With approximately 70 employees performing primarily administrative functions, the DNR needed dependable, cost-effective climate control for its single-story, 31,000-sq-ft-building with a basement. The ground floor is 13,400 sq ft and the basement is 9,500 sq ft. Heating-only units were used for the storage unit (4,900 sq ft) and the maintenance shop (3,200 sq ft).
The DNR selected local contractor Davis Electric to replace the heating and air units and wire them for gas instead of electric. Lennox Industries territory manager Lori Boyce, recommended the new Lennox L-Series and GSC 16 series. The LGA-300 and LGA 120 were used to replace the existing DSM-275 and CHA8-135 units. Two GCS16-060 units were used to replace CHA8-653 units because they were located in front of a window, and low-profile, shorter units were needed. The two multizone units were replaced with LGA-300 units and equipped with Thycurb Retro-Mate(tm) curb adapters and the California Economizer Control System.
"Our strategy of teamwork between our two vendors-Thycurb and California Economizer-gave us an edge which made this retrofit application more competitive than our competitors' conventional multizone replacements," Boyce said.
Curbing CostsOne of the requirements for the job was a minimal downtime for units. The DNR wanted minimal disruption of the work environment. And because the changeout was done in mid-July, the department didn't want the employees to be uncomfortable for any extended period of time. Thycurb stepped in and was able to mount the curbs from the unit over the existing curbs. This saved time, and prevented the DNR from having to renovate the roof.
Rather than use specially ordered multizone units that wouldn't be available for weeks, regular Lennox LGA configure-to-order units with factory-installed options were made into multizone units with the California Economizer multizone dampers that were installed in the curbs. Usually, the dampers are placed within the ductwork, but placing them in the curbs allowed for a shorter transition time. This also saved money by turning a single application into a multizone application with the multizone dampers and Retro-Mate(tm) application.
Bob Daugherty, sales manager for Thycurb, says using the multizone Retro-Mate(tm) replacement in an application rather than a complete multizone replacement saves about $2,000/ton on installation costs.
"We have been building this curb application for at least six years, and I have not heard of one complaint," Daugherty said. "Plus, it's a very cost effective way to replace the old multizone units without a lot of downtime and renovations."
In addition to the damper, California Economizer also supplied the thermostat, controllers, and multistage control. The capacity controller that California Economizer developed with Lennox's research and development division controls all four compressors on a Lennox rooftop unit. Previously, only two compressors in a unit could be controlled at once.
California Economizer regional supervisor Merv Allum also worked with Thycurb and Lennox to ensure the smooth transition and installation. The job was completed within the time frame allotted. The Thycurb adapters were labor saving and reduced the comfort downtime for DNR employees.
"The changeout and replacement market is big right now, and this is the ideal way of replacing the units because the old multizones aren't very efficient," said Allum.
Switch Nets ResultsThe installation was completed in July 2000. "The energy savings on this building should be phenomenal, considering the hot and cold deck total electric operation of DSM-275," said Boyce. "Even in the face of escalating utility costs, the Department of Natural Resources should see substantial savings on the hvac energy consumption," she added.
The DNR did in fact see remarkable differences in its gas bills this year. Converting the old multizone units from electric to gas cut the building's bills in half, according to Scott Knight, fiscal officer for the DNR.
"We are pleased with the system. It's working great, and we've got no complaints," said Bruce Evans, DNR maintenance director. "I know we've seen savings in the utility bills going from electric to gas, and we were pleased with Davis Electric's quick job completion during the unit replacements."ES