
Variations of arithmetical mean values Variation of individual readings from speci-
Readings
from specified test conditions fied test conditions
Interval Interval Interval Interval Interval Interval
a b c a b c
H D S H D S
hot water supply
— inlet tem-
±1 K ±1 K
perature
— volume ±5 % (≥10 l/min) ±10 % (≥10 l/min)
flow
±0,5 l/min (<10 l/min) ±1,0 l/min (<10 l/min)
Electrical
Voltage ±3 % ±3 %
Frequency ±2 % ±2 %
a
Interval H applies when the heat pump water heater is in the heating mode, except for the first 10 min after termination
of a defrost cycle, and the first 10 min after a restart of the heat pump water heater.
b
Interval D applies during a defrost cycle and during the first 10 min after the termination of a defrost cycle when the
heat pump water heater is operating in the heating mode.
c
Interval S applies when the compressor is stopped and during the first 10 min after the hot water thermostat has
started the heat pump water heater again.
d 2
For units with outdoor heat exchanger surfaces greater than 5 m , the deviation on the air inlet dry bulb temperature
is doubled.
Table 3 — Test conditions applicable to all systems
Measured variable Set value
Power supply voltage Rated voltage
Power supply frequency Rated frequency
Air flow rate Nominal, as indicated by the manufacturer.
When only a range is given, tests are to be carried out
at the minimum and maximum value.
Temperature of the incoming cold water (°C) 10
Hot water flow rate (l/min) (see load profiles in Annex A)
Table 4 — Test conditions for particular types of systems
Range of ambient
Heat source Ambient tempera-
temperature of
air dry (wet) bulb ture of
Type of heat source heat pump water
temperature storage tank
heater
in °C in °C
in °C
Outdoor air heat pump water heater 7 (6) from 15 to 30 20
(placed indoors)
Outdoor air heat pump water heater 7 (6) heat source temperature 20
(placed outdoors)
Non heated space air 15 (12) heat source temperature 15
Exhaust air 20 (12) from 15 to 30 20
8 © ISO 2019 – All rights reserved

7 Performance test and determination of the energy consumption
7.1 General
The test methods specified in this clause are designed to determine the performance of the heat pump
water heater when providing heat for hot water supply. The unit shall be installed and adjusted in the
initial state conditions and in the initial adjustment conditions as given in Clauses 5 and 6.
7.2 Basic principles
The test consists of the following six principal stages:
— [Stage A] Stabilisation (see 7.5);
— [Stage B] Filling and storage volume (see 7.6);
— [Stage C] Filling and heating up period (see 7.7);
— [Stage D] Standby power input (see 7.8);
— [Stage E] Water draw-offs (see 7.9);
— [Stage F] Mixed water at 40 °C and reference hot water temperature (see 7.10).
After the preparation of the test (stages A and B) the tests C to F are performed as shown in Figure 1.
Each individual stage can be carried out independently if the starting conditions are the ending
conditions of the previous stage.
Key
1 [Stage C] Filling and heating up period (see 7.7)
2 [Stage D] Standby power input (see 7.8)
3 [Stage E] Water draw-offs (see 7.9)
4 [Stage F] Mixed water at 40 °C and reference hot water temperature (see 7.10)
T temperature
t time
a
Set point temperature.
Figure 1 — Stages and order of the tests
All tests are performed with power supplied at the rated voltage and rated frequency as stated in the
installation and operation instructions. After the initial start of the heat pump water heater the power
supply is left for the duration of the test.
Any supplementary heat supply which can be switched off by the user shall be switched off during the
entire test, unless otherwise stated by the manufacturer.
7.3 Off-peak products
For off-peak products, the product shall be installed and connected as stated in the installation and
operation instructions. All appropriate information to set the time period for which the unit is not
allowed to be energized whereas the unit is under power supply shall be stated in the installation and
operation instructions, for conducting Stage E of the performance test.
For off-peak products, the power supply to the unit is shut down at the beginning of Stage E (load
profiles) and is reactivated 16 h later.
After that, the next switch off of the compressor by the thermostat sensing the water temperature in
the tank shall be obtained within 8 h, otherwise the product is not considered to be an off-peak product.
For off peak products the power consumption due to auxiliaries shall be included in the total power
consumption in Stage E.
10 © ISO 2019 – All rights reserved

If this measurement is not made during Stage E, then the average power consumption (P ) is
s
determined from the first 20 min of the standby period and shall be added to the measured power
consumption during Stage E.
The corresponding energy consumption is to be added to Stage E and shall be calculated according to
Formula (1).
W = 16·P (1)
EL-OFF s
where
W is the calculated energy consumption for off-peak products in kWh;
EL-OFF
16 is the compressor off time in h;
P is the measured average power consumption when the compressor is off in kW.
s
7.4 Power input corrections
7.4.1 Power input of fans for heat pump water heater with duct connection
In the case of heat pump water heater, which allows an external static pressure difference, only a
fraction of the input to the fan motor shall be included in the effective power absorbed by the heat
pump water heater.
If no fan is provided with the heat pump water heater, the proportional power input which is to be
included in the effective power absorbed by the heat pump water heater, W expressed in kWh,
EL-Corr
shall be calculated using Formula (2):
t
d
Vt ⋅Δp
()
air i
W = × dt (2)
EL−Corr
∫
3600×1000 η
where
η is the efficiency of the fan and is equal to 0,3 by convention;
Δp is the measured internal static pressure difference in Pa;
i
V is the nominal air volume flow rate in m /s;
air
t is the test duration in s.
d
If a fan is an integral part of the heat pump water heater, only a fraction of the input to the fan motor
shall be included in the effective power absorbed by the heat pump water heater. The fraction which
is to be excluded from the total power absorbed by the heat pump water heater, W expressed in
EL-Corr
kWh, shall be calculated using Formula (3):
t
d
Vt ⋅Δp
()
air e
W = × dt (3)
EL−Corr
∫
3600×1000 η
where
Η is the efficiency of the fan and is equal to 0,3 by convention;
V is the nominal air volume flow rate in m /s;
air
Δp is the measured external static pressure difference in Pa;
e
t is the test duration in s.
d
7.5 Stabilization [stage A]
The product is kept at ambient conditions until all parts of the product have reached ambient conditions
±2 K (at least 24 h).
7.6 Filling and storage [stage B]
The empty hot water storage tank is to be weighed; the weight of taps on inlet and/or outlet pipes
shall be included. Then the hot water storage tank is filled with water as stated in the installation and
operation instructions at cold water pressure. The water supply is then cut off. The filled hot water
storage tank r shall be weighed, including the taps. The difference of the two weights (m ) shall be
act
converted into volume in litres in accordance with Formula (4).
m
act
V =×1000 (4)
m
ρ T
()
where
V is the measured volume of a hot water storage tank in l;
m
m is the difference of the two weights in kg;
act
ρ(T) is the density of water in kg/m .
This volume shall be reported in litres to the nearest one-tenth litres. Filling and storage are not
applicable to heat pump water heater combination heaters.
7.7 Filling and heating up period [stage C]
The product shall be fully filled with cold water. Cold water shall circulate in the tank until the outlet
temperature is equal to the inlet temperature within the allowed variation given in Table 2. The test
consists of determining the heating up time t necessary to heat the storage quantity of water from
h
an initial state until the first time the compressor is switched off by the thermostat sensing the water
temperature in the tank.
This initial state is at the temperature of the incoming cold water specified in Table 3. The heat pump
water heater is switched on. The heating up time, t and the corresponding input of electrical energy,
h
W , are measured from the time the heat pump water heater is switched on until it is shut off by
eh-HP
the hot water thermostat situated in the tank, with the correction calculated according to 7.4, with test
duration t t .
d = h
The energy consumption is calculated according to Formula (5).
W = W − W (5)
eh-HP eh-M EL-Corr
where
12 © ISO 2019 – All rights reserved

W is the measured electricity consumption during the test duration t in kWh;
eh-M h
W is the correction due to electricity consumption of fan in kWh;
EL-Corr
W is the total electricity consumption during the test duration t in kWh.
eh-HP h
7.8 Standby power input [stage D]
The standby power input is determined by measuring the electrical power input over an integral
number of on-off cycles of the heat pump water heater, initiated by the thermostat situated in the tank,
when no hot water draw-offs are done.
After the thermostat shuts off the heat pump water heater following the heating up period, the system
is left to operate with no hot water draw-offs for a number of full cycles or a minimum duration.
The test shall be performed over a period of minimum 48 h or less if 6 on-off-cycles have occurred. Then
the duration t , and the energy input W , expressed in kWh, of the last on-off cycle are determined
es es-HP
using Formula (6).
W = W − W (6)
es-HP es-M EL-Corr
where
W is the measured energy consumption during the last on-off cycle, in kWh;
es-M
W is the correction due to electricity consumption of fan, in kWh according to 7.4 with test
EL-Corr
duration t t ;
d = es
W is the total energy input during the last on-off-cycle, in kWh. The
es-HP
standby power input, P expressed in kWh, is determined by Formula (7):
es
W
es−HP
P =⋅3600 (7)
es
t
es
where
P is the standby power input in kW;
es
W is the total energy input during the last on-off-cycle in kWh;
es-HP
t is the duration of the last on-off-cycle of the heat pump water heater in s.
es
7.9 Water draw-offs and COP calculation [stage E]
7.9.1 Determination of the useful energy content
There are different load profiles for different energy contents according to Annex A. For the test a
specific load profile shall be selected from Table A.1 to Table A.2. Each individual draw-off of the load
profile shall be completed; this means the valve shall be closed, and a delay of at least one minute is
required, before starting the following draw-off.
The test cycle starts directly after the last shut off of the heat pump water heater by the hot water
thermostat situated in the tank. The test cycle ends with the last shut off of the heat pump water heater,
if load profile time (duration) t is at least 24 h or more [see Figure 2 a)]. If the heat pump water
TTC
heater is not running when 24 h have passed from the start of the test cycle, the test cycle has to be
extended until the heat pump water heater restarts and stops again [see Figure 2 b)].
a) Heat pump water heater is still running at the end of the 24-h period
b) Heat pump water heater is not running at the end of the 24-h period
Key
1 first draw-off of the load profile
2 last draw-off of the load profile
3 running period of the heat pump water heater directly before the start of the test cycle
4 running period of heat pump water heater after last draw-off (2)
Q energy in kwh
t time in h:min
t load profile time/duration in h:min
TTC
Figure 2 — Illustration of a test for one possible load profile
The useful energy Q (kWh) during one single draw-off is given by Formula (8):
HP-tap
tap
 
QC= p⋅ρθTf⋅−⋅ ttθ dt (8)
() () ()
HP−tap WH WC
()t  
∫
60⋅⋅1000 3600
where
14 © ISO 2019 – All rights reserved

θ (t) − θ (t) is the temperature difference between hot water temperature at outlet and cold
WH WC
water at inlet of hot water supply storage in K;
f is the useful water flow rate, expressed in l/min;
(t)
t is the time duration of a draw-off of useful water in s;
tap
C is the specific heat capacity of water in kJ/(kgK);
p
ρ(T) is the density of the hot water at the flow meter in kg/m .
For draw-offs with a target temperature T of 55 °C, this temperature cannot always be achieved by
p
the heat pump water heater alone. During the draw-off it is then assumed that the missing temperature
difference to the required T is produced by an additional electrical resistance heater.
p
For that case, the following formulae are used:
tap
 
QC= p⋅ρθTf⋅+⋅ tT −−10 θ t dt (9)
() () (()
()
EL−tap ()tpWH WC
∫
 
60⋅⋅1000 3600
The overall tapping energy Q of the load profile is:
LP
n
tap
QQ= (10)
()
EL−LP ∑ EL−tap
il=
n
tap
QQ=+Q (11)
()
LP HP−−tapELLP
∑
il=
where
n is the number of draw-offs during the load profile;
tap
i is the index for the draw-off.
7.9.2 Determination of the energy consumption
The total measured electrical energy input W (kWh) of the unit during the measurement period
EL-M-LP
of the load profile t is corrected by the following energy consumptions to obtain the total energy
TTC
consumption W , using Formula (12):
EL-LP
— correction for fans, W (kWh);
EL-Corr
— heat loss of the tank for a duration of 24 h;
— additional electrical input, Q (kWh);
EL-LP
— energy consumption for off-peak product where applicable, W (kWh).
EL-OFF
W = W − W + (24 − t ) · P + Q + W (12)
EL-LP EL-M-LP EL-Corr TTC es EL-LP EL-OFF
where
W is the total electrical energy consumption during the whole load profile in kWh;
EL-LP
t is the load profile time/duration in h;
TTC
P is the standby power input in kW.
es
7.9.3 Coefficient of performance (COP )
HW
The coefficient of performance COP for the whole load profile is calculated by:
HW
Q
LP
COP = (13)
HW
W
EL−LP
where
Q is the total useful energy content during the whole load profile in kWh;
LP
W is the total electrical energy consumption during the whole load profile in kWh.
EL-LP
7.10 Reference hot water temperature and volume of mixed water at 40 °C [stage F]
This test is started when the compressor switches off at the end of the last measurement period for the
load profile. A continuous hot water draw-off is started and continues until the hot water temperature
θ (t) falls below 40 °C. The hot water flow rate, f , shall be set to maximum flow rate of the
WH max
considered load profile.
A reference value for the hot water temperature inside the tank is determined by measuring the
outlet water temperature. The average temperature during this draw-off is the reference hot water
temperature θ' according to Formula (15):
WH
t40
θθ′ = WH td⋅ t (14)
()
WH
∫
t
where
θ' is the reference hot water temperature in °C;
WH
θ (t) is the outgoing hot water temperature in °C;
WH
t is the time from starting the draw-off until θ is less than 40 °C in s.
40 WH
The maximum amount of mixed water at 40 °C in one single draw-off shall be determined. This is done
by calculating the hot water energy during the draw-off.
The hot water flow rate f together with the temperatures of the incoming cold water θ and the
max WC
outgoing hot water θ are measured during the draw-off at least e
...