Two manufacturers of plastic venting systems are pushing for a national fuel gas code in the United States that requires Underwriters Laboratories Inc. certification for use in some natural gas-fired water heaters, furnaces and boilers.
Albany, N.Y.-based Centrotherm Eco Systems LLC, which produces UL-certified polypropylene systems, and Pineville, N.C.-based Ipex USA LLC, which is introducing a UL-certified PVC formula in a couple of months, say venting components installed with high-efficiency appliances should be made from materials qualified for the application for safety reasons.
UL-listed vent pipes and accessories are engineered systems that connect appliances to a chimney or vent and then direct noxious gases produced by the combustion of fuels, namely carbon monoxide, to the outdoors.
However, the UL standard, called UL 1738, isn't well-known even though it has been around since the 1980s. And, since 2009, PP has been the only nonmetallic material capable of meeting it for so-called condensing Category II and IV appliances.
Even so, U.S. codes currently permit unlisted plastic vents to be installed with high-efficiency Category IV gas-fired appliances if installed according to the manufacturer's instructions, James Molloy, vice president of business development for Centrotherm, said in a phone interview. As a result, some installers are using PVC products designed for drain, waste and vent plumbing applications, not heating, he added.
"They do that because the equipment manufacturers approve PVC as a vent system in their lab testing," Molloy said. "The PVC manufacturers don't certify to the venting standard, yet the equipment manufacturers test them to be used as such. With that type of disconnect, there's apt to be problems, and there have been, like carbon monoxide poisoning."
Venting systems made with unlisted materials are susceptible to corrosion, cracking and joint separation, which can release the dangerous silent killer gas into living areas.
For example, PVC designed for plumbing vents is generally intended for applications where operating temperatures won't exceed 149° F. However, Molloy said situations can arise where gas-burning appliances run hotter. He pointed to incidents where a plumber sets a boiler at 180°-200° for it to be used with baseboard heaters in a home; or a water heater isn't maintained and scale buildup results in higher flue gas temperatures; or a furnace air filter gets clogged and restricts the air flow that cools flue gases.
"If the plastic doesn't have a high enough temperature rating, it can start to degrade, soften and melt," Molloy said.
In response, Centrotherm, a division of Brilon, Germany's Centrotec Sustainable AG, developed a PP formula that meets the UL-1738 standard for venting systems of gas-burning appliances. Their system, which is branded as InnoFlue, costs more than PVC but is warranteed for sustained flue gases up to 248° F (120° C).
In January, Ipex USA, part of the Oakville, Ontario-based Ipex Group, will introduce the second plastic system -- and first engineered PVC system -- to meet the standard, Gaetano Altomare, an Ipex product manager, said in a phone interview. Aptly called System 1738, the components are made from a certified compound PVC that is unlike DWV PVC, foam core PVC or foam core ABS. The soon-to-be-released flue gas venting option made the UL list because it can withstand all the test requirements, including temperature spikes up to 219° F, Altomare said. He is joining Molloy in calling for a national code update.
"There's got to be some level of importance to a subject matter when you've got competing materials uniting for the greater purpose of the industry," Altomare said. "Plastics have been used for decades, however, they have been using plumbing pipe and fittings certified for plumbing standards to vent combustion gases. It's enough of a problem to create a lot of chatter in the industry because of catastrophic failures that have happened."
Altomare wants to redirect the chatter to possible solutions with the System 1738 product launch and a technical session at the International Air-Conditioning, Heating, Refrigerating Exposition, scheduled for Jan. 14-16 in Atlanta.
"As a manufacturer of plastics that spends a lot of dollars on research and development, Ipex was able to engineer a plastic of PVC that's now capable of reaching the requirements of UL-1738 and we're the first ones to do it," Altomare said. "We've been working on it the last four to five years, and we're bringing it to market Jan. 1."
Meeting the UL-1738 standard requires passing more than 40 tests to qualify both the material and the performance of the pipe and fittings as a system. Some of the tests cover how the material and system handle low and elevated temperatures, UV light, joint load, vent sag, punctures, impact and flammability. The certification process also includes approval of detailed installation instructions and special labeling requirements. To ensure quality and compatibility, the standard stipulates that pipe, fittings and joining methods from different manufacturers shouldn't be mixed.
Altomare and Molloy would like the next version of the U.S. fuel gas code to mandate certification to the UL standard and eliminate the use of plumbing products for flue gas applications.
"The code for 2021 is being reviewed now and the two of us have submitted for changes that will get reviewed over the course of the next couple of years," Molloy said.