Off-site build
Owner Jay Bull and other fabricators at JB Sheet Metal built the frame, cabinet and duct takeoffs, while Capital City technicians filled the boxes. With the return fan and filters on one side and ductwork on the other, coils, power components, controls and refrigerant lines made for a tight fit in the middle.
Despite the adequate static pressure capability of the units, Avalon wanted an insurance measure which would eliminate the risk of inadequate flow. A small box was installed just above each duct elbow leading down through the roof. Here, a knockout could facilitate the addition of a booster fan in the future.
“Now, after completion of the project, we realize it was an unnecessary precaution, but it was cheap insurance,” said Pedersen. “With the systems up and running, there’s even better flow than before the retrofit.”
The units were tested and commissioned off-site with a generator before being delivered and craned onto the Rithet Building; the first one was placed in April and the second a month later.
Before delivery, building control and power rough-ins were completed as well. Once on the roof, it took about a day-and-a-half for Capital City Refrigeration to put the units into service.
Resounding success
The new air handlers tied into the existing direct digital control (DDC) control system with the building automation and control (BAC) network hardware and software, allowing off-site control and monitoring. A 3D traffic interface was also installed.
In the spirit of maintaining the historical integrity inside and outside, the building’s old cast iron radiation system remains in place, staged as a secondary heat source through the DDC system. The radiators, which line only the perimeter, run at a low temperature when outdoor conditions drop to freezing temperatures.
The building’s old boilers served both the radiators and the multi-zone hot water coils before the retrofit and were grossly oversized once the VRF system assumed the role of supplying primary heat. At the time of the project, the old boilers were replaced by a condensing boiler.
“All told, this was not a cheap retrofit alternative,” added Sykes. “But given that the building couldn’t be disturbed, and that the exterior had to meet historical guidelines, I think it was the very best alternative, especially considering lifecycle costs.”
According to Sykes, they have since had three inquiries from other companies about similar retrofits. Both Capital City and Avalon say the process will go more quickly next time though.
From everyone’s perspective, the project was a resounding success. The property owner did not have any building downtime, the systems are operating as designed, and energy consumption is expected to be comparable to a geothermal heat pump system.
Author
Derrick Paul is the director of variable refrigerant flow (VRF) sales at Fujitsu General America. He is a graduate of The University of Alabama, where he earned a mechanical engineering degree. Paul began his career at Fujitsu as a sales engineer in the southeast.
