Two Pipe vs. Four Pipe Heating/Cooling Systems

The University of Alabama has two different types of water circulating systems; two-pipe systems and four-pipe systems. These systems provide heating and cooling for the buildings on campus. Two-pipe systems are less flexible than a four-pipe system. When the season changes, the two-pipe system must be switched from cooling mode to heating mode or vice versa. There is always the possibility that unusual weather patterns might cause some occupant discomfort. A four-pipe system on the other hand has supply and return piping. Four-pipe systems can supply heat to one room while cooling another.

Overall, many of the buildings on campus are on a two-pipe system. Throughout the year, the Facilities Maintenance department and the Energy Management department are in continuous discussions as to the optimum time to start-up the campus heating systems. Facilities performs the system switchover based on priorities established to (1) provide comfort to students living in University Housing, (2) maintain required temperatures to protect equipment and research in progress, and (3) serve the greatest number of individuals and activities.

There is not an exact schedule for switching over the system; it is based upon several different criteria. Long range weather prediction, amount of sun, and wind chill are all taken into consideration. Remember that it takes a couple of days to switch between cooling and heating. Therefore, we must select the proper time where you have optimum conditions throughout the campus. Most people surveyed have stated they would rather be cold than hot. To stay comfortable during these days of varying weather conditions, dress appropriately to the season and weather. Wear layers of clothing so you can adapt to varying conditions in your classroom or work space and still be comfortable.

University Facilities will try to accommodate each building’s needs as much as possible with regard to University Policy and outside factors. Please contact your building representative if you would like your building switched. The building representative will assess the entire building needs and work with Energy Management to best serve the majority of the building occupants. Facilities does not have enough people to change buildings back and forth from heating to cooling, so once your building is switched over, it will not be switched back until the next seasonal change.

Two-pipe buildings include Morgan Hall, Woods Quad buildings, Little Hall, and Graves Hall. Four-pipe buildings include Ferguson Center, Student Services, Bevill, Bruno Library, and the Blount Building.

The Comer Steam Plant

Most buildings on campus are heated in the winter by circulating hot water through the building and cooled in the summer by circulating chilled water through the building. The two-pipe or four-pipe designation refers to the type of distribution system that carries the water through the building. Most buildings on campus get their hot water from the campus Steam Plant located in B.B. Comer. 

The Steam Plant is only operated during the winter months, so hot water may not be available to some buildings on a cool fall day. Steam is produced in large natural gas fired boilers and the steam is used to heat the water that is circulated through the building for heating. It can take ten to twelve hours to get the steam plant up and running. 

Operational and Fiscal goals justify delaying the startup of the Comer steam plant as long as possible without impacting comfort. The steam plant accounts for approximately 30 percent of the University’s natural gas use, and costs approximately $200,000 a week to operate. UA’s carbon footprint due to “direct emissions” is much lower than our peer institutions partly due to our policy for steam boiler start-up.  Every day the University can delay starting the steam plant reduces our overall carbon footprint; assisting us in our sustainability efforts and improving our position as environmental stewards. Weather forecasts will be watched closely, building temperatures monitored, and comments from faculty, students, and staff will be evaluated to determine possible start-up and shut down of the central steam plant. 

The Facilities Department always keeps the students and staff’s comfort in mind as it strives to be energy efficient and environmentally responsible.