Missouri contractor uses heat wheels to cool arena
The presence of the ice rink in the new arena, coupled with the building’s size and the humid climate of the Midwest, placed some unique demands on the building’s hvac contractor.
The arena needed a system that would minimize airflow over the ice, respond to rapid demand changes, and tightly control the humidity within the dome so that a high-quality ice surface could be maintained.
Wiegmann & Associates, a national firm located in St. Charles, MO, designed and installed a state-of-the-art hvac system that is keyed to dewpoint temperature — rather than space temperature or relative humidity — to keep moisture levels low for the benefit of the ice.
Saving energyThe arena has a maximum occupancy of 11,000 spectators, so the system has to import 110,000 cfm of outside air to meet code requirements. Ordinarily, such a load might require considerable tonnage of mechanical cooling.
However, the Wiegmann team designed a central system that uses four 13-ft-tall heat recovery wheels (manufactured by Semco Inc., Columbia, MO) to optimize energy efficiency and take advantage of low humidity and temperature levels within the arena.
Dave Wann, vice president of systems performance for Wiegmann, estimates that the wheels save approximately 450 tons of mechanical cooling.
“The heat wheels give us about 82.5% efficient recovery of both the sensible and the latent content of the exchanged air, which allows us to regain nearly all of the energy we’re exhausting out of the facility and transfer it into the incoming fresh airstream to precondition it before it gets to the cooling and heating coils,” says Wann.
“The cost of installing the wheels is similar to the cost of installing mechanical refrigeration, but the energy savings over the life of the equipment makes the wheels the logical choice. The wheels basically eliminate 80% of the outside air heating and cooling energy requirements.”
According to Dave Engle, the facility manager at the arena who operates the system, the heat wheels’ efficiency is indeed noticeable.
“If I shut down a heat wheel in just one of the houses that’s operating, I find that our equipment is a little slower on recovery,” says Engle. “That tells me we’re actually getting something back.”
More on the systemThe Wiegmann team individually selected oversized fans, coils, and filters to work with the heat wheels and then designed custom air-handling units to contain the equipment.
According to Engle, the identical nature of the air-handling units offers maintenance advantages. A technician trained to maintain one unit will automatically be familiar with the others.
The system also uses two 450-ton R-22 screw chillers (manufactured by York International).
The air distribution system is designed to provide even airflow throughout the seating area while minimizing air movement over the ice rink, which might adversely affect the quality of the skating surface.
A continuous loop of 54-in.-dia duct (custom manufactured by Wiegmann) feeds into specially designed and constructed air diffusers that quietly discharge the air at low velocities against the roof.
The air then cascades over the seating areas at the perimeter of the arena bowl. Once it reaches the lower levels, it is drawn out through the concourse and loading dock areas, where it enters the air-handling units and is eventually exhausted.
In the event of a fire or activity-generated smoke, air from the bowl area is exhausted directly outside to prevent smoke from entering the concourse and exit areas.
A digital control system manufactured by KMC Controls (Kreuter Manufacturing Co., New Paris, IN) allows the building’s climate to be adjusted and monitored through a central computer. Engle can monitor trend logs and recall other data for up to three days’ time.
In total controlThe system is also accessible through a modem or LAN connection, so Wiegmann’s engineers can access the system online and help troubleshoot problems without having to leave the office.
Courtney Mitchell, project manager for Wiegmann, says that the online capability allows them to respond faster to questions that arena personnel might have. Likewise, Engle can also access the system online from a remote location.
With one or two clicks of the mouse, Engle can change the climate anywhere in the building without having to leave the computer in his office. Since the arena also hosts professional basketball games, concerts, rodeos, and other events, the system is designed to respond quickly to demand changes between events. Usually maintained below 68Â°F for a hockey game, the temperature can be increased to a more comfortable level — 72Â° or 74Â° — for a different event within just a few hours.
“The control is almost instantaneous, which also helps with our bills,” says Engle. “We’ve found that for a facility of this size, our bills are well within, if not a little lower than, what I had anticipated when I saw the energy consumption.”
The system also self-diagnoses any trouble spots and automatically sends alarms to the central computer, which then alerts Engle to the problem and location.
According to Mitchell, the digital control system was thoroughly tested during a six- to eight-week start-up period near the end of construction. Control Systems Corp., the company that installed the controls, and McGrath & Associates, a third-party hvac consultant, both sent commissioning agents to evaluate the system and test every control point.
After all points were checked out, the team ran testing sequences and simulated various conditions to check programming responses.
Engle says he is extremely pleased with the thought process that went into the design, the quality of the equipment, and the overall responsiveness and efficiency of the system.
“In the past, systems that were attempted like this didn’t work. This one works,” says Engle.Â