ISO 11855-6:2012
(Main)Building environment design — Design, dimensioning, installation and control of embedded radiant heating and cooling systems — Part 6: Control
Building environment design — Design, dimensioning, installation and control of embedded radiant heating and cooling systems — Part 6: Control
ISO 11855-6:2012 establishes guidelines on the control of embedded radiant heating and cooling systems. It specifies uniform requirements for the design and construction of heating and cooling floors, ceiling and wall structures to ensure that the heating/cooling systems are suited to the particular application. The requirements specified by ISO 11855-6:2012 are applicable only to the components of the heating/cooling systems and the elements which are part of the heating/cooling surface and which are installed due to the heating/cooling systems. The ISO 11855 series is applicable to water based embedded surface heating and cooling systems in residential, commercial and industrial buildings. The methods apply to systems integrated into the wall, floor or ceiling construction without any open air gaps. It is not applicable to panel systems with an open air gap which is not integrated with the building structure. The ISO 11855 series applies also, as appropriate, to the use of other fluids instead of water as heating or cooling medium. It is not applicable for testing of systems. The methods do not apply to heated or chilled ceiling panels or beams.
Conception de l'environnement des bâtiments — Conception, construction et fonctionnement des systèmes de chauffage et de refroidissement par rayonnement — Partie 6: Contrôle
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11855-6
First edition
2012-11-15
Building environment design —
Design, dimensioning, installation and
control of embedded radiant heating
and cooling systems —
Part 6:
Control
Conception de l’environnement des bâtiments — Conception,
construction et fonctionnement des systèmes de chauffage et de
refroidissement par rayonnement —
Partie 6: Contrôle
Reference number
ISO 11855-6:2012(E)
©
ISO 2012
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ISO 11855-6:2012(E)
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ISO 11855-6:2012(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Controls . 1
4.1 General . 1
4.2 Central control . 4
4.3 Zone control . 5
4.4 Local (room) control . 5
4.5 Influence of thermal mass of embedded systems . 5
4.6 Self-regulating effect . 5
4.7 Control of TABS . 6
Annex A (informative) Control of radiant floor heating-cooling systems .7
Bibliography .11
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ISO 11855-6:2012(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 11855-6 was prepared by Technical Committee ISO/TC 205, Building environment design.
ISO 11855 consists of the following parts, under the general title Building environment design — Design,
dimensioning, installation and control of embedded radiant heating and cooling systems:
— Part 1: Definition, symbols, and comfort criteria
— Part 2: Determination of the design heating and cooling capacity
— Part 3: Design and dimensioning
— Part 4: Dimensioning and calculation of the dynamic heating and cooling capacity of Thermo Active
Building Systems (TABS)
— Part 5: Installation
— Part 6: Control
Part 1 specifies the comfort criteria which should be considered in designing embedded radiant heating
and cooling systems, since the main objective of the radiant heating and cooling system is to satisfy
thermal comfort of the occupants. Part 2 provides steady-state calculation methods for determination of
the heating and cooling capacity. Part 3 specifies design and dimensioning methods of radiant heating and
cooling systems to ensure the heating and cooling capacity. Part 4 provides dimensioning and calculation
method to design TABS (Thermo Active Building Systems) for energy-saving purposes, since radiant
heating and cooling systems can reduce energy consumption and heat source size by using renewable
energy. Part 5 addresses the installation process for the system to operate as intended. Part 6 shows a
proper control method of the radiant heating and cooling systems to ensure the maximum performance
which was intended in the design stage when the system is being actually operated in a building.
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ISO 11855-6:2012(E)
Introduction
The radiant heating and cooling system consists of heat emitting/absorbing, heat supply, distribution,
and control systems. The ISO 11855 series deals with the embedded surface heating and cooling system
that directly controls heat exchange within the space. It does not include the system equipment itself,
such as heat source, distribution system and controller.
The ISO 11855 series addresses an embedded system that is integrated with the building structure.
Therefore, the panel system with open air gap, which is not integrated with the building structure, is
not covered by this series.
The ISO 11855 series shall be applied to systems using not only water but also other fluids or electricity
as a heating or cooling medium.
The object of the ISO 11855 series is to provide criteria to effectively design embedded systems. To do
this, it presents comfort criteria for the space served by embedded systems, heat output calculation,
dimensioning, dynamic analysis, installation, operation, and control method of embedded systems.
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INTERNATIONAL STANDARD ISO 11855-6:2012(E)
Building environment design — Design, dimensioning,
installation and control of embedded radiant heating and
cooling systems —
Part 6:
Control
1 Scope
This part of ISO 11855 establishes guidelines on the control of embedded radiant heating and cooling
systems. It specifies uniform requirements for the design and construction of heating and cooling floors,
ceiling and wall structures to ensure that the heating/cooling systems are suited to the particular
application. The requirements specified by this part of ISO 11855 are applicable only to the components
of the heating/cooling systems and the elements which are part of the heating/cooling surface and
which are installed due to the heating/cooling systems.
The ISO 11855 series is applicable to water based embedded surface heating and cooling systems in
residential, commercial and industrial buildings. The methods apply to systems integrated into the wall,
floor or ceiling construction without any open air gaps. It is not applicable to panel systems with an open
air gap which is not integrated with the building structure.
The ISO 11855 series also applies, as appropriate, to the use of fluids other than water as a heating or
cooling medium. The ISO 11855 series is not applicable for testing of systems. The methods do not apply
to heated or chilled ceiling panels or beams.
2 Normative references
The following referenced documents are indispensable for the application 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
ISO 11855-1, Building environment design — Design, dimensioning, installation and control of embedded
radiant heating and cooling systems — Part 1: Definition, symbols, and comfort criteria
EN 7726, Ergonomics of the thermal environment — Instruments for measuring physical quantities
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11855-1 apply.
NOTE All terms and definitions in this part of ISO 11855 are consistent with ISO 7345, ISO 9229, ISO 9288,
ISO 9346 and ISO 16818.
4 Controls
4.1 General
This section describes the control of hydronic systems to enable all embedded systems to perform as
simulated. The design documents shall include specifications for the control system. The control system
shall be capable of varying heating or cooling outputs as well as maintaining predetermined room or
surface temperatures.
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ISO 11855-6:2012(E)
Control of the heating and cooling system shall enable the specified designed indoor temperatures to
be achieved under the specified variation on internal loads and external climate. The control system
shall, if specified, protect buildings and equipment against frost and moisture damage where necessary
(when normal comfort temperature level is not required) and prevent condensation from occurring.
The design of the control system shall take into account the building, its intended use and the effective
functioning of the embedded system, efficient use of energy and avoiding conditioning the building to full
design conditions when not required. This shall include keeping distribution heat losses as low as possible,
e.g. reducing flow rates and temperatures, when normal comfort temperature level is not required. Control
and operation of the system will enable control of the conditioning systems to obtain possible savings of
operational costs and enable the maintenance of required indoor environmental conditions.
In order to maintain a stable thermal environment, the control system needs to maintain the balance
between supplied energy from the system and the losses/gains of building environment under transient
conditions. Slowly varying energy flows in the form of energy losses or gains through the envelope are
determined by indoor and outdoor temperature, and direction and speed of wind.
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ISO 11855-6:2012(E)
Key
B boiler OTS outside temperature sensor
C chiller P pump
CU control unit RS room sensor
FTS floor temperature sensor RTS return medium temperature sensor
L limiter SOV shut off valve
M manifold STS supply medium temperature sensor
MC main controller THS temperature-humidity sensor
MV mixing valve
Figure 1 — Principal diagram of an embedded radiant heating and cooling system exemplified
by a floor system
Figure 1 shows a diagram on the principles of control. The supply water temperature is controlled by
a mixing valve, actuated to maintain the design condition. In the occupied space there is a sensor for
temperature and humidity, which can be used for zone control and/or give input to the control of the
mixing valve and provide information to the building management system to determine space dew point
temperature which is necessary to ensure condensation in the building (surface, construction). Outside
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ISO 11855-6:2012(E)
temperature sensors, supply-return water temperature sensors and in some cases surface temperature
sensors are to be installed to influence the control. The control modes of embedded systems are based
on three system levels:
1) Local (room) control, where the energy supplied to a room is controlled
2) Zone control normally consisting of several spaces (rooms)
3) Central control where energy supplied to the whole building is controlled by a central system
The control system classification is based on performance level:
1) Manual: The energy supply to the conditioned space is only controlled by a manually
operated device
2) Automatic: A suitable system or device automatically controls energy to the conditioned spaces
3) Timing: Function of energy supplied to a conditioned space is shut off or reduced during
scheduled periods, e.g. night setback (not necessarily applicable for cooling)
4) Advanced timing: Function of energy supply to the conditioned space is shut-off or reduced
during scheduled periods, e.g. daytime with more expensive electricity tariff. Re-starting of the
energy supply is optimized based on various considerations, including reduction of energy use (not
applicable in commercial buildings)
4.2 Central control
The central control shall control the water temperature through the embedded system. In residential
systems the control is normally done according to the outside climate (based on the heating/cooling
curve, which is influenced by building mass, heat loss, and differences in heat required by the individual
rooms) control the supply water temperature to the system.
To reduce losses in the distribution system the central control must control according to outside
temperature, i.e. higher water temperature for lower outside temperatures, for heating only.
Instead of controlling the supply water temperature it is recommended to control the water temperature
(supply and return water temperature) according to outside and/or indoor temperatures. This is more
directly related to the energy flux into the space. If during the heating period for example the internal
load in the space increases, the heat output of the floor system will decrease and the return temperature
will increase.
If the embedded system is operated intermittently (e.g. night and/or weekend set-back) the central
control is also important for providing high enough water temperatures (Boost effect) during the pre-
conditioning period in the morning. The energy savings by night set-back in residential buildings are,
however, relatively low due to the high thermal insulation standard in new houses.
For commercial systems the control is normally done according to the heat loss or gain, and differences in
heat or cooling required by the individual rooms which control the supply water temperature to the system.
For cooling it is also recommended to control the supply water temperature based on the zone with
the highest dew point temperature. In many buildings with cooling, the internal load is of significant
importance and it is recommended to let the room temperature and humidity of representative space
influence the control of the water temperature.
Radiant surface cooling systems shall include controls to avoid condensation on internal cooled surfaces
or condensation in critical parts of the building. This can be done by a central control of the supply
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