How does a door closer work: an overview

How Does a Door Closer Work: An Overview

Door closers are a common sight in most commercial buildings.  They are mechanical devices typically installed to ensure that doors get closed after patrons, residents and other building-users open them.

Local building codes usually determine what exits must be outfitted with door closers.  Some may require all doors have them.  At the very least, most regions require them on fire doors.  The reason for this is that fire doors are to remain closed at all times when not in immediate use.  This helps to ensure that, should a fire break out in the building, flames do not spread from one part of the building to another before firefighters can bring the blaze under control.

Door closers are either surface mounted or concealed, and are so-named due to how they are installed on (surface mounted) or within (concealed) the door.  Surface-mounted devices appear as a small box attached to the top corner of the door.  A jointed “arm” extends from the top of the box to the frame where it is bolted in. A concealed device is mounted within the material of the door itself, meaning that the only part visible to the eye is the arm.

Door closers come in two major types: manual and automatic.  The most common is the manual type.  Over seventy percent of those found in commercial buildings in North America are this type.

Additionally, manual door closers may be overhead or jamb mounted.  The overhead style is more common, particularly on older public buildings.  This type looks like the typical box and arm device. 

A jamb-mounted device is installed on the inner frame of the door and the inside edge of the door.  The mechanism is only visible when the door is open.  Once it closes, a jamb-mounted device is invisible on both the interior and exterior side.

Manual door closers (whether overhead or jamb-mounted) work on the principle of pneumatics (air pressure) and stored energy.  The device stores the energy that is generated when someone pushes the door open.  It then uses this energy to close it without any additional human force being applied.

Closing speed can be controlled and adjusted as desired.  Some use hydraulic dampers (these are most common,) others employ spring mechanisms.  Sets of screws are adjusted to achieve desired closing and latching speed.  (Many regions have building codes which mandate closing speed on door closers, usually in deference to disabled patrons who may take longer to enter and exit.)

Automatic door closers, as the name suggests, use electrical power instead of stored energy.  This style is less common, due to the amount of power required and the interest of economy and conservation.  Automatic devices are typically found on buildings where particular entrances/exits are highly controlled and monitored and buzz-in/out is employed, such as residential care homes.

Door closers that are intended for use on fire doors must be fire-rated.  Devices that are fire rated have been tested by a recognized testing facility to ensure that they can withstand heat/flames.  They must be able to hold fire at bay for as long as the fire door itself does; a typical one is usually required by law to contain fire/flames for a minimum of three hours.

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