CityCenter, an $8.5 billion resort development on the Las Vegas Strip, may be billed as the largest and most elaborate commercial construction project in U.S. history, but the mechanical systems that manage the indoor environment were chosen based on consistency and simplicity.

Owners of casino, hotels, and restaurants that operate around-the-clock require HVAC equipment that is reliable and easy to operate and maintain, according to a case history of the development provided by Danfoss which provided the variable-frequency drives.


The technology might be based on simplicity but there were a lot of them - close to 750 VLT drives, for example.

The MGM Resorts International-owned complex is 18-million-square-foot with 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. 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 knew that the project’s scope and the Las Vegas environment would place 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 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.

Variable frequency drives are being used throughout the CityCenter complex in Las Vegas.


The project started in 2006 and took four years to complete. MGM Resorts’ vision for CityCenter included creating a sustainable urban core that was significantly different than the 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,” said Todd Elwardt, senior sales engineer with Mechanical Products Nevada, which supplied HVAC equipment for CityCenter. “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 construction process, ranging in size from 1 to 600 hp. The drives, which are designed to work at maximum output in ambient temperatures up to 122°F, were installed in nearly every area of the HVAC system, including:

•    Primary-loop chilled water pumps (600 hp), which provide chilled water for comfort cooling to the entire CityCenter complex;

•    Condenser water pumps (450 hp), which return water to the chiller, maintaining the proper temperature and flow necessary for optimum chiller operation;

•    Hot water pumps (300 hp), which circulate hydronic heating water for applications such as comfort heat during the winter months and domestic water heating throughout the year;

•    Air handler system of supply fans and return fans containing more than 250 VFDs; and

•    Cooling tower fans (250 hp), which control the temperature of the condenser water for the facility’s six 5,500-ton chillers.


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.”

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.

Looking at these savings in real terms, this translates to energy savings just over 58 million kW per hour or 58,000 mW per hour.


In the Leadership in Energy and Environmental Design (LEED) program of 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, according to the Danfoss release.

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Publication date:04/25/2011