In September 2012, Ridgeview High School in Redmond, Ore., opened. Constructed at a cost of $73 million, the 280,000-sq-ft school incorporates four liquid-propane-fired Buderus SB615 condensing boilers tied into a variable-refrigerant-volume system controlled with a Honeywell WEBs control system. Multizone air handlers with refrigerant-fed coils in the ductwork supply heating or cooling throughout the school, which earned LEED Gold certification partly because of the optimization of mechanical-system energy performance. Energy savings using the Buderus SB615 boilers are projected to be 20 to 25 percent of a standard code-compliant system.
In 2013, Redmond School District’s other high school, Redmond High School, which opened in 1970, was in need of renovations. In the mechanical room, two original 60,000-lb water-tube boilers and a heat exchanger were in need of replacement. The district chose three Buderus SB745 natural-gas-fired condensing boilers, which were installed on a newly laid pad and tied into an existing header while allowing sufficient space for electrical equipment and flues.
“I used Buderus boilers as the basis of design because, in part, I had good experiences with them in previous projects,” Scott Miller, PE, of Portland, Ore.-based MFIA Inc. Consulting Engineers said. “We knew from previous experiences that they are very efficient. In this case, the added incentive was the ability to use heating units that looked and performed like those in other schools. There was initial hesitation on the owner’s part due to other school-district ‘horror stories’ with condensing boilers. But when I showed them how the Buderus boilers looked and operated, there was a willingness to try them. At Ridgeview, we needed the efficiency for LEED purposes. By the time we got to Redmond High School, the owner asked that we design around the Buderus product.”
Buderus SB Series at a Glance
High-mass SB Series boilers can use a range of fuels—natural gas, liquid petroleum gas, and oil—providing flexibility for both retrofit and new-construction projects, large ones in particular. Equipped with a two-staged or modulating forced-draft burner, they minimize pollutant emissions. They are equipped with two return-water connections, which allow for separate return flows, as well as efficiencies of up to 98 percent, with inputs of 563 to 5,443 MBH.
When return-flow temperature is reduced to below the dew point, additional heat is reclaimed from flue products. In the SB Series, low flue-gas temperature is ensured by low return-water flow temperature, highly efficient titanium-infused stainless-steel heat-exchanger surfaces, heating units, and continuous operation.
Boiler insulation comes pre-installed in SB Series boilers. Convenient top connections allow easy access for piping, reducing installation effort. Project costs for SB Series boilers are reduced because of simplified piping, and their high-water-content heat exchangers require no minimum flow rate, eliminating the need for a costly dedicated boiler circulator.