New Compressor Key To Renovation

August 25, 2004
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Keith Sinclair had a problem. He owned an attractive and ideally located office building in South Pasadena, Calif. The five-story building has 28,000 square feet of rentable office space, and Sinclair's goal was to keep it rented. But in recent years, an aging comfort system was causing occasional building cooling failures, and the rising costs of system maintenance were cutting into the profitability of the building.

Recommended Replacements

This building is more than 30 years old, and the comfort system for the facility was a double-duct air conditioning system with direct expansion (DX) cooling and two duct furnaces.

The system was centralized in a penthouse equipment room, which housed the DX cooling coils in the 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 breaking down frequently. Even when they were operating, the energy costs seemed to be out of line with those in other similar buildings.

Sinclair went to the local office of ACCO, a large design-build mechanical contractor headquartered in Los Angeles. He had dealt with the company in the past. He asked Jacob Coble from ACCO to evaluate the situation and make recommendations.

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 variable air volume system, and to add an outside air economizer. The second was to replace the existing evaporative condenser with a new unit, equipped with a variable-speed fan drive.

Compressor Options

But 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. That's when we started looking at the Turbocor compressor. We'd been learning about this technology, and it seemed extremely promising."

"Keith Sinclair had established priorities for us," said Coble. "He wanted a solution that would have high efficiency, high reliability, and would allow him to offer improved comfort to his tenants. With this in mind, the Turbocor seemed like a perfect fit."

He noted that they specifically were looking for a compressor that would be simple to install as a retrofit. In this area, the Turbocor got high marks for its small size and simple connections.

The old compressors were replaced with a single unit, a two-stage centrifugal compressor with an integrated variable-frequency drive.

Smaller, Lighter, And Oil-Free

ACCO asked for recommendations from Dan Thatcher, vice president of aftermarket businesses representing Turbocor in Westlake Village, Calif. He was able to answer questions about product performance and sizing, and to discuss suitability for retrofit applications.

For the Sinclair building, Thatcher recommended evaluating an 80-ton Turbocor unit, replacing the two existing 40-ton units, weighing a total of 6,400 pounds.

The Turbocor compressor only weighed 265 pounds. The unit is a two-stage centrifugal compressor with an integrated variable-frequency drive and can achieve an integrated part load value under Air-Conditioning and Refrigeration Institute conditions of less than 0.4 kW per ton. It would fit easily on just one of the two existing equipment pads in the mechanical room. Another benefit of the Turbocor compressor is that it uses R-134a as a refrigerant, whereas the former system used R-22.

Coble indicated that the efficiency improvement of the Turbocor compressor over the existing reciprocating machine would pay for itself in less than two years in energy savings alone.

In addition, because the Turbocor compressor is oil-free, the maintenance costs were projected to be cut in half. "That made it very attractive to Keith Sinclair," he noted.

In view of this evaluation, Sinclair approved going ahead with the project. Sinclair said, "I'm not a technical person, and I relied heavily on the representations of ACCO Engineered Systems. At the time of my decision, I was impressed with the technology; it made economic and operating sense."

You Don't Have To Shout

Coble pointed out that the compressor replacement went very easily. "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, ACCO also handled the air-side improvement and wrapped up the project in September 2003. Sinclair said the conversion went very painlessly.

"It was very well planned and ACCO has the staff and talent level to execute this type of a major undertaking. 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 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 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 also has noticed the combined impact of the improvements in his energy bills.

In the six months since startup, the monthly energy usage in the Sinclair Building has declined by an average of 29 percent. 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 said, "The tenants have definitely noticed a change in the comfort level of the building. And now, especially on hot days, the reliability of the system is no longer suspect."

The required maintenance work on the new compressor is minimal, consisting mostly of an annual dusting of the electronic cards, and replacing a set of capacitors every five years. The low maintenance is a result of the machine being oil-free, and having only one moving part.

Throughout the country, there are thousands of buildings that face the same problems found in the Sinclair Building. The Turbocor compressor is only a part of the solution for buildings like this, but it can be an important part.

Publication date: 08/30/2004

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