Electric Strikes

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Created: April 15, 2004

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Electric strikes come in two configurations: Fail-Secure and Fail-Safe. A Fail-Secure electric strike requires power to release the keeper. Once the keeper has been released, power is no longer required. When the door is closed and power is removed, the Fail-Secure electric strike keeps the door locked. Many intermittent duty solenoids are used in Fail-Secure electric strikes. No backup power supply is needed for a Fail-Secure electric strike.

Note: Fire rated electric strikes are Fail-Secure.

The Fail-Safe electric strikes operate using continuous duty solenoids. These electric strikes require power to remain locked. To open the door, power is turned off, releasing the keeper. For security purposes, most Fail-Secure electric strikes have a backup power source in case normal power is lost.

When choosing an electric strike, there are a number of considerations. They include:

Price the end-user is willing to pay
Number of people using the door each day (light, medium, or heavy traffic)
The type of mechanical lock mounted onto the door
The material of the jamb (wood, aluminum, or metal)
The construction of the jamb and what is behind it (amount of space)
Hand of the door (handed or non-handed electric strike)
Monitoring

The cost somewhat determines the number of features and the duty rating. For example, a more expensive unit may have a horizontally adjustable keeper that enables the electric strike to make minor compensations for changes in the swing and closings of a specific door.

Another consideration where price is important is the holding force of the electric strikes. There are different grades of electric strikes; like cylindrical locks, the smaller the number the heavier the duty. Electric strike manufacturer provide information about the capability of their products. There are tests that are performed to test the operation of electric strikes including cycle testing, holding strength, attack, etc.

Note: When purchasing an electric strike, know the features that will best satisfy the end-user's requirements.

The amount of traffic through the door should be considered when recommending an electric strike. Many electric strike manufacturers state the duty rating of their electric strikes. Remember that a heavy-duty electric strike can be used in a light-duty situation whereas a light-duty electric strike will probably not last in a heavy-duty situation.

Determine the type of lock the electric strike is securing. Is the lock a cylindrical (tubular), mortise, deadbolt, or rim mounted exit device? A mortise exit device uses the same type of electric strike as a mortise lock. Before ordering an electric strike, make sure that the electric strike can accept the latch.

At the same time as determining the lock type, determine the construction of the jamb. The construction of the jamb determines the type of electric strike. An electric strike designed for aluminum or metal jamb will normally have a smaller faceplate than an electric strike designed for installation into a wooden jamb. Having a longer faceplate enables the use of more screws to secure the electric strike to the wooden jamb.

When installing an electric strike into a wooden jamb, try to determine the construction of the jamb and if there is a nearby stud. Long wood screws can be used to secure a weak jamb to a nearby stud, strengthening the installation.

The jamb material can also determine the type of electric strike that can be installed. For example, it is advisable to install a low-profile electric strike into a 2-inch UL 10C fire rated 3-hour frame, having a 1/2-inch dry wall penetration. Low-profile electric strikes do not require much depth.

Electric strikes are available with removable or fixed faceplates. Fixed faceplate electric strikes are designed for specific purposes. Removable faceplate electric strikes are available with different length faceplates. This enables the electric strike to be installed into wood, metal or aluminum.

Most electric strikes require a cutout of the jamb of varying amounts to accommodate the electric strike. However, the type of lock to some point determines the type of electric strike and the amount of modification necessary. A few low-profile electric strikes require minimal modification to the jamb. For example, the Trine 3000 electric strike requires only a 5/8" modification to the jamb. In addition, there are surface-mounted models, for example, the HES Genesis electric strikes, that require no modification to the jamb for rim exit devices.