ISO 23551-9:2022

INTERNATIONAL ISO
STANDARD 23551-9
Second edition
2022-01
Safety and control devices for gas
burners and gas-burning appliances —
Particular requirements —
Part 9:
Mechanical gas thermostats
Dispositifs de commande et de sécurité pour brûleurs à fioul et pour
appareils à fioul — Exigences particulières —
Partie 9: Thermostats mécaniques
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification . 3
4.1 Classes of controls . 3
4.2 Groups of controls . 4
4.3 Types of DC supplied controls . 4
4.4 Classes of control functions . 4
5 Test conditions .4
6 Construction . 4
6.1 General . 4
6.2 Construction requirements. 4
6.2.1 Appearance . 4
6.2.2 Holes . 4
6.2.3 Breather holes . 4
6.2.4 Vent limiter . 4
6.2.5 Screwed fastenings . 4
6.2.6 Moving parts . 4
6.2.7 Sealing caps . 5
6.2.8 Dismantling and reassembling for servicing and/or adjustment for controls . 5
6.2.9 Auxiliary channels and orifices . 5
6.2.10 Pre-setting device . 5
6.3 Materials . 5
6.3.1 General material requirements . 5
6.3.2 Housing . 5
6.3.3 Springs providing closing force and sealing force . 5
6.3.4 Resistance to corrosion and surface protection . 5
6.3.5 Impregnation . 5
6.3.6 Seals for glands for moving parts. 5
6.3.7 Jointing . 5
6.4 Connections . 5
6.5 Gas controls employing with electrical components in the gas way . 6
6.6 Flow characteristics . 6
6.7 Temperature adjustment of adjustable thermostats . 6
6.7.1 Range adjustment . 6
6.7.2 Set point adjustment . 6
6.7.3 Fixed setting thermostat . 6
7 Performance . 6
7.1 General . 6
7.2 Leak-tightness . 7
7.2.1 General . 7
7.2.2 Requirements . 7
7.2.3 Test . . . 7
7.3 Torsion and bending . 7
7.4 Rated flow rate . 7
7.4.1 General . 7
7.4.2 Requirements . 7
7.4.3 Test . . . 8
7.5 Durability . 8
7.6 Functional requirements . . 8
iii
7.6.1 Calibration temperature set-point . 8
7.6.2 Backlash . 8
7.6.3 Opening of a snap-acting thermostat with a closed position . 9
7.6.4 Opening pressure and closing pressure for thermostats with a closed
position . 9
7.6.5 Operating characteristic of the thermostat . 9
7.6.6 Ambient temperature range of the body . 14
7.6.7 Effect of storage and transport temperatures . 14
7.6.8 Thermal overload of the thermal sensing element . 14
7.6.9 Operating torque of the thermostat set-point adjuster .15
7.6.10 Effect of high ambient temperature on performance of thermostats for top
burners and griddles .15
7.7 Endurance . 15
7.7.1 Mechanical cycling . .15
7.7.2 Thermal cycling . 16
8 Electrical equipment .17
9 Electromagnetic compatibility (EMC) .17
10 Marking, installation and operating instructions .17
10.1 Marking . 17
10.2 Installation and operating instructions . 18
10.3 Warning notice . 18
Annex A (informative) Leak-tightness test — Volumetric method .19
A
...