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"We had to find units that were small and light... plug into the EMS... (with) flexible venting..."
Sheikh A. Rahman,, P.E.,
president of SAR Engineering |
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AERCO Benchmark Units Pass Tricky Installation Test at Worcester State College
 Due to the need for a special emissions permit that could have delayed the construction of the new Science and Technology building at Worcester State College in Massachusetts, SAR Engineering decided to look for a viable alternative to their initial plan of using three 3.3M BTU/hr. boilers to anchor the space heating plant. The process of obtaining this permit, which was needed because the BTU output of each boiler would have exceeded state regulations, had the potential to delay construction for up to six months. In order to meet the schedule with equipment that was of equal or better quality, SAR Engineering opted to install five 2.0M BTU/hr. Benchmark boilers from AERCO as an eleventh-hour substitute for the original plant.
Even though the Benchmark units fell within state guidelines for individual energy output, thus eliminating the need for the special emissions permit, they had to fit into a space that was pre-designed for another type of plant. "We were dealing with a 'penthouse' installation, which means that the boiler room was on the building's top floor," said Sheikh A. Rahman, P.E., president of SAR Engineering. "We had to find units that were small and light, so that they could fit in the allotted space. We had to find boilers that could easily plug in to the building's Energy Management System (EMS) and we needed flexible venting to compensate for the lack of available natural draft height in the penthouse location."
 The Benchmark boilers fit comfortably into the space available, due to each unit's small 12-sq. ft. footprint and their ability to install pairs in a zero-side-clearance configuration. Each unit's light weight of 1,785 pounds eliminated the need to reinforce the floor with steel or grouting. AERCO's Boiler Management System (BMS), which regulates all five boilers to ensure that they run as one complete system, also integrated perfectly into the complex's Energy Management System.
"The building's Energy Management System interfaces with the boiler plant through the AERCO BMS to maximize the system's efficiency," said Rahman. "AERCO Benchmarks are modulating units with a 20:1 turndown to minimize cycling. If our Energy Management System registers a drop in temperature outside the building, it sends a 4-20 mA signal to the AERCO BMS, calling for greater output. The AERCO BMS regulates the 10.0M BTU boiler plant accordingly, providing, as a system, exactly the amount of heat needed in real time without wasteful overshooting."
The final challenge - a short flue run - was not problem for AERCO. Each Benchmark boiler is individually vented, and their forced-draft design drives flue gases up the stack without the need for any natural draft.
"An added bonus of the Benchmark is its condensing capability," said Rahman. "If we were to set our water temperatures below 135°F during fall and spring, the boiler would become even more efficient and there is no threat of thermal shock."
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