ISO 13256-1:1998

INTERNATIONAL ISO
STANDARD 13256-1
First edition
1998-08-15
Water-source heat pumps — Testing and
rating for performance —
Part 1:
Water-to-air and brine-to-air heat pumps
Pompes à chaleur à eau — Essais et détermination des caractéristiques de
performance —
Partie 1: Pompes à chaleur eau-air et eau glycolée-air
A
Reference number
ISO 13256-1:1998(E)

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ISO 13256-1:1998(E)
Contents Page
1 Scope. 1
2 Normative reference. 1
3 Definitions . 1
.....................................................
4 Rating and test conditions 3
4.1  Rating conditions for the determination of capacity. 3
4.2  Standard rating and part-load rating test conditions. 5
5 Performance requirements. 6
5.1  General. 6
5.2  Maximum operating conditions test . 7
5.3  Minimum operating conditions test . 8
5.4  Enclosure sweat and condensate test. 8
6 Test methods . 10
.............................................................................
6.1  General 10
6.2  Uncertainties of measurement . 10
6.3  Data to be recorded . 10
6.4  Test tolerances. 11
6.5  Test results. 11
7 Marking provisions. 12
7.1  Nameplate requirements . 12
7.2  Nameplate information . 12
7.3  Designation of capacity ratings. 12
7.4  Refrigerant designation. 12
8 Publication of ratings. 13
8.1  Standard ratings. 13
8.2  Application ratings. 13
Annex A: Test procedures. 14
Annex B: Indoor air-enthalpy test method . 15
Annex C: Liquid enthalpy test method . 16
Annex D: Airflow measurement. 17
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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ISO ISO 13256-1:1998(E)
Annex E: Calorimeter room test method. 19
Annex F: Instrumentation and measurements . 23
Annex G: Symbols used in annexes . 35
Annex H: Bibliography . 37
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ISO 13256-1:1998(E) ISO
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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
This part of ISO 13256 was developed by ISO Technical Committee TC 86,
Refrigeration, Subcommittee SC 6, Testing and rating of air-conditioners
and heat pumps.
ISO 13256 consists of the following parts, under the general title Water-
source heat pumps — Testing and rating for performance:
— Part 1: Water-to-air and brine-to-air heat pumps
— Part 2: Water-to-water and brine-to-water heat pumps
Annexes A, B, C, D and E form an integral part of this part of ISO 13256.
Annexes F, G and H are for information only.
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ISO ISO 13256-1:1998(E)
Introduction
This part of ISO 13256 covers heating and cooling systems which are
generally referred to as “water-source heat pumps.” These systems
generally include an indoor coil with air-moving means, a compressor, and
a refrigerant-to-water or refrigerant-to-brine heat exchanger. A system
may provide both heating and cooling, cooling-only, or heating-only
functions.
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INTERNATIONAL STANDARD  ISO ISO 13256-1:1998(E)
Water-source heat pumps — Testing and rating for performance —
Part 1:
Water-to-air and brine-to-air heat pumps
1  Scope
1.1  This part of ISO 13256 establishes performance testing and rating criteria for factory-made residential,
commercial and industrial, electrically-driven, mechanical-compression type, water-to-air and brine-to-air heat
pumps. The requirements for testing and rating contained in this part of ISO 13256 are based on the use of
matched assemblies.
1.2  Equipment designed for rating at one application under this part of ISO 13256 may not be suitable at all
applications covered in this part of ISO 13256.
1.3  This part of ISO 13256 does not apply to the testing and rating of individual assemblies for separate use, nor
to the testing and rating of heat pumps covered in ISO 5151, ISO 13253 or ISO 13256-2.
NOTE —  For the purpose of the remaining clauses, the terms “equipment” or “heat pumps” may be used to mean “water-to-air
heat pumps” or “brine-to-air heat pumps” and the term “liquid” refers to either “water” or “brine”.
2  Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this part of
ISO 13256. At the time of publication, the edition indicated was valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 13256 are encouraged to investigate the possibility of applying the
most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
1)
ISO 817:— , Refrigerants — Number designation.
3  Definitions
For the purposes of this part of ISO 13256, the following definitions apply.
3.1
water-to-air heat pump and/or brine-to-air heat pump
heat pump which consists of one or more factory-made assemblies which normally include an indoor conditioning
coil with air-moving means, compressor(s), and refrigerant-to-water or refrigerant-to-brine heat exchanger(s),
including means to provide both cooling and heating, cooling-only, or heating-only functions
NOTES
1  When such equipment is provided in more than one assembly, the separated assemblies should be designed to be used
together.
2  Such equipment may also provide functions of sanitary water heating, air cleaning, dehumidifying, and humidifying.
___________
1)
To be published. (Revision of ISO 817:1974)
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ISO 13256-1:1998(E)
3.1.1
water-loop heat pump application
water-to-air heat pump using liquid circulating in a common piping loop functioning as a heat source/heat sink
NOTE —  The temperature of the liquid loop is usually mechanically controlled within a temperature range of 15 °C to 40 °C.
3.1.2
ground-water heat pump application
water-to-air heat pump using water pumped from a well, lake or stream functioning as a heat source/heat sink
NOTE —  The temperature of the water is related to the climatic conditions and may vary from 5 °C to 25 °C for deep wells.
3.1.3
ground-loop heat pump application
brine-to-air heat pump using a brine solution circulating through a subsurface piping loop functioning as a heat
source/heat sink
NOTES
1  The heat exchange loop may be placed in horizontal trenches or vertical bores, or be submerged in a body of surface water.
2  The temprature of the brine is related to the climatic conditions and may vary from -5 °C to 40 °C.
3.2
total cooling capacity
amount of sensible and latent heat that the equipment can remove from the conditioned space in a defined interval
of time, in watts, as determined by the specified test methods
3.3
net total cooling capacity
total cooling capacity with fan power adjustment
(See 4.1.3.)
3.4
heating capacity
amount of heat that the equipment can add to the conditioned space in a defined interval of time, in watts, as
determined by the specified test methods
3.5
net heating capacity
heating capacity with fan power adjustment
(See 4.1.3.)
3.6
rated voltage
voltage shown on the nameplate of the equipment, in volts
3.7
rated frequency
frequency shown on the nameplate of the equipment, in hertz
3.8
energy efficiency ratio (EER)
ratio of the net total cooling capacity to the effective power input at any given set of rating conditions, in watts per
watt
3.9
coefficient of performance (COP)
ratio of the net heating capacity to the effective power input of the equipment at any given set of rating conditions, in
watts per watt
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3.10
standard air
3
dry air at 20,0 °C and 101,324 kPa having a mass density of 1,204 kg/m
3.11
effective power input
average electrical power input to the equipment within a defined interval of time, in watts; i.e. the sum of:
— the power input for operation of the compressor excluding additional electrical heating devices,
— the power input of all control and safety devices of the equipment, and
— the proportional power input of the conveying devices for the transport of the heat transfer media through the
heat pump only (e.g., fans, pumps, whether internal or external, whether provided with the equipment or not)
(See 4.1.3 and 4.1.4.)
3.12
latent cooling capacity
amount of latent heat that the equipment can remove from the conditioned space in a defined interval of time, in
watts
3.13
sensible cooling capacity
amount of sensible heat that the equipment can remove from the conditioned space in a defined interval of time, in
watts
4  Rating and test conditions
4.1  Rating conditions for the determination of capacity
4.1.1  Standard ratings
Standard ratings shall be established at the standard rating conditions specified in 4.2, using the test procedures
described in clause 6. Standard ratings relating to cooling and heating capacities shall be net values, including the
effects of circulating- fan heat, but not including supplementary heat. Standard efficiency ratings shall be based on
the effective power input as defined in 3.11.
4.1.2  Power input of fans for heat pumps without duct connection
In the case of heat pumps which are not designed for duct connection and which are equipped with an integral fan,
all power consumed by the fans shall be included in the effective power input to the heat pump.
4.1.3  Power input of fans for heat pumps with duct connection
4.1.3.1  If no fan is provided with the heat pump, a fan power adjustment is to be included in the effective power
input to the heat pump, using the following formula:
q ·Dp
f =
fa
h
where
f is the fan power adjustment, in watts;
fa
3
h = 0,3 x 10 by convention;
Dp is the measured internal static pressure difference, in pascals;
q is the nominal airflow rate, in litres per second.
This value shall be added to the heating capacity and subtracted from the cooling capacity.
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4.1.3.2  If a fan is an integral part of a heat pump, only the portion of the fan power required to overcome the
internal resistance shall be included in the effective power input to the heat pump. The fraction which is to be
excluded from the total power consumed by the fan shall be calculated using the following formula:
q ·Dp
f =
fa
h
where
f is the fan power adjustment, in watts;
fa
3
h = 0,3 x 10 by convention;
Dp is the measured external static pressure difference, in pascals;
q is the nominal airflow rate, in litres per second.
This value shall be subtracted from the heating capacity and added to the cooling capacity.
4.1.4  Power input of liquid pumps
4.1.4.1  If no liquid pump is provided with the heat pump, a pump power adjustment is to be included in the effective
power consumed by the heat pump, using the following formula:
q ·Dp
f =
pa
h
where
f is the pump power adjustment, in watts;
pa
3
h = 0,3 x 10 by convention;
Dp is the measured internal static pressure difference, in pascals;
q is the nominal fluid flow rate, in litres per second.
4.1.4.2  If a liquid pump is an integral part of the heat pump, only the portion of the pump power required to
overcome the internal resistance shall be included in the effective power input to the heat pump. The fraction which
is to be excluded from the total power consumed by the pump shall be calculated using the following formula:
q ·Dp
f =
pa
h
where
f is the pump power adjustment, in watts;
pa
3
h = 0,3 x 10 by convention;
Dp is the measured external static pressure difference, in pascals;
q is the nominal fluid flow rate, in litres per second.
4.1.5  Airflow rates
4.1.5.1  All standard ratings shall be determined at airflow rates as described below. All airflow rates shall be
expressed as litres per second of standard air as defined in 3.10.
4.1.5.2  Ducted heat pumps which have integral fans shall be tested at the airflow rates specified by the
manufacturer, or those obtained at zero external static pressure difference, whichever provides the lower airflow
rate.
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4.1.5.3  Ducted heat pumps which do not have integral fans, but which are tested in combination with a device
employing a fan, shall be tested as described in 4.1.5.2. Ducted heat pumps which do not have integral fans but
which are rated for general use with a variety of air moving devices, shall be tested at the airflow rates specified by
the manufacturer in the published ratings. However, the pressure drop across the indoor coil assembly and the
recommended enclosures and attachment means shall not exceed 75 Pa.
4.1.5.4  Non-ducted heat pumps shall be tested at the airflow rates obtained at zero external static pressure
difference.
4.1.5.5  The manufacturer shall specify a single airflow rate for all tests required in this part of ISO 13256 unless
automatic adjustment of airflow rate is provided by the equipment. A separate control signal output for each step of
airflow rate shall be considered as an automatic adjustement.
4.1.6  Liquid flow rates
4.1.6.1  All standard ratings shall be determined at a liquid flow rate described below, expressed as litres per
second.
4.1.6.2  Heat pumps with integral liquid pumps shall be tested at the liquid flow rates specified by the manufacturer
or those obtained at zero external static pressure difference, whichever provides the lower liquid flow rate.
4.1.6.3  Heat pumps without integral liquid pumps shall be tested at the flow rates specified by the manufacturer.
4.1.6.4  The manufacturer shall specify a single liquid flow rate for all of the tests required in this part of ISO 13256
unless automatic adjustment of the liquid flow rate is provided by the equipment. A separate control signal output
for each step of liquid flow rate will be considered as an automatic adjustment.
4.1.7  Requirements for separated assemblies
In the case of heat pumps consisting of separate matched assemblies, the following installation procedures shall be
followed.
a) Each refrigerant line shall be installed in accordance with the manufacturer’s instructions with the maximum
stated length or 7,5 m, whichever is shorter. If the interconnecting tubing is furnished as an integral part of the
equipment and not recommended for cutting the length, the equipment shall be tested with the complete length
of tubing furnished.
b) The lines shall be installed without any significant difference in elevation (not more than 2 m).
4.1.8  Requirements for heat pumps with capacity control
4.1.8.1  Part-load conditions shall be used for rating tests at levels or steps less than that of maximum capacity.
4.1.8.2  Heat pumps with fixed steps of capacity control shall be rated at each step of capacity. Heat pumps with
variable capacity control shall be rated at no less than two capacity levels, the minimum and the maximum
capacities.
4.1.9  Test liquids
4.1.9.1  The test liquid for water-loop heat pumps and ground water heat pumps shall be water.
4.1.9.2  The test liquid for ground-loop heat pumps shall be a 15 % solution by mass of sodium chloride in water.
4.1.9.3  The test liquid shall be sufficiently free of gas to ensure that the measured result is not influenced by the
presence of gas.
4.2  Standard rating and part-load rating test conditions
4.2.1  The test conditions for the determination of standard and part-load cooling ratings are specified in table 1.
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4.2.2  The test conditions for determination of standard and part-load heating ratings are specified in table 2.
4.2.3  Heat pumps intended for a specific application shall be rated at the conditions specified for that application,
for example, water-loop, ground-water, or ground-loop, and shall be identified as such (i.e. water-loop heat pump,
ground-water heat pump, or ground-loop heat pump). Heat pumps intended for two or three applications shall be
rated at the conditions specified for each of these applications and shall be so identified (see 7.3).
4.2.4  For each test, the equipment shall be operated continuously until equilibrium conditions are attained, but for
not less than one hour before capacity test data are recorded. The data shall then be recorded for 30 min at 5-min
intervals until seven consecutive sets of readings have been attained within the tolerances specified in 6.4. The
averages of these data shall be used for the calculation of the test results.
Table 1 — Test conditions for the determination of cooling capacity
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side
 — dry bulb, °C 27 27 27
 — wet bulb, °C 19 19 19
Air surrounding unit
 — dry bulb °C 27 27 27
Standand rating test
Liquid entering heat exchanger, °C 30 15 25
Part-load rating test
Liquid entering heat exchanger,°C 30 15 20
Frequency* Rated Rated Rated
Voltage** Rated Rated Rated
* Equipment with dual-rated frequencies shall be tested at each frequency.
** Equipment with dual-rated voltages shall be tested at both voltages or at the lower of the two voltages if only a single rating is
published.
Table 2 — Test conditions for the determination of heating capacity
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side
 — dry bulb, °C 20 20 20
 — wet bulb, °C 15 15 15
Air surrounding unit
 — dry bulb, °C 20 20 20
Standand rating test
Liquid entering heat exchanger, °C 20 10 0
Part-load rating test
Liquid entering heat exchanger, °C 20 10 5
Frequency* Rated Rated Rated
Voltage** Rated Rated Rated
* Equipment with dual-rated frequencies shall be tested at each frequency.
** Equipment with dual-rated voltages shall be tested at both voltages or at the lower of the two voltages if only a single rating is
published.
5  Performance requirements
5.1  General
5.1.1  To comply with this part of ISO 13256, water-to-air and brine-to-air heat pumps shall be designed and
produced such that any production unit will meet the applicable requirements of this part of ISO 13256.
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5.1.2  For heat pumps with capacity control, the performance requirements tests shall be conducted at maximum
capacity.
5.2  Maximum operating conditions test
5.2.1  Test conditions
The maximum operating conditions tests shall be conducted for cooling and heating at the test conditions
established for the specific applications (see 4.2.3) specified in tables 3 and 4. Heat pumps intended for use in two
or more applications shall be tested at the most stringent set of conditions specified in tables 3 and 4.
Table 3 — Maximum cooling test conditions
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side*
 — dry bulb, °C 32 32 32
 — wet bulb, °C 23 23 23
Air surrounding unit
 — dry bulb, °C 32 32 32
Liquid entering heat exchanger*, °C 40 25 40
Frequency** Rated Rated Rated
Voltage 1) 90 % and 110 % of 1) 90 % and 110 % of 1) 90% and 110 % of
rated voltage for rated voltage for rated voltage for
equipment with a single equipment with a single equipment with a single
nameplate rating. nameplate rating. nameplate rating.
2) 90 % of minimum 2) 90 % of minimum 2) 90 % of minimum
voltage and 110 % of voltage and 110 % of voltage and 110 % of
maximum voltage for maximum voltage for maximum voltage for
equipment with dual equipment with dual equipment with dual
nameplate voltage. nameplate voltage. nameplate voltage.
* Air and liquid flow rates shall be as established in 4.1.5 and 4.1.6.
** Equipment with dual-rated frequencies shall be tested at each frequency.
Table 4 — Maximum heating test conditions
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side*
 — dry bulb, °C 27 27 27
Air surrounding unit
 — dry bulb, °C 27 27 27
Liquid entering heat exchanger*, °C 30 25 25
Frequency** Rated Rated Rated
Voltage 1) 90 % and 110 % of 1) 90 % and 110 % of 1) 90 % and 110 % of
rated voltage for rated voltage for rated voltage for
equipment with a single equipment with a single equipment with a single
nameplate rating. nameplate rating. nameplate rating.
2) 90 % of minimum 2) 90 % of minimum 2) 90 % of minimum
voltage and 110 % of voltage and 110 % of voltage and 110 % of
maximum voltage for maximum voltage for maximum voltage for
equipment with dual equipment with dual equipment with dual
nameplate voltage. nameplate voltage. nameplate voltage.
* Air and liquid flow rates shall be as established in 4.1.5 and 4.1.6.
** Equipment with dual-rated frequencies shall be tested at each frequency.
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5.2.2  Test procedures
5.2.2.1  The equipment shall be operated continuously for one hour after the specified temperatures have been
established at each specified voltage level.
The 110 % voltage test shall be conducted prior to the 90 % voltage test.
5.2.2.2
5.2.2.3  All power to the equipment shall be cut off for 3 min at the conclusion of the one hour test at the 90 %
voltage level and then restored for one hour.
5.2.3  Test requirements
Heat pumps shall meet the following requirements when operating at the conditions specified in tables 3 and 4.
5.2.3.1  During the entire test, the equipment shall operate without any indication of damage.
5.2.3.2  During the test period specified in 5.2.2.1, the equipment shall operate continuously without tripping any
motor overload or other protective devices.
5.2.3.3  During the test period specified in 5.2.2.3, the motor overload protective device may trip only during the first
5 min of operation after the shutdown period of 3 min. During the remainder of the test period, no motor overload
protective device shall trip. For those models so designed that resumption of operation does not occur within the
first 5 min after the initial trip, the equipment may remain out of operation for no longer than 30 min. It shall then
operate continuously for the remainder of the test period.
5.3  Minimum operating conditions test
5.3.1  Test conditions
Heat pumps shall be tested at the minimum operating test conditions for cooling and heating at the test conditions
established for the specific applications (see 4.2.3) specified in tables 5 and 6. Heat pumps intended for use in two
or more applications shall be tested at the most stringent set of conditions specified in tables 5 and 6.
5.3.2  Test procedures
For the minimum operating cooling test, the heat pump shall be operated continuously for a period of no less than
30 min after the specified temperature conditions have been established. For the minimum operating heating test,
the heat pump shall soak for 10 min with liquid at the specified temperature circulating through the coil. The
equipment shall then be started and operated continuously for 30 min.
5.3.3  Test requirements
No protective device shall trip during these tests and no damage shall occur to the equipment.
5.4  Enclosure sweat and condensate test
5.4.1  Test conditions
The enclosure sweat and condensate test shall be conducted in the cooling mode at the test conditions established
for the specific applications specified in table 7.
All controls, fans, dampers and grilles shall be set to produce the maximum tendency to sweat, provided such
settings are not contrary to the manufacturer’s instructions to the user. Heat pumps intended for two or more
applications shall be tested at the most stringent set of conditions.
5.4.2  Test procedures
After establishment of the specified temperature conditions, the heat pump shall be operated continuously for a
period of four hours.
5.4.3  Test requirements
No condensed water shall drip, run or blow off the equipment’s casing during the test.
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Table 5 — Minimum cooling test conditions
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side*
 — dry bulb, °C 21 21 21
 — maximum wet bulb, °C 15 15 15
Air surrounding unit
 — dry bulb, °C 21 21 21
Liquid entering heat exchanger*, °C 20 10 10
Frequency** Rated Rated Rated
Voltage*** Rated Rated Rated
* Air and liquid flow rates shall be as established in 4.1.5 and 4.1.6.
** Equipment with dual-rated frequencies shall be tested at each frequency.
*** Equipment with dual-rated voltages shall be tested at the lower of the two voltages.
Table 6 — Minimum heating test conditions
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side*
 — dry bulb, °C 15 15 15
Air surrounding unit
  — dry bulb, °C 15 15 15
Liquid entering heat exchanger*, °C 15 5 -5
Frequency** Rated Rated Rated
Voltage*** Rated Rated Rated
* Air and liquid flow rates shall be as established in 4.1.5 and 4.1.6.
** Equipment with dual-rated frequencies shall be tested at each frequency.
*** Equipment with dual-rated voltages shall be tested at the lower of the two voltages.
Table 7 — Enclosure sweat and condensate test conditions
Water-loop Ground-water Ground-loop
heat pumps heat pumps heat pumps
Air entering indoor side*
 — dry bulb, °C 27 27 27
 — wet bulb, °C 24 24 24
Air surrounding unit
 — dry bulb, °C 27 27 27
Liquid entering heat exchanger*, °C 20 10 10
Frequency** Rated Rated Rated
Voltage*** Rated Rated Rated
* Air and liquid flow rates shall be as established in 4.1.5 and 4.1.6.
** Equipment with dual-rated frequencies shall be tested at each frequency.
*** Equipment with dual-rated voltages shall be tested at the lower of the two voltages.
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6  Test methods
6.1  General
The standard capacity ratings shall be determined by the test methods and procedures established in this clause
and annex A. The total cooling and heating capacities shall be the average of the results obtained using the liquid
enthalpy test method (annex C) and the indoor air enthalpy test method (annex B), or optionally, for non-ducted
equipment, the calorimeter room test method (annex E). The results obtained by these two methods must agree
within 5 % in order for a particular test to be valid. Measurements shall be made in accordance with the provisions
of annexes D and F.
6.2  Uncertainties of measurement
The uncertainties of measurement shall not exceed the values specified in table 8.
Table 8 — Uncertainties of measurement for indicated values
1
Measured quantity Unit Uncertainty of measurement
Water
° C 0,1 °C
— temperature –
— temperature difference ° C –0,1 °C
— volume flow l/s –1 %
— static pressure difference Pa –5 Pa (p < 100 Pa)
–5 % (p > 100 Pa)
Air
— dry bulb temperature ° C –0,2 °C
— wet bulb temperature ° C –0,2 °C
— volume flow l/s –5%
— static pressure difference Pa –5 Pa (p < 100 Pa)
–5 % (p > 100 Pa)
Electrical inputs 0,5 %
Time 0,2 %
Mass 1,0 %
Speed 1,0 %
1
Uncertainty of measurement: an estimate characterizing the range of values within which the true value of a measurand lies
(measurand: a quantity subject to measurem
...