Heat Exchanger & Chimney Flue Damage From Heating Equipment Condensation
CONDENSING BOILERS/FURNACES DAMAGE - CONTENTS: Review of damage to high efficiency heating boilers and furnaces (condensing boilers or condensing furnaces) due to condensation and corrosion. Can older furnaces or boilers also cause condensation damage when duty-cyclers are installed? Problems Connecting a Higher Efficiency Furnace or Boiler to an Old Chimney and Flue. Effect of Duty Cyclers on Heating System Efficiency & Performance. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
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Condensatin in chimneys & heating flues or equipment:
This article discusses damage to high efficiency heating equipment caused by condensation and corrosion to heat exchangers or flues, and we address the question of condensation and corrosion damage with older heating equipment that uses duty cycle controls.
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Topic: High Efficiency & Conventional Heating Furnace or Boiler Damage from Condensation
Question: Did the change to stainless steel heat exchangers fix the condensation damage worry with high efficiency heating furnaces and boilers? What about older heating equipment that uses a duty cycle timer?
A heating salesman mentioned that lawsuits were pending (in 1985) against some manufacturers of high-efficiency furnaces (and boilers) - that although condensation problems had been solved through the use of stainless-steel heat exchangers, there were new problems arising from the lower-temperature flue gases.
Also, are there any documented cases of condensation damage in older furnaces (or boilers) stemming from the use of duty-cyclers lowering flue gas temperature? - Jeff A. Pendl, Enervision, Cincinnati OH
Answer: Higher Efficiency Heating Systems are Designed to Handle Corrosive Condensate
Higher-efficiency heating boilers and furnaces have cooler exhaust gases, which may condense in different parts of the system. If the entire system, including the heating unit itself and its venting components were not designed to handle the corrosive condensate, problems may occur.
See HIGH EFFICIENCY BOILERS/FURNACES
The very high-efficiency condensing furnaces and boilers are designed to condense liquid in the heat exchanger. While some early models had troubles (, we are not aware of any current problems or lawsuits.
Condensing furnaces (warm air heat) or condensing boilers (hot water heat) use stainless-steel heat exchangers, plastic flue vent piping, and other system components that resist corrosion.
Watch out: if plastic vent piping for high efficiency heating equipment is not properly installed so that condensate is drained to a proper location, the system may become blocked or unsafe, as is happening in our photo, above left.
Problems Connecting a Higher Efficiency Furnace or Boiler to an Old Chimney and Flue
You are more likely to run into trouble when fitting a new, more efficient furnace or boiler to an old flue [especially with gas-fired heating equipment], or when retrofitting devices that lower flue gas temperatures.
In particular, problems are likely when the draft is already marginal due to a cold exterior chimney, extra long flue-vent-connector piping between the heater and the chimney, or other flue problems such as inadequate combustion air and very tight house construction.
Watch out: inadequate draft, backdrafting, and inadequate combustion air significantly increase the risk of production of dangerous, possibly fatal carbon monoxide gas. Be sure that your home is protected by working, properly-installed, properly located smoke detectors and CO detectors.
Effect of Duty Cyclers on Heating System Efficiency & Performance
As for the particular device you mentioned, a duty cycler, researchers at the America Gas Association Laboratory (AGA) suggest that they are unlikely to cause condensation problems.
[In at least part, that's because a properly designed and installed duty cycler must assure that the heating equipment runs long enough to reach proper operating temperature and thus also to vent properly.- Ed.]
Nor are duty cyclers likely to boost the efficiency of the heating system more than 1 or 2 percent.
Other energy savers such as heat reclaimers and automatic flue vent dampers (see Automatic Vent Dampers) like the one shown at left are more effective.
But stick with certified devices, follow the installation specifications, and consult with the manufacturer to be sure you have and are following the installation manual for the device.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
The link to the original Q&A article in PDF form immediately below was preceded (above) by an expanded/updated online version of this article.
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Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: firstname.lastname@example.org
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Links to our list of additional information on heating system inspection, repair, maintenance