ISO 21978:2023

INTERNATIONAL ISO
STANDARD 21978
Second edition
2023-12
Air to water heat pumps — Testing
and rating at part load conditions and
calculation of seasonal coefficient of
performance for space heating
Chauffe-eau à pompe à chaleur — Essais et détermination des
caractéristiques à charge partielle et calcul de performance
saisonnière
Reference number
© ISO 2023
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 8
5 Installation requirements .9
5.1 Test apparatus and uncertainties of measurement . 9
5.2 Test room for the airside . 10
5.3 Installation and connection of the heat pump . 10
5.4 Installation of heat pumps consisting of several parts . 11
5.5 Environment conditions for indoor unit installation and electrical power supply
requirements . . . 11
6 Setting and part load test conditions .11
6.1 General . 11
6.2 Setting for capacity ratio . 11
6.3 Setting the external static pressure difference for ducted units . 11
6.4 Setting of units with integral pumps .12
6.5 Part load test conditions . 12
7 Space heating test .15
7.1 Heating capacity test . 15
7.2 Heating capacity correction . 16
7.2.1 General . 16
7.2.2 Capacity correction due to indoor liquid pump . 16
7.2.3 Effective power input . 17
7.3 Test procedure . 19
7.3.1 General . 19
7.3.2 Permissible deviations . 19
7.3.3 Preconditioning period.20
7.3.4 Equilibrium period . 21
7.3.5 Data collection period . . 21
7.4 Heating capacity calculation . 21
7.4.1 Steady state capacity test . 21
7.4.2 Transient capacity test . 21
7.5 Effective power input calculation . 21
7.5.1 Steady state test . 21
7.5.2 Transient capacity test . 21
7.6 Determination of degradation coefficient C . 21
d
7.7 Test methods for electric power input during thermostat-off mode, standby mode,
crankcase heater mode and off mode . 22
7.7.1 Uncertainties of measurement . 22
7.7.2 Measurement of electric power input during thermostat-off mode .22
7.7.3 Measurement of electric power input during standby mode .23
7.7.4 Measurement of electric power input during crankcase heater mode .23
7.7.5 Measurement of electric power input during off mode .23
8 Calculation methods for seasonal coefficient of performance (S ) .23
COP
8.1 General formula for calculation of S . 23
COP
8.2 Calculation of the reference annual heating demand, Q . 24
H
8.3 Calculation of the annual energy consumption, Q . 24
HE
8.4 Calculation of S and S . 24
COP,on COP,net
8.5 Calculation procedure for determination of C values at part load conditions A to G .26
Pb
iii
8.5.1 General . 26
8.5.2 Calculation procedure for fixed capacity units . 26
8.5.3 Calculation procedure for staged and variable capacity units .26
9 Test results and test report .27
9.1 Data . 27
9.2 Test report .28
10 Marking provisions .29
10.1 General .29
10.2 Nameplate requirements . 29
10.3 Nameplate information .29
Annex A (normative) Heating capacity test procedures given in 7.3 .30
Annex B (normative) Determination of the liquid pump efficiency .36
Annex C (informative) Examples of set of bin hours and hours for active mode, thermostat-
off mode, standby mode, off mode and crankcase heater mode .40
Annex D (informative) S and S calculation for fixed capacity for 35 °C
COP,on COP,net
temperature application — Example .42
Annex E (informative) S and S calculation for variable capacity unit for 35 °C
COP,on COP,net
temperature application — Example .46
Bibliography .50
iv
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
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
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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.
This second edition cancels and replaces the first edition (ISO 21978:2021), which has been technically
revised.
The main changes are as follows:
— values of uncertainties have been corrected;
— descriptive terms or names have been revised following ISO/IEC Directives;
— errors in Annex A have been corrected;
— typos have been corrected.
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.
v
Introduction
Air to water heat pumps are, at present, selected and compared at a rated condition. This condition does
not represent the usual operating conditions of the equipment over a season. This operating condition
can be better assessed by comparing equipment at representative reduced capacities and determining
the seasonal coefficient of performance.
This document provides part load conditions and calculation methods for calculating the seasonal
coefficient of performance (S and S ) of such units when they are used to fulfil the heating
COP,on COP,net
demands.
Other energy consumptions can occur when the unit is not used to fulfil the heating demands such as
those from a crankcase heater or when the unit is on standby. These consumptions are considered in
the calculation methods for reference S .
COP
Reference S /S /S calculations may be based on calculated or tested values. For the purpose
COP COP,on COP,net
of S /S /S , three design conditions average (A), colder (C) and warmer (W) are considered,
COP COP,on COP,net
as well as three temperature applications. In case of tested values, this document gives the methods for
testing air to water heat pumps at part load conditions.
vi
INTERNATIONAL STANDARD ISO 21978:2023(E)
Air to water heat pumps — Testing and rating at part
load conditions and calculation of seasonal coefficient of
performance for space heating
1 Scope
This document specifies test conditions for determining the seasonal performance characteristics
of air to water heat pumps for space heating with electrically driven compressors with or without
supplementary heater. In the case of air to water heat pumps for space heating consisting of several
parts with refrigerant or water connections, this document applies only to those designed and supplied
as a complete package.
The seasonal coefficient of performance depends, inter alia, on the climate conditions and temperature
regime of the space heating distribution network.
This document specifies:
— three design conditions, each of them being characterized by a design temperature which represents
the lowest temperature that can occur in that design condition;
— three water temperature distribution regimes, namely “temperature application” in the text.
This document also provides a full description of three heating seasons that can be used with the
associated design conditions.
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 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
35 °C application
temperature application where an indoor heat exchanger water(brine) outlet temperature of 35 °C is
met at design temperature
3.2
45 °C application
temperature application where an indoor heat exchanger water(brine) outlet temperature of 45 °C is
met at design temperature
3.3
55 °C application
temperature application where an indoor heat exchanger water(brine) outlet temperature of 55 °C is
met at design temperature
3.4
active mode
mode corresponding to the hours with a heating load of the building and whereby the heating function
of the unit is activated
Note 1 to entry: This condition can involve on/off-cycling of the unit in order to reach or maintain a required
indoor air temperature.
3.5
active mode seasonal coefficient of performance
S
COP,on
average coefficient of performance of the unit in active mode (3.4) for the designated design condition,
determined from the part load, supplementary heating capacity (where required) and bin-specific
coefficients of performance (3.12) and weighted by the bin hours (3.11) where the bin condition occurs
Note 1 to entry: For calculation of S , the energy consumption during thermostat-off mode (3.47), standby
COP,on
mode (3.44), off mode (3.36) and crankcase heater mode (3.22) are excluded. The energy consumption of a
supplementary heater is added for the part load conditions where the declared capacity of the unit is lower than
the heating load, regardless whether this supplementary heater is included in the unit or not included in the unit.
Note 2 to entry: Expressed in kWh/kWh.
3.6
air to water heat pump
heat pump which consists of one or more factory-made assemblies which includes at space side
refrigerant to water heat exchanger (load side), electrically driven compressor(s), and outdoor-side air-
to refrigerant heat exchanger(s) (source side), including means to provide space heating and/or space
cooling functions.
Note 1 to entry: It can include supplementary heater for space heating.
Note 2 to entry: This is also referred to as heat pump in this document.
3.7
annual energy consumption for heating
Q
HE
energy consumption required to meet the reference annual heating demand for a designated design
condition and set of bin hours and calculated as the reference annual heating demand divided by
the active mode seasonal coefficient of performance (3.5) and the energy consumption of the unit for
thermostat-off-, standby-, off- and crankcase heater-mode during the heating season
Note 1 to entry: Expressed in kWh.
3.8
annual heating demand
Q
H
heating demand for a designated design condition and set of bin hours, to be used as basis for calculation
of seasonal coefficient of performance (3.43) and calculated as the product of the design load (3.26) for
heating and the equivalent active mode hours for heating (3.32)
Note 1 to entry: Expressed in kWh.
3.9
available external static pressure difference
Δp
e
positive pressure difference measured between the air (or water) outlet section and the air (or water)
inlet section of the unit, which is available for overcoming the pressure drop of any additional ducted
air (or water) circuit
3.10
bin
outdoor temperature interval of 1 K
3.11
bin hours
h
j
hours per heating season for which an outdoor temperature occurs for each bin (3.10) j
3.12
bin-specific coefficient of performance
C (T,j)
Pb,
coefficient of performance specific for every bin (3.10) j with outdoor temperature T in a heating season
j
3.13
bin temperature
T
j
outdoor air dry bulb temperature
Note 1 to entry: Expressed in °C.
Note 2 to entry: The relative humidity can be indicated by a corresponding wet bulb temperature.
3.14
bivalent temperature
T
biv
lowest outdoor temperature point at which the unit is declared to have a capacity able to meet 100 % of
the heating load without supplementary heater, whether it is integrated in the unit or not
Note 1 to entry: Below this point, the unit can still provide capacity, but additional supplementary heating is
necessary to fulfil the heating load.
3.15
capacity control
ability of the unit to change its capacity by changing the volumetric flow rate of the refrigerant
Note 1 to entry: Units are indicated as ‘fixed’ if the unit cannot change its volumetric flow rate, 'two-staged' if
the volumetric flow rate is changed or varied in series of not more than two steps, 'multi-stage’ if the volumetric
flow rate is changed or varied in series of three or four steps or ‘variable' if the volumetric flow rate is changed or
varied in series of five or more steps to represent continuously variable capacity.
Note 2 to entry: Multi-stage capacity units are considered as variable capacity units in this document.
3.16
capacity ratio
C
R
heating part load or full load divided by the declared heating capacity of the unit at the same
temperature conditions
3.17
coefficient of performance at the declared capacity
C
Pd
declared heating capacity of the unit divided by the effective power input of the unit at specific
temperature conditions, A, B, C, D, E, F and G, where applicable
Note 1 to entry: Expressed in kW/kW.
3.18
coefficient of performance at part load
C
Pb
coefficient of performance at the declared capacity (3.17), corrected with the degradation coefficient,
where applicable
Note 1 to entry: When the declared capacity of the unit is higher than the heating load, the coefficient of
performance- includes degradation losses. When the declared capacity of the unit is lower than the heating load
(i.e. below the bivalent temperature (3.14) condition), the coefficient of performance of the declared capacity is
used.
Note 2 to entry: Expressed in kW/kW.
3.19
compressor-off state
condition where the compressor is not running while the unit is operating in active mode (3.4)
Note 1 to entry: This is the “off” phase in on/off cycling.
3.20
crankcase heater mode operating hours
H
CK
annual number of hours the unit is considered to be in crankcase heater mode, the value of which
depends on the designated design condition and set of bin hours
Note 1 to entry: Three examples of crankcase heater mode hours are given in Annex C.
Note 2 to entry: Expressed in h.
3.21
crankcase heater mode power input
P
CK
power input of the unit due to crankcase heater operation mode
Note 1 to entry: Expressed in W.
3.22
crankcase heater mode
condition where the unit has activated a heating device to avoid the refrigerant migrating to the
compressor in order to limit the refrigerant concentration in oil at compressor start
3.23
declared capacity in heating
Φ
dh
heating capacity a unit can provide at any temperature condition A, B, C, D, E, F or G, as declared by the
manufacturer
Note 1 to entry: This is the capacity provided by the refrigerant cycle of the unit without supplementary heaters,
even if those are integrated in the unit.
3.24
degradation coefficient
C
d
measure of efficiency loss due to the cycling
Note 1 to entry: If the Cd is not determined by measurement, the default degradation coefficient is 0,9.
3.25
design condition
condition characterized by a design temperature condition and that is to be associated with a set of bin
hours
Note 1 to entry: Three design conditions are defined in this document.
3.26
design load
Φ
dlh
space heating load declared by the manufacturer at design temperature (3.27)
Note 1 to entry: It is possible to calculate the S /S /S of a unit for more than one Φ value.
COP COP,on COP,net dlh
Note 2 to entry: Expressed in kW.
3.27
design temperature
T
d
lowest outdoor air temperature considered for each design condition
3.28
effective power input during compressor-off state
P
Coff
total power input of the unit when the compressor is switched off in active mode (3.4), used for the
determination of the degradation coefficient (3.24) including corrections for fans and pumps where
applicable.
Note 1 to entry: Expressed in kW.
3.29
effective power input with declared capacity
P
Con
total power input when the unit is operating at part load condition, used for the determination of the
degradation coefficient (3.24) including corrections for fans and pumps where applicable.
Note 1 to entry: Expressed in kW.
3.30
electric supplementary heater
real or assumed electric supplementary heater, with a coefficient of performance of 1, considered in the
calculation of S (3.43) and S (3.5)
COP COP,on
3.31
electric supplementary heater capacity
Φ (T,j)
esh,
heating capacity of a real or assumed electric supplementary heater supplementing the declared
capacity for heating when the capacity of the unit is lower than the heat load for a specific bin
temperature (3.13) T
j
Note 1 to entry: Expressed in kW.
3.32
equivalent active mode hours for heating
H
HE
assumed annual number of hours while the unit is assumed to operate at the design load for heating
(Φ ) in order to satisfy the reference annual heating demand
dlh
Note 1 to entry: Expressed in h.
3.33
fixed outlet
water(brine) outlet temperature that is used when the control of the unit has no means to automatically
vary the water(brine) outlet temperature with the outdoor temperature
3.34
internal static pressure difference
Δp
i
negative pressure difference measured between the air (or water) outlet section and the air (or water)
inlet section of the unit, which corresponds to the total pressure drop of all components on the air (or
water) side of the unit”
3.35
net seasonal coefficient of performance
S
COP,net
seasonal efficiency of a unit in active heating mode without supplementary heaters which is determined
from selected conditions
Note 1 to entry: For calculation of S , the energy consumption during active mode (3.4) is used. This excludes
COP,net
the energy consumption during thermostat-off mode (3.47), standby mode (3.44), off mode (3.36) or that of the
crankcase heater. For the part load conditions where the declared capacity of the unit is lower than the heating
load, the energy consumption of a supplementary heater is not included.
Note 2 to entry: Expressed in kWh/kWh.
3.36
off mode
mode wherein the unit is completely switched off and cannot be reactivated by control device, external
signal or by a timer
Note 1 to entry: Off mode means a condition in which the equipment is connected to the mains and is not providing
any function. The following will also be considered as off mode: conditions providing only an indication of off
mode condition; conditions providing only functionalities intended to ensure electromagnetic compatibility.
3.37
off mode operating hours
H
OFF
annual number of hours the unit is considered to be in off mode (3.36), the value of which depends on
the designated design condition and set of bin hours
Note 1 to entry: Three examples of off mode operating hours are given in Annex C.
Note 2 to entry: Expressed in h.
3.38
off mode power input
P
OFF
power input of the unit while in off mode (3.36)
Note 1 to entry: Expressed in W.
3.39
operation limit temperature
T
OL
outdoor temperature below which the declared capacity is equal to zero
Note 1 to entry: Expressed in °C.
3.40
part load for heating
Φ (T,j)
h,
heating load at a specific bin temperature (3.13) T , calculated as the design load multiplied by the part
j
load ratio
Note 1 to entry: Expressed in kW.
3.41
part load ratio
p
l
bin temperature (3.13) minus 16 °C divided by the design temperature minus 16 °C
Note 1 to entry: TT−16 / −16
()
()
j d
3.42
reactivation function
function facilitating the activation of other modes, including active mode (3.4), by remote switch
including remote control, internal sensor, timer to a condition providing additional functions, including
the main function, but excluding thermostats
3.43
seasonal coefficient of performance
S
COP
overall coefficient of performance of the unit, representative for the designated design condition and
set of bin hours
Note 1 to entry: S is calculated as the annual heating demand (3.8) divided by the annual energy consumption
COP
for heating (3.7).
Note 2 to entry: Expressed in kWh/kWh.
3.44
standby mode
mode wherein the unit is switched off partially and can be reactivated by a control device (such as a
remote control), an external signal or a timer
Note 1 to entry: The unit is connected to the mains, depends on signal input to work as intended and provides
only the following functions, which may persist for an indefinite time: reactivation function (3.42), or reactivation
function and only an indication of enabled reactivation function, and/or information or status display.
3.45
standby mode operating hours
H
SB
annual number of hours the unit is considered to be in standby mode (3.44), the value of which depends
on the designated design condition and set of bin hours
Note 1 to entry: Three examples of standby hours are given in Annex C.
Note 2 to entry: Expressed in h.
3.46
standby mode power input
P
SB
power input of the unit due to standby mode (3.44) operation
Note 1 to entry: Expressed in W.
3.47
thermostat-off mode
mode corresponding to the hours with no heating demand of the building, whereby the heating function
of the unit is switched on, but is not operational, as there is no heating demand
Note 1 to entry: Cycling on/off in active mode (3.4) is not considered as thermostat-off.
3.48
thermostat-off mode operating hours
H
TO
annual number of hours the unit is considered to be in thermostat-off mode (3.47), the value of which
depends on the designated design condition and set of bin hours
Note 1 to entry: Three examples of thermostat-off mode operating hours are given in Annex C.
Note 2 to entry: Expressed in h.
3.49
thermostat-off mode power input
P
TO
power input of the unit due to thermostat-off mode (3.47) operation
Note 1 to entry: Expressed in W.
3.50
variable outlet
water(brine) outlet temperature that is used when the control of the unit has means to automatically
vary the water(brine) outlet temperature with the outdoor temperature
4 Symbols
Symbol Definition Units
C Degradation coefficient —
d
C Coefficient of performance kW/kW
P
c Specific heat kJ/(kg·K)
p
C Coefficient of performance at part load kW/kW
Pb
C (T, ) Bin-specific coefficient of performance kW/kW
Pb, j
C Coefficient of performance at the declared capacity kW/kW
Pd
C Capacity ratio kW/kW
R
E Energy efficiency index of liquid pump —
EI
H Crankcase heater mode operating hours h
CK
H Equivalent active mode hours for heating h
HE
H Off mode operating hours h
OFF
H Standby mode operating hours h
SB
H Thermostat-off mode operating hours h
TO
h Bin hours h
j
j Bin number —
n Total number of bin —
P Annual power input with supplementary heat kW
ASH
P Crankcase heater mode power input W
CK
P Effective power input during compressor-off state kW
Coff
P Effective power input with declared capacity kW
Con
P Off mode power input W
OFF
Symbol Definition Units
P Standby mode power input W
SB
P Thermostat-off mode power input W
TO
p Part load ratio —
l
p Part load ratio for bin temperature T —
l,T,j j
Q Annual heating demand kWh
H
Q Annual energy consumption for heating kWh
HE
S Seasonal coefficient of performance kW/kW
COP
S Net seasonal coefficient of performance kW/kW
COP,net
S Active mode seasonal coefficient of performance kW/kW
COP,on
T Bivalent temperature °C
biv
T Design temperature conditions for heating °C
d
T Bin temperature (outdoor temperature) °C
j
T Operation limit temperature °C
OL
u Maximum uncertainty %
max
Φ (T, ) Electric supplementary heater capacity kW
esh, j
Φ Declared capacity in heating kW
dh
Φ Design load heating kW
dlh
Φ (T, ) Part load for heating kW
h, j
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 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.
If, in the instructions, the manufacturer indicates a value for the temperature set on the control device
for a given part load conditions, this value shall be used.
Temperature and pressure measuring points shall be arranged in order to obtain mean significant
values.
For free air intake temperature measurements, it is required either:
— to have at least one sensor per square metre, with not less than four measuring points and by
restricting to 20 the number of sensors equally distributed on the free air surface; or
— to use a sampling device that shall be completed by four sensors for checking uniformity if the
surface area is greater than 1 m .
Air temperature sensors shall be placed at a maximum distance of 0,25 m from the free air surface.
For water and brine, the density and specific heat in Formulae (2), (3) and (4) shall be determined in the
temperature conditions measured near the volume flow measuring device.
The uncertainties of measurement shall not exceed the values specified in Table 1.
Table 1 — Uncertainties of measurement
Measured quantity Unit Uncertainty
Liquid
Temperature °C 0,15 K
Temperature difference K 0,15 K
Volume flow l/min 1 %
1 kPa (≤20 kPa)
Static pressure difference kPa
5 % (>20 kPa)
Concentration (for brine) % 2 %
Air
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
Electric power W 1 %
Electrical energy kWh 1 %
Voltage V 0,5 %
Current A 0,5 %
Additionally, the heating capacity measured on the liquid side shall be determined within a maximum
uncertainty of 5 % at standard rating conditions for the determination of the water flowrate and
calculated according to Formula (1) at part load conditions, independently of the individual uncertainties
of measurements including the uncertainties on the properties of the fluid.
 3 
u =+2 (1)
max  
p
 
l
5.2 Test room for the airside
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.
Any direct heat radiation (e.g. solar radiation) onto heating units in the test room onto the heat pump or
onto the temperature measuring points shall be avoided.
5.3 Installation and connection of the heat pump
The heat pump shall be installed and connected for the test as recommended by the manufacturer in
the installation and operation manual. If a supplementry heater is provided (as an option or not), it shall
be switched off or disconnected to be excluded from the testing.
5.4 Installation of heat pumps consisting of several parts
In the case of heat pumps consisting of several refrigeration parts (split heat pumps), the following
installation conditions shall be met 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.
5.5 Environment conditions for indoor unit installation and electrical power supply
requirements
Temperature conditions of parts of the unit located in the indoor side shall be between 15 °C to 30 °C.
The dry bulb temperature shall be measured.
For all units, electrical power voltage and frequency shall be given by the manufacturer.
6 Setting and part load test conditions
6.1 General
Set points for internal control equipment of the unit, i.e. 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.
6.2 Setting for capacity ratio
The capacity ratio to be tested shall be set according to the instructions of the manufacturer. The
manufacturer shall provide laboratories with the necessary information on the setting of the unit for
operating at the required capacity conditions upon request. The unit shall operate continuously during
the part load test. The only discontinuity allowed is the defrost cycle of a unit.
For staged or variable capacity units, the setting of the compressor (stage, frequency) shall be done
for each part load condition. The manufacturer shall provide in the documentation information
instructions on how to obtain the necessary data to set the required frequencies. To set up a system
with staged or variable capacity control, skilled personnel with knowledge of control software may be
required. The manufacturer or his nominated agent may be present when the system is being installed
and prepared for tests.
6.3 Setting the external static pressure difference for ducted units
The volume flow and the pressure difference shall be related to standard air and with 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 ESP is lower than 30 Pa, the fan speed shall be adjusted to reach this minimum value. If no fan speed
is available, the air flow rate shall be decreased.
If the installation and operating instructions state that the maximum allowable duct length is for inlet
and outlet together less than 2 m, the unit shall be tested with the duct length and the ESP is considered
to be 0.
6.4 Setting of units with integral pumps
For units with integral water or brine pumps, the external static pressure shall be set at the same time
as the temperature difference.
In case of liquid pump with several fixed speeds or with variable speed, the manufacturer shall provide
information on the settings of the pump (speed or external static pressure to achieve).
6.5 Part load test conditions
For the part load tests, the appropriate test conditions shall be chosen from Tables 4 to 6 depending
on the selected design conditions and temperature applications. One or several design conditions and
temperature applications can be applied.
Three design conditions average (A), colder (C) and warmer (W) are considered as well as three
temperature applications, 35 °C, 45 °C and 55 °C, as given in Table 2 and Table 3, respectively.
Table 2 — Design conditions
Design conditions
Design
temperature
Average Warmer Colder
T
(A) (W) (C)
d
Dry bulb −10 °C 2 °C −22 °C
Wet bulb −11 °C 1 °C —
Table 3 — Temperature applications
Temperature application
Water (brine) outlet
35 °C 45 °C 55 °C
temperature
For each temperature application, the heat pump can either operate with a fixed or a variable water
outlet temperature.
For outdoor air dry bulb temperatures higher or equal to −10 °C the wet bulb temperature equals the
dry bulb temperature –1 K. For dry bulb temperatures below −10 °C, the wet bulb temperature is not
defined.
If the declared T is lower than T , then the outdoor dry bulb temperature is equal to T for the part
OL d d
load condition E in Table 4, Table 5 and Table 6.
The part load ratios shall be based on the part load ratio formulae and not on the rounded values given
for each condition in Table 4 to
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