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Part 2: BAS: Direct-Digital Controls, HVAC Equipment Improve Energy Efficiency
By Dan Hounsell, Editor
March 2010 -
Once engineers completed the energy review, engineers had to determine whether the engineering center was the best candidate for an upgrade, Barsun says. They reviewed a series of criteria, including total opportunities for savings, the building's age and overall condition, work already done on the building, and whether the building is scheduled for future renovation.
Then the department made its decision: Minimize energy use in the Farris Engineering Center by upgrading its direct-digital control (DDC) system and incorporating new, energy-efficient HVAC system components.
Among the project's components: replacing 75 horsepower (hp) supply-fan motors with 60-hp premium-efficiency motors; replacing return-fan motors with new 15-hp premium-efficiency motors; installing 15-hp variable-frequency drives (VFD) on motors; and replacing a 7.5-ton rooftop unit with a 10-ton unit featuring microprocessor controls with a thermostat, a factory-installed disconnect, and an economizer.
Funding for the $100,000 project came from state funds allocated for facility renewal and renovation projects.
"Our director has been willing to give us a ready stream of funding for these kinds of projects," Barsun says.
Contractors did most of the work, but staff technicians handled some tasks.
"Our in-house techs installed the space sensors and updated the existing DDC system, including expansion cards and programming to incorporate the setbacks and control the VFDs," Barsun says.
Initially, engineers contemplated a larger upgrade for the BAS, but the building's concrete and plaster construction forced engineers to scale back their plans.
"We looked at the retrofit down to the box level, but the hard ceilings prevented us from going in that direction," Barsun says. "If we had, it would have been bigger, more expensive and more involved."
The BAS upgrade presented challenges for specifiers and installers, Chavez says. An unexpected challenge involved finding key replacement parts, such as bearings. Because the system and some of its components were more than 40 years old, some vendors had gone out of business. As a result, specifiers had to take more time than anticipated to find replacements.
Once the BAS upgrade was complete, the department used in-house staff from its controls group to perform commissioning and ensure the new components and technology performed as intended.
"Maintenance got a lot of good information on the new systems during the commissioning process," Chavez says.
Project Profile: Building Automation Retrofit
Part 1: Building-Automation System: Retrofit Starts with Metering
Part 3: BAS Upgrade Lowers University's Energy Bills 20 Percent