Smart Solutions Category: Compressors

Advances in Oil-Free Compressors

In the air- and water-cooled chiller markets, oil-free compression technology is emerging as a more efficient, quieter, more easily applied, and easier-to-maintain alternative to legacy screw compressors. For original equipment manufacturers (OEMs) and end-users of mission-critical chillers in large HVAC applications, oil management adds costs and complexities to system designs—which typically result in declining energy efficiencies throughout their lifecycles.

Currently available oil-free compressors rely on costly magnetic levitation (maglev) bearings, which tend to decline in performance in warm climates and complicate system design. In recent years, environmental regulations and sustainability initiatives have driven design changes in air-cooled chillers. OEMs and industry stakeholders are pursuing the next generation of oil-free compression technologies that can achieve high operating efficiencies and simplify application complexities while supporting the imminent transition to lower global warming potential (GWP) refrigerants.

Emergence of Oil-Free Compression

Air- or water-cooled chillers provide essential cooling—and heat recovery in many cases—in data centers, health facilities, and other large buildings. Because of the high-tonnage cooling requirements of these applications, large screw compressors have traditionally been deployed. While reliable and robust, screw compressors pose oil management challenges:

  • Maintenance and upkeep costs and requirements
  • Declining energy efficiencies and performance over time
  • Increased risk of performance degradation and potential chiller failure

In recent years, air-cooled chillers have been adopted, primarily in response to concerns about water availability and sustainability. Although an air-cooled chiller with screw compression and a flooded evaporator can deliver efficiency gains, the need for oil return and management mechanisms significantly increases system design complexities. A similar system designed with an oil-free compressor can provide the same performance benefits without the added oil management complexities, conserving water and reducing environmental impacts while improving application reliability.

The annual energy consumption of an air-cooled chiller is an important factor in determining both lifecycle costs and sustainability footprint. Chiller and compressor selection starts by matching a building’s cooling load with chiller capacity. Then, the system’s lifecycle costs or return on investment is calculated, including estimated operational and maintenance costs.

Air-cooled chiller and oil-free compression solutions deliver the highest possible energy efficiencies without sacrificing reliability or introducing unnecessary operational complexities. Compressor modulation technologies can provide significant efficiency gains over the operating envelope and allow precise load matching in both full- and part-load conditions. Moreover, an air-cooled chiller solution can achieve these goals in some of the most demanding design conditions, such as the high-lift, warm-climate cooling load requirements found in many data center installations.

With the global phasedown of hydrofluorocarbon (HFC) and high-GWP refrigerants, the HVAC industry is moving toward new, lower-GWP refrigerant alternatives. The Environmental Protection Agency has set a maximum GWP of 700 for the chiller sector, which will drive the market toward emerging A2L alternatives—many of which have lower flammability designations under ASHRAE classifications.

Upgrading Existing Technology

Today’s oil-free compressors, designed with maglev technology, require multiple permanent electromagnetic bearings to levitate the compressor rotor (i.e., shaft). Radial and axial proximity sensors are needed to regulate the position of the rotor, and sophisticated, on-board, compressor controls are required to maintain reliable, frictionless operation. In the event of a power disruption, the compressor is no longer energized, and standard auxiliary (nonmagnetic) bearings are needed to maintain low-speed operation. This inherent design feature can increase compressor costs and application complexities.

Oil-free compressors with maglev bearings can experience performance-related limitations:

  • Insufficient envelope range for high-lift conditions (i.e., significant cooling in high ambient temperatures)
  • Reliability concerns and efficiency loss in part-load, turndown conditions
  • Prone to surging (i.e., flow reversal) and choking (i.e., maximum flow) in stop/start conditions
  • Short cycling, which can impact cooling performance

Current oil-free technology relies on the integration of a compressor, on-board controls, and a variable frequency drive. But this preconfigured architecture can present design customization challenges for OEMs who are unable to decouple the compressor from the controls and drive. In hot, humid climates, for example, this inflexible architecture could result in on-board electronics issues—potentially increasing maintenance, threatening operational reliability, and limiting chiller applicability.

Oil-free centrifugal technologies are raising the standards for chiller performance—delivering high-lift reliability, improved efficiency and sustainability, and a broader application range for the next generation of air- and water-cooled chillers. For example, Copeland’s oil-free centrifugal compressor leverages frictionless Aero-lift™ bearing technology to optimize energy efficiency, simplify design complexities, and maximize the performance of air- and water-cooled chillers in demanding conditions—and in full- or part-load cooling scenarios. Aero-lift bearings enable the Copeland oil-free centrifugal compressor to operate independently—without reliance on electromagnetics, proximity sensors, and complex controls. Compared to existing screw compressor technology, the Copeland oil-free centrifugal compressor delivers significant energy efficiency gains in full- and part-load conditions.

For more information, visit www.copeland.com.

ACCO Gets Creative, Uses Single BITZER Compressor to Replace Tandem Units

When a major animation studio needed to replace a compressor and upgrade its systems, ACCO Engineered Systems took an unusual approach, replacing a tandem scroll set with a BITZER single semi-hermetic reciprocating 15-ton Varispeed™ model compressor with an integrated VSD. The new unit was easy to install and satisfied the customer’s demands.

The studio, based in Northern California, lost a 10-ton scroll that was part of a 20-ton circuit on a condensing unit that serves a projector room and 50 percent of a theater. Jay Blundell, ACCO’s project manager on this job, said the customer is very technology-driven, extremely conscious of noise and vibration, and concerned about energy savings.

Blundell consulted Steve Esslinger, BITZER’s regional sales manager, and requested a compressor recommendation to meet his customer’s needs while also converting the system to R407C. Rather than replace the tandem scroll set with new scrolls, Esslinger recommended BITZER’s 4PCS-15.F4Y Varispeed compressor. It operates from 25 Hz to 87 Hz, generating nearly 22 tons of capacity at 87 Hz. As the load on the auditorium changes, the compressor speed changes to match the load requirement. This seamless capacity control minimizes suction pressure fluctuations and cycling rates, thus reducing energy costs.

ACCO has performed numerous retrofit upgrades, so the mounting, piping, and wiring changes were easy. The built-in, maintenance-free, suction-gas-cooled VSD is fully parameterized for easy commissioning, and the unit has been running quietly and efficiently for months. Blundell said the customer is pleased with the results, and he intends to use the Varispeed for other retrofit jobs.

For more information, visit www.bitzerus.com or contact techsupport@bitzerus.com.

ACCO Installs BITZER Compressors To Breathe New Life Into Medical Office Towers

By installing new BITZER compressors to replace aging, inefficient, and unreliable technology, ACCO Engineered Systems of Glendale, CA, helped Cedars Sinai Medical Towers in Los Angeles improve the health of its two 11-story buildings. The upgrade not only met the needs of the building’s inhabitants but also qualified for a substantial rebate.

The two 166,000-square-feet medical office buildings were in need of a mechanical upgrade. Each of the buildings had its own central plant made up of four 150-ton open-drive compressors that used 1950s reciprocating technology. In addition to being inefficient, the compressors and refrigeration components had been experiencing high failure rates.

ACCO conducted an engineering study to identify the system components that would deliver the best return on investment. They took into account the retrofit cost, energy efficiency, sound levels, ongoing maintenance costs, and reliability. Eight BITZER high-efficiency CSW9573-160Y-4DU screw compressors were specified for the job.

The preeminent challenge for ACCO came in replacing 1,200 tons of cooling apparatus (coils, pipe, and compressors) without disrupting building operations during construction. The equipment was replaced in stages over fourweekends. The job took five well-choreographed and specialized crews to accomplish the technically challenging changeover, ensuring that the new A/C system would be operational when the fully occupied towers opened for business each Monday.

BITZER is known for manufacturing reliable, relatively quiet semi-hermetic screw compressors that are well suited for direct expansion retrofits. This compressor upgrade, along with other system enhancements, justified a $250,000 rebate from the Los Angeles Department of Water and Power.

For more information, visit www.bitzerams.com.

Industrial Cooling Corporation Retrofits Reciprocating Compressor with BITZER Scroll

Project Saves Thousands, Lowers Power Consumption, and Reduces Noise

Industrial Cooling Corporation (ICC) of Metuchen, NJ, recently retrofitted a 10-ton reciprocating compressor with a BITZER scroll compressor (ESH736-4SU) to keep overall client costs down, reduce power consumption, and minimize noise. Replacing large, inefficient recips with high-efficiency screw compressors on chillers and rooftop units is standard practice in many areas, but it is unusual to convert smaller recips to scrolls.

Because scroll compressors are taller than recips, Daniel Greenhalgh, the job foreman, had to modify the sheet metal panel above the compressor compartment to gain 5”. Once the recip was removed and the scroll mounted in the cabinet, Greenhalgh mounted an APR valve on the left side of the new compressor. He then installed a solenoid valve on the APR outlet and electrically paralleled it with the liquid-line solenoid to allow the compressor to pump down. A discharge check valve was also installed for pumpdown and to make sure no liquid refrigerant backed up into the compressor dome.

Mike Chiovaro, ICC account executive, explained that the APR valve is a capacity modulation and dehumidification device for direct expansion A/C systems. By regulating refrigerant flow, it allows direct expansion systems designed for full load to maintain acceptable air quality during varying load conditions. He added that the active portion of the coil stays below dew point at all times, thereby keeping the system in the dehumidification mode and ensuring longer run-times.

Isolation refrigerant ball valves were installed on all three lines of the APR to allow for complete isolation. “This enabled us to be sure the system was charged and operating to the original specifications,” said Chiovaro. “After pulling down the system and charging with R22, we then opened the APR isolation valves and checked operation. We created a low load on the unit to make sure the APR reacted correctly.”

After completing the startup procedures, the BITZER scroll was running at full load (no APR operation) with 75° F intake air and 50° F discharge air and only using 13 amps. The scroll used 2 amps less than the second-stage recip compressor beneath the scroll that was running unloaded with the same temperatures and voltage.

When the customer walked into the room to inspect the installation, he commented on how quiet the new scroll compressor was compared with the old recip model. He did not hear it running at all, because the recip compressor below it was also running.

Chiovaro said the installation required more time to retrofit, but the overall cost was thousands less than installing a “drop-in,” and the customer benefited by seeing lower power consumption and lower sound levels in his data center.

Steps in the Retrofit

  1. Reclaim the R22 refrigerant (to be reused at completion).
  2. Remove and dispose of failed compressor.
  3. Modify sheet metal panel, located above stage-one compartment.
  4. Install mounting plate and set new BITZER scroll compressor (model ESH736-4SU).
  5. Modify refrigerant piping to meet compressor discharge and suction connections.
  6. Provide and install one new liquid line filter drier.
  7. Provide and install one new discharge check valve.
  8. . Provide and install one new APR valve.
  9. Provide and install all needed piping, fittings, refrigerant solenoid, and ball valves to install the APR.
  10. Install a new contractor.
  11. Terminate and reconnect power.
  12. Evacuate and charge circuit with reclaimed refrigerant.
  13. Start up system and record pressures, amperage, voltage, superheat (adjust if needed), and sub-cooling.

For more information, visit www.bitzer.de/eng/Home.

Pyke Mechanical Chooses High-Efficiency BITZER Screw for Compressor Retrofit

When the Miami International University of Arts and Design needed to upgrade its chiller, Pyke Mechanical was able to install a new, high-efficiency BITZER Screw compressor at only marginally higher cost than rebuilding the original compressor. The conversion went so well that Pyke plans to install BITZER screws whenever an upgrade opportunity presents itself.

BITZER’s Senior Application Engineer Dave Streby used the system conditions to determine the best BITZER model to match the desired capacity and recommended BITZER’s CSH8553-110-4PU. It operates at 45° saturated suction temperature, and 120° condensing temperature provides 109.9 tons of air conditioning capacity. The model comes standard with a 4-1/8” suction service valve and a 3-1/8” discharge service valve and has an integrated oil separator. The compressor uses 460 volts, 136 run load amps, and 895 locked rotor amps with direct-on-line starting.

Pyke Mechanical’s technicians completed the retrofit conversion as follows:

Step 1:  Removed the existing screw compressor and external oil separator, including all components and piping. Removed all piping associated with the heat exchanger on this circuit, as the BITZER CSH screw compressor provided the required capacity without the use of an economizer.

Step 2:  Installed two 7’-long U channels for mounting the BITZER CSH screw. The channel was attached to the base frame by drilling 3/4” holes. The BITZER CSH was attached to the mounted channel with 5/8” bolts after holes were drilled to match the footprint.

Step 3: Repiped the existing suction and discharge connections from each end of the existing compressor to the top of the CSH8553-110-4PU screw compressor. The existing piping was only removed to allow one 90° elbow in the suction piping and two 90° elbows in the discharge piping.

Step 4: Removed the existing economizer piping to the original screw compressor, capped it off, and left it in place.

Step 5: Reused the existing suction and discharge pressure transducers. The suction transducer was reinstalled into the BITZER service valve. The discharge transducer was installed into the upper pipe plug underneath the BITZER discharge service valve. The upper connection allows for the system pressure to be read by the controller.

Step 6: Installed liquid injection oil cooling using the existing piping from the economizer. Pyke also used the existing solenoid valve and only required two feet of 5/8” copper tubing and 4-5/8” 90° elbows to allow 8” of tubing rise from the inlet to the compressor.

Step 7: Installed the liquid injection controller inside the control cabinet and drilled a 3/8” hole through the panel to route the sensor cable to the compressor. Mounted the liquid injection sensor 6” from the discharge service valve and insulated the sensor. With the existing operating parameters, liquid injection oil cooling is not required, but Pyke decided to install liquid injection to address a “worst case scenario.”

Step 8: Because the existing compressor used only one capacity control solenoid, Pyke installed a stand-alone controller to control the BITZER capacity control solenoids. A simple dual-set-point capacity controller is suitable. Pyke installed the BITZER capacity controller into the control cabinet and then installed the temperature probe into the same location as the existing system probe on the fluid outlet piping.

Step 9: Evacuated and charged the system, checked all the electricals, and then bump-started the compressor to ensure proper rotation.

Since this initial retrofit conversion, Pyke has installed two more BITZER retrofit screws at Miami International University of Arts and Design. John Marinello, vice president of Pyke, said that he and his technicians were impressed with how quietly a BITZER Screw runs.

For more information, visit www.bitzer.de/eng/Home.

“Plug-and-Play” BITZER Screw Compressors Slash ACCO’s Installation Time

Engineering Support Paves the Way for Retrofit Solution

Confronted with correcting the performance problems of an R22 direct expansion system with two magnetic levitation, oil-less centrifugal compressors at a building in Newport Beach, CA, ACCO Engineered Systems staff ran energy comparisons between oil-less, centrifugal compressor models and screw compressors. To their surprise, BITZER CSW Screw Compressors provided full load and part load efficiencies comparable to the oil-less, centrifugal compressors.

The BITZER screw compressors were easy to install, saving ACCO time and money. Moreover, John Delmatoff, ACCO’s lead chiller technician, said, “being able to solve a customer’s A/C problem with a much less expensive, positive displacement screw compressor without sacrificing power consumption is a win-win.”

According to William Brown, P.E., CEM, chief systems engineer at ACCO, the compressor system at the Olen Properties Building suffered reliability issues that affected the building’s tenants. ACCO’s challenge was to find alternate R22 compressors that would provide reliable air conditioning to the building and still minimize compressor power consumption.

Dave Streby, lead screw application engineer at BITZER’s Atlanta area manufacturing plant, had consulted on replacing other oil-less, centrifugal compressors, so he assisted ACCO with planning the conversion. Screw compressors are heavier than oil-less, centrifugal models, so ACCO had to plan for a crane to lift them to the rooftop penthouse. Streby recommended that ACCO go with the infinite capacity option rather than four-step capacity. Though BITZER offered a controller for the Screws, ACCO elected to develop its own compressor control logic program using the existing system.

Delmatoff had installed many oilless, centrifugal compressors, but this was his first experience with BITZER. “BITZER’s engineering support and documentation was fantastic, and I can’t believe how quietly the BITZER Screw operates,” he said. “It’s nearly as quiet as the oil-less, centrifugal compressor.”

The installation and commissioning were basically “plug and play,” said Delmatoff. He did not have to spend days load balancing or tweaking the complex electronics, and the compressors pulled the building temperature down quickly. BITZER’s regional sales manager, Steve Esslinger, even stopped by to support the start-up. “You can’t beat the engineering support that BITZER offers,” Delmatoff added.

Based on the results of this job, ACCO is preparing to commission two BITZER Screw Compressors for the United Talent Agency Plaza in Beverly Hills, which qualified for a substantial Southern California Edison Customized Solutions energy rebate.

ACCO Engineered Systems staff ran energy comparisons between oil-less, centrifugal compressor models and screw compressors; they found that BITZER CSW Screw Compressors provided full load and part load efficiencies comparable to the oil-less, centrifugal compressors.

For more information, visit www.bitzerus.com or contact techsupport@bitzerus.com.