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Fuel Oil News - November 2016

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38 NOVEMBER 2016 | FUEL OIL NEWS | www.fueloilnews.com energy creation with varying system demands. All of our initial efforts have been with oil-fired hydronic sys- tems—the focus of my work (and this article). However, much of this effort—what we've learned—is very applicable to other-fueled hydronic systems. The ability to vary output (energy creation rate) of heating equipment plays an important role. This has been achieved in gas-fired boilers by "modulating" combustion with sophisticated valving and controls. Typically they adjust from 20% to 100% of capacity—from "idle" to "full speed," using an automotive analogy. But there's a challenge: direct modulation of oil-fired systems isn't feasible under normal circumstances. A fixed (capacity) fir- ing rate via pressurized, nozzle-induced fuel atomization is the norm. The only option is to adjust the operating temperature and cycling of an oil-fired hydronic boiler with controls to follow heating demand. This is reasonably well managed with mod- ern "cold-start" boiler aquastats, external temperature sensors, etc. Referring back to our five factors of total system efficiency, circulation is number three on the list, but in reality is the founda- tion of any hydronic system improvement. Taco reports accurately that Delta-T cir- culator-only systems improve fuel use by up to 15%; they also reduce electrical con- sumption by up to 85% when compared to non-ECM, single-speed circs. Unfortunately, we do not have the benefit of data recording equipment, so our observations are admittedly empirical; in other words—based on and verifiable by observation, experience and the reviewing of a lot of customer utility bills. I'll point out that we have had the additional benefit of devel- oping and operating our personal integrated dual-fuel (oil-wood) hydronic system for the past 40 years that features a wholly convec- tive inter-system loop (no circulator) and manually controllable convective zones. No electricity, no problem! This personal hydronic convection experience is designed into our near-boiler piping configuration, complimenting and optimiz- ing Delta-T delivery. Disable the system circulator and actuated zones will continue to convect, albeit at a significantly reduced level. This is very dependent upon zone piping layout however, and the effect will vary widely. Energy storage capacity or "thermal mass" in both iron and water compliments hydronic operation, smoothing cycling and enhancing convection. Our boiler-of-choice has been the Weil- McLain Ultra Oil with the Beckett NX Burner for the past ten years. (Only one "no heat" service call—a failed aquastat.) It also happens to be the "heavyweight champion" at over 600 pounds for a three-section, 100 MBH, 87% triple-pass boiler. A service life of 30 years or more is not an unreasonable expectation, based on our experience with these and other oil-fired boilers. Our system packaging typically also reduces floor space, sim- plifies piping, valving, and wiring and controls as well. We also accentuate serviceability: every service and control component is within an arm's reach. Our general system observations are: 1. Dramatically reduced burner cycling, extending boiler and component service. "This thing seldom runs" is the first customer observation, "and is so quiet." 2. Multiple individual zones cycling between burner cycles, drawing from thermal mass storage (iron and water). 3. Reduced average boiler operating temperatures. 4. A pressure-fired burner seems to stabilize operation particu- larly under "cold-chimney" conditions, a frequent event in our "frosty north" external chimneys. 5. The "close-coupled" HTP SuperStor Ultra (typically provided with our systems) acts as an integrated boiler protection device, being the shortest path in fail-mode convection. System radiation, outside the scope of our rT system development, is still important in that it completes the hydronic heating system "package." Anything beyond basic series and split loops must be considered as affecting total system distribution energy. The more sophisticated the radiation scheme, the greater the installed cost and the pro- jected system life-cycle operating cost. The control algorithm has surprisingly become a non-issue in our system result. The high-mass oil boiler that we install uses a Hydrolevel 3250-Plus aquastat and paired with the Taco VT2218 Delta-T logic provides seamless operation. Despite not being physically interconnected, they work well under the thermal damping provided by the boiler's high mass. If any tweaking is necessary it can be done by adjusting the circulator's rT and/or boiler aquastat settings. In our experience, residential Delta-T hydronic distribution steps beyond evolutionary advantage, becoming revolutionary in its impact. It will benefit any forced hot water system in degree, and thus is not a question of if it will become generally appreciated and applied, but when. Adding thermal mass into the equation further enhances system performance. The "AFUE Wars" between boiler manufacturers and installers dissolves when Delta-T distribution is applied to improve fuel and electrical efficiencies. Combining the two is a sure path to improv- ing any hydronic system's total efficiency. l F O N Paul D. Mercier, Sr. d-b-a Mercier Engineering, of Antrim, N.H., is a manufacturing process and hydronic system design engineer who also manages his family's residential and light commercial HVAC systems installation and service firm, BoilersOnDemand. com. He studied mechanical engineering at L'Université d' Ottawa, Ontario, Canada, the University of New Hampshire, and elsewhere. Delta-T circulator- only systems improve fuel use by up to 15%; they also reduce electrical consumption by up to 85% when compared to non-ECM, single- speed circs. BEYOND AFUE: HYDRONIC HEATING SYSTEM EFFICIENCY

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