Furnace
Techical Safety BC: Gas Furnace Report
Furnace
Techical Safety BC: Gas Furnace Report

We like to keep an eye on the industry to make sure we are always up to speed on the latest developments. We feel when we're informed, you're informed, and that's important to us.

We found this particular report from Technical Safety BC to be very interesting. It investigates the failure of gas furnaces with polypropylene lined condensing heat exchangers, and why it's important that the customer is made aware of the problem. Following is an excerpt of the report:


Technical Safety BC received multiple notifications of carbon monoxide exposures that involved failures in a common product line of residential gas burning furnaces manufactured between 1989 and 2011. Although the manufacturer ceased production of these furnaces in 2011, a large number of existing furnaces remain in operation throughout the province. Exposure to carbon monoxide (CO) can be hazardous to health and quickly life threatening if not detected. Technical Safety BC decided to investigate these incidents together to ensure that common factors were identified and thoroughly examined as part of the investigation process.

Technical Safety BC’s investigation has found that each of the incidents resulted from furnaces that had a common design feature that contributed to the failures, specifically, polypropylene lined secondary heat exchangers. This component was found to be susceptible to corrosion, which interfered with combustion air flow, producing CO. CO was found in occupied living spaces, having escaped the furnaces due to corrosion holes in the heat exchangers or due to corrosion blockage that allowed CO gases to circulate back into the home in certain venting configurations. It was further determined that built-in automatic safety devices did not reliably detect the conditions produced by the corroded secondary heat exchangers.

Service and maintenance instructions provided with the furnace did not include processes to support owners or contractors in detecting a corroding secondary heat exchanger in advance of failure. Subsequent service bulletins distributed through authorized dealers included procedures to properly diagnose furnace failures that produced elevated CO levels. Efforts to communicate this important procedure with other contractors or homeowners were not evident.

Technical Safety BC found that the manufacturer’s repair instructions called for replacement of a failed heat exchanger with a new part of the same design and materials. Failures investigated occurred within 20 - 60% of the service life of the furnace heat exchangers and therefore repaired units remain susceptible to repeated failures. The manufacturer stopped producing these furnaces in 2011 but existing furnaces continue to operate, and some failures were reported to Technical Safety BC.

These furnaces have the potential to release elevated levels of CO for some time before being identified, and occupants may not be made aware of the potential hazard in their homes.

Exposure to CO can be hazardous or fatal to humans and animals. Heath effects of CO exposures are identified in acute exposure guidelines published by the National Research Council, Appendix F. Disabling effects can occur with 8-hour exposures to concentrations as low as 27 ppm (parts per million), death can occur with 8-hour exposures as low as 130 ppm and in as little as 10 minutes with concentrations of 1700 ppm. Long term exposure to lower levels of CO can also lead to adverse health outcomes...

If you are interested in more details, here is the full report: Click here for the full report

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