Compact Condensing Boilers Simplify Installation, Reduce Fuel Consumption

Posted on January 10, 2017

In Santa Fe, New Mexico, Rosewood Inn of the Anasazi welcomes guests with luxurious accommodations that echo the spirit of the desert. Ochre-colored walls, exposed wooden beams, and intricately crafted Native American pottery and textiles evoke the warmth of the local peoples and their beloved landscape. But with an elevation of 7,000 feet above sea level, Santa Fe winters can challenge residents and guests alike with bitter cold temperatures. At Rosewood Inn of the Anasazi, a commitment to comfort makes heating an important investment.

In 2014, the Inn’s original boiler, a 3-pass, flexible tube Bryan CL300-A-FDG, was reaching the end of its lifespan. Installed in 1991, the boiler’s ignition had become unreliable, frequently locking out or not firing properly. Designed for 80% efficiency, it tested at only 76%. Worse, flue gas measurements revealed excess carbon monoxide production at over 8,000 parts per million. Getting appropriate service for the boiler was becoming increasingly difficult.

Making everything fit on the elevator

In its original replacement plans, the Inn intended to swap one conventional boiler for another. But dropping in another flex-tube boiler not only meant hiring a crane, but opening a hatch to the boiler room that had been sealed to prevent rain water leaks; the installation would have been a tricky and expensive undertaking.

Fortunately, the project contractor, Architectural Metals of Santa Fe, came up with a more attractive alternative. Stephen Sanders, the firm’s HVAC department manager, describes the revised thinking: “Why not just chop the old boiler into pieces, then replace it with smaller boilers?”

Sanders led a design team that sized the heat load and recommended the installation of three Viessmann Vitodens 200-W, B2HA-150 condensing boilers, each rated at 523,000 BTUs each for a total of 1,590,000 BTUs for the project. Using Viessmann’s pre-piped racks—the first ever installed in New Mexico—saved even more time. The three units were installed in a lead-lag configuration, governed by a Viessmann controller running an outdoor air temperature reset. All the components—boilers, rack, the low-loss header, the pumps, and more—fit in the Inn’s elevators, requiring no special expenses or inconveniences.

Better still, the condensing boilers, rated up to 98% efficiency, are consistent with Rosewood’s commitment to environmental responsibility. With the installation completed in September 2014, the hotel is already benefitting from the system’s quality. “On a 10° F day,” Sanders notes, “only two of the three boilers are running, pushing water at just 120°--and everyone’s completely comfortable.”

The hotel received an $8,500 rebate from New Mexico Gas Company upon completion of the project, and estimates that Rosewood will save $8,500 - $10,000/year in fuel costs. The Vitodens boilers, constructed with durable materials such as the titanium reinforced heat exchanger, are designed for service lives well in excess of twenty-five years. Yet with savings achieved by the Viessmann boilers, Sanders notes, “the hotel will see a payback on these boilers, absorbing the difference in cost between them and a conventional 80% boiler, in just five years.”

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