John Smart, a technical and training manager for boiler manufacturer Weil-McLain, has a passion for hydronics. His 23 years serving the company—first in new product development working among engineers, and now in sales force and customer support in the field—have positioned him to also teach boiler maintenance at Weil-McLain’s School of Better Heating. Smart appreciates the different properties found with all types of conventional equipment, whether copper, cast iron or steel. According to Smart, following the manufacturer’s recommendation for proper flow is critical to maintaining the overall performance of the heat exchanger. However, copper boilers may be sensitive to improper flow rate. Too much flow will result in erosion corrosion, too little flow will cause localized boiling in the heat exchanger. In regards to heat transfer, cast iron boilers are superior to steel boilers. While copper is the most effective heat transfer material known today, cast iron boilers are more durable and resilient to handling the extremes that come with marginal flow fluctuations. “Our industry is in a transitional phase,” says Smart. He agrees that a paradigm shift happened somewhere around 15 years ago when technicians were becoming aware that older steam systems are not so efficient. Many began being converted into hot water. “The cooler we run our systems, the more efficient they become,” says Smart. Some of this comes from adding more surface area to the heat exchanger, thereby increasing heat transfer. “It is possible to get 10 to 12% better efficiency over traditional boilers,” he says. Smart explains that “a condensing boiler, on the combustion side, will use either oil, natural gas, propane or a mixture of gases and will combine the fuel with an oxidizer to produce a chemical, exothermic reaction.” Condensing heat exchangers are made of aluminum or stainless steel to withstand the harsh acidity created in the combustion process. As a point of reference, it takes 1,000 BTUs to change one pound of water into steam. These BTUs are latent energy and are therefore unusable in heating the building. Because the flue gases contain superheated steam and acids, if the gas can be condensed back into a liquid by cooling it, the byproduct is not only water, but also additional matter, thus reclaiming the BTUs that were initially used in the process. “Day to day, the cost and energy savings may appear small, he says. “Per heating season, per year, and over the long-term vision of the appliance lifetime, the savings that accumulate are vastly substantial.” Because of the acidity produced during the condensing process, “physically cleaning the surface of the heat exchanger once a year on a routine scheduled basis is vital,” according to Smart. “This allows for the efficient energy transfer.” The flame rod and igniter are also exposed to the warm, moist, acidic environment, and keeping the boiler running efficiently means catching problems and replacing parts before they wear out entirely.
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