GAMA Venting Tables

VENTING TABLES

CATEGORY I CENTRAL FURNACES

COPYRIGHT

1990GAS APPLIANCE MANUFACTURERS ASSOCIATION

GAMA Venting Tables

7507-183 REVISED: JULY, 1991

Form: IM-GA1A-09 Cancels: IM-GA1A-06 Printed in U.S.A. 1-95 Catalog No. 92-33GA-1A15

This document was created with FrameMaker 4.0.4

NOTICE

When using Venting Tables Category I Central Furnaces supplement furnished with this Installation Instructionpackage, use the Terms table below to explain American and Canadian terminology which differs.

TERMS

Section III. General Venting Requirements:

Item 8 of this section applies only to United States instructions. Figures 1 and 2 should not be used as a referencefor vent termination in Canada. Use the procedures established by local authorities or in the absence of localauthorities, those set by the CAN/CGA–B149 Installation Codes.

AMERICAN TERM CANADIAN TERM AND DEFINITION

Category I Central Furnaces In Canada, this type of furnace is a conventionally vented (vertical natural draft) furnace with or without a drafthood.

National Fuel Gas Code-NFPA 54/ANSI Z223. 1-1992

National Standard of Canada, CAN/CGA–B149.1 and .2–M91 Natural Gas and Propane Installation Codes with Amendment No. 1

GAMA VENTING TABLESFOR

CATEGORY I CENTRAL FURNACES

This booklet contains new venting tables designed specifically for use with Category I central furnaces.These tables are unique, in that, industry wide venting tables now exist for fan-assisted combustion system centralfurnaces. Venting tables for these types of appliances are not contained in the National Fuel Gas Code (NFPA 54/ANSI Z223.1-1988).

All requirements contained in this booklet apply to both Category I drafthood equipped central furnaces aswell as fan-assisted combustion system central furnaces. At no time should a venting system for a listed CategoryII, III, or IV central furnace be sized with these tables. The National Fuel Gas Code (NFPA 54/ANSI Z223.1-1988)may also be used to size venting systems for drafthood equipped central furnaces. However, at this time, theNational Fuel Gas Code does not include alternate sizing methods for fan-assisted combustion systems. There-fore, until engineering data is developed to allow alternate sizing methods for Category I fan-assisted central fur-naces, the enclosed venting tables must be used for fan-assisted combustion system central furnaces. Thesetables apply to venting single appliances and common venting multiple appliances in both metal and masonrychimneys.

The new venting tables were developed by Battelle under contract (GRI-5088-245-1728) to the GasResearch Institute (GRI). The computer program (VENT-II) developed by Battelle Columbus generated the vent-ing tables in this booklet and this procedure has been accepted by the American Gas Association Laboratories asan appropriate engineering methodology for determining venting requirements of Category I central furnaces.

For your information, the general venting requirements listed in this booklet are not intended to be used ascomplete installation instructions and represent only a partial list of venting considerations.

For venting applications that fall outside the parameters of the new venting tables, refer to the furnacemanufacturer’s complete installation instructions, the specific vent manufacturer’s complete installation instruc-tions, and state and local codes.

GRI DISCLAIMER

LEGAL NOTICE:

This information is, in part, a result of work performed by Battelle under the sponsorship ofthe Gas Research Institute (GRI). Neither GRI, members of GRI, nor any person acting on behalf of either:

a. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, orusefulness of this information, or that the use of any apparatus, method, or process disclosed may notinfringe privately owned rights; or

b. Assumes any liability with respect to the use of, or for damages resulting from the use of, any information,apparatus, method, or process disclosed.

1

I. INTRODUCTION

This booklet contains the current definitions, instruc-tions, and tables necessary to vent todays modernCategory I Gas Fired Appliance. A variety of defini-tions of new terms describing today’s gas appliancesare included to supplement the actual venting tableswhich have been generated to correctly vent variouscombinations of Category I Appliances using Type Bor single-wall metal vent connectors attached toType B vents or masonry chimneys. Tables are alsoincluded covering similar venting material combina-tions when applied to common venting arrangementsof two or more appliances.

Finally, a series of examples are presented demon-strating how the vent tables are used to size the ventconnector and the vertical vent for a variety of typicalapplications.

II. DEFINITION OF TERMS

“Fan Assisted Combustion System”

An appliance equipped with anintegral mechanical means toeither draw or force products ofcombustion through the com-bustion chamber and/or heatexchanger.

“FAN Min” refers to the minimum applianceinput rating of a Category I appli-ance with a fan-assisted com-bustion system that could beattached to the vent.

“FAN Max” refers to the maximum applianceinput rating of a Category I appli-ance with a fan-assisted com-bustion system that could beattached to the vent.

“NAT Max” refers to the maximum applianceinput rating of a Category I appli-ance equipped with a drafthoodthat could be attached to the vent.There are no minimum applianceinput ratings for drafthood-equipped appliances.

“FAN+FAN” refers to the maximum combinedinput rating of two or more fan-assisted appliances attached tothe common vent.

“FAN+NAT” refers to the maximum combinedinput rating of one or more fan-assisted appliance and one ormore drafthood-equipped appli-ance attached to the commonvent.

“NAT+NAT” refers to the maximum combinedinput rating of two or moredrafthood-equipped appliancesattached to the common vent.

“NR” means not recommended due topotential for condensate forma-tion and/or pressurization of theventing system.

“NA” means not applicable due tophysical or geometric constraints.

DraftHood A device built into an appliance,or made a part of the vent con-nector from an appliance, whichis designed to (1) provide for theready escape of the flue gasesfrom the appliance in the event ofno draft, backdraft, or stoppagebeyond the drafthood, (2) preventa backdraft from entering theappliance, and (3) neutralize theeffect of stack action of the chim-ney or gas vent upon the opera-tion of the appliance.

Vent A passageway used to conveyflue gases from gas utilizationequipment, or their vent connec-tors, to the outside atmosphere.

Vent Connector The pipe or duct which connectsa fuel-gas burning appliance to avent or chimney.

Flue Collar That portion of an appliancedesigned for the attachment ofa drafthood, vent connector, orventing system.

Categorized Vent Diameter

The minimum vent diameter per-missible for Category I appli-ances to maintain a nonpositivevent static pressure when testedin accordance with nationally rec-ognized standards.

VENTING REQUIREMENTS FOR CATEGORY I APPLIANCES

2

III. GENERAL VENTING REQUIREMENTS

All requirements contained in this document apply toboth Category I draft hood equipped and fan-assisted combustion appliances. At no time should aventing system for a listed Category II, III, or IV appli-ance be sized with these Tables. The alternate sizingmethods described in the National Fuel Gas Code(NFPA54/ANSI Z223.1-1988) may also be used tosize the venting system for a drafthood equippedappliance. At this time, alternate sizing methodshave not been developed for fan-assisted appli-ances. Therefore, until engineering data is devel-oped to allow alternate sizing methods for Category Ifan-assisted appliances, the vent tables must beused.

1) The venting tables included in this instructionapply to vents and chimneys internal to thestructure below the roof line. Exterior chimneysor vents not enclosed by the structure or achase below the roof line may experience con-tinuous condensation depending on locality.Consult local gas utility, appliance manufac-turer and/or local codes. A chimney with one ormore sides exposed to the outside of the struc-ture is considered to be an exterior chimney. AType B or listed chimney lining system passingthrough an unused masonry chimney flue is notconsidered to be exposed to the outdoors.

2) If the vent or connector size determined fromthe tables is smaller than the appliance draft-hood outlet or flue collar, the smaller size maybe used provided:

a) The total vent height “H” is at least 10 FT.

b) Vents or connectors for appliance draft-hood outlets or flue collars 12 inches indiameter or smaller are not reduced morethan one table size (e.g. 12 inches to 10inches is a one size reduction).

c) Vents or connectors for appliance draft-hood or flue collars above 12 inches indiameter are not reduced more than twotable sizes (e.g. 24 inches to 20 inches is atwo size reduction).

d) The maximum capacity listed in the tablesfor a fan-assisted appliance is reduced by10% (0.90 x maximum capacity).

e) The drafthood outlet is greater than 4inches in diameter. Do not connect a 3inch diameter vent or connector to a 4 inchdiameter drafthood outlet. This provisiondoes not apply to fan-assisted appliances.

3) Single appliance venting configurations withzero lateral lengths, Tables 1 & 2, are assumedto have no elbows in the vent system. For allother vent configurations, the vent system isassumed to have two 90

°

elbows. For eachadditional 90

°

elbow, or equivalent* beyondtwo, the maximum capacity listed in the ventingtable should be reduced by 10 percent (0.90 xmaximum listed capacity).

* Two 45

°

elbows are equivalent to one 90

°

elbow.

4) The common venting Tables 3, 4, 7, & 8 weregenerated using a maximum horizontal ventconnector length of 1 1/2 feet (18 inches) foreach inch of connector diameter as follows:

The vent connector should be routed to thevent utilizing the shortest possible route. Con-nectors with longer horizontal lengths thanthose listed above are possible under the fol-lowing conditions:

a) The maximum capacity (Fan Max. or NatMax.) of the vent connector shall bereduced 10% for each additional multipleof the length listed above. For example,the maximum length listed above for a 4inch connector is 6 feet. With a connectorlength greater than 6 feet but not exceed-ing 12 feet, the maximum capacity mustbe reduced by 10% (0.90 x maximum ventconnector capacity). With a connectorlength greater than 12 feet but not exceed-ing 18 feet, the maximum capacity mustbe reduced by 20% (0.80 x maximum ventcapacity).

CONNECTOR DIAMETER

(INCHES)

MAXIMUM HORIZONTALCONNECTOR LENGTH

(FEET)3 4 1/2 4 65 7 1/26 97 10 1/28 129 13 1/2

10 1512 1814 2116 2418 2720 3022 3324 36

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b) The minimum capacity (Fan Min.) shall bedetermined by referring to the correspond-ing single appliance table (Tables 1 and 2).In this case, for each appliance the entirevent connector and common vent from theappliance to the vent termination would betreated as a single appliance vent, as if theother appliances were not present.

5) If vent connectors are combined prior to enter-ing the common vent, the maximum commonvent capacity listed in the common ventingtables must be reduced by 10%, the equivalentof 1 (one) 90

°

elbow (0.90 x maximum commonvent capacity). See Figure 7. The horizontallength of the common vent connector manifold(L) should not exceed 1-1/2 feet (18 inches) foreach inch of common vent connector manifolddiameter.

6) If the common vertical vent is offset as shownin Figure 8, the maximum common vent capac-ity listed in the common venting tables shouldbe reduced by 20%, the equivalent of 2 (two)90

°

elbows (0.80 x maximum common ventcapacity). The horizontal length of the offsetshall not exceed 1 1/2 feet for each inch ofcommon vent diameter.

7) The common vent diameter must always be atleast as large as the largest vent connectordiameter. All interconnection fittings must alsobe the same size as the common vent.

8) Type B gas vents shall terminate above theroof surface with a listed cap or a listed roofassembly in accordance with the terms of theirrespective listings and the vent manufacturer’sinstructions.

VENT CAPS 12˝ AND SMALLERListed gas venting systems using listed ventcaps 12˝ and smaller in size may terminate inaccordance with the VENT TERMINATIONTABLE. (SEE FIGURE 1)

VENT CAPS LARGER THAN 12˝Listed vent caps larger than 12˝ must belocated at least 2 feet above the highest pointand at least 2 feet higher than any portion of abuilding within a horizontal distance of 10 Feet.(SEE FIGURE 2)

9) Use sea level input rating when determiningmaximum capacity for high altitude installation.Use actual input rating for determining mini-mum capacity for high altitude installation.

GAS VENT TERMINATION TABLE

*THIS REQUIREMENT COVERS MOST INSTALLATIONS

ROOF PITCH MINIMUM HEIGHT

FLAT TO 7/12 1.0 FEET*OVER 7/12 TO 8/12 1.5 FEETOVER 8/12 TO 9/12 2.0 FEETOVER 9/12 TO 10/12 2.5 FEETOVER 10/12 TO 11/12 3.25 FEETOVER 11/12 TO 12/12 4.0 FEETOVER 12/12 TO 14/12 5.0 FEETOVER 14/12 TO 16/12 6.0 FEETOVER 16/12 TO 18/12 7.0 FEETOVER 18/12 TO 20/12 7.5 FEETOVER 20/12 TO 21/12 8.0 FEET

VERTICAL WALL

LISTED CAP

MINIMUM HEIGHT

8′ MIN.

LOWEST DISCHARGE OPENING

THE VENT TERMINATION SHOULD NOT BE LESS THAN 8 FT. FROM A VERTICAL WALL

FIGURE 1 – VENT CAPS 12″ OR SMALLER

12

X

ROOF PITCH IS X/12

2′ MIN.

10′ MIN.

FIGURE 2 – VENT CAPS LARGER THAN 12″

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10) No portion of the venting system can extendinto, or pass through any circulating air duct orplenum.

11) All vent pipe passing through floors, walls, andceilings must be installed with the listed clear-ance to combustible materials and be firestopped according to local codes. In theabsence of local codes, refer to NFGC (Z223.1)

12) Vent connectors serving Category I appliancesshall not be connected to any portion ofmechanical draft systems operating under pos-itive pressure such as Category III or IV Vent-ing Systems.

13) A Category I appliance must never be con-nected to a chimney that is servicing a solidfuel appliance. If a fireplace chimney flue isused to vent this appliance, the fireplace open-ing must be permanently sealed.

14) A vent connector shall be supported withoutany dips or sags and shall slope a minimum of1/4 inch per lineal foot of connector, backtowards the appliance.

15) Vent connectors shall be firmly attached todrafthood outlets or flue collars by sheet-metalscrews or other approved means, except ventconnectors of listed Type B vent material whichshall be assembled in accordance with themanufacturer’s instructions. Joints betweensections of single wall connector piping shall befastened by sheet-metal screws or otherapproved means.

16) When the vent connector used for Category Iappliances must be located in or pass througha crawl space or other area which may be cold,that portion of the vent connector shall be oflisted double-wall Type B vent material or mate-rial having equivalent insulation qualities.

17) The entire length of single wall metal vent con-nector shall be readily accessible for inspec-tion, cleaning, and replacement.

18) For appliances with more than one input rate,the minimum vent or connector (Fan Min) capac-ity determined from the tables shall be less thanthe lowest appliance input rating and the maxi-mum vent or connector (Fan or Nat Max.) capac-ity determined from the tables shall be greaterthan the highest appliance input rating.

19) For single appliance vents:

a) If the vertical vent or tile lined chimney hasa larger diameter or flow area than thevent connector, use the vertical vent diam-eter to determine the minimum ventcapacity and the vent connector diameterto determine the maximum vent capacity.The flow area of the vertical vent, however,shall not exceed 7 times the flow area ofthe listed appliance categorized vent area,drafthood outlet area or flue collar areaunless designed in accordance withapproved engineering methods. See Table9 for calculated areas.

b) For multiple appliance vents:

The flow area of the largest section of ver-tical vent or chimney shall not exceed 7times the smallest listed appliance catego-rized vent area, flue collar area, or drafthood outlet area unless designed in accor-dance with approved engineering meth-ods. See Table for calculated areas.

Maximum vent or tile lined chimney flow area =

x

7

*

Drafthood outlet diameter, flue collar diameter, or listed appli-ance categorized vent diameter.

c) In no case, shall the vent connector beupsized more than 2 consecutive tablesize diameters over the size of the draft-hood outlet, flue collar outlet, or listedappliance categorized vent. Example: Anappliance with a 4 inch diameter flue outletcollar or drafthood outlet cannot be ventedwith a connector diameter larger than 6inches.

20) Masonry chimneys used to vent Category Icentral furnaces must be either tile-lined orlined with a listed metal lining system or dedi-cated gas vent. Unlined masonry chimneys areprohibited. (See Note 1).

21) A fan assisted furnace may be common ventedinto an existing masonry chimney provided:

a. The chimney is currently serving at leastone drafthood equipped appliance.

b. The vent connectors and chimney aresized in accordance with Tables 7 & 8.

SINGLE APPLIANCE VENTING OF A FANASSISTED FURNACE INTO A TILE LINED,MASONRY CHIMNEY IS PROHIBITED. THECHIMNEY MUST FIRST BE LINED WITHEITHER TYPE B VENT SIZED IN ACCOR-DANCE WITH TABLES 1 OR 2 OR A LISTEDSINGLE WALL, METAL LINING SYSTEM,SIZED IN ACCORDANCE WITH NOTE 22.

TT D

∗( )

2

4-------------------------

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22) Listed, corrugated metallic chimney liner sys-tems in masonry chimneys shall be sized byusing Tables 1 or 2 for dedicated venting andTables 3 or 4 for common venting with the max-imum capacity reduced by 20% (0.80 x maxi-mum capacity) and the minimum capacity asshown in the applicable table. Corrugatedmetal vent systems installed with bends or off-sets require additional reduction of the ventmaximum capacity (See Note 6).

23) For multiple units of gas utilization equipmentall located on one floor, available total height“H” is measured from the highest drafthoodoutlet or flue collar up to the level of the cap orterminal. Connector rise “R” is measured fromthe drafthood outlet or flue collar to the levelwhere the vent gas streams come together.(Not applicable to multi-story).

24) For multi-story installations, available totalheight for each segment of the system “H” isthe vertical distance between the highest draft-hood outlet or flue collar entering that segmentand the centerline of the next higher intercon-nection tee (See Figure 13).

25) The size of the lowest connector and of thevertical vent leading to the lowest interconnec-tion of a multi-story system must be in accor-dance with Table 1 OR 2, for available totalheight “H” up to the lowest interconnection(See Figure 14).

26) Common vents in multi-story systems shall betype B when used in multi-story systems andhave no offsets.

27) Numbers followed by an asterisk (*) in Table 6,indicate the possibility of continuous condensa-tion, depending on locality. Consult appliancemanufacturer, local serving gas supplier, and/orauthority having jurisdiction.

28) In a single run of vent or vent connector, morethan one diameter and type of pipe are permit-ted to be used, provided that all the sizes arepermitted by the tables.

29) If the desired vent height and connector riseand/or lateral are between the table entries, lin-ear interpolation is permitted for calculation ofthe permissible appliance input ratings. Extrap-olation beyond the table entries is not recom-mended. (See Example 7)

30) All combinations of pipe sizes, single-wall, anddouble-wall metal pipe are allowed within anyconnector run(s) or within the common ventprovided ALL of the appropriate tables permitALL of the desired sizes and types of pipe, as ifthey were used for the entire length of the sub-ject connector or vent. If single-wall and Type Bdouble-wall metal pipe are used for vent con-nectors, the common vent must be sized usingTable 4.

31) Locate draft hood outlet or flue collar of small-est input appliance closest to or under commonvent.

32) When vent table permits more than one diam-eter of pipe to be used for a connector or vent,the smallest permitted diameter should bepreferred.

TYPICAL VENTING APPLICATIONS

FIGURE 3

Table 1 should be used when Type B vent is used for both the vent connector and the vertical vent.

VENT

VENT CONNECTOR

D

HL

FIGURE 4

Table 2 should be used when a single-wall metal vent connector is attached toType B vertical vent.

VENT

VENT CONNECTOR

D

HL

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FIGURE 5

Table 3 should be used when Type B vent connectors are attached to a Type B common vent.

TYPE B COMMON VENT

APPLIANCE 1 APPLIANCE

2

D2

D1

H

R2

R1


2

H

R1R2

D

L

Schematic Diagram showing a typical manifolded common vent section “L” of the vent connector. (See Note 5)

“L” Less than or equal to 1.5 feet x D

FIGURE 7


2

H

R1R2

D

L

Schematic Diagram showing offset in the common vent section of the vertical vent. (See Note 6)

FIGURE 8

FIGURE 6

Table 4 should be used when single-wall metal vent connectors are attached to a Type B common vent.

TYPE B COMMON VENT


2

D2

D1

H

R2

R1

7

FIGURE 9

Table 5 shall be used when a Type B, double- wall vent connector is attached to a tile lined masonry chimney.

TILE-LINED MASONRY CHIMNEY

VENT CONNECTOR

A

L

D

H

FIGURE 12

Table 8 shall be used when single-wall metal vent connectors are attached to a tile lined masonry chimney.


A

D

D

H

RR

FIGURE 10

Table 6 shall be used when a single-wall metal vent connector is attached to a tile lined masonry chimney.


VENT CONNECTOR

A

L

D

H

FIGURE 11

Table 7 shall be used when Type B double-wall vent connectors are attached to a tile lined masonry chimney.


A

D

D

H

RR

8

VENT TABLES

Capacity of Type B Double-Wall Vents with Type B Double-Wall ConnectorsServing a Single Category I Appliance

TABLE 1

Height aLateralH a aa L

(ft) aa(ft)

Vent and Connector Diameter - D (inches)

3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝

Appliance Input Rating in Thousands of Btu Per Hour

FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max

6 0246

0132125

78514946

46363432

0183036

152979491

86676461

0273947

251157153149

141105103100

0325059

375232227223

205157153149

0446678

524321316310

285217211205

0537993

698425419413

370285279273

06393

110

897543536530

470370362354

8 0258

0122328

84575349

50403835

0163239

16510910398

94757166

0254251

276178171164

155120115109

0285364

415263255247

235180173165

0427084

583365356347

320247237227

0508399

780483473463

415322313303

06099

117

1006619607596

537418407396

10 02510

0122330

88615751

53424036

0173241

175118113104

100817770

0234154

295194187176

166129124115

0265267

447289280267

255195188175

0406888

631402392376

345273263245

04881

104

847533522504

450355346330

05795

122

1096684671651

585457446427

15 0251015

011222935

9469655953

5848454137

015304048

191136130121112

11293878276

020395161

327226219206195

187150142135128

022496476

502339330315301

285225217208198

038648498

716475463445429

390316300288275

0457699

115

970633620600580

525414403386373

05390

116134

1263815800777755

682544529507491

20 025101520

01021283448

977571645852

615148444035

01429384655

202149143133124116

11910096898478

01838505969

349250242229217206

202166160150142134

02047627384

540377367351337322

307249241228217206

033628194

107

776531519499481464

430346337321308295

0417395

111125

1057711697675654634

575470460443427410

05086

112129145

1384917902877853830

752612599576557537

30 02510152030

09

21273356

NR

1008177706458

NR

64565450

NRNRNR

0132837445373

213166160150141132113

1281121081029690

NR

0143648576688

374283275262249237214

220185176171163154NR

01845597080

104

587432421405389374346

336280273261249237219

027587790

102131

853613600580560542507

475394385371357343321

0336991

105119149

1173826811788765743702

650535524507490473444

04282

107124139171

15481072105510281002977929

855700688668648628594

50 02510152030

08

202659

NRNR

10186827670

NRNR

6761

NRNRNRNRNR

0112735425069

216183177168158149131

134122119114NRNRNR

0143545546384

397320312299287275250

232206200190180169NR

0154356667699

633497487471455440410

363314308298288278259

02255738597

123

932715702681662642605

518445438426413401376

0266586

100113141

1297975960935911888844

708615605589572556522

03377

101117131161

1730127612591230120311761125

952813798773747722670

100 0251015203050

NRNRNRNRNRNRNRNR

NRNRNRNRNRNRNRNR

NRNRNRNRNRNRNRNR

01026334047

NRNR

218194189182174166NRNR

NRNRNRNRNRNRNRNR

0123343505978

NR

407354347335321311290NR

NRNRNRNRNRNRNRNR

0134053627192

147

665566557542528513483428

400375369361353344NRNR

01852688090

115180

997831820801782763726651

560510504493482471449405

021608093

105131197

1411115511411118109510731029944

770700692679666653627575

0257194

109122149217

19081536151914921465143813871288

1040935926910895 880849787

9

VENT TABLES

Capacity of Type B Double-Wall Vents with Type B Double-Wall ConnectorsServing a Single Category I Appliance

TABLE 1 (Cont’d)

Height aLateralH a aa L

(ft) a a(ft)


10˝ 12˝ 14˝ 16˝ 18˝ 20˝ 22˝ 24˝


FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max

6 0246

075

110128

1121675668661

570455445435

0103147171

1645982975967

850650640630

0138191219

2267134613381330

1170890880870

0178242276

2983176917611753

1530117011601150

0225300341

3802225022422235

1960148014751470

0296390437

4721278227742767

2430185018351820

0360469523

5737337733703363

2950222022152210

0426555618

6853403040234017

3520267026602650

8 0258

071

115137

1261770758746

660515503490

098

154180

1858112411101097

970745733720

0130199231

2571154315281514

1320102010101000

0168251289

3399203020132000

1740134013301320

0212311354

4333258425632552

2220170016851670

0278398450

5387319631803163

2750211020902070

0336476537

6555388238633850

3360256025452530

0401562630

7838463446124602

4010305030403030

10 02510

068

112142

1377852839817

720560547525

093

149187

2036124412291204

1060850829795

0124192238

2825171316961669

1450113011051080

0161243298

3742225622382209

1925148014611430

0202300364

4782286828492818

2450189018711840

0264382459

5955355635363504

3050234023182280

0319458546

7254432243014268

3710284028182780

0378540641

8682515351325099

4450339033713340

15 0251015

063

105135155

159610191003977953

840675660635610

086

140177202

23801495147614461418

1240985967936905

0114182227257

33232062204120091976

17201350132712891250

0147229283318

44232719269626592623

22701770174817121675

0186283346385

56783467344234023363

29002260223521932150

0239355432479

70994304427842344192

36202800277727392700

0290426510564

86655232520451595115

44103410338533433300

0346501599665

103936251622261756129

53004080405740193980

20 025101520

059

101130150167

175611501133110510781052

930755738710688665

081

135172195217

263716941674164116091578

13501100107910451018990

0107174220248273

370123432320228222452210

190015201498146014251390

0139219273306335

494830973071302929882948

252020001978194019101880

0175270334372404

637639553926388038353791

325025702544250024652430

0220337413459495

798849164885483547864737

406032003174313030903050

0269403489541585

978559835950589658445792

498039103880383037953760

0321475573631689

1175371547119706370076953

600047004662460045754550

30 02510152030

05496

125143160195

1977135113321301127212431189

1060865851829807784745

074

127164187207246

3004200419811944190818731807

1550131012891254122011851130

098

164209237260305

4252278627592716267426332555

2170180017751733169216501585

0127206259292319369

5725369636663617357035233433

2920238023502300225022002130

0159252316354384440

7420473447014647459445424442

3770305030202970292028702785

0199312386431467540

9341590058635803574456865574

4750381037833739369536503565

0241373456507548635

11483719471557090702669646842

5850465046224574452744804375

0285439535590639739

13848861785748505843783708239

7060560055525471539153105225

50 02510152030

04190

118136151183

2231162016001567153615051446

11951010996972948924876

066

118154177195232

3441243124062366232722882214

1825151314951466143714081349

086

151196222244287

4934340933803332328532393150

2550212521022064202619871910

0113191243274300347

6711455445204464440943564253

3440284028132767272126752631

0141234295330361412

8774586458265763570156415523

4460367036393585353434813431

0171283355396433494

11129733972957224715570866953

5635463045974542451144794421

0209336419465506577

13767898089338855877987048557

6940569556545585554655065444

0251394491542586672

16694107881073710652105701048810328

8430686068186749671066706603

100 0251015203050

03082

108126141170241

24911975195519231892186118021688

13101170115911421124110710711000

044

107142163181215292

39253027300229612920288028032657

20501820180317751747171916631550

072

136180206226265350

57294313428242314182413340373856

29502550253125002469243823752250

095

172223252277319415

79145834579757375678561955055289

40503500347534343392335132673100

0120208268304330378486

104857591754874787409734172096956

53004600456645094451439442794050

0138245318358387446572

134549577952894479367928991368841

67005800576957175665561355095300

0169293374418452514659

1681711803117481165811569114821131010979

86007200716271007037697568506600

0204341436487523592752

2057814264142041410514007139101372013354

103008800875686838610853783918100

10

VENT TABLES

Capacity of Type B Double-Wall Vents with Single-Wall Metal ConnectorsServing a Single Category I Appliance

TABLE 2

Height aLateral

H aa a L

(ft)

a a

(ft)


3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝ 12˝


FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max

6 0246

3839

NRNR

7751

NRNR

45363331

59607483

151969289

85666360

8585

102114

249156152147

14010410299

126123146163

373231225220

204156152148

165159187207

522320313307

284213208203

211201237263

695423416409

369284277271

267251295327

894541533526

469368360352

371347409449

1118673664656

569453443433

537498584638

1639979971962

849648638627

8 0258

3739

NRNR

8356

NRNR

50393733

58597790

16410810295

93756964

8383

107122

273176168161

154119114107

123121151175

412261252243

234179171163

161155193223

580363352342

319246235225

206197245280

777482470458

414321311300

258246305344

1002617604591

536417404392

360339418470

1257768754740

658513500486

521486598665

1852112011041089

967743730715

10 02510

373952

NR

876156

NR

53413934

57597697

174117111100

99807668

8282

105132

293193185171

165128122112

120119148188

444287277261

254194186171

158153190237

628400388369

344272261241

202193241296

844531518497

449354344325

253242299363

1093681667643

584456443423

351332409492

1373849834808

718559544520

507475584688

2031124212241194

1057848825788

15 0251015

363851

NRNR

936963

NRNR

57474439

NR

56577595

NR

190136128116NR

11193867972

8080

102128158

325225216201186

186149140131124

116115144182220

499337326308290

283224217203192

153148182228272

713473459438418

388314298284269

195187231284334

966631616592568

523413400381367

244232287349404

1259812795768742

681543526501484

336319392470540

15911015997966937

838673657628601

488457562664750

23741491146914331399

1237983963928894

20 025101520

353750

NRNRNR

967468

NRNRNR

60504741

NRNR

54567393

NRNR

200148140129NRNR

11899948680

NR

7878

100125155186

346248239223208192

201165158146136126

114113141177216254

537375363344325306

306248239224210196

149144178222264309

772528514491469448

428344334316301285

190182224277325374

1053708692666640616

573468457437419400

238227279339393448

1379914896866838810

750611596570549526

326309381457526592

175111461126109210601028

927754734702677651

473443547646730808

263116891665162615871550

13461098107410371005973

30 02510152030

343749

NRNRNRNR

998074

NRNRNRNR

635652

NRNRNRNR

53557291

115NRNR

211164157144131NRNR

12711110698

NRNRNR

767698

122151181NR

372281271255239223NR

219183173168157NRNR

110109136171208246NR

584429417397377357NR

334279271257242228NR

144139171213255298389

849610595570547524477

472392382367349333305

184175215265312360461

1168823806777750723670

647533521501481461426

229219269327379433541

1542106910491017985955895

852698684662638615574

312296366440507570704

1971134613241287125112161147

1056863846821794768720

454424524620702780937

2996199919711927188418411759

1545130812831243120511661101

50 02510152030

333648

NRNRNRNR

998480

NRNRNRNR

6661

NRNRNRNRNR

51537089

112NRNR

213181174160148NRNR

133121117NRNRNRNR

737394

118145176NR

394318308292275257NR

230205198186174NRNR

105104131162199236315

629495482461441420376

361312305292280267NR

138133164203244285373

928712696671646622573

515443435420405389NR

176168204253299345442

1292971953923894866809

704613602583562543502

220209257313363415521

1724127312521217118311501086

948811795765736708649

295280347418481544674

2223161515911551151214731399

11891007991963934906848

428401496589668741892

3432242623962347229922512159

1818150914901455142113871318

100 0251015203050

NRNRNRNRNRNRNRNR

NRNRNRNRNRNRNRNR

NRNRNRNRNRNRNRNR

49516785

132NRNRNR

214192186175162NRNRNR

NRNRNRNRNRNRNRNR

697090

113138168231NR

403351342324310295264NR

NRNRNRNRNRNRNRNR

10098

125153188224301NR

659563551532511487448NR

395373366354343NRNRNR

131125156191230270355540

991828813789764739685584

555508501486473458NRNR

166158194238281325418617

140411521134110410751046988866

765698688672656639NRNR

207196240293342391491711

19001532151114771443141013431205

1033933921902884864824NR

273259322389447507631895

24791970194519051865182517471591

1300116811531133111010871041

NR

395371460547618690834

1138

39123021299029382888283827392547

20421817179617631730169616271489

11

VENT TABLES

Capacity of Type B Double-Wall Vents with Type B Double-Wall ConnectorsServing Two or more Category I Appliances

TABLE 3

Vent Connector Capacity

Common Vent Capacity

VentHeight

H(ft)

ConnectorRise

R(ft)

Vent Connector Diameter - D (inches)

3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝

Appliance Input Rating Limits in Thousands of Btu Per Hour



6 123

222324

374144

263135

353738

667581

465562

464849

106121132

728696

586062

164183199

104124139

777982

225253275

142168189

929597

296333363

185220248

109112114

376424463

237282317

128131134

466526575

289345386

8 123

222324

404447

273236

353637

728087

485764

495153

114128139

7690

101

646667

176195210

109129145

848688

243269290

148175198

100103105

320356384

194230258

118121123

408454492

248294330

138141143

507564612

303358402

10 123

222324

434750

283337

343637

788692

505967

495152

123136146

7893

104

656769

189206220

113134150

899194

257282303

154182205

106109111

341374402

200238268

125128131

436479515

257305342

146149152

542596642

314372417

15 123

212224

505355

303540

333536

8996

102

536371

474951

142153163

8399

111

646668

220235248

120142160

889193

298320339

163193218

110112115

389419445

214253286

134137140

493532565

273323365

162165167

609658700

333394444

20 123

212223

545760

313742

333435

99105110

566674

464850

157167176

87104116

626466

246259271

125149168

868991

334354371

171202228

107110113

436463486

224265300

131134137

552587618

285339518

158161164

681725764

347414466

30 123

202122

626466

333944

313334

113118123

597079

454748

181190198

93110124

606264

288299309

134158178

838588

391408423

182215242

103105108

512535555

238282317

125129132

649679706

305360405

151155158

802840874

372439494

50 123

192122

717375

364348

303233

133137141

647686

434546

216223229

101119134

575961

349358366

145172194

788183

477490502

197234263

97100103

627645661

257306343

120123126

797820842

330392441

144148151

98410141043

403478538

100 123

181920

828384

374450

283031

158161163

667989

404244

262267272

104123138

535557

442447452

150178200

737578

611619627

204242272

919497

810822834

266316355

112115118

103810541069

341405455

135139142

128513061327

417494555

VentHeight

H(ft)

Common Vent Diameter - D (inches)

4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝

Combined Appliance Input Rating in Thousands of Btu Per Hour

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

6 92 81 65 140 116 103 204 161 147 309 248 200 404 314 260 547 434 335 672 520 410

8 101 90 73 155 129 114 224 178 163 339 275 223 444 348 290 602 480 378 740 577 465

10 110 97 79 169 141 124 243 194 178 367 299 242 477 377 315 649 522 405 800 627 495

15 125 112 91 195 164 144 283 228 206 427 352 280 556 444 365 753 612 465 924 733 565

20 136 123 102 215 183 160 314 255 229 475 394 310 621 499 405 842 688 523 1035 826 640

30 152 138 118 244 210 185 361 297 266 547 459 360 720 585 470 979 808 605 1209 975 740

50 167 153 134 279 244 214 421 353 310 641 547 423 854 706 550 1164 977 705 1451 1188 860

100 175 163 NR 311 277 NR 489 421 NR 751 658 479 1025 873 625 1408 1215 800 1784 1502 975

12

VENT TABLES

Capacity of Type B Double-Wall Vents with Type B Double-Wall ConnectorsServing two or more Category I Appliances

TABLE 3 (cont’d)



VentHeight

H(ft)

ConnectorRise

R(ft)


12˝ 14˝ 16˝ 18˝ 20˝ 22˝ 24˝


FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT FAN NAT

Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max Min Max Max

6 246

174180NA

764897NA

496616NA

223230NA

10461231

NA

653827NA

281287NA

13711617

NA

8531081

NA

346352NA

17722069

NA

10801370

NA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

NANANA

8 246

186192198

822952

1050

516644772

238244252

112613071445

696884

1072

298305313

147817191902

91011501390

365372380

192022112434

115014601770

NA471478

NA27373018

NA18002180

NA560568

NA33193665

NA21802640

NA662669

NA39574373

NA25903130

10 246

196201207

870997

1095

536664792

249256263

119513711509

730924

1118

311318325

157018041989

95512051455

379387395

204923322556

120515351865

NA486494

NA28873169

NA18902290

NA581589

NA35023849

NA22802760

NA686694

NA41754593

NA27103270

15 246

214221228

96710851181

568712856

272279286

133414991632

79010061222

336344351

176019782157

103013201610

408416424

231725792796

130516652025

NA523533

NA31973470

NA20602510

NA624634

NA38814216

NA24903030

NA734743

NA46315035

NA29603600

20 246

223230237

105111621253

596748900

291298307

144315971726

84010641288

357365373

191121162287

109513951695

430438450

253327782984

138517652145

NA554567

NA34473708

NA21802650

NA661671

NA41904511

NA26303190

NA772785

NA50055392

NA31303790

30 246

216223231

121713161400

632792952

286294303

166418021920

91011601410

367376384

218323662524

119015101830

461474485

289131103299

154019202340

NA619632

NA38404080

NA23652875

NA728741

NA46814976

NA28603480

NA847860

NA56065961

NA34104150

50 246

206213221

147915611631

689860

1031

273281290

202321392242

100712911575

350359369

265928142951

131516852055

435447461

354837303893

166521352605

NA580594

NA46014808

NA26333208

NA709724

NA55695826

NA31853885

NA851867

NA66336943

NA37904620

100 246

192200208

192319842035

712888

1064

254263272

264427312811

105013461642

326336346

349036063714

137017602150

402414426

470748424968

174022202700

NA523539

NA59826143

NA27503350

NA639654

NA72547453

NA33304070

NA769786

NA86508892

NA39504810

VentHeight

H(ft)


12˝ 14˝ 16˝ 18˝ 20˝ 22˝ 24˝


FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

6 900 696 588 1284 990 815 1735 1336 1065 2253 1732 1345 2838 2180 1660 3488 2677 1970 4206 3226 2390

8 994 773 652 1423 1103 912 1927 1491 1190 2507 1936 1510 3162 2439 1860 3890 2998 2200 4695 3616 2680

10 1076 841 712 1542 1200 995 2093 1625 1300 2727 2113 1645 3444 2665 2030 4241 3278 2400 5123 3957 2920

15 1247 986 825 1794 1410 1158 2440 1910 1510 3184 2484 1910 4026 3133 2360 4971 3862 2790 6016 4670 3400

20 1405 1116 916 2006 1588 1290 2722 2147 1690 3561 2798 2140 4548 3552 2640 5573 4352 3120 6749 5261 3800

30 1658 1327 1025 2373 1892 1525 3220 2558 1990 4197 3326 2520 5303 4193 3110 6539 5157 3680 7940 6247 4480

50 2024 1640 1280 2911 2347 1863 3964 3183 2430 5184 4149 3075 6567 5240 3800 8116 6458 4500 9837 7813 5475

100 2569 2131 1670 3732 3076 2450 5125 4202 3200 6749 5509 4050 8597 6986 5000 10681 8648 5920 13004 10499 7200

13

VENT TABLES

Capacity of Type B Double-Wall Vent with Single-Wall ConnectorsServing Two or more Category I Appliances

TABLE 4



VentHeight

H(ft)

ConnectorRise

R(ft)


3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝




6 123

NRNRNR

NRNRNR

263134

NRNRNR

NRNRNR

465562

NRNR121

NRNR131

718595

NR168174

NR182198

102123138

207215222

223251273

140167188

262271279

293331361

183219247

325334344

373422462

234281316

447458468

463524574

286344385

15 123

NRNRNR

NRNRNR

293439

798387

8794

100

526270

116121127

138150160

8197

109

177185193

214230243

116138157

238246255

291314333

158189215

312321331

380411438

208248281

397407418

482522557

266317360

556568579

596646690

324387437

30 123

475054

606264

313742

778185

110115119

576776

113117122

175185193

89106120

169177185

278290300

129152172

226236244

380397412

175208235

296307316

497521542

230274309

378389400

630662690

294349394

528541555

779819855

358425482

50 123

464953

697172

334045

757983

128132136

607282

109114119

207215221

96113128

162170178

336345353

137164186

217226235

460473486

188223252

284294304

604623640

245293331

364376387

768793816

314375424

507520535

951983

1013

384458518

VentHeight

H(ft)


4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝


FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

6 89 78 64 136 113 100 200 158 144 304 244 196 398 310 257 541 429 332 665 515 407

8 98 87 71 151 126 112 218 173 159 331 269 218 436 342 285 592 473 373 730 569 460

10 106 94 76 163 137 120 237 189 174 357 292 236 467 369 309 638 512 398 787 617 487

15 121 108 88 189 159 140 275 221 200 416 343 274 544 434 357 738 599 456 905 718 553

20 131 118 98 208 177 155 305 247 223 463 383 302 606 487 395 824 673 512 1013 808 626

30 145 132 113 236 202 179 350 286 257 533 446 349 703 570 459 958 790 593 1183 952 723

50 159 145 128 268 233 204 406 337 296 622 529 410 833 686 535 1139 954 689 1418 1157 838

14

VE

NT

TA

BL

ES

Cap

acity

of M

ason

ry C

him

ney

with

Typ

e B

Dou

ble-

Wal

l Ven

t Con

nect

ors

Ser

ving

a S

ingl

e C

ateg

ory

I App

lianc

e

TAB

LE

5

Hei

ght L

ater

al

H

L

(ft)

(ft)

Con

nect

or D

iam

eter

- D

(in

ches

)To

be

used

wit

h ch

imne

y ar

eas

wit

hin

the

size

lim

its

at b

otto

m

3˝4˝

5˝6˝

7˝8˝

9˝10

˝12

˝

App

lianc

e In

put

Rat

ing

in T

hous

ands

of

Btu

Per

Hou

r

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

T

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

62 5

NR

NR

NR

NR

28 25*

NR

NR

NR

NR

52 49N

RN

RN

RN

R 8

6 8

2N

RN

RN

RN

R13

011

7N

RN

RN

RN

R18

016

5N

RN

RN

RN

R24

723

1N

RN

RN

RN

R32

029

8N

RN

RN

RN

R40

137

6N

RN

RN

RN

R58

156

1

102 5 10

NR

NR

NR

NR

NR

NR

31 28*

25*

NR

NR

NR

NR

NR

NR

61 57 50*

NR

NR

NR

NR

NR

NR

103

96

87

NR

NR

NR

NR

NR

NR

162

148

139

NR

NR

NR

NR

NR

NR

221

204

181

NR

NR

NR

NR

NR

NR

298

277

263

NR

NR

NR

NR

NR

NR

388

365

347

NR

NR

NR

NR

NR

NR

491

466

444

NR

NR

NR

NR

NR

NR

724

712

668

152 5 10 15

NR

NR

NR

NR

NR

NR

NR

NR

35*

33*

28*

NR

NR

NR

NR

NR

NR

NR

NR

NR

67 62 55*

48*

NR

NR

NR

NR

NR

NR

NR

NR

114

107

97

89*

NR

NR

NR

NR

NR

NR

NR

NR

179

164

153

141

NR

NR

NR

NR

NR

NR

NR

NR

250

231

216

201

NR

NR

NR

NR

NR

NR

NR

NR

336

313

296

281

NR

NR

NR

NR

NR

NR

NR

NR

441

416

394

375

NR

NR

NR

NR

NR

NR

NR

NR

562

533

567

485

NR

NR

NR

NR

NR

NR

NR

NR

841

828

777

742

202 5 10 15 20

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

38*

36*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

74 68*

60*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

124

116

107*

97*

83*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

201

184

172

159

148*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

274

254

237

220

206

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

375

350

332

314

296

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

491

463

440

418

397

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

627

597

566

541

513

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

953

933

879

840

807

302 5 10 15 20 30

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

41*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

82*

76*

67*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

137

128*

115*

107*

91*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

216

198

184*

171*

159*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

303

281

263

243*

227*

188*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

421

393

373

353

332

288*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

558

526

500

476

450

416

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

717

683

648

621

592

555

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

1112

1094

1025 981

940

877

502 5 10 15 20 30

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

92*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

161*

151*

138*

127*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

251*

230*

215*

199*

185*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

351*

323*

304*

282*

264*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

477

445

424*

400*

376*

327*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

633

596

567

539*

511*

468*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

812

774

733

702

669*

623*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

1243

1225

1147

1099

1050 984

Min

imum

Inte

rnal

Are

a of

Chi

mne

y Sq

uare

Inc

hes

1219

2838

5063

7895

132

Max

imum

In

tern

al A

rea

of C

him

ney

Squa

re In

ches

4988

137

198

269

352

445

550

792

15

VE

NT

TA

BL

ES

Cap

acity

of M

ason

ry C

him

ney

with

Sin

gle-

Wal

l Ven

t Con

nect

ors

Ser

ving

a S

ingl

e C

ateg

ory

I App

lianc

e

TAB

LE

6

* S

ee N

ote

27

Hei

ght a

Lat

eral

H a

a a

L(f

t)aa

(ft

)

Con

nect

or D

iam

eter

- D

(in

ches

)To

be

used

wit

h ch

imne

y ar

eas

wit

hin

the

size

lim

its

at b

otto

m

3˝4˝

5˝6˝

7˝8˝

9˝10

˝12

˝

App

lianc

e In

put

Rat

ing

in T

hous

ands

of

Btu

Per

Hou

r

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

TFA

NN

AT

FAN

NA

T

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

Min

Max

Max

62 5

NR

NR

NR

NR

28 25*

NR

NR

NR

NR

52 48N

RN

RN

RN

R 8

6 8

1N

RN

RN

RN

R13

011

6N

RN

RN

RN

R18

016

4N

RN

RN

RN

R24

723

0N

RN

RN

RN

R31

929

7N

RN

RN

RN

R40

037

5N

RN

RN

RN

R58

056

0

102 5 10

NR

NR

NR

NR

NR

NR

31 28*

24*

NR

NR

NR

NR

NR

NR

61 56 49*

NR

NR

NR

NR

NR

NR

102

95

86

NR

NR

NR

NR

NR

NR

161

147

137

NR

NR

NR

NR

NR

NR

220

203

189

NR

NR

NR

NR

NR

NR

297

276

261

NR

NR

NR

NR

NR

NR

387

364

345

NR

NR

NR

NR

NR

NR

490

465

441

NR

NR

NR

NR

NR

NR

722

710

665

152 5 10 15

NR

NR

NR

NR

NR

NR

NR

NR

35*

32*

27*

NR

NR

NR

NR

NR

NR

NR

NR

NR

67 61 54*

46*

NR

NR

NR

NR

NR

NR

NR

NR

113

106

96

87*

NR

NR

NR

NR

NR

NR

NR

NR

178

163

151

138

NR

NR

NR

NR

NR

NR

NR

NR

249

230

214

198

NR

NR

NR

NR

NR

NR

NR

NR

335

312

294

278

NR

NR

NR

NR

NR

NR

NR

NR

440

414

392

372

NR

NR

NR

NR

NR

NR

NR

NR

560

531

504

481

NR

NR

NR

NR

NR

NR

NR

NR

840

825

774

738

202 5 10 15 20

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

38*

35*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

73 67*

59*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

123

115

105*

95*

80*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

200

183

170

156

144*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

273

252

235

217

202

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

374

348

330

311

292

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

490

461

437

414

392

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

625

594

562

536

510

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

950

930

875

835

800

302 5 10 15 20 30

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

41*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

81*

75*

66*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

136

127*

113*

105*

88*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

215

196

182*

168*

155*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

302

279

260

240*

223*

182*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

420

391

370

349

327

281*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

556

524

496

471

445

408

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

715

680

644

615

585

544

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

1110

1090

1020 975

932

865

502 5 10 15 20 30

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

91*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

160*

149*

136*

124*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

250*

228*

212*

195*

180*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

350*

321*

301*

278*

258*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

475

442

420*

395*

370*

318*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

631

593

562

533*

504*

458*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

810

770

728

695

660*

610*

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

NR

1240

1220

1140

1090

1040 970

Min

imum

In

tern

al A

rea

of C

him

ney

Squa

re In

ches

1219

2838

5063

7895

132

Max

imum

In

tern

al A

rea

of C

him

ney

Squa

re In

ches

4988

137

198

269

352

445

550

792

16

VENT TABLES

Capacity of Masonry Chimney with Type B Double-Wall ConnectorsServing two or more Category I Appliances

TABLE 7



VentHeight

H(ft)

ConnectorRise

R(ft)


3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝




6 123

242627

NR4349

212834

394142

627992

405261

525355

106133155

678597

656769

194230262

101124143

878991

274324369

141173203

104107109

370436491

201232270

124127129

479562633

253330349

145148151

599694795

319378439

15 123

242526

485559

233135

383941

93105115

445564

545657

154174189

7489

102

727476

277299319

114134153

100103105

384419448

174192215

125128131

511558597

229260292

153156159

658718760

297339382

184187190

824900960

375432486

30 123

242526

546064

253236

373840

111122131

485866

525456

192208221

8295

107

697274

357376392

127145163

9699

101

504531554

187209233

119122125

680715746

255287317

145149152

883928968

337378418

175179182

111511711220

432484535

50 123

232426

525964

263137

363739

116127135

495866

515355

209225237

8296

108

677072

405421435

133152170

929598

582604624

198222247

115118121

798827854

271304334

140143147

104910851118

362400439

168172176

133413791421

462510558

VentHeight

H(ft)

Minimum Internal Area of Chimney, Square Inches

12 19 28 38 50 63 78 113


FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

6 NR 74 25 NR 119 46 NR 178 71 NR 257 103 NR 351 143 NR 458 188 NR 582 246 NR 853 NR

8 NR 80 28 NR 130 53 NR 193 82 NR 279 119 NR 384 163 NR 501 218 NR 636 278 NR 937 408




30 NR NR NR NR NR NR NR 270 137 NR 404 198 NR 564 278 NR 747 381 NR 969 496 NR 1473 749

50 NR NR NR NR NR NR NR NR NR NR NR NR NR 620 328 NR 831 461 NR 1089 606 NR 1692 922

17

VENT TABLES

Capacity of Masonry Chimney with Single-Wall ConnectorsServing two or more Category I Appliances

TABLE 8



VentHeight

H(ft)

ConnectorRise

R(ft)


3˝ 4˝ 5˝ 6˝ 7˝ 8˝ 9˝ 10˝




6 123

NRNRNR

NRNRNR

212834

NRNRNR

NRNRNR

395261

NRNR134

NRNR153

668497

179186193

191227258

100123142

231239247

271321365

140172202

292301309

366432491

200231269

362373381

474557634

252299348

499509519

594696793

283331375

15 123

NRNRNR

NRNRNR

233034

NR9296

NR103112

435463

129135141

151170185

7388

101

199207215

271295315

112132151

268277286

376411439

171189213

349359368

502548586

225256289

445456466

646706755

291334378

623634646

808884945

360402437

30 123

NRNRNR

NRNRNR

243135

869195

108119127

475765

126132138

187203216

8093

105

193201209

347366381

124142160

259269277

492518540

183205229

338348358

665699729

250282312

430442452

864908946

330372412

600613626

108911451193

455490521

50 123

NRNRNR

NRNRNR

253135

858994

113123131

485765

124130136

204218231

8094

106

188196205

392408422

130149167

252262271

567588607

194218243

328339349

778806831

265298328

417429440

102210581090

355393431

582596610

130213461386

537567595

VentHeight

H(ft)

Minimum Internal Area of Chimney, Square Inches

12 19 28 38 50 63 78 113


FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

FAN+FAN

FAN+NAT

NAT+NAT

6 NR 73 25 NR 118 45 NR 176 71 NR 255 102 NR 348 142 NR 455 187 NR 579 245 NR 846 NR





30 NR NR NR NR NR NR NR 266 135 NR 398 195 NR 558 275 NR 739 377 NR 957 490 NR 1447 740

50 NR NR NR NR NR NR NR NR NR NR NR NR NR 612 325 NR 821 456 NR 1076 600 NR 1672 910

18

TABLE 9

MASONRY CHIMNEY LINER DIMENSIONSWITH CIRCULAR EQUIVALENTS

When liner sizes differ dimensionally from those shown in Table 9equivalent diameters may be determined from published tables forsquare and rectangular ducts of equivalent carrying capacity or byother engineering methods.

NOMINALLINER SIZE

INCHES

INSIDEDIMENSIONS INLINER INCHES

INSIDE DIA.OR EQUIVALENT

DIA. INCHES

EQUIVALENTAREA

SQ. INCHES4 x 8 2 1/2 x 6 1/2 4

567

12.219.6 28.338.3

8 x 8 6 3/4 x 6 3/4 7.48

42.750.3

8 x 12 6 1/2 x 10 1/2 910

63.6 78.5

12 x 12 9 3/4 x 9 3/4 10.411

83.3 95

12 x 16 9 1/2 x 13 1/2 11.81214

107.5113

153.916 x 16 13 1/4 x 13 1/4 14.5

15162.9176.7

16 x 20 13 x 17 16.218

206.1254.4

20 x 20 16 3/4 x 16 3/4 18.220

260.2314.1

20 x 24 16 1/2 x 20 1/2 20.122

314.2380.1

24 x 24 20 1/4 x 20 1/4 22.124

380.1452.3

24 x 28 20 1/2 x 24 1/4 24.1 456.228 x 28 24 1/4 x 24 1/4 26.4

27543.3572.5

30 x 30 25 1/2 x 25 1/2 27.930

607706.8

30 x 36 25 1/2 x 31 1/2 30.933

749.9855.3

36 x 36 31 1/2 x 31 1/2 34.436

929.41017.9

19

Example 1:

Single Draft-Hood-Equipped Appliance

Suppose that an installer has a 120,000 Btu/hr input appli-ance with a 5 inch diameter draft hood outlet that needs tobe vented into a 10 foot high Type B vent system. Whatsize vent should be used assuming (a) a 5-Ft lateral sin-gle-wall metal vent connector is used with two 90

°

elbows,(b) a 5-Ft lateral single-wall metal vent connector is usedwith three 90

°

elbows in the vent system?

Solution

Table 2 should be used to solve this problem because sin-gle-wall metal vent connectors are being used with a TypeB vent: Refer to Figure 4 of Typical Applications.

(a) Read down the first column in Table 2 until the row associated with a 10-Ft height and a 5-Ft lateral is found. Read across this row until a vent capacity greater than 120,000 Btu/hr is located in the shaded columns labeled “NAT Max” for draft-hood-equipped appliances. In this case, a 5 inch diameter vent has a capacity of 122,000 Btu/hr and may be used for this application.

(b) If three 90

°

elbows are used in the vent system, then the maximum vent capacity listed in the tables must be reduced by 10 percent (see Note 3). This implies that the 5 inch diameter vent has an adjusted capacity of only 110,000 Btu/hr. In this case, the vent system must be increased to 6 inches in diameter. See calculations below:

122,000 x .90 = 110,000 for 5˝ Vent

From Table 2—Select 6˝ Vent 186,000 x .90 = 167,000; This is greater than the required120,000, therefore use a 6˝ Vent and connector whenthree elbows are used.

10′

5′

EXAMPLE 1

DRAFT HOOD EQUIPPED APPLIANCE 120,000 BTUH INPUT

B-VENT

ELBOW

SINGLE WALL

Example 2: Single Fan-Assisted Appliance

Suppose an installer has an 80,000 Btu/hr input fan-assisted appliance that must be installed using 10 feet oflateral connector attached to a 30-Ft high Type B vent.Two 90° elbows are needed for the installation. Can a sin-gle-wall metal vent connector be used for this application?

Solution

Table 2 refers to the use of single-wall metal vent connec-tors with Type B vent. In the first column find the row asso-ciated with a 30-Ft height and a 10-Ft lateral. Read acrossthis row, looking at the “FAN Min” and “FAN Max” columns,to find that a 3 inch diameter single-wall metal connectorvent is not recommended. Moving to the next larger sizesingle wall connector (4˝) we find that a 4 inch diametersingle-wall metal connector has a recommended minimumvent capacity of 91,000 Btu/hr and a recommended maxi-mum vent capacity of 144,000 Btu/hr. The 80,000 Btu/hrfan-assisted appliance is outside this range, so we con-clude that a single-wall metal vent connector cannot beused to vent this appliance using 10 feet of lateral for theconnector.

However, we see that if the 80,000 Btu/hr input appliancecould be moved to within 5 feet of the vertical vent, then a4 inch single-wall metal connector could be used to ventthe appliance. Table 2 shows the acceptable range of ventcapacities for a 4 inch vent with 5 feet of lateral to bebetween 72,000 Btu/hr and 157,000 Btu/hr.

If the appliance cannot be moved closer to the vertical vent,then Type B vent could be used as the connector material.In this case, Table 1 shows that for a 30-Ft high vent with 10feet of lateral, the acceptable range of vent capacities for a4 inch diameter vent attached to a fan-assisted applianceare between 37,000 Btu/hr and 150,000 Btu/hr.

30′

10′ LATERAL

EXAMPLE 2

FAN ASSISTED APPLIANCE 80,000 BTUH INPUT

EXAMPLES USING SINGLEAPPLIANCE VENTING TABLES

20

Example 3:

Common Venting Two Draft-Hood Appliances

Suppose a 35,000 Btu/hr water heater is to be commonvented with a 150,000 Btu/hr furnace using a commonvent with a total height of 30 feet. The connector rise is 2feet for the water heater and 3 feet for the furnace.Assume single-wall metal connectors will be used withType B vent. What size connectors and combined ventshould be used in this installation?

Solution

—(Table 4 applies in this example)

Table 4 should be used to size single-wall metal vent con-nectors attached to Type B vertical vent. In the vent con-nector capacity Table 4, find the row associated with a 30-Ft vent height. For a 2-Ft rise on the vent connector for thewater heater, read the shaded columns for draft-hood-equipped appliances to find that a 3 inch diameter ventconnector has a capacity of 37,000 Btu/hr.

Therefore, a 3 inch single-wall metal vent connector maybe used with the water heater. For a draft-hood-equippedfurnace with a 3-Ft rise, read across the appropriate row tofind that a 5 inch diameter vent connector has a maximumcapacity of 120,000 Btu/hr (which is too small for the fur-nace) and a 6 inch diameter vent connector has a maxi-mum vent capacity of 172,000 Btu/hr. Therefore, a 6 inchdiameter vent connector should be used with the 150,000Btu/hr furnace.

For the capacity of the combined vent, the lower portion ofTable 4 should be used. The combined vent capacityrequired is 185,000 Btu/hr. Table 4 shows that the com-bined vent capacity of a 6 inch diameter vent with a 30-Ftvent height is 257,000 Btu/hr. This is more than adequateto handle the 35,000 Btu/hr input water heater and the150,000 Btu/hr input furnace.

2′

3′

30′

Combined Capacity 35,000 + 150,000 = 185,000

EXAMPLE 3

DRAFT HOOD EQUIPPED WATER HEATER

35,000 BTUH INPUT

DRAFT HOOD EQUIPPED FURNACE 150,000 BTUH INPUT

ASSUME B VENT

SINGLE WALL CONNECTOR

Example 4: Common Venting a Draft Hood Water Heater with a Fan-Assisted Furnace

In this case, a 35,000 Btu/hr input draft-hood-equippedwater heater with a 2 foot connector rise is to be commonvented with a 100,000 Btu/hr fan-assisted furnace with a3-Ft connector rise. The common vent consists of a 30-Ftrise of Type B vent. What are the recommended ventdiameters for each connector and the common vent?

Solution—(Table 4)

Water Heater Vent Connector Diameter. Let us assumethe installer would like to use a single-wall metal vent con-nector. Using Table 4, Vent Connector Capacity, readdown the Total Vent Height “H” column to 30 feet and readacross the 2-Ft Connector Rise “R” row to the first Btu/hrrating in the “NAT Max” column that is equal to or greaterthan the water heater input rating. The table shows that a 3inch vent connector has a maximum input rating of 37,000Btu/hr. Since this is greater than the water heater input rat-ing, a 3 inch vent connector is adequate. Furthermore,since the water heater is equipped with a draft hood, thereare no minimum input rating restrictions.

Furnace Vent Connector Diameter.

Again, let us assumethe installer would like to use a single-wall metal vent con-nector. Using Table 4, Vent Connector Capacity, read downthe Total Vent Height “H” column to 30 feet and across the3-ft Connector Rise “R” row. Since the furnace has a fan-assisted combustion system, find the first “FAN Max” col-umn with a Btu/hr rating greater than the furnace input rat-ing. The 4 inch vent connector has a maximum input ratingof 119,000 Btu/hr and a minimum input rating of 85,000 Btu/hr. The 100,000 Btu/hr furnace in this example falls withinthis range, so a 4 inch connector is adequate. If the furnacewould have had an input rating of 80,000 Btu/hr, then aType B vent connector (see Table 4) would have to be usedin order to meet the minimum capacity limit.

2′

3′

30′

EXAMPLE 4

WATER HEATER 35,000 BTUH INPUT

FAN ASSISTED FURNACE

100,000 BTUH INPUT

TYPE B

SINGLE WALL CONNECTORS

EXAMPLES USING COMMONVENTING TABLES

21

Example 4:

(cont’d)

Common Vent Diameter.

The total input to the commonvent is 135,000 Btu/hr. Using Table 4, Common VentCapacity, read down the Total Vent Height “H” column to30 feet and across this row to find the smallest vent diame-ter in the “FAN+NAT” column that has a Btu/hr rating equalto or greater than 135,000 Btu/hr. The 4 inch common venthas a capacity of 132,000 Btu/hr and the 5 inch commonvent has a capacity of 202,000 Btu/hr. Therefore, the 5inch common vent should be used in this example.

Summary.

In this example, the installer may use a 3 inchdiameter, single-wall metal vent connector for the waterheater and a 4 inch diameter, single-wall metal vent con-nector for the furnace. The common vent should be a 5inch diameter Type B vent

Example 5:

Single Draft Hood Equipped Furnace Vented into a Masonry Chimney

A 135,000 Btu/hr draft hood equipped furnace is to bevented into a 15´ high tile lined masonry chimney. Thechimney is not exposed to the outside except above theroof line. The furnace has a 6˝ diameter draft hood outletand requires a 10´ lateral vent connector with 3 elbows.The chimney is constructed using a 8˝ x 8˝ liner. What sizesingle wall vent connector is required?

Solution:

Table 6 should be used. Refer to the figure for Example 5.

EXAMPLE 5


VENT CONNECTOR WITH THREE

ELBOWS

8″ x 8″

10′

D

15′

DRAFT HOOD EQUIPPED FURNACE

To determine the required vent connector diameter, readdown the height column in Table 6 until 15´ is found. Findthe row for a 10´ long lateral. The table shows that a 6˝diameter connector will allow a maximum capacity of151,000 Btu/hr for “Nat Max.” (draft-hood equipped) fur-nace. Because 3 elbows are required, however, the maxi-mum capacity must be reduced by 10% (See Note 3).Allowing for the additional elbow the corrected maximumcapacity is 135,900 Btu/hr. A 6˝ diameter connector islarge enough and should be used. The internal area of thechimney is 8˝ x 8˝ = 64 sq. in. and is within the acceptablerange (38 sq. in. to 198 sq. in.) for a 6˝ vent connector asshown in Table 6.

Example 6: Common Venting into a Masonry Chimney

In this case, a 35,000 Btu/hr input 4 inch diameter outletdraft hood-equipped water heater with 2 feet of connectorrise and 4 feet of horizontal length is to be common ventedwith a 100,000 Btu/hr fan-assisted furnace with a 4 inchdiameter flue collar, 3 feet of connector rise and 6 feet ofhorizontal length. The common vent is an 8 x 12 tile linedchimney that is 30 feet tall. What are the recommendedvent diameters for each connector? Is this an acceptableinstallation?

Solution:

Table 8 is used to size common venting installationsinvolving single wall connectors into masonry chimneys.

Water Heater Vent Connector Diameter. Using Table 8,Vent Connector Capacity, read down the Total Vent Height“H” column to 30 feet and read across the 2 ft ConnectorRise “R” row to the first Btu/hr rating in the “NAT MAX” col-umn that is equal to or greater than the water heater inputrating. The Table shows that a 3 inch vent connector has amaximum input of only 31,000 Btu/hr while a 4 inch ventconnector has a maximum input of 57,000 Btu/hr. A 4 inchvent connector must therefore be used.

Furnace Vent Connector Diameter. Using Table 8 VentConnector Capacity, read down the Total Vent Height “H”column to 30 feet and across the 3 ft Connector Rise “R”row. Since the furnace has a fan-assisted combustion sys-tem, find the first “FAN MAX” column with a Btu/hr ratinggreater than the furnace input rating. The 4 inch vent con-nector has a maximum input rating of 127,000 Btu/hr and aminimum input rating of 95,000 Btu/hr. The 100,000 Btu/hrfurnace in this example falls within this range, so a 4 inchconnector is adequate.

EXAMPLES USING COMMONVENTING TABLES

22

EXAMPLE 6:

(cont’d)

Masonry Chimney.

From Table 9, the Equivalent Area fora Nominal Liner size of 8 inches x 12 inches is 63.6 squareinches. Using Table 8, Common Vent Capacity, read downthe “Fan + Nat” column under the Minimum Internal Areaof Chimney value of 63 to the row for 30-ft height, to find acapacity value of 739,000 Btu/hr. The combined input rat-ing of the furnace and water heater 135,000 Btu/hr, is lessthan the Table value, so this is an acceptable installation.

Note 19 requires the common vent area to be no greaterthan seven times the flow area of the smallest applianceoutlet area. Both appliances in this installation use 4 inchdiameter outlets. From Table 9, the Equivalent Area for anInside Diameter of 4 inches is 12.2 square inches. Seventimes 12.2 is 85.4, which is greater than 63.6, so this con-figuration is acceptable.

Note 1 specifies that the Table values are for vents orchimneys which are not exposed to the outdoors below theroofline. If the masonry chimney in this case were exposedbelow the roofline, then the appliance manufacturer, localgas utility, and/or authority having jurisdiction must be con-sulted.

EXAMPLE 7:

Interpolating Between Table Values

An installer has an 80,000 Btu/hr input appliance with a 4inch diameter draft hood outlet that needs to be ventedinto a 12-ft high Type B vent. The vent connector has a 5 ftlateral length and is also Type B. Can this appliance bevented using a 4 inch diameter vent?

Solution

Table 1 is used in the case of an all Type B vent system.However, since there is no entry in Table 1 for height of 12feet, interpolation must be used. Read down the 4 inchdiameter “NAT Max” column to the row associated with 10ft. height and 5 ft. lateral to find the capacity value of77,000 Btu/hr. Go down further to the 15 ft. height, 5 ft. lat-eral row to find the capacity value of 87,000 Btu/hr. The dif-ference between the 15 ft. height capacity value and the10 ft. height capacity value is 10,000 Btu/hr. The capacityfor a vent system with a 12 ft. height is equal to the capac-ity for a 10 ft. height plus 2/5 of the difference between the10 ft. and 15 ft. height values, or 77,000 + 2/5 x 10,000 =81,000 Btu/hr. Therefore, a 4 inch diameter vent may beused in the installation.

23

Rise

Other Inputs From Below

• Common Vent Size Based on All Inputs Entering This Segment

and Available Total Height • Available Total Height “H” Equals Rise Plus

Distance Between Tees

Vent Connector Size Depends On: • Input • Rise • Available Total Height “H” • Table 3 Connectors

Common Vent Size Depends On: • Combined Inputs • Available Total Height “H” • Table 3 Common Vent • Vertical Common Vent With No Offsets

• Total Input

Tee Same Size as Segment Above

Increase Vent

Connector Size If

Necessary

Multi-story Gas Vent Design Procedure for Each Segment of System

Vent Connector

BTUH Input

Tee Tee Same Size as Segment Above

Figure 13

24

1995 CAC / BDP P.O. Box 70, Indianapolis, IN 46206 imga1a09 Catalog No. 92-33GA-1A15

Design Vent Connector for First Floor Appliance as an Individual Vent of This Total Height for Input of First Floor Appliance

Each Interconnection Tee is Same Size as Segment of Common Vent Directly Above

✽

Principles of Design of Multi-story Vents Using Vent Connector and Common Vent Design Tables

Available Total Height for Second Floor Appliance

Use Vent Connector Table

Rise

Multi-story Vent System

4

3

Available Total Height for Third Floor Appliance

Rise

Available Total Height for Top

Floor Appliance

Rise

Figure 14

2

1

Tee With Cap Optional

Listed Cap

Third Connection Tee ✽

Second Connection Tee ✽

First Connection Tee ✽

Top Floor Appliance


Third Floor Appliance


Second Floor Appliance

First Floor Appliance

Use Available Total Height for Second Floor Appliance and Combined Heat Input of Two Appliances

Use Individual Ventfor Top Floor Appliance if Connector Requirement for Rise or Total Height Cannot be Met

Available Total Height for Third Floor Appliance and Combined Input of Three Appliances (If Top Floor Appliance is Not Connected, Measure Total Height to Vent Top)

Use Available Total Height for Top Floor Appliance and Combined Input of All Appliances on Common Vent

GAMA Venting Tables

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Transcript of GAMA Venting Tables