ANSI Z21.23-2010

(reaffirmed 2020)

American National Standard For Gas Appliance Thermostats

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ANSI Z21.23-2010

August 2010

Title: American National Standard For Gas Appliance Thermostats

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Eleventh Edition - 2010

The standards is a revised edition of the former standard for Gas Appliance Thermostats,

Z21.23-2000 Z21.23a-2003 Z21.23b-2005

Approved August 27, 2010

American National Standards Institute, Inc.

Standard Developer CSA AMERICA INC.

8501 East Pleasant Valley Road Cleveland, Ohio 44131

Published - October 2010

Copyright © 2010 CSA America, Inc.

Permission is granted to republish material herein in laws or ordinances, and in regulations, administrative orders, or similar documents issued by public authorities. Those desiring permission for other republication should consult CSA America, Inc., 8501 East Pleasant Valley Road, Cleveland, Ohio 44131.

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Preface

This publication represents a basic standard for safe operation, substantial and durable construction, and acceptable performance of gas appliance thermostats. It is the result of years of experience in the manufacture, testing, installation, maintenance, inspection and research on gas appliance thermostats designed for the utilization of gas. There are risks of injury to persons inherent in some appliances that, if completely eliminated, would defeat the utility of the appliance. The provisions in this Standard are intended to reduce such risks while retaining the normal function of the appliance.

Nothing in this standard is to be considered in any way as indicating a measure of quality beyond compliance with the provisions it contains. It is designed to allow compliance of gas appliance thermostats, the safety construction and performance of which may exceed the various provisions specified herein. In its preparation, recognition has been given to possibilities of improvement through ingenuity of design. As technical advances take place, revisions may become necessary. When they are believed desirable, recommendations or suggestions should be forwarded to the Chairman of Standards Committee Z21/83, 8501 East Pleasant Valley Road, Cleveland, Ohio 44131. A proposal form is provided in the back of this document.

Safe and satisfactory operation of gas appliance thermostats depends to a great extent upon its proper installation, use and maintenance. It should be installed, as applicable, in accordance with the National Fuel Gas Code, ANSI Z223.1/NFPA 54; the (U.S.) Manufactured Home Construction and Safety Standard, Title 24 CFR, Part 3280, or when such standard is not applicable, Manufactured Home Installations, ANSI/NCSBCS A225.1 or the Standard for Manufactured Home Installations, Sites, and Communities, ANSI/NFPA 501A, manufacturers’ installation instructions, and local municipal building codes.

Users of this American National Standard are advised that the devices/products/activities within its scope may be subject to regulation at the Federal state or local level. Users are strongly urged to investigate this possibility through appropriate channels. In the event of a conflict with this standard, the Federal, state or local regulation should be followed.

CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute, Inc., require that action be taken to reaffirm, revise or withdraw this standard no later than five (5) years from the date of approval. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute, Inc., 25 West 43rd Street, Fourth Floor, New York, N.Y. 10036, (212) 642-4900.

EFFECTIVE DATE: An organization using this standard for product evaluation as a part of its certification program will normally establish the date by which all products certified by that organization should comply with this standard.

History Of The Development Of Standard For Gas Appliance Thermostats

(This History is informative and is not part of the standard.)

There appears to be no evidence of the existence of construction and performance standards for gas appliance thermostats prior to the preparation of this standard, except for certain performance provisions in previous American Gas Association standards for domestic gas appliances, such as gas ranges and gas water heaters. These standards were primarily concerned with appliance performance, and thermostats were considered only to the extent of their effect on appliance operation.

In September 1930, a representative of the National Gas Appliance Manufacturer’s Association appeared before American Standards Association Sectional Committee Z21 requesting recognition of various accessories used on, or in conjunction with, gas appliances. A special committee was appointed to study this problem which resulted in the formation of the Subcommittee on Listing Requirements for Gas, Pressure and Temperature Control Accessories in May 1931 for the development of standards for various control accessories.

At the first meeting of this group in March 1932, the general scope of its assignment was considered and, since there were a number of distinct types of accessories to be considered, representative subgroups were appointed to draft standards for specific classes of accessories.

One of these subgroups was the Subcommittee on Listing Requirements for Thermostats and Thermostatic Pilots. A draft standard for thermostats was developed by this group and distributed to the industry for review and comment during August 1933. The draft standard was reconsidered in April 1934 in conjunction with the comments received and was adopted with minor revisions. The resultant draft standard was adopted by the Z21 Committee at its June 1934 meeting. The first edition of this standard was subsequently approved as American Standard by the American Standards Association in February 1935.

An expansion of the standard to cover thermostats used on various gas appliances, including substituting the words “gas appliance thermostats” for the term “water heater, gas range and space heater thermostats” was distributed for review and comment in April 1939. The revisions were adopted by the Z21 Committee, and the second edition of this standard was subsequently approved as American Standard in February 1940.

The development of new types of gas appliance thermostats, such as range top burner thermostats and low temperature oven thermostats, and general progress in the development of gas appliance thermostats prompted the subcommittee to prepare extensive revisions to the standard. Following the procedures outlined above, these revisions were adopted by the Z21 Committee at its March 1961 meeting. This third edition was subsequently approved as American Standard by the American Standards Association, Inc., in October 1961.

The increasing use of electric switch type thermostats prompted further revisions to the standard to cover this type of thermostats, in addition to integral gas valve type thermostats, and revisions covering thermostats of both types for use in gas refrigerators. These revisions were subsequently adopted by the Z21 Committee at its March, 1963 meeting. The fourth edition was approved as American Standard by the American Standards Association, Inc., in December 1963.

In August, 1966, the American Standards Association, Inc., was reconstituted as the United States of America Standards Institute which, in October, 1969, was in turn renamed the American National Standards Institute, Inc. As a result, the fifth through seventh editions of the gas appliance thermostat standard were approved as American National Standards by the American National Standards Institute, Inc., between 1971 and 1980.

Following the procedure outlined above, further revisions to this standard were developed in line with industry developments. This, the tenth edition of the gas appliance thermostat standard was approved as an American National Standard by the American National Standards Institute, Inc., on August 27, 2010.

Previous editions of the gas appliance thermostat standard, and addenda thereto, approved by ANSI or its predecessor organizations are as follows:

NOTE: This edition incorporates changes to the 2000 edition of Z21.23, and addenda thereto.

Changes other than editorial, are denoted by a vertical line in the margin.

Z21/83 Technical Committee on Performance and Installation of Gas Burning Appliances and Related Accessories

DARYL L. HOSLER, Chairman PAUL E. BEACH, Vice Chairman

REPRESENTING AIR CONDITIONING, HEATING AND REFRIGERATION INSTITUTE:

REPRESENTING AMERICAN ASSOCIATION OF FAMILY AND CONSUMER SCIENCE:

JoAnn Emmel

REPRESENTING AMERICAN GAS ASSOCIATION:

Jim Ranfone

REPRESENTING AMERICAN PUBLIC GAS ASSOCIAITION

Mike Deegan

REPRESENTING ASSOCIATION OF HOME APPLIANCE MANUFACTURERS:

Peter Hoekstra

REPRESENTING ATMOS ENERGY:

Ronnie Ray Frazier

REPRESENTING CRANE ENGINEERING

Matthew Wilber

REPRESENTING BURNER TECHNOLOGY UNLIMITED, INC.:

Carl Suchovsky

REPRESENTING CRANE ENGINEERING:

Matthew Wilber

REPRESENTING CONSUMER:

Hall Virgil Amy Sherwin

Z21/83 Technical Committee on Performance and Installation of Gas Burning Appliances and Related Accessories (con’t.)

REPRESENTING DIRECT ENERGY CORPORATION:

Geoff Adkinson

REPRESENTING HEARTH, PATIO AND BARBEQUE ASSOCIATION:

Thomas Stroud

REPRESENTING INDIVIDUAL MEMBERS:

Daryl L. Hosler Issac Sargunam

REPRESENTING NATIONAL GRID:

Edward J. Angelone

REPRESENTING NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION:

Gerard Winstanley

REPRESENTING NATIONAL PROPANE GAS ASSOCIATION:

Bruce J. Swiecicki

REPRESENTING NORTH AMERICAN ASSOCIATION OF FOOD EQUIPMENT MANUFACTURERS:

Charles Souhrada Terry Wiseman (Alternate)

REPRESENTING SOUTHERN CALIFORNIA GAS COMPANY:

Lance DeLaura Ron Caudle (Alternate)

REPRESENTING UNDERWRITERS LABORATORIES:

Robert Wozniak Travis Hardin (Alternate)

REPRESENTING U.S. CONSUMER PRODUCT SAFETY COMMISSION (Non-voting):

Donald W. Switzer

REPRESENTING U.S. DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT:

Victor J. Ferrante

Technical Advisory Group On Standards For Automatic Gas Controls

SCOTT J. DALEY, Chairman

REPRESENTING GAS COMPANIES:

Scott J. Daley Gene McPherson

REPRESENTING MANUFACTURERS:

Paul E. Beach John Bieritz Kevin Carlisle

Thomas A. Chodacki Richard Cowen David Delequila Robert Dunn

David Fallon

Alex Gafford (Alternate) Greg Filkovski

Jim Jollay Don Kasprzy

Paul Kinningham Florin Lazar Kerry Leason Gene McPherson Ken Minkler

Jim Myers Kevin Norby Joe Rose

Robert Rothrock John Schlachter Tom Stroud Franklin Switzer

Contents

Part I Construction

Page

1. Scope 1

2. General 1

3. Data Furnished By Manufacturer 3

4. Connections 3

5. Mounting 4

6. Bolts, Nuts, Screws And Other Threaded Parts 4

7. Adjustments 4

8. Strength 5

9. Materials 5

10. Temperature Markings 5

11. Resistance To Corrosion 6

12. Assembly 6

13. Electrical 7

14. Instructions 10

15. Marking 11

Part II Performance

1. General 15

2. Leakage 16

3. Strength And Deformation 17

4. Accuracy Of Temperature Set Point 20

5. Effect Of High Ambient Temperature On Performance Of

   Thermostats For Top Burners And Griddles 23

6. Capacity 24

7. Valve Opening Characteristics Of Snapacting Thermostats 26

8. Continued Operation 27

9. Dielectric Strength 30

10. Maximum Allowable Operating Temperatures For

    Various Component Parts Of Electric Thermostats 31

11. Overload 31

12. Current Input 32

13. Resistance To Permanent Damage At Excessive Supply Pressure 32

14. Exemptions 32

15. Marking Material Adhesion And Legibility 33

Tables

Table I Minimum Thread Length And Length To Shoulder 34

Table II Recommended Dial Temperature Markings 34

Table III Calibration Reference Point(s) 35

Table IV Minimum Spacings Line Voltage Circuits For Safety Circuits 36

Table V Minimum Spacings - Millivoltage Circuits Intended for Access After the Control Manufactured and

for Class 2 Low Voltage Safety Circuits (0-30 Volts) 37

Table VI Minimum Spacings - Isolated Limited Secondary Circuits for Safety Controls 38

Table VII 39

Contents (Continued)

Page

Table VIII Permissible Temperature Variation From Set Point 40

Table IX Loads For Bending Moments Test (kg) 41

Table X Torques For Turning Effort Test 41

Table XI Number of Cycles for Thermostat

Temperature Selecting Mechanism 41

Table XII Maximum Allowable Rise Operating

Temperatures For Various Component Parts 42

Figures

Figure 1 Typical Arrangement of Thermostat Capacity Test Apparatus 44

Figure 2 Typical R/T curve for a ceramic PTC thermistor 45

Figure 3 Typical R/T curve for a NTC thermistor 46

EXHIBIT A List Of Reference Standards 47

Part III Manufacturing And Production Tests 49

Part IV Definitions 51

APPENDIX A Preferred Graphic Symbols Of Commonly Used Items, Extracted From ANSI/IEEE Standard 315, Graphic Symbols For Electrical And

Electronics Diagrams, And Abbreviations For These Items 55

APPENDIX B Table of Conversion Factors 63

American National Standard For Gas Appliance Thermostats

Part I: Construction

1. Scope

   1.1.1

   This standard applies to newly produced gas appliance thermostats of the integral gas valve type having a maximum operating gas pressure of 1/2 psi (3.5 kPa) or electric type (see Part IV, Definitions), constructed entirely of new, unused parts and materials.

   
   

   This standard does not apply to an electric type comfort heating thermostat (wallmounted) for installation remote from an appliance.

   
   

   When the operating performance characteristics of the thermostat can be affected by the separate components, such as power supply, transformer and valve(s), the thermostat shall be tested as part of a complete system.

   
   

   Compliance of a device with this standard does not imply that such device is acceptable for use on gas appliances without supplemental tests with the device applied to the particular appliance design.

   
   

   1.1.2

   An accessory incorporated as an integral part of a thermostat shall comply with all provisions of the applicable standard for such a device.

   
   

   1.1.3

   If a value for measurement as given in this standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification.

   
   

   1.1.4

   All references to psi throughout this standard are to be considered gauge pressures unless otherwise specified.

   
   

2. General

1.2.1

Representative complete thermostats, together with necessary adapters or connectors, shall be provided for examination under this standard as specified by the testing agency. If the thermostat assembly includes accessories which are covered by other standards, but which have not been certified under those standards, additional quantities of each accessory shall be provided as specified by the testing agency.

1.2.2

A description of the operating principle and necessary installation and service instructions of the thermostat shall be provided.

1.2.3

The manufacturer shall specify the maximum recommended ambient temperature(s) for the thermostat and its components. The specified maximum ambient temperature shall not be less than 125°F (51.5°C), and the specified minimum ambient temperature shall not be greater than 32°F (0°C).