The Combustion Air Conundrum

November 23, 2005
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As I was listening to the evening news recently, the home improvement "specialist" said something like this: "Want to save energy? Seal up that home! Install new windows, caulk around the foundation and sill plate, add weather stripping, install backdraft dampers on the exhaust fans and clothes dryer, and seal any other openings that will allow air to infiltrate your home's structure. Put plastic over windows and consider installing storm doors and windows. Energy costs will soar this year, and you don't want to pay to heat the outdoors!"

It's true that heating costs probably will go up again this year. People will want to conserve as much as possible. However, if homes are sealed up so tightly that their combustion appliances don't have enough ventilation/combustion air, it can lead to dire health risks.

Way back in the 18th century, Benjamin Franklin wrote these words of wisdom:

"I considered fresh air an enemy, and closed with extreme care every crevice of the room I inhabited. Experience has convinced me of my error. I am persuaded that no common air from without is so unwholesome as the air within a closed room that has been breathed and not changed."

Franklin knew this to be true. Others knew it before him. Now, nearly 300 years since Ben Franklin's birth, we still need to remind our customers. Today's combustion appliances make air changes even more necessary.

Combustion Needs Oxygen

Houses require air exchanges: air to breathe, air to burn (combustion air), and air to replace what is lost through the exhaust of clothes dryers, bathroom fans, and kitchen equipment. Yet year after year we hear of CO poisonings, cases of Sick Building Syndrome, and other problems related to insufficient infiltration or ventilation air.

Cost-effective solutions to these problems range from mechanical-powered ventilators to passive vents. The technician and/or designer is responsible for providing the solution and testing for problems each time an air handler or combustion appliance is serviced.

Heating technicians may be alarmed by a cracked heat exchanger because it's what they can see. Truth is, as few as 1 percent of CO poisonings are due to heat exchanger failures alone. Far more are caused by ventilation and combustion air problems which are not always visible but always measurable.

If the furnace has proper combustion and ventilation air and it's burning properly, in the worst case a cracked heat exchanger will cause the home to become too humid due to moisture produced by the combustion process, and then only if the furnace is leaking into the airstream.

It is far more likely that the distribution air will be forced into the furnace's heat exchanger than it is for flue gases to be forced out into the distribution air under almost all conditions.

Don't give that furnace enough air to burn, however, and you have a huge potential problem on your hands. Poor combustion due to lack of combustion air and/or lack of ventilation is far more dangerous under nearly all circumstances. Compound that with a failed heat exchanger and you have the worst-case scenario.

Your Responsibility

As a heating contractor, you are responsible for ensuring that the HVAC system operates properly. This means performing the ventilation air test outlined in the International Fuel and Gas Code, performing a combustion analysis, checking ambient CO levels in every building for which you service the heating systems, and inspecting heating equipment to make sure it meets or exceeds industry standards.

Several tests are suggested by the 2003 International Fuel and Gas Code. Maintenance procedures also are outlined by state building codes and several other competent organizations, including weatherization departments, manufacturers, and gas utilities. Manufacturers' detailed instructions reference the code, specific maintenance procedures, and specific ventilation and combustion air requirements.

Over the next few weeks I will be detailing, through a series of articles, how, when, and why you should use a combustion analyzer in the print edition of The NEWS. A complete furnace inspection, including a detailed procedure and check sheet, is available in the online Extra Edition section of The NEWS.

If you are not a subscriber, you can get temporary online access by purchasing a 24-hour pass. Just go to the Web site, www.achrnews.com, and log on to Extra Edition.

These inspection procedures aren't my standards; they are industry standards. I just took the time to incorporate them into a procedure that addresses the concerns with logic, and that protects the technician while respecting his time on the job.

Any comments, suggestions, or feedback you would like to send me would be greatly appreciated. Even though I have been performing these inspections and using an analyzer for five years now, there is always something to learn. That's the best part about this business.

There are other solutions for heating energy conservation that you can offer to your customers. Getting rid of the combustion air is not the answer.

Jim Bergmann is an HVACR instructor at Cuyahoga Valley Career Center, Brecksville, Ohio, and HVACR specialist with Testo Inc. He may be contacted at jbergmann@testo.com.

Publication date: 11/28/2005

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