The HVAC Factor: Variable Refrigerant Flow
By Fred Rogers
Originally published in the October 2012 issue of Today's Facility Manager
Anyone who manages multiple facilities projects knows that the old adage, “If it ain’t broke, don’t fix it,” holds a great deal of sound advice. And, every facility manager (fm) faced with bringing a new construction project (or two) online looks first at incorporating the equipment and systems that have proven themselves in the past, as referenced in another old adage, “go with what you know (works well).”
When I was tasked with bringing two new (and very different) acute care hospitals out of the ground for Rush Health Systems based in Meridian, MS, and having them ready to open within one year of each other, I relied on lessons learned in 2008 when major renovations were made to the Women’s Services area of our flagship hospital, Rush Foundation Hospital.
This Women’s Services renovation marked the first time we incorporated a variable refrigerant flow (VRF) zoning system to provide HVAC services in a facility. The VRF system replaced the four pipe chilled water and boiler setup that had been serving the area that was renovated.
VRF is an HVAC configuration where there is one outdoor condensing unit and multiple indoor units. The term “variable refrigerant flow” refers to the ability of the system to control the amount of refrigerant flowing to the multiple evaporators (indoor units), enabling the use of many evaporators of differing capacities and configurations connected to a single condensing unit. The arrangement provides an individualized comfort control and simultaneous heating and cooling in different zones.
With a higher efficiency and increased controllability, a VRF system can help achieve a sustainable design. A downside is that the design of VRF systems is more complicated and requires additional work compared to designing a conventional direct expansion (DX) system. However, the benefits can outweigh the initial installation requirements and costs.
Since the Women’s Services installation at Rush Foundation Hospital in 2008, the VRF system there has helped to reduce maintenance costs, minimize energy consumption, virtually eliminate duct losses, and, most importantly, deliver personalized, zoned comfort to each room in the renovated area. Post renovation patient satisfaction has soared, and positive comments from patients and staff members have been many. The replacement VRF system was definitely a winning approach. To top it off, we estimate the annual energy cost savings following the renovation project to be in the range of $35,000.
A few years later, when the Rush Health Systems leadership put two acute care hospitals on the drawing board with openings slated for early 2011 (John C. Stennis Memorial Hospital in DeKalb, MS) and early 2012 (Choctaw General Hospital in Butler, AL), there were two large (and very different) construction projects to oversee.
While both hospitals have 25 patient rooms and an emergency department, the footprints of the two facilities are very different. Therefore, both projects featured very different designs and, ultimately, HVAC demands. The DeKalb, MS facility was a totally new construction, while the Butler, AL hospital would make use of an existing structure once operated by Vanity Fair as a sewing plant. This plant was renovated to house some of the hospital’s non-inpatient care services such as the dining room, administration, and community classroom areas.
John C. Stennis Memorial Hospital—the first of the two projects—was planned and built with no chiller; it uses one 25 ton and two 30 ton HVAC units which operate in concert with the VRF system equipment. That configuration serves a total of 44,340 square feet, and the VRF system provides air control for approximately 80% of the patient care areas.
The design for Choctaw General Hospital required the use of air handling units for some areas including the hallways and dining room. The solution for this project incorporated air handling units capable of bringing in outside (fresh) air; these remove humidity and heat from the outside air. These units work in concert with the VRF equipment. The configuration in this facility serves a total of 74,000 square feet, and the VRF system provides air control for 100% of the patient care areas.
We have been extremely pleased with the functionality, performance, and efficiency of the systems in both facilities. With over a year of ongoing operations at John C. Stennis Memorial Hospital and having come through the extremely hot summer months at Choctaw General (the hospital began taking patients in March 2012), we’ve found the VRF systems meet the HVAC needs for both of these facilities.
Fms who have construction projects on the drawing board may want to consider VRF technology, especially where it is important that air heating and cooling systems are highly responsive to the needs of occupants in small areas, such as the patient rooms involved in these Rush Health Systems projects.
Rogers is vice president and chief resource officer and facility manager at Rush Health Systems, a Meridian, MS-based integrated health system comprised of hospitals, clinics, and physician practices. He has been with Rush for 17 years and has served as a board member of Meridian Surgery Clinic, a board member of Executives Services of MedAssets, and is Chairman of the Board of the East Mississippi Correctional Facility Board.
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