The home heating oil industry has a long and proud history, and Fuel Oil News has been there supporting it since 1935. It is an industry that has faced many challenges during that time. In its 77th year, Fuel Oil News is doing more than just holding
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36 NOVEMBER 2016 | FUEL OIL NEWS | www.fueloilnews.com W ith the introduction of super-efficient, variable speed, ECM-driven Delta- T circulators for residential use, I've taken a keen interest in selectively ap- plying them in radiant and other heat- ing systems. The results have exceeded my expectations. More on what I've found from various installations in a moment. As a bit of background, I'm a semi-retired "high-tech" man- ufacturing process engineer who also worked in the family's heating business for over 50 years (you can't raise ten kids on a single job!). PHOTOS COURTESY OF TACO, INC. Beyond AFUE: Hydronic Heating System Efficiency Before I jump into an expla- nation of my study, I'll add that I've also been aware, but haven't yet tried to use, non-ECM, variable Delta-T (rT) circs. I know they're out there, but I've simply not tried them. I'll also note that I've only used rP as an expedient means of converting a two- pipe reverse-return steam system into a single-zone forced hot-water system. My "process brain" has led me to appreciate and prefer Delta-T systems. And, by using a r T circulator with a super-efficient ECM motor, you get the best of both worlds—the best pumping strategy with greatest efficiency. With a r T variable-speed circulator, the pump varies its speed to maintain the designed-for r T. That means the Delta T will always be 20 degrees F—or whatever you dial it in for (5 -50° F)—even with heating load or outdoor temperature changes. A circulator changing its speed based on rP, however—whether the rP is dialed in based on estimated system head loss or is automatically selected—will vary its speed to maintain a fixed system pressure differential. The rT system will fluctuate, often decreasing energy expended to do the job optimally. How does a reduced r T affect the system? Consider the impact on a mod- ulating-condensing boiler. If the system is designed for a 20°F rT, but gets only a 12-15°F rT, the amount of run-time the boiler spends below the point of flue gas condensation will be affected. Keep in mind that these boilers are designed for the higher rT and provide greatest energy performance under those conditions. If the boiler is supplying heat to radia- tors, and the boiler's reset control is telling it to fire to a high limit of 142°F on a 20°F day, a rP circ programmed on an esti- mated system head loss may wind up sending 130°F water back to the boiler. That's right at the condensing point, mak- ing the boiler work at, say, 87% AFUE (annual fuel utilization efficiency) or higher, by design. But a circulator programmed to deliver a 20°F rT will send water back to the boiler at 122°F, creating more condensate, allow- ing a boiler to hum along at 89% AFUE. For the jobs I've been doing lately, we opted to see how far and effectively the ECM rT circulators would perform as stand-alone system circulators, co-joined with zone valves to govern flow to any number of hydronic zones. By Paul D. Mercier, Sr. Above: Paul Mercier, left, and son-in-law installer, Armond Gerritsen. Left: Mercier's customers get cold weather early in the year, colder temps than most, and are some of the last to see the signs of spring.