EN 12828:2003

SLOVENSKI STANDARD
01-februar-2004
Grelni sistemi v stavbah – Projektiranje toplovodnih grelnih sistemov
Heating systems in buildings - Design for water-based heating systems
Heizungssysteme in Gebäuden - Planung von Warmwasser-Heizungsanlagen
Systemes de chauffage dans les bâtiments - Conception des systemes de chauffage a
eau
Ta slovenski standard je istoveten z: EN 12828:2003
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 12828
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2003
ICS 91.140.10
English version
Heating systems in buildings - Design for water-based heating
systems
Systèmes de chauffage dans les bâtiments - Conception Heizungssysteme in Gebäuden - Planung von
des systèmes de chauffage à eau Warmwasser-Heizungsanlagen
This European Standard was approved by CEN on 4 July 2002.
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. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovak Republic, Spain, Sweden, Switzerland and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12828:2003 E
worldwide for CEN national Members.

Contents
page
Foreword.4
1 Scope .5
2 Normative references .5
3 Terms and definitions.6
4 System design requirements.9
4.1 Requirements for preliminary design information .9
4.2 Heat supply.10
4.2.1 General.10
4.2.2 Sizing.10
4.3 Heat distribution .11
4.3.1 General.11
4.3.2 Design criteria .11
4.4 Heat emission.12
4.4.1 General.12
4.4.2 Sizing.13
4.4.3 Positioning.13
4.4.4 Thermal environment .13
4.4.5 Surface temperatures .13
4.5 Controls .13
4.5.1 General.13
4.5.2 Classification.14
4.5.3 Central control.14
4.5.4 Zone control .15
4.5.5 Local control.15
4.5.6 Timing control .15
4.6 Safety arrangements .16
4.6.1 General.16
4.6.2 Equipment required for sealed sysems.16
4.6.3 Equipment required for open vented systems .18
4.7 Operational requirements .19
4.7.1 General.19
4.7.2 Provision for monitoring operating conditions .20
4.7.3 Temperature controller.20
4.7.4 Pressure maintaining device .20
4.7.5 Water level adjustment.20
4.8 Thermal insulation .20
4.8.1 General.20
4.8.2 Undesirable heat losses.21
4.8.3 Harmful effects of too high temperatures .22
4.8.4 Frost protection.22
5 Instructions for operation, maintenance and use .22
6 Installation and commissioning .22
Annex A (informative) Control system classification .23
A.1 Control system classification.23
A.1.1 General.23
A.1.2 Heating control system modes.23
A.1.3 Control system performance modes .23
A.1.4 Control system classification table .23
A.2 Examples of control system classification .24
A.2.1 Local manual control.24
A.2.2 Local manual control and central automatic control.25
A.2.3 Local automatic control and central automatic control.25
A.2.4 Local automatic control and automatic zone control .26
A.2.5 Local automatic control and central automatic control with optimization.27
Annex B (informative) Thermal Environment .28
Annex C (informative) Thermal insulation .30
Annex D (informative) Guidance for dimensioning diaphragm expansion vessels (sealed systems).33
D.1 General.33
D.2 Expansion vessel size calculation.34
Annex ZA (informative) A-deviation .38
Bibliography.39
Foreword
This document EN 12828:2003 has been prepared by Technical Committee CEN/TC 228 “Heating systems in
buildings”, the secretariat of which is held by DS.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by September 2003, and conflicting national standards shall be withdrawn at the
latest by March 2004.
Annexes A, B, C, D and ZA are informative.
This document includes a Bibliography.
The subjects covered by CEN/TC 228 are the following:
design of heating systems (water based, electrical, etc.);
installation of heating systems;
commissioning of heating systems;
instructions for operation, maintenance and use of heating systems;
methods for calculation of the design heat loss and heat load;
methods for calculation of the energy performance of heating systems.
Heating systems also include the effect of attached systems such as hot water production systems.
All these standards are system standards, i.e. they are based on requirements addressed to the system as a whole
and not dealing with requirements to the products within the system.
Where possible, reference is made to other CEN or ISO standards, a.o. product standards. However, use of
products complying with relevant product standards is no guarantee of compliance with the system requirements.
The requirements are mainly expressed as functional requirements, i.e. requirements dealing with the function of
the system and not specifying shape, material, dimensions or the like.
The guidelines describe ways to meet the requirements, but other ways to fulfil the functional requirements might
be used if fulfilment can be proved.
Heating systems differ among the member countries due to climate, traditions and national regulations. In some
cases requirements are given as classes so national or individual needs may be accommodated.
In cases where the standards contradict with national regulations, the latter should be followed.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,
Slovak Republic, Spain, Sweden, Switzerland and the United Kingdom.
1 Scope
This standard specifies design criteria for water based heating systems in buildings with a maximum operating
temperature of up to 105°C. In case of heating systems with maximum operating temperatures over 105°C other
safety aspects than those described in 4.6 may apply. The other clauses of this standard are still valid for those
systems.
This standard does not cover additional safety requirements which may be applicable to heating systems greater
than 1 MW design heat load.
This standard does not amend product standards or product installation requirements.
This standard covers the design of:
heat supply systems;
heat distribution systems;
heat emission systems;
control systems.
This standard takes into account heating requirements of attached systems (e.g. domestic hot water, process heat,
air conditioning, ventilation) in the design of a heat supply, but does not cover the design of these systems.
This standard does not cover requirements for installation or commissioning or instructions for operation,
maintenance and use of water based heating systems.
This standard does not cover the design of fuel and energy supply systems.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN 215-1
Thermostatic radiator valves - Part 1: Requirements and test methods.
EN 442-1
Radiators and convectors - Part 1: Technical specifications and requirements.
EN 442-2
Radiators and convectors – Part 2: Test methods and rating.
EN 442-3
Radiators and convectors – Part 3: Evaluation of conformity.
EN 563
Safety of machinery – Temperatures of touchable surfaces – Ergonomics data to establish temperature limit
values for hot surfaces.
prEN 806-2
Specifications for installations inside buildings conveying water for human consumption – Part 2: Design.
EN 1264-1
Floor heating - Systems and components – Part 1: Definitions and symbols.
EN 1264-2
Floor heating - Systems and components – Part 2: Determination of the thermal output.
EN 1264-3
Floor heating - Systems and components – Part 3: Dimensioning.
prEN 1268-1
Safety devices for the protection against excessive pressure - Part 1: Safety valves.
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 12831
Heating systems in buildings - Method for calculation of the design heat load.
EN 13202
Ergonomics of the thermal environment - Temperatures of touchable hot surfaces - Guidance for establishing
surface temperature limit values in production standards with the aid of EN 563.
prEN 13831
Closed expansion vessels with built-in diaphragm for installations in water systems.
EN 60730-2-9
Automatic electrical controls for household and similar use – Part 2-9: Particular requirements for temperature
sensing controls (IEC 730-2-9:2000, modified).
EN ISO 7730
Moderate thermal environments - Determination of the PMV and PPD indices and specification of the
conditions for thermal comfort (ISO 7730:1994).
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
attached system
ancillary system which may influence the design and heat load of the system but does not form an integral part of
the space heating system. Examples of such ancillary systems include:
domestic hot water systems;
ventilation and air conditioning systems;
process heating systems
3.2
central control
method of controlling the heat flow to a heat emission system by changing the flow rate and/or the flow temperature
at a central point
3.3
design heat load
heat flow required to achieve the specified design conditions
3.4
design heat losses
quantity of heat per unit time leaving the building to the external environment under specified design conditions, i.e.
heat losses calculated according to EN 12831
3.5
external design temperature
external air temperature which is used for the calculation of the design heat losses
3.6
external air temperature
air temperature outside the building
3.7
frost inhibitor
supplement to a heating medium lowering its freezing point
3.8
heat distribution system
configuration of interconnected components for the dispersal of heat between the heat supply system and the heat
emission system or any attached system
3.9
heated space
space which is to be heated to the specified internal design temperature
3.10
heat emission system
configuration of interconnected components for the dispersal of heat to a heated space
3.11
heat gains
quantity of heat generated within or entering into a heated space from heat sources other than the heating system
3.12
heating period
time during which heating is required to maintain the internal design temperature
3.13
heat supply system
configuration of interconnected components/appliances for the supply of heat to the heat distribution system
3.14
internal design temperature
operative temperature at the centre of the heated space (between 0,6 and 1,6 m height) used for calculation of the
design heat losses
3.15
local control
method of controlling the heat flow to a heat emission system by changing the flow rate or the flow temperature
locally on the basis of the temperature of the heated space
3.16
open vented system
heating system in which the heating medium is open to the atmosphere
3.17
maximum operating pressure
maximum pressure at which the system, or parts of the system, is designed to operate
3.18
maximum operating temperature
maximum temperature at which the system, or parts of the system, is designed to operate
3.19
operative temperature
arithmetic average of the internal air temperature and the mean radiant temperature
3.20
pressure limiter
automatic operating device that causes shutdown and lock out of the heat supply when the maximum operating
pressure of the heating medium is exceeded. The heat supply can only be restored when the pressure of the
heating medium falls below the pressure limit and after resetting manually or using a tool
3.21
sealed system
heating system in which the heating medium is closed to the atmosphere
3.22
safety temperature limiter
automatic operating device that causes shutdown and lock out of the heat supply when the maximum operating
temperature of the heating medium is exceeded. The heat supply can only be restored manually when the
temperature of the heating medium falls below the operating temperature
3.23
temperature controller
automatic operating device that causes shutdown of the heat supply when the set operating temperature of the
heating medium is exceeded. The heat supply will be restored automatically when the temperature of the heating
medium falls below the set operating temperature
3.24
timing control
method of controlling the heat flow to a heat emission system by using a timed program for starting and shutdown
of the heat flow
3.25
water level limiter
automatic operating device that causes shutdown and lock out of the heat supply when the set minimum water
level of the heating medium is reached. The heat supply can only be restored when the water level of the heating
medium rises above the set minimum water level and after resetting manually or using a tool
3.26
zone
space or groups of spaces with similar thermal characteristics
3.27
zone control
local control of a zone consisting of more than one space
4 System design requirements
4.1 Requirements for preliminary design information
The heating system shall be designed, installed and operated in a way that does not damage the building or other
installations and with due consideration of costs and energy use.
The heating system shall be designed with due consideration to installation, commissioning, operation, maintenance
and repair of components, appliances and the system.
At the planning stage or during the progress of design work the following items shall be agreed upon and
documented:
a) clarification of the responsibilities of the designer and the installer and whether or not a qualified operator is
required;
b) compliance with relevant local or statutory regulations;
c) thermal characteristics of the building for calculation of heat requirements and possible improvements of
energy conservation;
d) external design temperature;
e) internal design temperature;
f) method of heat load calculation;
g) energy source;
h) position of the heat generator, bearing in mind access for maintenance, means of flueing and provision of
combustion air;
i) type, location, dimensions, construction and suitability of chimney and flue terminal, if required;
j) location and size of fuel storage and access thereto, if required;
k) consideration of solid fuel, ash removal and disposal;
l) position of feed and expansion cistern for open vented systems or expansion vessel, filling point and pressure
gauge for sealed systems;
m) facilities for filling and draining the system;
n) requirements for any attached system;
o) type and position of heat emitters;
p) control system of heating and attached system, including frost protection;
q) route and method of installing piping and insulation;
r) provisions and specification for balancing the system;
s) provision for measurement of energy consumption;
t) surface temperatures of exposed heating system surfaces;
u) provision for water treatment;
v) requirements for extra heating up capacity, including night-set-back or intermittent heating according to EN
12831 and buffer storage for hot water systems;
f f f
w) determination of the design factors , and (see 4.2.2).
HL DHW AS
4.2 Heat supply
4.2.1 General
The heat supply system shall be designed to satisfy the design heat load of the building and the requirements of any
attached system. The design heat load shall be calculated in accordance with EN 12831.
Any other recognized heat load calculation method may only be used if accepted by the client.
The heat supply system shall be designed and dimensioned taking into account the type of energy source.
General consideration should be given to energy efficiency of the heating system.
4.2.2 Sizing
The heat supply to serve the system shall be sized to meet the design heat load and the necessary additional heat
supply requirements of any ancillary domestic hot water and other attached systems in accordance with the
specifications agreed upon in 4.1.
If the total heat supply is provided by more than one heat generator or heat source, the following points shall be
considered:
the heat load;
different operating periods, such as summer and winter;
different operating conditions, such as for heating or for hot water;
operating requirements, such as standby.
The capacity of the heat supply system shall be calculated as follows:
F = f F + f F + f F (1)
SU HL HL DHW DHW AS AS
where:
is the capacity of the heat supply system in kilo Watts (kW);
F
SU
is the design factor for the heat load;
f
HL
is the heat load capacity in kilo Watts (kW);
F
HL
is the design factor for domestic hot water systems;
f
DHW
is the domestic hot water capacity in kilo Watts (kW);
F
DHW
is the design factor for attached systems;
f
AS
is the capacity of attached systems in kilo Watts (kW);
F
AS
The design factors f , f and f shall be determined on an individual basis subject to national limitations. It
HL DHW AS
should be considered that the above heat load capacities may not be cumulative and the heat supply capacity
should be determined based on agreed criteria for their demand.
4.3 Heat distribution
4.3.1 General
The heat distribution system shall be designed to distribute the heat supply to the heat emission system and, if
necessary, to any attached systems.
The heat distribution system, including sub-circuits, shall be designed so as to enable hydraulic balancing.
Consideration shall be given to any variety of demand for attached systems and to the quality of the water.
Consideration shall be given to separate circuits for each type of heat emission system, the zoning requirement of
buildings and the supply temperature and temperature difference of each heat emission system.
Provision for filling, draining and venting shall be provided for each circuit.
4.3.2 Design criteria
4.3.2.1 Water specification
The quality of the water in the heating circuit shall conform to the design and the selected components of the
heating system.
Consideration shall be given to:
the chemical characteristics of the water, e.g. pH, O , Cl and carbonates;
2 2
supplements for water treatment and/or anti-freeze, when necessary. These shall be used in accordance
with the appliance, component and chemical manufacturers’ requirements.
4.3.2.2 Water flow rate
The water flow rate and the initial setting of the balancing devices, where required in accordance with the
specification, shall be stated and documented according to the flow rate requirements of the heat supply system as
well as the heat emission system and any attached systems.
Consideration shall be given to:
balancing devices;
hydraulic decoupling devices;
speed-controlled circulation pumps.
4.3.2.3 Circulation pumps
Circulation pumps shall be sized to circulate water at the flow rate required to distribute the heat load to the heat
emission system and any attached systems.
Consideration shall be given to:
the number of pumps, including stand-by provision;
characteristic curves and the optimum range of application;
the variable flow control system;
minimizing the electric power required;
provisions for insulation;
noise transmittance;
speed controlled circulation pumps;
automatic on- off control;
the static height provided at the suction side of the circulation pump, in accordance with the pump
manufacturer’s instructions, e.g. to avoid cavitation.
4.3.2.4 Pipework
Pipework shall be designed and sized to carry water at the appropriate heat flow rate to ensure required circulation
to all parts of the heating system. Pipework and thermal insulation material shall be compatible.
Consideration shall be given to:
temperature;
design pressure;
pressure drop;
energy demand regarding electric power of the circulation pumps;
corrosion and component compatibility, including glands and seals;
noise transmittance, i.e. flow velocity and mechanical noise;
thermal expansion and contraction;
pipework routing and physical protection, accessibility for inspection and repairs;
measurement of energy consumption;
resistance to fire;
service and maintenance, including filling, draining down and venting.
4.4 Heat emission
4.4.1 General
Heat emitters shall be selected on the basis of design heat load.
Consideration shall be given to:
the design heat load;
the system flow temperature;
thermal comfort and noise in occupied spaces;
safety of the occupants, e.g. surface temperature of the heat emitters;
protection and prevention of damage to the building components;
maintenance requirements, e.g. cleaning and repair;
compatibility with heat supply, heat distribution and control system.
Thermal comfort should be in accordance with EN ISO 7730, where specified.
4.4.2 Sizing
Heat emitters shall be sized in accordance with the space by space design heat load calculated in accordance with
EN 12831, with due allowance for heat emission from other system components, such as pipework.
The size of the emitter, temperature of the emitter and water flow rates shall be determined on the basis of
manufacturer's data sheets according to EN 442-1 to 3 or EN 1264-1 to 3.
The design shall include consideration of factors that can affect the output of the emitter and take into account, that
such effects are often cumulative, e.g. casing, connections, water flow rate, covering, paint, carpets, drapes.
Depending on the original design parameters, the designer may consider an additional allowance on the heat
emitter output, e.g. for systems that are being operated intermittently (see EN 12831).
In rooms with high ceilings, a high vertical air-temperature difference may occur, rather than the uniform
temperature assumed in the heat loss calculations. In such cases, the heat loss through the upper part of the
heated space is larger, and an additional allowance on emitter output may be desired.
4.4.3 Positioning
When positioning heat emitters, the manufacturer's specific mounting requirements shall be considered.
In choosing the location of heat emitters, consideration shall be given to the overall effect upon the control of room
temperatures and comfort conditions.
The positioning, type, number and size of the heat emitters in a space, together with the thermal transmittance of
windows and/or walls, will influence the differences in the operative temperatures in the space, the radiant
temperature asymmetry and draught.
4.4.4 Thermal environment
If required by the client, documentation and, if appropriate, calculation criteria of the thermal environment shall be
fulfilled in accordance with EN ISO 7730, i.e. difference in operative temperature, radiant temperature asymmetry
and draught.
4.4.5 Surface temperatures
In special cases, e.g. schools, nurseries and homes for the elderly, infirm or disabled, the surface temperatures of
heat emitters shall be limited in accordance with local or statutory requirements (see EN 563 and EN 13202).
4.5 Controls
4.5.1 General
Control of the heating system shall enable the specified designed indoor temperatures to be achieved under the
specified variation of internal loads and external climate and, if specified, protect buildings and equipment against
frost and moisture damage when normal comfort temperature level is not required.
Heating systems shall be equipped with automatic and/or manual control devices. Classes for devices are given in
annex A.
The design of control systems shall take into account the building, its intended use and the effective functioning of
the heating system, the efficient use of energy and avoiding heating the building to full design conditions when not
required. This shall include keeping distribution heat losses as low as possible, e.g. reducing flow temperature
when normal comfort temperature level is not required.
Return water temperatures and/or the temperature drop across the supply and return connections shall be selected
in accordance with the requirements of the manufacturer of the heat emitters.
Additional control requirements may be necessary in accordance with other component manufacturer's instructions.
Thermostatically controlled radiator valves shall comply with EN 215-1.
4.5.2 Classification
The control system shall be classified as follows:
a) classification based on heating control system level:
Central control (C);
Zone control (Z);
Local control (L).
b) classification based on control system performance level:
Manual (M),
Automatic (A),
Timing function (T),
Advanced timing function (O).
For details, see annex A.
4.5.3 Central control
4.5.3.1 General
Central control of the heat flow to the heat distribution system shall be provided.
The central control, or part of it, can in some cases be part of the heat supply, e.g. a temperature controller on a
heat generator.
In heating systems with single heating circuits, the indoor temperature may be controlled by the boiler control
thermostat, draught regulator, circulation pump or time and central temperature control.
4.5.3.2 Heat flow to the distribution system
The heat flow to the heat distribution system shall be controlled to supply water with a heat content required by the
heat emission system.
The heat flow to the heat distribution system depends on design criteria for the heating system relative to indoor
and outdoor conditions, e.g. air temperature, wind and direct solar radiation.
The heat flow can be manually or automatically controlled. Care should be taken when locating and fixing sensors
to ensure that the position chosen is representative. Outside air temperature sensors should be positioned so as
not to be exposed to direct solar radiation and to avoid influences from any hot or cold sources, unless the control
is designed to take account of such factors.
4.5.3.3 Heat flow rate to attached systems
The heat flow rate to the attached systems shall be controlled by central control of the heat supply in accordance
with the heat demand of the attached systems.
4.5.4 Zone control
If specified, the heating system shall be divided into zones in the interests of energy conservation, measurement of
energy consumption and indoor zone temperature control.
The temperature sensor for the controller shall be located in a position representative of the entire zone.
If the system is subdivided into zones, the design shall ensure that all emitters in different spaces of a zone have
the same required operational parameters.
The spaces of a zone shall be selected in such a way that internal and solar gains are approximately the same both
in rate and value.
Examples for controlling indoor zone temperature are given in annex A.
4.5.5 Local control
In order to achieve specific indoor temperatures, under varying loads, each heated space shall be equipped with
local control. Local control can be achieved by manual or automatic regulation.
Local control shall enable the user to set up individual temperature preferences within the specified range.
The local controller shall be fitted in a position readily accessible to the user.
A local control may control one individual heat emitter or a group of heat emitters.
The control of the indoor temperature is influenced by the response time of the building (thermal mass), the
response time of the heating system and the control strategy.
Automatic local control is especially useful for convenience of the users, for achieving possible energy savings and
for adjusting for heat gains from internal loads or solar radiation.
Temperature sensors shall be fitted in a representative location to maintain design conditions, and so that
undesirable effects from direct solar radiation, curtains, etc. are prevented.
4.5.6 Timing control
Timing control shall be considered in the interest of energy conservation and reduced operating costs.
If timing control is fitted, the supply of heat shall be controlled according to the use of the building, e.g. residential
buildings, office buildings, schools, and its thermal characteristics, such as insulation, thermal inertia, etc., in one of
the following ways:
ON/OFF control;
set-back control;
intermittent control;
optimizing control.
Timing control can be used to provide a variable heat flow rate. Timing control can regulate the supply temperature
or supply flow rate.
4.6 Safety arrangements
4.6.1 General
Heating systems shall be equipped with safety arrangements against:
exceeding the maximum operating temperature;
exceeding the maximum operating pressure.
Safety arrangements shall be designed in accordance with:
the type of heating system, i.e. sealed or open vented system;
the type of energy source;
the way in which the heat supply is provided to the heating system, i.e. automatically controlled or
manually operated;
the nominal output of the heat supply system.
Safety arrangements, whether provided by the appliance manufacturer as a built-in part of the heat generator or
heat source or not, shall be an integral part of the heating system. The appliance manufacturer’s installation
instructions shall be complied with.
4.6.2 Equipment required for sealed sysems
4.6.2.1 Protection against exceeding the maximum operating temperature
Each heat generator shall be served by a safety temperature limiter, including a specific sensor, which shall
respond in case of the temperature rising to the set limit.
If the heat generator is not equipped with a safety temperature limiter by the manufacturer, such a device shall be
fitted on the system flow pipe as near as possible to the heat generator, in order to achieve that the temperature at
the heat generator shall not rise by more than 10 K after switching off the heating or fuel supply or restricting the
fuel flow to a minimum, (see Figure 1).
Key
1 Maximum operating temperature
2 Activation of safety temperature limiter
3 System shutoff
Temperature in degrees Celsius ( C)
q =
Time in hours (h)
t =
Figure 1 — Typical system temperature development in a fault condition
If the heat supply system is a heat exchanger and the temperature on the primary side can cause a risk of steam
formation in the secondary side of the system, a temperature limiter shall interrupt the supply of energy to the
secondary side of the heat exchanger by a blocking valve connected to the primary side of the heat exchanger.
For temperatures up to 105 C on the primary side of the heat exchanger, it is only necessary to have an operating
temperature controller on the secondary side.
Non-automatically controlled heat supply systems shall include special temperature limiters for emergency cooling.
If the heating system is equipped with a heat exchanger for emergency cooling, the temperature limiter shall
operate as an over-temperature safeguard device if the maximum operating temperature rises by more than 10 K.
The temperature limiter shall conform to EN 60730-2-9.
Any system heated by a heat exchanger shall be equipped with a safety temperature detector that switches off the
heating so that the operating temperature does not exceed the maximum operating temperature. For solid fuel
appliances a heat distribution circuit shall be provided to operate in an overheat situation.
4.6.2.2 Protection against exceeding the maximum operating pressure
4.6.2.2.1 Safety valves, rating and arrangements
Each heat generator of a heating system shall be served by at least one safety valve in order to protect the system
against exceeding the maximum operating pressure. If the heat generator is not equipped with a safety valve by
the manufacturer, such a device shall be fitted on the system as near as possible to the heat generator.
In using more than one safety valve, the smaller valves shall have a discharge capacity of at least 40 % of the total
flow.
The safety valve(s) shall be sized to serve the total pressure developed in the system or parts of the system.
Safety valve(s) shall:
conform to prEN 1268-1, with a minimum size of DN 15;
open at a pressure not exceeding the maximum design pressure of the system and shall be designed to
prevent the maximum operating pressure from being exceeded by more than 10 %;
be installed so that the pressure drop of the inlet pipe does not exceed 3 %, and the pressure drop of the
discharge pipe does not exceed 10 % of the safety valve set pressure.
Safety valves shall be installed in an accessible location in the immediate vicinity of the heat generator flow pipe.
There shall be no isolation valve between the heat generator and the safety valve(s).
Safety valves shall discharge safely. Therefore suitable installations shall be provided.
This can be achieved by a relief pipe of the safety valve(s) that discharges to a drain in a safe location. Special
provisions may apply to heat generators greater than 300 kW nominal heat output. These shall be served by liquid
separator(s) in the immediate vicinity of the safety valve(s) and a vapour discharging pipe rising to the open air.
Liquid separators may not be necessary in cases in which each heat generator is served by an additional
temperature limiter and an additional pressure limiter.
4.6.2.2.2 Pressure limiter
Each heat generator greater than 300 kW nominal heat output shall be served by a pressure limiter. If the heat
generator is not equipped with a pressure limiter by the manufacturer, such a device shall be fitted on the system
as near as possible to the heat generator.
Where other assisting heat supply systems are present, e.g. solar systems, their specific safety requirements shall
apply.
If the operating pressure of the heating system exceeds the given pressure limit, or in the case of auxiliary power
interruption, the pressure limiter shall shut-off the heating or fuel supply and interlock it against automatic restoring.
The pressure limiter shall be adjusted so that it responds before the safety valve(s) operate.
Systems served by heat exchangers may not require pressure limiters.
4.6.2.3 Safeguard against lack of water
Sealed heating systems, except electrode type heat generators and heating systems on the secondary side of heat
exc
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