Installer-friendly PVC Venting Spurs Contractor Demand for High-efficiency Condensing Tankless Water Heaters By Jason Corey
O
ffering thermal efficiencies in the mid-90s, con- densing tankless water heaters use a secondary heat exchanger to lower combustion-gas temper-
atures in the flue, allowing the use of less costly PVC piping, instead of stainless steel, to build vent runs. The popularity of condensing technology in tankless
water heaters has risen steadily in recent years, despite the worst construction market in memory. Once building revives in earnest around the country, even more dramat- ic growth in this category is anticipated. Greater energy savings have played an important, but
still secondary, role in the rising profile of condensing tankless water heaters, which offer efficiency gains of approximately 10 to 15 percentage points over conven- tional units, from percentages in the low to mid 80s to around 95%. Like their conventional counterparts, all condensing units carry the Energy Star label. But as impressive as these energy savings are, ease of installa- tion remains the main growth driver for this technology. Condensing tankless water heaters use a secondary
heat exchanger to boost efficiency by capturing more heat from combustion gases as they escape up the flue. This heat-absorption process, in turn, cools these gases enough to permit venting with less costly, more installer- friendly PVC piping, rather than with category III stain- less steel. PVC venting makes tankless far more attractive for
first-time installers, many of whom have never used Category III Stainless Steel. When attendees are told at workshops that they can use PVC, their eyes light up. Virtually every service tech knows PVC inside and out. What’s more, the material requires zero clearance to combustibles. All of which is why, as more and more homeowners request a tankless replacement for their tank-type water heaters, the path of least resistance will be to go with condensing tankless to vent with PVC. This article, done in a question-and-answer format,
will delve deeper into the factors behind the popularity gains for condensing technology, while explaining how it works and how its installation differs from that of con- ventional tankless (very little). Moreover, the primary discussion here is based on how to present this technolo- gy to your customers, be they homebuilders, commercial specifiers or consumers. Tankless technology has been the preferred method of
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The author shows a condensing tankless water heater with the front cover removed and with the secondary heat exchanger at the top of the unit. A condensing unit incor- porates a secondary heat exchanger, located at the top of the water heater, to capture more heat from the combus- tion gases before they enter the venting at the top of the flue. This secondary heat exchanger then preheats the incoming water on its way to the primary heat exchanger, increasing the unit’s efficiency.
heating water for domestic use for decades in numerous countries worldwide. Condensing technology hasn’t been around for as long, but it has proven itself equally reliable in numerous applications, residential and commercial. The hope is that, once you clearly understand both
technologies and the positive impact they can have on your water heating business, you will embrace condens-
February 2011
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