oSIST prEN 17671:2021

SLOVENSKI STANDARD
01-junij-2021
Sistemi za ogrevanje in hlajenje z vodo v stavbah - Projektiranje sistemov za
hlajenje z vodo
Heating systems and water based cooling systems in buildings - Design for water based
cooling systems
Heizungsanlagen und wassergeführte Kühlanlagen in Gebäuden - Planung von
wassergeführten Kühlanlagen
Ta slovenski standard je istoveten z: prEN 17671
ICS:
91.140.30 Prezračevalni in klimatski Ventilation and air-
sistemi conditioning systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2021
ICS 91.140.30
English Version
Heating systems and water based cooling systems in
buildings - Design for water based cooling systems
Heizungsanlagen und wassergeführte Kühlanlagen in
Gebäuden - Planung von wassergeführten Kühlanlagen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 228.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17671:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and subscripts . 9
4.1 Symbols . 9
4.2 Subscripts . 10
5 System design requirements . 10
5.1 General requirements . 10
5.2 Requirements for preliminary design information . 11
5.3 Chilling system . 12
5.3.1 General . 12
5.3.2 Sizing . 12
5.3.3 Devices for water-based heat rejection system (recooler) . 12
5.4 Primary and secondary distribution circuits. 13
5.4.1 General . 13
5.4.2 Requirements for the chilled water . 13
5.4.3 Flow rate . 14
5.4.4 Circulation pumps . 14
5.4.5 Pipework . 14
5.4.6 Hydronic balancing . 15
5.5 Cooling emission system - coolers . 15
5.5.1 General . 15
5.5.2 Sizing . 16
5.5.3 Positioning of coolers . 16
5.5.4 Protection against damage to buildings and installations . 16
5.5.5 Unnecessary cooling consumption . 17
5.5.6 Cleaning . 17
5.6 Cooling system controls . 17
5.6.1 General . 17
5.6.2 Central control . 17
5.6.3 Local temperature control . 17
5.6.4 Zone control . 18
5.6.5 Supply temperature control . 18
5.6.6 Time control of cooling . 18
5.7 Safety arrangements . 19
5.7.1 General . 19
5.7.2 Protection against temperatures falling below the minimum system safety
temperature . 19
5.7.3 Safety valves, rating, design and arrangements . 19
5.7.4 Flow control device . 20
5.7.5 Pressurization systems . 20
5.8 Operational requirements . 21
5.8.1 General . 21
5.8.2 Provision for monitoring operating conditions . 21
5.8.3 Temperature/power controller . 21
5.8.4 Pressure maintaining control device . 22
5.8.5 Filling and feeding device . 22
5.9 Thermal insulation. 22
5.10 Preventing corrosion . 23
5.11 Documentation . 23
5.12 Instructions for mainainance, operation and use . 24
5.13 Installation and commissioning . 24
Annex A (informative) Information for the design of diaphragm expansion vessels (static
pressurization and pressurization stations (dynamic pressurization) for closed
systems . 25
A.1 General . 25
A.2 Expansion vessel size calculation . 27
Annex B (informative) Hydraulic schemes for heating and cooling . 30
B.1 General . 30
Bibliography . 33

European foreword
This document (prEN 17671:2021) has been prepared by Technical Committee CEN/TC 228 “Heating
systems and Water based Cooling Systems in Buildings”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
1 Scope
This document specifies design criteria for closed water-based cooling systems in buildings. The
requirements aim at achieving a proper technical quality level and maintaining the desired thermal
indoor climate with minimum energy consumption.
Systems for dissipating process heat from industrial processes, for example, are not covered by this
document.
This document does not amend product standards or product installation requirements. The standard
covers cooling systems of the following type (see Figure 1):
1) devices for the water-based heat rejection of the chilling system;
2) devices for chilling and storage of chilled water;
3) devices for the distribution of chilled water;
4) devices for the absorption of heat (“cooling emission”);
5) control devices;
6) safety devices.
Figure 1
The design of such systems is described in this document. In the case of water-based cooling systems with
local operating temperatures ≤ 0 °C separate safety aspects may apply. The other Clauses of this
document are still valid for those systems.
This document does not cover the chilling system itself, but only the parts of the chilling system which
are an integral part of the cooling system, including determination of the design
performance.Furthermore this document does not cover:
— the requirements for installation or instructions for operation, maintenance and use;
— the design of the system components (e.g. recooler, chilling system, coolers, pipes, safety devices
etc.).
The relevant technical rules with regard to the prevention of corrosion are to be observed in the material
selection for the system components and the nature of the heat transfer medium.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 1717, Protection against pollution of potable water in water installations and general requirements of
devices to prevent pollution by backflow
EN 12170, Heating systems in buildings - Procedure for the preparation of documents for operation,
maintenance and use - Heating systems requiring a trained operator
EN 12171, Heating systems in buildings - Procedure for the preparation of documents for operation,
maintenance and use - Heating systems not requiring a trained operator
EN 16798-1:2019, Energy performance of buildings – Ventilation for buildings - Part 1: Indoor
environmental input parameters for design and assessment of energy performance of buildings addressing
indoor air quality, thermal environment, lighting and acoustics - Module M1-6
EN 14336, Heating systems in buildings - Installation and commissioning of water based heating systems
EN ISO 52000-1:2017, Heating systems in buildings - Installation and commissioning of water based
heating systems
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.electropedia.org/
3.1
chilling system
configuration of interconnected components/appliances for the supply of chilled water to the
distribution system
3.2
chilled water
circulation water on the heat-absorbing side of a chiller (primary and secondary circuit)
Note 1 to entry: Usually with a temperature ≤ 25 °C.
3.3
combined system (combined heating and cooling systems)
system used both for covering a heat load and the cooling load of a building, and for which there is a
temporary or permanent hydraulic connection between the two respective circuits
3.4
cooler
component for extracting heat from a cooled space, such as a fan coil unit, embedded cooler, cooling
terminal and coil
3.5
cooling period
time period during which cooling is required to maintain the internal design temperature
3.6
cooling water
circulation water on the heat-rejection side of a chiller
Note 1 to entry: Usually with a temperature > 25 °C and ≤ 40 °C.
3.7
cooled space
room or enclosure which is to be cooled to the specified internal design temperature under defined
boundary conditions
3.8
design cooling load
maximum cooling capacity required from the cooling system of a building in order maintain the required
internal temperature and/or humidityunder defined boundary conditions
3.9
external air temperature
air temperature outside the building
3.10
external design temperature
external air temperature which is used for the calculation of the design cooling load
3.11
free cooling
cooling without the use of a chilling system, e.g. through ventilation during the day or night or through
the direct use of cooling towers, dry coolers, seawater, groundwater or embedded coils with energy
consumption for any pumps and fans
3.12
frost inhibitor
supplement to a cooling medium lowering its freezing point
3.13
heat rejection system
part of the cooling system which emits the rejected heat produced by the chiller to the external
environment including pipes, valves, pumps and mixing systems
3.14
lockout
default condition resulting in a shutdown of the system and requiring a manual reset
Note 1 to entry: The intention of a lockout is to require the operator to investigate and eliminate the cause of the
lockout.
3.15
maximum operating pressure
maximum pressure at which the system, or parts of the system, is designed to operate
3.16
maximum/minimum operating temperature
maximum or minimum temperature at which the system, or parts of the system, is designed to operate
3.17
maximum/minimum system safety temperature
highest/lowest temperature any component of the cooling system can accommodate
3.18
operative temperature
arithmetic average of the internal air temperature and the mean radiant temperature
3.19
partial cooling load
fraction of design cooling load occurring unter typical dynamically varying cooling system operating
conditions
3.20
pressure limiting device
automatic operating device which prevents the maximum operating pressure from being exceeded
3.21
pressurization system
system equipment (diaphragm expansion vessels, compressor-controlled pressurization units and
pump-controlled pressurization units) for pressure maintenance in closed cooling systems
Note 1 to entry: The equipment provides to maintain the system pressure between defined limits and ensures
the required minimal working pressure of the cooling system. The equipment holds the accruing expansion water
when the system water is heated and restores the volume when the cooling system is cooling down and contracting.
Due to the design of construction the expansion system simultaneously protects the expansion water from corrosion
producing ingress of oxygen.
3.22
primary distribution circuit
part of the cooling system which distributes chilled water from the chilling system to the individual
cooling circuits including pipes, valves, pumps and mixing systems
3.23
response overpressure
pressure at which a safety valve opens at operating conditions
3.24
room set point temperature
operative temperature of a cooled space which is used for the calculation of the design cooling load
3.25
secondary distribution circuit
part of the cooling system which distributes chilled water from the primary distribution circuit to the
individual coolers at the appropriate temperatures and/or flowrates including pipes, valves, pumps and
mixing systems
3.26
sealed system
cooling system in which the cooling medium is closed to the atmosphere
3.27
temperature controller
automatic device intended to keep the temperature at a set point
3.28
timing control
method of controlling the generation, extraction or transfer of heat by using a timed program for starting
and shutting down the system
3.29
water level limiter
automatic operating device that causes shutdown and lockout of the heat absorption when the set
minimum operating pressure of the cooling system is reached
3.30
control
method of controlling the chilled water flow to a cooling emission system by changing the flow rate
and/or the flow temperature
3.31
central control
control at a central point
3.32
local control
control locally on the basis of the temperature of the cooled space
3.33
zone control
local control of a zone consisting of more than one space
3.34
zone
space or groups of spaces with similar thermal characteristics
4 Symbols and subscripts
4.1 Symbols
For the purposes of this document, the symbols given in EN ISO 52000-1:2017 and the specific symbols
listed in Table 1 apply. Symbols and subscripts may have more than one denotation.
Table 1 — Symbols and units
Symbol Name Unit
ϑ Temperature on the Celsius scale °C
≥
ρ Density
kg/m  or kg/l
η utilization efficiency –
e expansion coefficient –
V Volume
m
h Height m
P Pressure bar
4.2 Subscripts
For the purposes of this document, the subscripts given in EN ISO 52000-1:2017, and the specific
subscripts listed in Table 2 apply. Subscripts may have several denotations.
Table 2 — Subscripts
Index Meaning/Use
st static
v vapor
O operating
ini initial
fin final
wr water reserve
ex expansion
N nominal
min minimal
5 System design requirements
5.1 General requirements
Cooling systems shall be designed and selected to provide satisfactory thermal comfort and to enable an
economically optimized operation with a minimum energy consumption within the framework of the
specified operating parameters. This includes operation at design cooling load and partial cooling loads.
The following general aspects shall be taken into account:
— external cooling loads shall be minimized e.g. by using external sunlight protection and sunshade
equipment.
NOTE In new constructions, this is combined with an appropriate design of the building and windows as
well as the use of materials with a high heat capacity.
— internal cooling loads shall be reduced as far as possible e.g. by using energy efficient lighting and
technical appliances.
— methods of passive- and free cooling shall be made use of first, where possible. Mechanical cooling
should only be activated if it is not otherwise possible to reduce the room temperatures in
accordance with the selected values (e.g. EN 16798-1:2019 Clause B.1.2).
— simultaneous heating and cooling of individual rooms shall be avoided.
— chilled water temperatures shall be as high as possible in accordance with the respective cooling
emission system. Unnecessary low temperatures in the primary and secondary distribution cicuits
shall be avoided.
— cooling water temperatures in the heat rejection cicuit shall be as low as possible in accordance with
the respective heat rejection system e.g. by means of a generously dimensioned recoolers.
NOTE Mechanical cooling is not usually installed in domestic premises.
5.2 Requirements for preliminary design information
The cooling system shall be designed, installed and operated in a way that does not damage the building
or other technical building systems.
The cooling system shall be designed with due consideration to: installation, commissioning, operation,
and maintenance of the entire system under full cooling load and partial cooling load conditions.
At the planning stage or during the progress of design, the following items shall be taken in consideration
and documented:
a) thermal characteristics of the building for calculation of cooling load and possible improvements
regarding energy savings;
b) external design temperature and absolute air humidity for the design case;
c) internal design temperature;
d) method of design cooling load calculation;
e) permissible exceedances of the operative temperature according to EN 16798-1;
f) energy sources for cooling;
g) position of the chiller, bearing in mind access for maintenance as well as the cooling water and chilled
water piping layout;
h) position of the heat rejection system. If possible protection against direct sunlight and contamination
in compliance with separate (e.g. hygienic) requirements of the heat rejection system;
i) choice of suitable pressurization;
j) position of expansion vessels, filling point and pressure gauge;
k) facilities for filling and draining the system and parts;
l) power requirements of any attached system;
m) type and position of coolers and cooling surfaces;
n) type of control system for cooling and any attached systems, especially when controlled together
with heating systems;
o) pipework routing and laying method of the installation;
p) specifications for hydronic balancing of the system;
q) provisions for measurement of energy consumption;
r) provisions for protection against condensation;
s) provisions for system filling and water treatment;
t) requirements for extra cooling capacity for intermittent operation (e.g. utility locking times) as well
as chilled water storage;
u) technical rooms, location and size;
v) relevant national and statutory regulations can be consulted.
5.3 Chilling system
5.3.1 General
According to 5.2 e), the method for determing the design cooling load shall be agreed upon with the client.
The chilling system shall be designed in such a way that it covers the determined design cooling load of
the building.
The chilling system shall be designed and dimensioned taking into account the type of chiller and the type
of heat rejection and its control mode.
The temperature in the distribution system shall be as high possible with regard to the output and
operation of the coolers.
If necessary, a chilled water storage tank shall be installed. Sizing can be based on a maximum number of
operation cycles or minimum running time of the chiller.
5.3.2 Sizing
If the total cooling power is provided by more than one chiller, the following points shall be considered:
— the fraction of the cooling load supplied by each chiller, if necessary depending on their respective
running times;
— hydraulic balancing during simultaneous operation of multiple chillers;
— isolation of standby chillers;
— operational requirements, such as standby modes.
5.3.3 Devices for water-based heat rejection system (recooler)
The design of the heat rejection system shall consider the following points:
— minimizing return temperatures to the chiller;
— variable control of fans in dry coolers and cooling towers;
— hygenic aspects of wet cooling towers including water treatment requirements;
— noise aspects;
— connection to free cooling;
— minimizing the use of auxiliary energy.
The devices for the water-based heat rejection of the chiller (see Figure 1) shall be designed to ensure
rejection of heat in all operating states.
5.4 Primary and secondary distribution circuits
5.4.1 General
The primary and secondary distribution cicuits shall be designed and dimensioned so that the desired
thermal indoor climate can be controlled and maintained, and the necessary cooling flows are available
at the coolers, and if necessary any attached systems.
The required temperatures and pressure at the coolers are to be maintained under full cooling load and
partial cooling load operating conditions, so as to minimize energy usage.
The distribution system shall be designed, placed and insulated such that cooling loss to the surroundings
is kept at a minimum.
If possible, the distribution system shall be placed so that the cooling emission from the system benefits
the building. Pipes, ducts, components, etc. shall if possible not be placed in areas with high temperatures.
In case of combined heating/cooling systems, the higher volumetric flow rates required for cooling shall
be considered. Suitable components are to be used.
The distribution system, including sub-circuits, shall be designed so as to enable hydraulic balancing.
Consideration shall also be given to any variety of demand for connected systems. Consideration shall be
given to separate circuits for each type of cooling emission system, the zoning requirement of buildings
and the supply temperature and temperature difference of each cooling emission system.
Provision for filling, draining and venting shall be provided for each circuit according to EN 14336.
5.4.2 Requirements for the chilled water
The requirements stated below also apply for the heat rejection system.
To ensure the quality of the chiller medium and protect the system from malfunction, three factors should
be managed during the design phase:
— All chilled water distribution circuits should be designed to prevent air ingress and facilitate the
collection and removal of air during filling and operation.
— The rate of corrosion should be minimized by preventing oxygen ingress, selecting appropriate and
compatible materials and/or by specifying a chemical corrosion inhibitor.
Note In some systems, maintaining complete oxygen (air) tightness is impractical due to defective
pressurization or diffusion/permeation at membranes, joints, plastic pipes, seals, etc.
— Chilled water distribution systems should be designed and operated so that sedimentation of
suspended, circulating particulate matter and biological fouling are prevented. Design should ensure
that circulating solids are easily removed during operation (i.e. by use of an appropriate filter).
The necessity of using frost inhibitorsand chemicals in the chiller medium shall be considered. In
particular, repercussions on the environment and and waste disposal of the medium shall be taken into
account.
When using frost inhibitors, the modification of the properties in the chiller medium shall be considered
in the selection and dimensioning of the system components (e.g. circulation pump, sealing materials), in
particular the modifications of the heat capacity, the viscosity and the corrosion potential.
All frost inhibitors shall be combined with a corrosion inhibitor. Frost inhibitors should not be mixed
onsite and kept in closed containers.
5.4.3 Flow rate
The flow rates and heat losses shall be calculated and documented according to the required cooling
power for every flow path under design cooling load.
Based on these calculations, set values are to be stated and documented for any required hydronic
balancing devices.
5.4.4 Circulation pumps
Cooling systems shall be designed with minimum pressure loss with due regard to the operation and
economy of the system.
Circulation pumps shall be sized and set so that the required flow rates and pressure differences at any
point of the system and in any operating phase are available.
When pumps are selected, it is important to ensure minimum electricity consumption for the operation
and control of pumps.
Pumps shall be controlled automatically based on the water flow and pressure demand of the cooling
system depending on the relevant operation mode. An exception to this requirement are pumps requiring
a constant water flow, e.g. in connection with ventilation cooling surfaces. Control shall not limit the
possibility of obtaining the desired indoor climate or meeting any requirements for minimum water flow.
Further consideration shall be given to:
— the suitability of the circulation pump for the task;
— characteristic curves and the optimum range of application;
— thermal insulation;
— sound insulation and noise emission.
5.4.5 Pipework
Pipework shall be designed and sized so that at any point of the system, the flow rate and the pressure
difference required to fulfil the cooling load of the system are achievable.
Condensation on the pipe surface and within the insulation material shall be avoided. For this reason and
to minimize energy losses, all pipes, ducts, components etc. of the distribution system shall be insulated
also those components leading through brackets.
Parts involving a risk of condensation shall be placed visibly. Parts in central cooling systems involving a
significant risk of leakage shall be placed visibly or in such a way that leaking water is led to a visible
place. When assessing the risk, the nature and number of joints and the suitability of the prescribed
tightness test for detecting leaks shall be taken into account.
Further consideration shall be given to:
— Pipe dimension with effects on:
— pressure drop;
— noise transmittance, e.g. due to flow velocity.
— Operating and ambient temperatures:
— design pressure;
— material selection;
— corrosion prevention (e.g. restriction of oxygen permeability);
— compatibility of individual components.
— Pipework routing:
— accessibility (e.g. for installation and maintenance);
— thermal expansion and contraction;
— fixing (suitability for the scope, protection against noise transmittance);
— precautions for filling, emptying and venting;
— the use of sleeves when crossing walls.
— Fire protection;
— Thermal insulation:
— suitability for the scope (e.g. diffusion-tight against water vapour, thickness of insulation);
— compatibility with the pipe material.
5.4.6 Hydronic balancing
All distribution systems and circuits for chilled and cooling water shall be provided with hydronic
balancing capabilities. All distribution systems shall be hydronically balanced prior to commissioning.
The method of balancing shall be specified during the design phase.
5.5 Cooling emission system - coolers
5.5.1 General
Coolers shall be selected and controlled on the basis of the design cooling load. Consideration shall be
given to:
— the design cooling load;
— the system flow temperature;
— thermal comfort in occupied spaces (should be in accordance with EN ISO 7730, where specified);
— the noise level in occupied spaces;
— protection and prevention of damage to the building components (prevention of condensation);
— maintenance requirements, e.g. cleaning and repair;
— compatibility with supply, distribution and control system.
Cooling emission systems with a high thermal inertia, e.g. pipes embedded in concrete, should not be the
only cooler in rooms with rapidly varying internal loads.
5.5.2 Sizing
Coolers shall be sized on a space-by-space basis. The local cooling loads may be determined according to
relevant technical regulations.
The dimensioning of the devices and their operating parameters, such as temperatures and flow rates,
shall be determined on the basis of the product data sheets of the respective manufacturer.
The design should include consideration of factors that can affect the capacity of the devices for space
cooling and take into account that such effects are often cumulative, e.g. casing, floor coverings or types
of connection.
Depending on the original design parameters, the design may consider an additional allowance on the
capacity, e.g. for systems that are being operated intermittently (e.g. utility locking times in active cooling
mode through heat pumps).
5.5.3 Positioning of coolers
In choosing the location of devices for space cooling, consideration shall be given to the overall effects
upon the control of room temperatures and comfort conditions. Consideration may also be given to
centrally or decentrally arranged devices for mechanical ventilation of the spaces.
Criteria for assessing the thermal environment can be determined with EN ISO 7730.
Coolers shall be placed and designed so that:
— they contribute to a satisfactory thermal indoor climate in the room;
— building and installation elements are not damaged;
— people are not exposed to injury or inconvenience;
— unnecessary use of resources is avoided.
5.5.4 Protection against damage to buildings and installations
Coolers with low surface temperatures shall be designed so as not to cause inconvenience or damage due
to condensation.
This can be done by:
— keeping the surface temperature of the coolers above the dew point; and
— draining condensation.
5.5.5 Unnecessary cooling consumption
Coolers shall be placed and incorporated so as to provide minimum cooling to the space they do not serve.
Embedded coolers such as floor cooling, ceiling cooling, wall cooling, etc. shall be used only where the
building elements, in which they are incorporated, are properly insulated to adjacent spaces. With the
exception of Thermally Activated Building Systems (TABS), surface insulation to adjacent spaces shall
have a thermal heat transfer coefficient U < 0,5 W/m K.
W
5.5.6 Cleaning
Coolers shall be cleanable in situ by a normal standard method. If a standard method is not possible, the
the manufacturer shall specify an appropriate method.
5.6 Cooling system controls
5.6.1 General
The information on controls stated in document exclusively relates to the extraction of heat from the
cooled space (primary and secondary chilled water circuits, see Figure 1). The control functions listed in
this part refer to the control capabilities of the chilled water circuit which, in conjuction with dynamic
hydronic balancing capabilities, are required for optimizing cooling system performance under partial
cooling load operating conditions.
The control of the heat rejection system is to be adapted to the control concept of the chilled water circuit,
so that full load, partial load and start-up behaviour of the chillers are taken into consideration.
The thermal indoor climate shall be controllable in a simple manner, e.g. by using individual room
temperature control in combination with supply temperature control.
The user’s ability to control the thermal indoor climate should be limited if this results in inconvenience
to other users, e.g. thermal discomfort and increased energy consumption.
Requirements for control are the same for mechanical cooling and for free cooling.
5.6.2 Central control
Central control of the chiller flow temperature shall be provided.
If the primary side is separated from the secondary side by, for example, a hydraulic separator, a separate
control is required for the secondary side. In this case, the flow rate on the secondary side shall be lower
than the flow rate through the chiller.
5.6.3 Local temperature control
Coolers shall be equipped with devices for automatic control of cooling emission according to the room
temperature in each room so that the intended thermal indoor climate is obtained, and unnecessary
energy consumption is avoided. At the same time, operation shall be simple for the user.
Room temperature sensors shall be placed so that the measured temperature is representative of the
operative temperature in the occupied zone.
Individual setting of the desired room temperature in each room shall be possible.
Proportional controllers are dimensioned with a proportional band not exceeding 2 °C under stationary
conditions.
The controller is designed to ensure that the desired tolerances are achieved with a fairly short settling
time. Change of outdoor climate or additional heat shall not require a change in the setting values of the
controller.
There shall be a suitable dead band between heating and cooling in the individual rooms so as to avoid
simultaneous heating and cooling and repeated shift between heating and cooling.
5.6.4 Zone control
A zone control is used to control different devices for space cooling with similar operating parameters.
If a zone control is used, a corresponding hydraulic distribution network is to be provided.
5.6.5 Supply temperature control
Central cooling systems shall be provided with automatic control of the supply temperature. Control of
the supply temperature shall be based on the room or subsystem, e.g. ventilation cooling surface, which
currently requires the lowest supply temperature. Control of the supply temperature shall not be based
on one particular room or subsystem in systems serving multiple rooms or subsystems.
When using embedded cooling terminals or chilled beams, the supply temperature control shall ensure
that condensation is not inadvertently formed in the coolers and that the heat loss from the distribution
system is limited to the largest possible extent.
The controller may be combined with compensation in relation to the return temperature or the
temperature increase over the system.
In case of different requirements for supply temperature in the various parts of the building or the
system, the system shall be divided into separate zones with individual control of the supply temperature.
In large buildings the system is divided according to the orientation of the façades and compensation for
the solar radiation on the façade.
One zone with common supply temperature control shall only comprise coolers with the same design
supply temperature.
In systems also used for process cooling of e.g. servers or equipment, the supply temperature control may
be omitted if the design output to the ordinary space cooling is below 70 % of the overall design output
of the system for comfort reasons, and there is a requirement for constant supply temperature for the
process cooling.
Control is designed so that the cooling supply is shut off and the circulation pump stops when there is no
cooling requirement.
NOTE Unintended condensation is condensation against which no measure has been taken to counteract or
dissipate.
5.6.6 Time control of cooling
Cooling systems shall be provided with time control. The time control design shall take into account the
building's heat capacity and use as well as the cooling system and supply system characteristics.
Time control can be central for the entire building, divided into zones with equal periods of activity or it
can be individual for each room. If there is a big difference between the periods of activity, large cooling
systems shall be divided into zones with equal periods of activity.
Time control setting can be done either by controlling the cooling supply to coolers or by controlling the
individual coolers directly, e.g. by shutting off the cooler or by increasing the room temperature setting
outside the period of activity. If there is no cooling requirement in the building or a zone of the cooling
system, the cooling supply shall be shu
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