ANSI CSA AM Z21.12A-1993 Draft Hoods (Fifth Edition).pdf

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1、Addenda to American National StandardZ21.12-1990forDRAFT HOODSANSIZ21.12a-1993PART ICONSTRUCTION1.6MINSTALLATION INSTRUCTIONS1.6.2MEach draft hood shall be accompanied bythe manufacturers instructions for properinstallation and shall include at least the following:a. Manufacturers name and address a

2、s itappears on the draft hood; model, type orseries number.b. Proper method of attachment of the drafthood to the appliance.c. Proper method of attachment of the flueor vent pipe.d. Minimum clearances from combustiblematerials.e. A statement that the draft hood shall notbe installed on an appliance

3、with aninput rating greater than Btu/hr.(The input rating shall be as determinedunder 2.5.)f. Statements to the effect that if the drafthood is to be used as a replacement onlisted vented gas utilization equipment(refer to 7.12.2 in the National Fuel GasCode, ANSI Z223.1) (1) it must be at leastthe

4、same size as the draft hood beingreplaced; (2) it must not be altered; and(3) it must be located with the draft hoodrelief opening in the same position,relative to the appliance, as the reliefopening of the draft hood being replaced.g. Instructions requiring the installation ofa blocked vent shutoff

5、 system (see PartIV, Definitions) on the draft hood. Theblocked vent shutoff system shall be ofthe manual reset type and its compo-nents shall comply with applicablenationally recognized standards.h. Information relative to the purpose andfunction of the blocked vent shutoffsystem.i. If the draft ho

6、od is provided with ablocked vent shutoff system, informationrelative to the purpose and function ofthe blocked vent shutoff system and clearand concise instructions for therecommended action to be taken in theevent that the system has actuated toshut off the main burner gas. Theseinstructions may b

7、e one of the following:1. Instructions not to attempt to placethe appliance in operation, but tocontact a qualified service agency.2. Instructions for resetting of theblocked vent shutoff system. Theseinstructions shall also advise the userto contact a qualified service agencyif the appliance cannot

8、 be restored tonormal operation.j. The step-by-step inspection procedureproper operation as specified inExhibitiA.k. A statement that the draft hood must beinstalled in conformance with local codes,or with the absence of local codes, withthe National Fuel Gas Code, ANSI Z223.1,or the Standard for In

9、stallation ofDomestic Gas Conversion Burners, ANSIZ21.8.These instructions shall be reviewed by thetesting agency for accuracy and compatibility withthe results of test from a technical standpoint, andwith the National Fuel Gas Code, ANSI Z223.1, orthe standard for Installation of Domestic GasConver

10、sion Burners, Z21.8.NOTE:MChanges, other than editorial, are denoted by a vertical line in the margin.Approved April 23, 1993 by American National Standards Institute, Inc.Secretariat:MAmerican Gas AssociationSecretariat:M1515 Wilson Boulevard, Arlington, Virginia 22209 page 1 of 2PART IIPERFORMANCE

11、2.4MPILOT GAS VENTING TESTThe maximum gas-air ratio anywhere within adraft hood shall not exceed 75 percent of the lowerflammable limit at any time following simulatedappliance pilot flame outage when the draft hood istested as specified in the following Method of Test.Method of TestThe draft hood s

12、hall be attached to the test appliancein accordance with the manufacturers instructions. A drafthood for installation on appliances for use with natural,manufactured and mixed gases only shall be tested withthe test appliance using test Gas A. A draft hood forinstallation on appliances for use with

13、natural,manufactured, and liquefied petroleum gases mixed and LPgas-air mixtures shall be tested with the test applianceusing both test Gases A and E. Two tests shall beconducted on the draft hood, one under each of thefollowing test conditions:Test Condition 1The test appliance at room temperature.

14、Test Condition 2The test appliance adjusted in accordance with TestCondition A of 2.5.Under each test condition pilot gas shall be permittedto flow at the following rates:a. 2,000 Btu per hour (586 W) for draft hoodshaving nominal outlet diameters of 8 inches orless.b. 5,000 Btu per hour (1 465 W) f

15、or draft hoodshaving nominal outlet diameters greater than8iinches.The gas-air ratio within the draft hood shall bemonitored until equilibrium conditions are attained. Themonitoring locations within the draft hood shall be at thediscretion of the testing agency. At no time during the testshall the g

16、as-air ratio exceed 75 percent of the lowerflammable limit anywhere within the draft hood.PART IVDEFINITIONSBLOCKED VENT SHUTOFF SYSTEM.MA systemdesigned to interrupt appliance main burner gasflow if the appliance venting system is totallyblocked.FLAMMABLE LIMITS.MThe lowest (lower limit)and highest

17、 (upper limit) concentrations of a specificgas or vapor in mixture with air that can be ignitedat ordinary temperature and pressure of the mixture.Also called COMBUSTIBLE LIMITS.Copyright 1993 American Gas AssociationPermission is granted to republish material herein in laws or ordinances,and in regulations, administrative orders, or similar documents issued by publicauthorities. Those desiring permission for other republication should consult theAmerican Gas Association Laboratories, 8501 East Pleasant Valley Road,Cleveland, Ohio 44131.Printed in U.S.A.