Bringing The Controls Up To Date

Bruce Merges of Control Technologies, Inc. - a Manchester, NH, subcontracting firm involved with the HVAC installation -was influential in selecting the school's BAS. Merges said his company chose the Invensys LonWorks Control system because of its open protocols and ability to easily integrate with other systems.

Per project specifications, Control Technologies designed energy-recovery controls for the Trane rooftop units to monitor overall operating efficiency and determine system functions such as when the economizer should run, cooling vs. heat recovery, or exhaust of return air.

Though analysis revealed no IAQ concerns, Wayne Blais of Hutter Construction said the HVAC upgrade was necessary because many of the prior AHUs did not meet current code requirements for outside air. "Since the renovation began, we've installed 30 Trane rooftop units of various sizes with capacities ranging from 4,000 to 23,000 cfm," Blais said.

With a current student population of 1,100 and the ability to expand to 1,400 students, Blais said the school's new HVAC system includes three firetube boilers with an output of 8,034 MBtuh each for heating and two air cooled water chiller units for a system-wide cooling capacity of 500 tons.

Constant Communication

Significant coordination was necessary during the entire HVAC upgrade, from the rooftop installations to multiple ductwork throughout the school. To ensure timely completion and optimal HVAC performance throughout the school, Blais said constant communication was necessary among the construction crew as well as those installing the various sprinkler, plumbing, electrical, and duct systems.

Tobey Sheet Metal, a commercial/industrial sheet metal fabricator, worked on various aspects of the high school renovation with a primary focus on updating the facility's HVAC system. A significant part of their work involved installation of HVAC ducting inside the existing gymnasium measuring 150 ft by 100 ft. "We used more than 700 feet of double-wall spiral ducting with runs ranging in size from 26 inches to 44 inches outside diameter," said Tobey Sheet metal project manager Geoff Safford.

Due to the gymnasium's large size and 35-ft ceiling height, Safford said double-wall ducting was selected for adequate sound reduction and ventilation. However, this decision meant the gym's ducting would be more difficult to handle than other areas of the school because double-wall has much wider dimensions and is heavier than standard single-wall configurations.

"Though we didn't encounter any major glitches during installation, it proved challenging," Safford said. A four-man crew and two platform lifts with two men per lift allowed one crew to stabilize the ducting while the other secured a wire rope hanging system to hold ductwork in place.

Tobey Sheet Metal selected the Clutcher™ Mechanical System Hanger by Ductmate Industries for the installation. In addition a variety of other Ductmate items were also utilized for the job, from assorted access doors to flange systems for 16-gauge spiral and rectangular ducting rated for medium pressure loads.

"It took our four-man crew three weeks to install the Clutcher™," Safford said, "which cut roughly a week off this portion of the high school's overall renovations." He added that installation would have been further reduced but the crew had to maneuver around ceiling girders and a 10-ft truss system for the gymnasium's large curtain divider. ES