Advanced compressor technology solves no-cool problem in SoCal offices
The building's comfort system was a double-duct A/C system with DX cooling and two duct furnaces. The system was centralized in a penthouse equipment room that housed the DX cooling coils in an air handler, which in turn was served by two 40-ton reciprocating compressors. These were connected to a rooftop evaporative condenser. The compressors were at the heart of the problem. They had outlived their useful life, and were prone to frequent breakdown. Further, even when they were operating, the energy costs seemed to be out of line with those in other similar buildings.
Sinclair turned to Jacob Coble from ACCO, a Los Angeles-based D-B mechanical contractor. Coble said, "Keith told us to do a complete evaluation, to tell him what needed to be done to solve the comfort system problem. We made several recommendations." The first was to upgrade the conditioned air delivery system, going from a constant volume system to a double-duct VAV system, and to add an outside air economizer. The second was to replace the existing evaporative condenser with a new unit, equipped with a VSD.
Considering CompressorsBut the most important recommendation was to get rid of the existing compressors and replace them with new equipment. Coble said, "New compressors were a given. We considered screw compressors, but were concerned about noise levels and vibration."
Sinclair wanted a solution that would have high efficiency, high reliability, and would allow him to offer improved comfort to his tenants. Coble noted that they specifically were looking for a compressor that would be simple to install as a retrofit. Dan Thatcher, Turbocor vice president of aftermarket businesses, recommended an 80-ton unit, which would replace the two existing 40-ton units weighing a total of 6,400 lbs. The Turbocor compressor only weighed 265 lbs and would fit easily on just one of the two existing equipment pads in the mechanical room. Additionally, the compressor uses R-134a as a refrigerant, and replaced the existing system that used R-22.
Coble indicated that the efficiency improvement of the new compressor over the existing reciprocating machine was critical to the sale. He demonstrated that the conversion would pay for itself in less than two years in energy savings alone. In addition, because the compressor is oil-free, the maintenance costs were projected to be cut in half. Sinclair approved the project.
Coble pointed out that the compressor replacement went smoothly. "We had to do a little work matching pipe sizes and matching the building controls to the compressor, but that's normal in any retrofit." In addition to the compressor replacement, they also did the airside improvement and wrapped up the project in September 2003. Sinclair said the conversion went off painlessly. "It was very well planned. The demolition, installation, piping, and startup were consistent with my schedule that had been prepared, so there were no surprises for me or my tenants," Sinclair said.
Sinclair noticed the results of the improvements right away. "First of all, the compressor is so quiet. It used to be that you had to shout at each other in the mechanical room. Now you can talk in a normal voice, and given the ongoing background noise of the equipment room, you can almost not hear the compressor run." He indicated that he is also very pleased with the performance of the new compressor. "When I'm in the equipment room, it's almost incredible to believe that something that small can cool the entire building." He has also noticed the combined impact of the improvements in his energy bills.
Major Energy SavingsIn the six months since startup, the monthly energy usage in the Sinclair Building has declined by an average of 29%. From January through June 2004 the average savings were 32%.
Sinclair has been so pleased with the performance of the building that he is now offering an additional half-day of air conditioning to tenants on Saturdays at no extra charge. He also said, "The tenants have definitely noticed a change in the comfort level in the building. And now, especially on hot days, the reliability of the system is no longer suspect." ES