This article describes 650-C chimneys, also called Super Chimneys designed for use with wood stoves and wood burning appliances.

This article series on chimneys, chimney construction, and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects.

Chimney inspection methods and chimney repair methods are also discussed. Page top illustration of a 650-C chimney courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Super Chimneys, 629 Chimneys or 650-C Chimneys Replace Class-A Metal Chimneys & Flues

A 650-C Chimneys are required for use with wood burning stoves and, as Carson Dunlop's sketch explains, they have replaced Class A metal chimneys.

Type 650-C chimneys, also called Super Chimneys are tested for fire safety to 2000 deg.F. and provide an extra measure of fire safety.

Image at left: Selkirk 650C-rated insulated chimney installed using a cathedral ceiling support box.

650C chimneys, developed ca. 1983, are insulated and designed to withstand continuous flue gas temperatures of 650 degrees or less.

650-C chimneys are considered a suitable alternative to masonry chimneys used to vent woodstoves, heating appliances (boilers, furnaces, water heaters), and fireplaces.

Watch out: typically a 650-C chimney requires a 2-inch clearance to combustible framing or other combustibles. Depending on local building code approval, this distance can be reduced by appropriate heat shielding.

The 650-C or Super Chimnney is designed to resist corrosion both by its material and by the use of insulation that, by maintaining internal flue temperatures at a higher level (not as cooled by outside air) reduces the degree of condensation on the chimney flue interior.

Since Type A chimneys were discontinued for these applications after 1983 (to 1990 - citation needed), those venting systems are commonly replaced by a 650C chimney. [Type A chimneys do not have the same temperature tolerance and do not comply with current building codes in North America.]

Selkirk offers some important heating appliance and chimney safety advice concerning the 650C chimney illustrated above:

All chimneys should be inspected at least once a year to determine that their physical integrity is being maintained. The need for chimney maintenance also depends on the kind of appliance and how it is operated.

Wood and coal-burning appliances may need a great deal of chimney maintenance. Open front fireplaces without doors usually dilute their smoke with large amounts of air. Thus the buildup of chimney deposits is generally very low.

“Air tight” or controlled draft wood stoves and heaters produce dense smoke if they are loaded for long duration or overnight fires, and can rapidly produce heavy, thick creosote deposits. It is possible, by having a short duration daily hot fire, to burn off these deposits or prevent them from building up to dangerous levels.

This takes skillful operation and an appreciation of how to get the correct temperature. - Selkirk [1]

Definition of "Factory Built Chimney"

Factory-built chimney means a chimney consisting entirely of factory-made parts, each designed to be assembled with the other without requiring fabrication on site. - http://www.nationalcodes.nrc.gc.ca 11/13/2013

Super Chimney or 650C Chimney Product Sources & Standards

• [1] "Installation Instructions for Roof Supported Model CF Chimney with a Cathedral Ceiling Support Box", Selkirk Canada, Inc., 1400 California Ave., PO Box 160, Brockville, Ontario K6V 5V3, Tel: 800-267-3620. Selkirk's product line includes a Model CF Chimney with a cathedral ceiling support box. [The author, DF, installed this type of chimney and support box - a design that permits the chimney to "hang" from the roof structure, making installation of a woodstove easier - Ed.] Available in 6", 7" and 8" chimney sizes (this is the internal flue diameter). Retrieved 11/14/2013, un-dated document.
• [2] ASTM Standard ULCS629M 650C Factory-Built Chimneys, www.astm.org, U.S. standard retrieved 11/13/2013
• [3] CAN/ULC- S629-M, 650°C Factory-Built Chimneys, Canadian standard, http://www.nationalcodes.ca, retrieved 11/13/2013
• [4] "Safety Tips Installing a Fireplace", Alberta Safety Council Suite 1000, 10665 Jasper Ave NW, Edmonton, Alberta T5J 3S9 Toll-free within Alberta: 1-888-413-0099 - Quoting: Factory-built chimneys serving solid-fuel-burning appli- ances and their installation shall conform to CAN/ULC- S629-M, 650°C Factory-Built Chimneys . This document warns that "The chimney for a factory-built fireplace must be specifically designed, tested, and labeled for the particular unit".

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question:

(Mar 31, 2012) Caroline Slater said:
We bought our detached house new from a builder on a development. There is a gas mains where the fire should go. The wall is an external wall. There is no obvious space where a flue would be. The builder told us we have a 'super flue' and that would allow us to install any gas fire. However a lot of gas fires require depth and all we have is a flat external wall. How can we tell if we have a super flue without causing damage to our property? Can we install a gas or wood burning stove if we have a super flue? What would be required if we did that? There is no chimney.

Reply:

Caroline, a "superflue" is a type of metal chimney. If one is actually installed in your home, you'd see it - or at least some sort of metal chimney - protruding above the roof. It may have been boxed in with wood framing or even built into the structure entirely depending on the home's design, but to be used it has to be accessible at bottom and top. Find the chimney, inspect the labels on it. Send me a photo if you can.

Before we know what sort of chimney is installed and where it is, we can't get far in thinking about where you can install a gas fireplace.

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Continue reading at FIRE CLEARANCES INDOORS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CHIMNEY HEIGHT & CLEARANCE CODE
• FIRE CLEARANCES, METAL CHIMNEYS
• METAL CHIMNEY CONNECTIONS - home

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SUPER CHIMNEYS, 629 CHIMNEYS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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