For the purpose of this article, we will discuss surface-mounted door closer basics to better understand the design, operation and limitations of a mechanical door closer. Optimizing the installation of a door closer can be very beneficial by requiring less opening and resulting closing force. Less force means more possibility to meet code requirements.
MOST IMPORTANT: Before installing or servicing a door closer, make sure the door hardware is in proper operation. A door that rubs along the threshold, floor or jamb edges will most likely not close under the power of a proper sized door closer. On rare occasions a latch bolt has worn to a point, making it difficult to retract when pressing against the strike plate. This results in the door not latching. No matter what the problem is, it must be resolved to ensure smooth, non-restricted closing and latching.
In the non-residential world, for almost every door a person physically opens, a mechanical door closer closes the door. The door closer closes, rather than slams shut, a door.
Simplified, a door closer is a spring loaded, adjustable hydraulic system and through the use of specifically located valves, it is capable of safely closing and latching a door using only the power provided by the person who opened the door. When a person opens a door, the closer spring compresses and the hydraulic fluid moves away from the compressing spring. As the door closes, the spring expands and the fluid is forced into the area of the expanding spring. Valves positioned along the closer body determine how fast the fluid moves as the spring expands.
The process of opening and closing a door equipped with a mechanical door closer can be divided into four or five stages.
The first stage is when the person swings open the door. Depending upon the obstructions within the swinging area, the door may be able to be opened slightly more than 100 degrees (providing sufficient room for traffic flow) to fully open, up to 180 degrees. The opening can also vary by the type of closer arm installed.
Note: When installing, you will usually gain additional adjustability if the door closer is mounted to allow the greatest degree of opening.
When there is a choice of how far to open the door, consider the traffic flow. If there is high traffic through the doorway, the greater the opening, the longer the time the door is in the opening area, the more people who will walk through.
The second stage is the backcheck when a special valve in most door closers controls the opening swing. The door then slows smoothly prior to the end of the swing.
Note: A solid stop should always be installed, as the closer’s backcheck was never designed to be a doorstop. Without a solid doorstop, additional pressure is exerted against the mounting screws, and the spindle, arms and shoe or foot shortening the operational life expectancy of the door closer.
The additional stage is Delayed Action, an available feature on many door closers. Delayed Action holds the door fully open for a minimum number of seconds, providing additional time for passage through the doorway.
If the door closer is equipped with a delayed action valve, the door will stay in the open position for an adjustable amount of time. For high traffic doorways, holding the door open does increase traffic flow.
The next stage is the closing speed that controls how fast the door swings from open to about six to ten inches or approximately 15 degrees from the closed position. Remember, because the spring has been compressed, its power is very high at the open position. Standard door closer power decreases dramatically as the spring expands. If the spring power is released too quickly, the door may slam shut or there may not be enough force remaining to latch and secure the door.