ISO 11855-6:2018

INTERNATIONAL ISO
STANDARD 11855-6
Second edition
2018-09
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 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Controls . 2
4.1 General . 2
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
4.8 Flow control. 6
Annex A (informative) Control of radiant floor heating-cooling systems .7
Bibliography .12
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
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.org/iso/foreword .html.
This document was prepared by ISO/TC 205, Building environment design.
This second edition cancels and replaces the first edition (ISO 11855-6:2012), which has been
technically revised. The main changes compared to the previous edition are as follows:
— addition of 4.8 (Flow control);
— correction of errors.
A list of all the parts in the ISO 11855 series, can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

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 is intended to be applied to systems using not only water but also other fluids or
electricity as a heating or cooling medium.
The objective 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.
The ISO 11855 series consists of the following:
— 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 actually being
operated in a building.
1)
— Part 7 addresses the connection to the energetic calculation in ISO 52031 and provides input
parameters for ISO 52031 based on the product properties.
1) Under preparation. Stage at time of publication: ISO/CD 52031:2018.
INTERNATIONAL STANDARD ISO 11855-6:2018(E)
Building environment design — Design, dimensioning,
installation and control of embedded radiant heating and
cooling systems —
Part 6:
Control
1 Scope
This document establishes guidelines for 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 in this document 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.
This document 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.
This document also applies, as appropriate, to the use of fluids other than water as a heating or cooling
medium. This document 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 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.
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11855-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at http: //www .iso .org/obp
NOTE All terms and definitions in this document are consistent with ISO 7345, ISO 9229, ISO 9288, ISO 9346
and ISO 16818.
4 Controls
4.1 General
This clause 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.
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 dynamics of 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., by 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. Annex A provides
further informative control concepts as well as examples for central systems.
2 © ISO 2018 – All rights reserved

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 of an embedded radiant heating and cooling system exemplified by
a floor system
Figure 1 shows 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 o
...