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Reliability and Consistency Make Danfoss VLT® Drives a Sure Bet in Las Vegas

07 February 2011
18-million-square-foot CityCenter features more than 700 VLT drives
Las Vegas may be the capital of variety and excess, with seemingly unlimited choices of entertainment and food. But for the mechanical systems that manage the indoor environment in this desert city, consistency and simplicity are more desirable traits. Owners of casino hotels and restaurants that operate around-the-clock require HVAC equipment that is reliable and easy to operate and maintain.

Those criteria became vitally important to the developer of CityCenter, an $8.5 billion resort destination on the Las Vegas Strip that was the largest and most elaborate commercial construction project in U.S. history.

MGM Resorts International opened the 18-million-square-foot development in December of 2009. It contains a smorgasbord of facilities, including 6,000 hotel rooms, 2,400 condominiums, 38 restaurants and bars, a convention center, a shopping mall, a Cirque du Soleil theater, and a 150,000-square-foot casino. In addition, an 8.5-megawatt, natural-gas-fired cogeneration plant provides a portion of CityCenter’s electricity, hot water and heat.

MGM Resorts project managers and consulting engineers WSP Flack and Kurtz knew that the project’s scope and the Las Vegas environment would place extraordinary demands on its HVAC system. They needed to make the system operation as simple and efficient as possible. As part of their solution, they chose during the planning stages in 2006 to integrate variable frequency drives on every HVAC system motor 5 HP and larger. MGM Resorts eventually selected the line of VLT® HVAC Drives from Danfoss because of the product’s performance history and consistent interface.

“MGM Resorts had nearly 20 years of experience using Danfoss products in other facilities,” said Todd Elwardt, senior sales engineer with Mechanical Products Nevada, which supplied HVAC equipment for CityCenter. “Their products had a solid track record.”

That familiarity was an important concern because of the scope of the CityCenter project, which took more than four years to complete. MGM Resorts’ vision for CityCenter included creating a sustainable urban core that was significantly different than the isolated, sprawling casinos typically found in Las Vegas. Several architects and more than 250 consultants worked to create that vision by managing development of multiple structures on 67 acres.

“There were several buildings under construction at one time, so there was pressure to stay on track and deliver a product the day it was needed,” Elwardt said. “And because of that aggressive construction schedule, we had to be confident that the products we were installing were going to perform.”

Mechanical contractors installed 744 VLT drives during the four-year construction process, ranging in size from 1 HP to 600 HP. The drives, which are designed to work at maximum output in ambient temperatures up to 122° C, were installed in nearly every area of the HVAC system, including:
  • Secondary-loop chilled water pumps (600 HP), which provide chilled water to much of the CityCenter complex.
  • Condenser water pumps (450 HP), which return water to the chiller, maintaining a constant temperature necessary for proper chiller operation.
  • Hot water pumps (300 HP), which circulate hot water for applications such as heat during the winter months and the hotel laundry throughout the year.
  • Air handler system of supply fans and return fans containing more than 100 VFDs.
  • Cooling tower fans (250 HP), which control the temperature of the sump for the return water to the chillers, boilers, condenser pumps, air handlers, cooling tower fans, etc.
Because of the variety of applications, consistency among the drives was a major consideration. The project team at MGM Resorts preferred variable frequency drives with a modular design and related interface, programming, and software. Team members were concerned that drives using different programming and interfaces would add unnecessary complexity.

“A big factor in the decision to choose Danfoss was the ‘family’ consistency of the VLT drives,” Elwardt said. “Whatever the size of the drive, it had the same look and feel. That’s important because it simplifies operation and maintenance of the system by MGM Resorts’ operations personnel. Having multiple systems would be impractical.”

MGM Resorts’ officials are compiling energy usage data from the initial year of operations at the CityCenter complex. This data shows that the property-wide implementation of Danfoss drives on all HVAC motors over 5 HP has improved the complex’s projected energy performance by 45 percent over ASHRAE Standard 90.1-1999 standards. Furthermore, according to energy savings data from typical VFD usage, the drives have the potential to save as much as 10,049 kW per hour, which exceeds amount of energy that a second central plant would produce if the complex required that much energy for operations.

Looking at these savings in real terms—in a complex that operates 16 hours a day for 365 days a year, this translates to energy savings just over 58 million kW per hour or 58,000 mW per hour. Significant energy savings like these also help to reduce annual CO2 emissions by 43,500 tons—which is the equivalent of taking a typical power plant off the grid for a full six days of operation.

In addition to the obvious utility cost benefit, the use of Danfoss drives also contributed to Leadership in Energy and Environmental Design (LEED®) points awarded by the U.S. Green Building Council. The Council awarded LEED Gold certification to ARIA Resort & Casino’s hotel tower, convention center and theater; Vdara Hotel & Spa; Mandarin Oriental, Las Vegas; Veer Towers and Crystals retail and entertainment district at CityCenter. This marks the highest LEED achievement of any hotel, retail district or residential development in Las Vegas.