In addition to temperature extremes, increasing humidity places additional demands on the chillers. As the Las Vegas community grows, so does the humidity level in the area. Five years ago these levels averaged approximately 5 to 6 percent. Today, with the addition of golf courses, swimming pools and other byproducts of population growth, humidity levels run between 14 and 20 percent. "The increase in humidity levels has put a much bigger demand on our system," said Hughes. "That also increases energy costs."

HVAC SYSTEM TARGETED FOR SAVINGS

The first step involved monitoring the building temperature more closely. This included utilizing the building automation system as well as having the staff record temperatures throughout the property to identify those areas where temperature adjustments could be made.

Next, the engineering department added variable orifices to the chillers, saving energy by allowing the tower water entering the chillers to run as low as 55°. Expanding the size of the cooling towers also improved plant efficiency by increasing the capacity of each chiller from 1,000 to 1,050 tons at peak design conditions.

According to Hughes, the new cooling towers and the addition of variable orifices enabled the facility to run three chillers and three towers under conditions that previously demanded the operation of four chillers and five cooling towers. The larger towers also increased opportunities for free cooling, utilizing the plate-and-frame heat exchangers as waterside economizers during cooler months.

In a third step, taken this year, the resort became the first building in the world to install medium-voltage, variable-speed drives (VSDs) offered by a chiller manufacturer - York OptiSpeedâ„¢ drives.

Previously, low-voltage VSDs for chillers were available for facilities using medium voltage, but required an additional step-down voltage transformer. Existing 4,160V chillers also required the additional expense of a low-voltage motor.

The extension of OptiSpeed drive enables building owners to reduce energy cost as much as 30 percent on chillers up to 2,500 horsepower at voltage levels up to 4,160V.

DRIVE DESIGN IS THE KEY

"First of all," explained Fred Berry, senior product technical manager, "The drives allow for soft starts, eliminating the in-rush current and higher demand charges associated with constant-speed motors. Soft starts also reduce motor heating during startup, thereby extending the life of the motor."

The medium-voltage drive also incorporates a 24 pulse-converter design with an integral phase shifting transformer. This advanced technology provides a sinusoidal input current load to the power grid, eliminating any concern over harmonic-current distortion proliferation on the building's power grid.

The use of the drive's multi-level, pulse-width modulated (ML PWM) technology provides extremely low voltage- and current-harmonic distortion at the motor, eliminating concerns with "standing waves" and long-term stator-winding-insulation degradation. When medium-voltage OptiSpeed drives are matched with standard York chiller motors, as is the case at Monte Carlo, building owners have a single system-supplier solution.

"When an OptiSpeed drive is added to a chiller," Berry continued, "the noise typically associated with that chiller is significantly reduced.

"Noise reduction happens when lower entering-condenser-water temperature is available from the tower, which reduces the amount of lift/work required of the compressor. This allows the chiller to operate at a slower speed and noise levels can drop as much as 10 decibels. These drives also offer operators all the advantages of the OptiViewâ„¢ Control Center. The animated screen displays real-time data, as well as trends and troubleshooting information."

For Hughes, this means access to trending graphs and historical reports that simplify chiller operating decisions and guide troubleshooting. "The OptiView feature provides us with a wealth of valuable information, right down to the dollars we are saving at any given time by using OptiSpeed drives."

The drive's footprint also worked to the advantage of the resort. The three drives fit in the space occupied by three of the original electromechanical starters, under and behind an air-handling unit. The modular design made installation in such tight quarters easier because the cabinet could be broken down into sections and then bolted together in place.

The drives and the EMS will reduce the Monte Carlo's electricity usage by as much as 1.5 million kWh, officials said. "I think the numbers we'll see this year in terms of savings are going to be pretty incredible," said Hughes.

"Everything we did on this property boils down to tools, and if the tools are used correctly, they're going to save money. The only way these tools work is with the right people; people make everything happen, using their heads and the knowledge that they have to make tools like drives work to their advantage."

For more information, visit www.johnsoncontrols.com.

Publication date: 07/24/2006