Uniontown Schools

Thirty-two-year-old elementary school in Kansas. Leaky roof. Old rooftops units. Looking for solutions. Energy savings a bonus. Serious inquiries only. Ask for Uniontown.

If the Uniontown school district had placed a classified ad in the paper, it probably would have read something like that. Faced with these challenges in early 2010, the district had some tough decisions to make.

The Issue

West Bourbon Elementary – part of the USD 235 Uniontown school district - is located in the tiny southeastern Kansas community of Uniontown. At 32,000 square feet, the building is a learning and working environment for more than 270 students, teachers and staff. At the time it was conditioned with two dozen packaged rooftop units, each one responsible for a specific area. “Very inadequate,” is how Randy Rockhold, Uniontown superintendent, describes the setup.

Comfort issues were a problem because the system did not allow teachers to adjust the temperature to meet their specific classroom needs. So when a new roof was needed, it made sense to consider a new HVAC system design to avoid the risk of future roof leaks and meet current comfort needs.

“The school wanted a new mechanical system but did not want any equipment on the roof,” says Brett Miller, a Kansas Trane business development leader who worked with Rockhold and other school leaders throughout the project. “We made a presentation with the roofer at the school board meeting and sold them on the value that our team could bring them. The decision was based on value, not low price.”

The Solution

When school leaders chose to go with a new HVAC system design – one without rooftop units – Miller and Ed Lange, Kansas Trane sales engineer, suggested Mitsubishi’s Variable Refrigerant System (VRFZ) product. The benefits were many.

“Basically, the cooling and heating needs of individual spaces can be handled by connecting small refrigerant line sets between system components in lieu of routing large ductwork to each space, as is needed with most conventional systems,” Lange says. “Additionally, one Mitsubishi VRFZ R2 system has the ability to heat or cool different spaces simultaneously,” a process known as energy recovery mode.

Lange gives the example of a cool Kansas spring day when a classroom on the outside of a building needs heating while an interior classroom needs cooling. One Mitsubishi unit cools the interior classroom by removing the heat in that space and carrying it to a Mitsubishi unit heating the exterior classroom, all via the units’ refrigerant system. “In this way the exterior space is heated for ‘free,’” Lange says. “Conventional systems would have just rejected that heat energy outdoors and used ‘new’ energy to heat the other space.”

Sean Miller, mechanical engineer with MKEC of Wichita who designed the project’s HVAC replacement system, agrees that Mitsubishi was a good fit for the school. “The variable refrigerant system lends itself well to remodel projects such as this. Instead of being forced to demo all of the existing systems above the ceiling, we were able to save money by only demolishing the materials that were in the way. The system also allows each classroom to have its own thermostat, which was an improvement over the old system with two to three classrooms fighting over the same thermostat.”

Another added feature was acoustics. “The system is extremely quiet with very low noise levels, which is very conducive to a school or learning environment,” Sean Miller says.

The Challenges

Convinced, school officials choose the Mitsubishi VRFZ System. Sean Miller and his team then began the mechanical design process, using 3D building information modeling technology. “We developed a 3D model of the existing building and placed in accurate 3D models of the existing systems to remain in place, abandoned, and the new VRFZ system and associated ductwork,” Sean Miller says. “With this we were able to place all materials where needed in the layout, and it was fully coordinated with existing materials, ceilings, lights and structure, helping to avoid any costly change orders for unforeseen items.”

The project had its own unique challenges, he says, chiefly the design of the ventilation system. “Classrooms require a large amount of ventilation air, and the Mitsubishi VRFZ ductless cassettes are not designed to handle large volumes of fresh air.”

To address this challenge while maintaining cost effectiveness, Sean Miller designed a ventilation system to pre-treat ventilation air using restroom exhaust air. “By pre-treating the ventilation air, we were able to deliver it directly to each classroom through a ceiling mounted, perforated diffuser next to the ceiling mounted units. By over-sizing the supply duct and using a perforated diffuser, we were able to slow down the velocity of the incoming air to the room enough to allow the delivered air from the ceiling-mounted VRFZ units to capture and entrain the ventilation air in the airstream and mix it as it is delivered to the space. A portion of the air is also included in the return to the unit.”

Better Than Expected

With these hurdles cleared the next challenge would be installing all 41 indoor and outdoor units in about 90 days, in time for the start of fall classes. Work on the project began June 1 and was completed by the August 1 deadline. “This really was an amazing feat,” Brett Miller says.

The Mitsubishi units’ efficiency has been remarkable. Rockhold says since the system was installed the school has seen monthly energy savings of about 10 percent. And that’s not all. “The environmental quality in the building is exceptional. The temperature is always exactly where the individual teacher desires.”

Mitsubishi’s VRFZ system has performed so well that Rockhold says the district will replace the high school’s HVAC system with it once funding becomes available. He used one word to describe his pleasure with the school’s new system: “Very.”