Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents
where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

POST a QUESTION or COMMENT about size requirements for chimney flues

Chimney & flue sizing tables for venting multiple heating appliances thorugh a B-vent with double-wall B-vent connector between appliance and chimney.

Uniform Mechanical Code Tables plus commentary to assist in sizing metal or masonry chimneys according to chimney diameter, height, materials, and the input BTUH of the appliance(s) to be vented.

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Sizing of Metal & Masonry Chimney Flues, Flues, Vents Table C-9-D

Table C-9-D (Excerpts): Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

Watch out: the first portion of Table C-9-D specifies the maximum input BTUH capacity of any individual heating appliance that is to be vented along with other appliances out through a single chimney. The Continuation of C-9-D-2 below gives the chimney specifications for the total input BTUH of all of the appliances, combined.

Total Chimney/Vent Height (ft)	Connector Rise (ft) over its run	Table of B-Vent Diameter (inches) for a Multiple Appliance Chimney
		3 in.	4 in.	5 in.	6 in.	7 in.	8 in.
		Maximum [Individual] Appliance BTU Input Rating (thousands of BTUs)
6 ft.	1	26	46	72	104	142	185
	2	31	55	86	124	168	220
	3	35	62	96	139	189	248

8 ft	1	27	48	76	109	148	194
	2	32	57	90	129	175	230
	3	36	64	101	145	198	258

10 ft	1	28	50	78	113	154	200
	2	33	59	93	134	182	238
	3	37	67	104	150	205	268

15 ft.	1	30	53	83	120	163	214
	2	35	63	99	142	193	253
	3	40	71	111	160	218	286

20 ft.	1	31	56	87	125	171	224
	2	37	66	104	149	202	265
	3	42	74	116	168	228	300

30 ft.	1	33	59	93	134	182	238
	2	39	70	110	158	215	282
	3	44	79	124	178	242	317

Table C-9-D (Excerpts Continued): Multi-Appliance BTUH Venting Capacity of Type-B Double-Wall Vents [Chimneys] with Type-B flue vent connectors

This table gives the chimney specifications for the total input BTUH of all of the appliances combined and joined into a single vent when the flue is a Type-B double wall metal chimney and when the flue vent connector (between the appliance and the chimney entry point) is also a Type-B double wall unit.

Common [2 or more heating appliance] Vent Capacity in BTUH
Total Vent [Chimney] Height (feet)	*Diameter (inches) of the Commmon Vent [Chimney]*

	3 in	4 in	5 in	6 in	7 in	8 in	10 in
6		65	103	147	200	260	410
8		73	114	163	223	290	465
10		79	124	178	242	315	495
15		91	144	206	280	365	565
20		102	160	229	310	405	640
30		118	185	266	360	470	440
40		131	203	295	405	525	820

Guide to Chimney Sizing Tables for Venting Heating Appliances: Which Chimney Sizing Table to Use

Here is a quick guide to the UMC's chimney sizing & BTUH venting capacity tables when sizing a metal or masonry chimney diameter to match the total input BTUH of the heating appliances (boiler, furnace, water heater) being vented. Note that different chimney sizes are required for venting fireplaces and woodstoves.

Masonry fireplace chimney size requirements are at FIREPLACES & HEARTHS.

Chimney Type	Number of Appliances to be Vented
Metal B-Vent Chimney (Vent) Type of Flue Vent Connector:¹	Single Appliance	Multiple Appliances
	Which Chimney Flue / Vent Sizing Table to Use
Single Wall Flue Vent Connector	Table C-9-A	Table C-9-E (two part table)
Double Wall B-vent Flue Vent Connector¹	Table C-9-B	Table C-9-D (two part table)
Masonry Chimney²	Which Chimney Flue / Vent Sizing Table to Use
Single Wall Flue Vent Connector	Table C-9-C	Table C-9-F (two part table)
Minimum Input BTUH, Single appliance, natural gas, B-vent connector vs chimney height, size, & outdoor temperature	504.2(6)

Notes to the Table Above

1. A flue vent connector is the horizontal/sloped metal pipe connecting the heating appliance to the entry point of the chimney. Flue vent connectors and their materials, sizing requirements, & fire clearances are

at FLUE VENT CONNECTORS, HEATING EQUIPMENT

At double-wall B-vent chimneys the flue vent connector between the appliance and the chimney entry point may be single-wall metal flue vent connector or it may be a double-wall Type-B flue vent material.

2. At most masonry chimneys the flue vent connector or "stackpipe" or "smokepipe" is single wall metal, though for fire clearance needs it may be amended to use sections of insulated metal chimneys.

See CHIMNEY CROSS SECTION SHAPE EFFECTS for the effects of square vs round chimney sectional areas

Types of metal chimneys and their properties and fire clearances are at METAL CHIMNEYS & FLUES.

...

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Citations & References

In addition to any citations in the article above, a full list is available on request.

[4] NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)

NFPA #211-3.1 1988 - Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
[6] NFPA # 54-7.1 1992 - Specific to venting of equipment with fan-assisted combustion systems.
[7] GAMA - Gas Appliance Manufacturers' Association has prepared venting tables for Category I draft hood equipped central furnaces as well as fan-assisted combustion system central furnaces.
[8] National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
[9] Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
[10] Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys, refers to Chapters 23, 29, and 37 of the Building Code.
See the complete table of the "Capacity of Double-Wall or Asbestos-Cement (Transite) Type B vents with Single Wall Connectors Serving a Single Appliance", Table C-9-A in Appendix C.
See the complete table of the "Capacity of Type B Double Wall Vents with Type B Double Wall Vent Connectors Serving a Single Appliance", Table C-9-B in Appendix C.
New York 1984 Uniform Fire Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
[11] New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a flue liner was listed in the One and Two Family Dwelling Code for New York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979 Building and Fire Prevention Code:
[12] "Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
[13] Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
"Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
[14] "Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
[15] "Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: CHIMNEY INSPECTION DIAGNOSIS REPAIR . Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
[16] Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
[17] US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
Thanks to Luke Barnes for suggesting that we add text regarding the hazards of shared chimney flues. USMA - Sept. 2008.
[7] GAMA - Gas Appliance Manufacturers' Association has prepared venting tables for Category I draft hood equipped central furnaces as well as fan-assisted combustion system central furnaces.
[8] National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
[9] Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
[10] Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys, refers to Chapters 23, 29, and 37 of the Building Code.
See the complete table of the "Capacity of Double-Wall or Asbestos-Cement (Transite) Type B vents with Single Wall Connectors Serving a Single Appliance", Table C-9-A in Appendix C.
See the complete table of the "Capacity of Type B Double Wall Vents with Type B Double Wall Vent Connectors Serving a Single Appliance", Table C-9-B in Appendix C.
New York 1984 Uniform Fire Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
[11] New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a flue liner was listed in the One and Two Family Dwelling Code for New York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979 Building and Fire Prevention Code:
[12] "Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
[13] Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
"Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
[14] "Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
[15] "Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: CHIMNEY INSPECTION DIAGNOSIS REPAIR . Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
[16] Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
[17] US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Ceramic Roofware, Hans Van Lemmen, Shire Library, 2008, ISBN-13: 978-0747805694 - Brick chimneys, chimney-pots and roof and ridge tiles have been a feature of the roofs of a wide range of buildings since the late Middle Ages. In the first instance this ceramic roofware was functional - to make the roof weatherproof and to provide an outlet for smoke - but it could also be very decorative.
The practical and ornamental aspects of ceramic roofware can still be seen throughout Britain, particularly on buildings of the Victorian and Edwardian periods. Not only do these often have ornate chimneys and roof tiles but they may also feature ornamental sculptures or highly decorative gable ends. This book charts the history of ceramic roofware from the Middle Ages to the present day, highlighting both practical and decorative applications, and giving information about manufacturers and on the styles and techniques of production and decoration.
Hans van Lemmen is an established author on the history of tiles and has lectured on the subject in Britain and elsewhere. He is founder member and presently publications editor of the British Tiles and Architectural Ceramics Society.
Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003 - These guidelines address the inspection of chimneys and stacks. Each guideline assists owners in determining what level of inspection is appropriate to a particular chimney and provides common criteria so that all parties involved have a clear understanding of the scope of the inspection and the end product required. Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Such degradation may be managed via a prudent inspection program followed by maintenance work on any equipment or structure determined to be in need of attention. Sample inspection report specifications, sample field inspection data forms, and an example of a developed plan of a concrete chimney are included in the guidelines. This book provides a valuable guidance tool for chimney and stack inspections and also offers a set of references for these particular inspections.
Fireplaces, a Practical Design Guide, Jane Gitlin
Fireplaces, Friend or Foe, Robert D. Mayo
NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
Principles of Home Inspection: Chimneys & Wood Heating, in (Principles of Home Inspection), Carson Dunlop, Associates, Toronto, Ontario
NFPA 211 - 3-1.10 - Relining guide for chimneys
NFPA 211 - 3-2 - Construction of Masonry Chimneys
NFPA 211 - 3-3 - Termination Height for chimneys
NFPA 211 - 3-4 - Clearance from Combustible Material
NFPA 54 - 7-1 - Venting of Equipment into chimneys
Brick Institute of America - Flashing Chimneys
Brick Institute of America - Proper Chimney Crowns
Brick Institute of America - Moisture Resistance of Brick
American Gas Association - New Vent Sizing Tables
Chimney Safety Institute of America - Chimney Fires: Causes, Effects, Evaluation
National Chimney Sweep Guild - Yellow Pages of Suppliers
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested

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Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The HOME REFERENCE BOOK - the Encyclopedia of Homes and to use illustrations from The ILLUSTRATED HOME .

Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.

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Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents
where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

Sizing of Metal & Masonry Chimney Flues, Flues, Vents Table C-9-D

Table C-9-D (Excerpts): Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

Table C-9-D (Excerpts Continued): Multi-Appliance BTUH Venting Capacity of Type-B Double-Wall Vents [Chimneys] with Type-B flue vent connectors

Guide to Chimney Sizing Tables for Venting Heating Appliances: Which Chimney Sizing Table to Use

Notes to the Table Above

Recommended Articles

Suggested citation for this web page

INDEX to RELATED ARTICLES: ARTICLE INDEX to CHIMNEYS & FLUES

Ask a Question or Search InspectApedia

Citations & References

InspectAPedia®

FREE Encyclopedia of Building & Environmental Construction, Diagnosis, Maintenance & Repair No ChatBot Pledge: The accuracy & trustworthiness of every InspectApedia article or Q&A is researched by human experts.

Question? Just ask us!

Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

Sizing of Metal & Masonry Chimney Flues, Flues, Vents Table C-9-D

Table C-9-D (Excerpts): Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney

Table C-9-D (Excerpts Continued): Multi-Appliance BTUH Venting Capacity of Type-B Double-Wall Vents [Chimneys] with Type-B flue vent connectors

Guide to Chimney Sizing Tables for Venting Heating Appliances: Which Chimney Sizing Table to Use

Notes to the Table Above

Recommended Articles

Suggested citation for this web page

INDEX to RELATED ARTICLES: ARTICLE INDEX to CHIMNEYS & FLUES

Ask a Question or Search InspectApedia

Citations & References

InspectAPedia^®

FREE Encyclopedia of Building & Environmental Construction, Diagnosis, Maintenance & Repair
No ChatBot Pledge: The accuracy & trustworthiness of every InspectApedia article or Q&A is researched by human experts.

Multiple Appliance BTU Vent Capacity of Type B Double-Wall Vents
where a Double Wall Metal B-Flue Vent Connector is Used Between the Appliance and the Chimney