Posted on:
08/25/2004
New
Compressor Key To Renovation
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.
Smaller,
Lighter, And Oil-Free
The old compressors were replaced with a
single unit, a two-stage centrifugal compressor with an integrated
variable-frequency drive. |
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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