HIGH & LOW ENERGY DOOR SYSTEMS – WHAT MAKES THEM DIFFERENT?
Automatic doors are generally grouped into two major categories. Low energy and high energy doors. The difference between the two types of doors pertain to the ways that the doorways operate.
LOW ENERGY DOORS
Low energy doors are often thought of as “handicap accessible automatic doorways”. These doorways usually have signage showing the universal symbols that are understood as wheelchair accessible openings. In most installations, low energy door systems are either swinging or sliding doors. They are predominantly activated by a “knowing act” on the part of the doorway user. A button or push plate is used to activate the door operating mechanism. A person wishing to enter the doorway must push the button to start the door opening function. The low energy requirement of these doorways pertains to the forces exerted by the moving door through all aspects of the opening and closing cycle.
Some of the low energy door systems are strictly power assisted door openers. In their most basic form, these doors use motor controls to push or pull open a door. After reaching the fully opened position a basic timer will keep the door open for a specific set time. This allows a person in a wheel chair access without having to push or pull open the door in front of their path of travel. When the timer has counted down, the door will close, and cannot be reactivated to reopen without another push of the button.
Every low energy door system must operate slowly and with minimal force upon impact or resistance. A properly adjusted low energy doorway will stop, stall, or reverse when an obstruction is encountered during its operations.
The more complex or sophisticated the low energy door control, the more potential features will be available. Some possible options include a power assisted feature that will sense the force exerted by a user and activate the door motor control to take over the opening effort. A feature called “Push and Go” is often available which performs this type of function. There are also obstruction reactive elements that will stop, reverse or recycle the opener that may be included in the motor control command options.
According to specific industry wide safety standards, no optical sensor or proximity sensor of any kind is required on any low energy door system that is operated by a push of a button known as a “Knowing Act”. For this reason, these types of doorways are practical for low volume traffic. They are safe when used appropriately and regularly tested for proper force and speed when moving. These doors can be problematic when installed in place of a more costly high energy, fully automated doorway.
Daily inspections of all low energy door systems is an industry wide requirement. Most manufacturers provide signage and stickers that are positioned on door frames instructing the manager of any facility that the observation of these doorways is needed routinely. In an effort to improve the low energy products, retrofitted sensors and threshold protective devices used on fully automatic high energy door systems have been installed on low energy doors. This has become an industry wide practice that is acceptable. The sensors are often placed on these low energy openers to keep a “tailgating” pedestrian from being hit by a closing door that has “timed out” after the first user has passed through the doorway. When actual pedestrian traffic counts exceeds the original expectations of the architect or designer, it is a good idea to replace the low energy door system with a fully automatic high energy doorway.
HIGH ENERGY DOORS
High energy door systems are available in many different configurations. Swingers, sliders, revolving, bi-parting, and telescoping are the most prevalent types in usage today. Their application and installation are dictated by design choices, weather requirements and location parameters. These doorways differ from low energy door systems in the way that the door operates and the force and speed that the doors possess when moving.
In general, automatic door systems have an approach sensor, a threshold protection sensor and an egress sensor. The complexity of the automated door system dictates the level of sophistication of the entire door component control and sensor package. As discussed in previous automatic door articles, specific requirements of different automatic door systems govern the types and locations of door sensors and safety devices.
The one consistent requirement of every automatic door system is the need to perform daily safety inspections. Industry wide accepted standards have been adopted to help maintain the safety of all users of all pedestrian doorways. In the most general sense, no properly maintained and functioning automatic door should ever hit a user of that doorway.
Industry standards stating the importance of daily safety checks and component inspections are normally positioned on warning labels provided by the product manufacture adjacent to the door control activation panels. The proper methods of determining the correct functions and operations of the doorway are listed along with test procedures and instructions to seek professional service assistance if any of the safety devices fail to work as described. There is usually a warning to discontinue the usage of the doorway until all safety features function consistently and properly.
Because high energy doorways move at a much faster speed and force than low energy doorways when opening and closing, it is very important to know that all of the built in safety sensors are functioning properly at all times when the doorway is in use.
HOW THE STANDARDS FOR HIGH & LOW ENERGY DOORS ARE DETERMINED
Most standards are compiled from suggestions and the informed input from manufacturers, installers, architects, engineers, and door designers. The general public has the ability to suggest additions to these standards as well. When the standards are developed, written, and finally accepted, there is often a delay in instituting the new ideas until the next revision is printed and published.
Products that are produced during an interim period between standard revision editions are considered compliant at the time of manufacturing. However, they may not always comply with the revised standards shortly after their production period. In most cases the previous standards are incorporated into the newer editions. The basic parameters and ideas behind the earlier version of the standards have been more refined or finely tuned, not generally changed from the original concept.
With changes in technologies certain aspects of door controls, activation devices, door sensors, and safety equipment have made prior standards obsolete. An example of this is the current usage of overhead door sensing devices to control door functions. Originally, on the early automatic door systems, prior to the development of consistent and dependable sensors, floor mats with electric or hydraulic contacts were the most common form of door activation. Pressure sensitive mats are now in limited installations and considered outdated in most applications. soundproof door
There are generally provisions in the standards that refer to older equipment that has been in service and still functioning adequately. But, the emphasis on safety is always the primary basis for automatic door standards and the reason that improved designs and newer technology products have taken over.
GENERAL OBSERVATIONS FROM A DOOR SERVICE PROVIDER & DOOR EXPERT WITNESS
As the retained expert witness for both plaintiff and defense in hundreds of personal injury and wrongful death automatic door cases, there have been severe injuries and deaths occur as a result of every type and design of malfunctioning door systems.
In older automatic door installations, failure of the sensor floor mats often caused injuries. These older technology mats, and, in some cases, original system components were generally installed in grocery stores. They were most frequently associated with automatic swinging doors and were considered a great convenience to shoppers that no longer had to hold open the store doorways as they pushed their shopping cart in or out of the store.
Some old door standards make reference to control mat usage in sliding door installations. In actual practice, multiple scanning sensors were typically installed in place of the pressure activated floor mats in those systems. Pressure sensitive control mats would ultimately deteriorate due to heavy shopping carts constantly running over them. Weather related issues such as exposure to ultraviolet rays from the sun, or effects from freezing rain, snow, and ice, would cause the mats to become brittle, have contact problems, and fall apart. Pedestrians using these doorways would become confused as the mats failed to consistently signal the door operator. The doors would either fail to open, fail to remain open, or react erratically when stepped upon.