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Retro-Engineering Case Study #1: Atlanta, GA

Case Study #1: Atlanta, Georgia

A large data center facility was 70% unoccupied with a chiller plant that contained two sets of series connected chiller pairs. This configuration was considered efficient in the mid-90s because the chilled water was operating at an 18 degree temperature differential (TD) to reduce the quantity of chilled water circulation by approximately 23%, keeping each individual chiller operating at a 9 degree TD.

The data center expansion was continuing, and plans were being made to install two additional chillers also in the series configuration when the design engineer was called to provide design services for the expansion.

After reviewing of the existing configuration and a discussion with the technicians that were managing the plant, it became apparent that the systems were not being used as efficiently as possible. Also, as the load was growing, it became difficult to operate the chiller plant when the load required an odd number of chillers. Additionally, this configuration made it difficult for the single chiller to produce an 18 degree TD and the result was a reduction in efficiency.

The design engineer recognized these issues and proposed the addition of plate and frame heat exchangers. The system connections reduced the chiller loading during intermediate ambient temperatures by precooling the returning chilled water. As a result, the system produces the chilled water supply temperatures selected for the data center without any chillers, when the outside air wet-bulb temperature drops below 50 degrees. This addition also allowed a single chiller to operate in series with two heat exchangers when conditions allowed.

After more than a year of operation, the configuration resulted in the expected energy savings, which paid for the cost of the heat exchangers within the first year, while also increasing the lifespan of the chillers (since they were off 30% of the year.)

Subsequently, the owner applied this upgrade to provide these new features to the remaining systems. The plant increased in size to a total of eight chillers, all equipped with the heat exchanger configuration that was implemented in the initial project.

Are you looking to gain efficiency and better performance from your existing systems?

Our experienced engineers can help you determine if retro-engineering makes sense for your building. Give us a call at (816) 358-1790 to discuss your project.

Written by:
Steve Peterson, PE
Sr. Mechanical Engineer