Air systems can be either stand-alone or multiple-units integrated into a vestibule assembly. Often, these systems don't seal the opening well, and proper alignment of the air units is critical for best performance. Vestibules can also require a large footprint that takes up valuable floor space.
Air units typically include heaters to reduce the relative humidity of the infiltrating air, and often a tremendous amount of energy is required to operate them to the point where they keep the opening free of frost and ice.
The bottom line is that high energy cost is a recurring theme with traditional doors. Substantial air leakage at the opening makes it difficult to maintain proper freezer temperatures. In addition, frost and ice on the door can often cause significant issues unless an operationally expensive door panel defrost system is included. Overall, these high costs have driven the need for innovation.
Door technology fills the void: Recent improvements in door technology combine fast cycling with high-efficiency insulation and sealing. These innovations contribute to low, long-term energy costs, improved efficiency and increased safety. In short, high R-value is no longer the main driver in door selection.
Major advances in door design have focused on improved bi-parting doors and insulated upward-acting doors. Advanced bi-parting door designs include high speeds to minimize door open time. Some doors can operate up to 84 inches per second, which is up to four times faster than old-style, rigid side-acting doors.
Another advantage of technically advanced doors is their ability to withstand forklift impact, which minimizes maintenance and downtime while maintaining a tight seal over the life of the door. Some impactable doors also offer higher R-values to avoid the need for heated panel defrost systems. Automatic reversing capability on some models eliminates safety and maintenance concerns with doors that use pneumatic or electrical reversing edges for the same purpose.
Significant improvements in the upward-acting design category include reduced cycle times and the use of insulated door panels. These insulated curtain panels provide the necessary R-value to avoid expensive panel defrost systems.
At the same time, some doors can operate as fast as 100 inches per second to minimize air infiltration and ensure optimal productivity. As with bi-parting doors, newer upward-acting doors also incorporate a perimeter thermal air seal for added energy savings through a tighter seal.
No need to sacrifice: Door selection is no longer a matter of giving something to get something. Improved technology has led to more choices that result in low, long-term energy costs, improved efficiency and increased safety.
Boerger is director of technology and innovation, Rite-Hite Doors Inc., Milwaukee.