Warming Up with the Cleveland Browns

Cleveland Browns Stadium plays host to more than 73,000 football fans during home games. Down on the playing field, winning may be more of a challenge at this point for the fledgling franchise than it was when Jim Brown, Otto Graham and Lou Groza were running, passing and kicking their way to victory.

But with an underground hydronic radiant heating system that keeps the playing field from freezing in the face of icy winds off of Lake Erie, the new generation of Browns find it easier to keeping their footing.

Contractors installed 210,000 ft.—nearly 40 mi.—of 3/4-in. PEX tubing divided into four zones, each with 189 loops. The tubing is installed on 6-in. centers, 10 in. below the playing surface.

A solution of 40% inhibited ethylene glycol-based heat transfer fluid and water circulates through the underground system. Nine gas-fired boilers feed 7,000 gals. of the solution to the field through two primary pumps and eight secondary pumps. The boilers heat the solution to 180°F. Solution temperature to each zone is 140°F. The flow rate is controlled to keep the temperature at the root zone between 60°F and 65°F.

While the glycol solution keeps the playing field from freezing, another heat-transfer solution protects the stadium's cooling system throughout the winter.

"The cooling system is not a conventional design, where you have the chiller indoors and a cooling tower outside to enable easy draining," says Jerry Zelenka, project mechanical engineer for URS, the Cleveland-based firm that designed the mechanical and electrical systems. "The life-cycle study we conducted indicated that outside air-cooled chillers, combined with electric heat, provided the best cooling and heating combination overall."

The chilled water is fed to air-handling units up to 1,000 ft. away from the chillers via an extensive system of 6- to 12-in.—mostly Schedule 40—steel piping. The piping branches out around the stadium on two sides, then up vertical shafts. A major consideration involved drainage. Draining even portions of the system during the winter months, when the cooling system is not required to operate, could be inconvenient, time-consuming and uneconomical. In addition, the cooling system also needed to be available for operation through the late fall, to satisfy any mechanical cooling requirements that might prove necessary for special events held at that time in the large club areas.

With these factors in mind, URS decided to use an industrially inhibited glycol-based solution year-round as a preventative against freezing. It also makes the system available to accommodate event scheduling right through the fall.

To help keep things cool in the summer and fall, approximately 15,000 gals. of a solution of 40% heat-transfer fluid and water are circulated throughout the system according to schedules set by a central building management system. Chillers are cycled on and off depending on facility demand.

During the winter, the cooling system normally remains shut down, its piping and system components protected from freezing by the glycol-based solution.