The NEWS - February 18, 2008 - (Page 56)

service & maintenance this particular article is this: I was scheduled to testify on Dec. 7, 2007 at a trial on the behalf of a deceased man’s family. This gentleman rented his house for over 15 years and died in February 2002 from carbon monoxide poisoning from a furnace with a 12-inch crack in the heat exchanger. The expert that was going to be used in this case for the defendant (the landlord) has 18 years of experience in the HVAC field. After he examined the heat exchanger, he pulled the blower and found the unit was missing a filter and the blower was working at 40 percent capacity so the heat exchanger was stressed by lack of airflow, in his opinion. He said he conducted a CO test and found 0 ppm. This furnace was manufactured in 1976 and was installed in a wide-open basement with approximately six windows and no partitions. The furnace was removed and put into storage to be used as evidence for the trial. When I conducted the research for my testimony on the trial, I inspected the furnace at the storage facility. In less than 10 minutes I found at least one 12-inch crack in the heat exchanger cell. Now this is the part that infuriated me: the expert for the Tubular type chamber showing collector box where tube failed. Side view of a 90 percent efficient serpentine chamber missing an eyelet and vertical crack from dimple. defendant, upon hearing my findings, said he thoroughly inspected the furnace and that the heat exchanger must have cracked when it was transported to storage. This was a seasoned technician who was trusted to determine if the furnace was safe. How could he miss a crack like this in the heat exchanger, especially when it was of such importance? This case was eventually settled out of court. HOW CRACKS OCCUR Our industry lacks education on proper heat exchanger safety inspection. There is an easy inspection method for every 56 style of furnace heat exchanger manufactured. I have trained HVAC technicians, gas company technicians and home and building inspectors from coast to coast for nearly 30 years. I look at furnaces across the country, and have determined that the same defects occur consistently across the board. I can assure you that approximately one out of two furnaces over five years old will have a crack in the heat exchanger. How can this happen? In a have previously stated I only cared where heat exchangers crack, not why. The fact is I do care why. There are usually combinations of causes which create excessive stress on the metal of heat exchangers. For starters, older homes, 40-50 years and older, were built with very ample duct systems. Every room had a custom trunk line for return air. The ductwork was designed to take all the pressure off of the furnace. Years ago, the original cost of the heating system was 10 times the cost, or more, compared to what is spent on the heating systems of new homes today. Today, most new homes don’t have proper air returns. Add the fact that installers now oversize many furnaces, which the returns can’t handle. This in turn causes metal stress, which causes cracks. Other causes may include: • Filters that are too restrictive not allowing proper airflow over the heat exchanger, cause metal stress. • Filters that aren’t changed often enough, which also restrict the airflow over the heat exchanger, again cause stress. • Furnace running during the home construction process often referred to as dry-in. The out-gassing from the construction materials damages the heat exchanger. • Water leaks from a humidifier that is not properly maintained. • Water leaks from the evaporator coil. • A poor manufacturing design. It is inappropriate to simply blame the manufacturer. The items listed above are the usual causes of heat exchanger failures. In some cases, heat exchangers that last a long time usually operate in a near perfect world where the above causes never come into play. However, looking closely at the list again, you will find that contractors and owners must sometimes bear responsibility. COMMON FAILURES All heat exchangers have one thing in common: the style of the chamber, regardless of brand, will fail in the same place. In a lot of cases, replacing the heat exchanger won’t solve the ■ AIR CONDITIONING, HEATING & REFRIGERATION NEWS February 18, 2008

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The NEWS - February 18, 2008 Turnout Contents Newsline FYI Unitary Oil-Fired Products Furnaces Hydronics Ductless Rooftops Drives & Motors Controls Transmitters, Sensors Zoning Valves Refrigerants Condensers & Coils Heat Exchangers Cooling Towers Chillers Duct Products Humidification IAQ Monitors, Instruments Trucks Tools Software Installation, Maintenance of HVAC Coils Munters MCS Dries Up Water Concerns at Hospital Michigan Home Show Brings out Contractors Investigating Furnace Failures Mold/Bacteria Protection of A/C Coil Learning Center Classifieds Advertisers Opinions

The NEWS - February 18, 2008

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