Electric Strikes

April 15, 2004

An electric strike is a latching mechanism that operates electrically to secure or release the extended latch or bolt of a mechanical lock or exit device. When an electric strike releases the latching mechanism, the lock/device remains locked. The electric strike's keeper releases, opening a path that permits the extended latch or bolt to exit the electric strike, permitting the door to be swung open. The keeper either remains released until after the latch or bolt re-enters the electric strike or, in the case of electric strike' designed for retractable latches, the keeper closes and the latch retracts over the keeper as the door closes.

An electric strike takes the place of the strikeplate for a mechanical lock. There are electric strikes designed to operate cylindrical locks, mortise locks, deadbolts, and exit devices. There are electric strikes designed to be installed into wood, aluminum, and/or metal jambs.

The components of an electric strike are the faceplate, keeper, lip, body, and locking/unlocking mechanism. The faceplate is used to attach the electric strike onto the door jamb. The keeper is the breakaway portion of the electric strike, which opens to release the latch/bolt, and closes once the latch/bolt re-enters the electric strike securing the door. Most electric strike keepers hinge against the body along the lip. The body attaches to or is part of the faceplate, which contains the electrical components, the keeper and the lip.

All electric strikes have an opening designed to contain the latch or bolt. The length and depth of this opening varies depending upon the specific model of electric strike. Some electric strikes are designed to accommodate a 1/2” throw cylindrical lock latch. Other electric strikes are designed to accommodate up to a 1 inch deadbolt. In addition, specialty electric strikes are designed to accommodate the Pullman bolt of a rim design exit device. Some models of electric strikes have the capability of operating with more than one lock configuration.

All electric strikes operate similarly. Just about every electric strike operates using a solenoid or coil. For our purposes, we will discuss the solenoid-equipped electric strikes. A solenoid is comprised of a plunger (movable armature) surrounded by a coil of wire. When the coil of wire is electrified, it becomes a magnetic field that moves the solenoid in a prescribed direction for a specific distance. In this condition, the keeper is either secured or released. When power is removed, the plunger moves back into the original position, and the keeper in the opposite condition.

There are two types of solenoids: the intermittent duty solenoid and the continuous duty. The intermittent duty solenoid is designed to be powered sporadically, just to release the door for someone to gain access. Most intermittent duty electric strikes are Fail-Secure, requiring power only to release the keeper and open the door. Continuous duty electric strikes are designed to be powered constantly and can function as Fail-Safe or Fail-Secure.

In the recent history of electric strikes, the heavy-duty electric strikes were equipped with external solenoids. These solenoids could be about three-quarters of an inch in diameter and extend out of the electric strike body approximately three to four inches. There was a choice of the solenoid position — extending up, out, or down. As electronics evolved, many solenoids were moved into the bodies of the electric strikes.

Electric strike solenoids are usually operated by low voltage electrical power sources, such as transformer or power supply. They are usually 12 or 24 volts, AC or DC or convertible. A convertible electric strike can be configured to operate as either AC or DC. The operational difference between a AC and a DC electric strike is the DC electric strike is just about silent when operating. Whereas, an AC electric strike buzzes when powered. An AC electric strike uses a DC solenoid with an attached full wave bridge rectifier. The full wave bridge rectifier converts the AC to DC current. If you do not need this buzzing sound, consider a DC electric strike.

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.

NOTE: When installing an electric strike into an aluminum jamb, make sure the faceplate has radiused corners. There are two reasons for radiused corners in an aluminum jamb; it's easier to install and a radiused corner eliminates cracking occurring at the corners of the cutout.

When installing an electric strike, having a horizontally adjustable keeper provides a horizontal adjustment capability to insure the proper closing of the door.

Do you as a locksmith stock electric strikes, or do you just order electric strikes when there is a job? If you do stock electric strikes, either know your customers or order electric strikes that can be used in as may applications as possible. For example, a non-handed electric strike can operate with the four door configurations: Left Hand (LH), Right Hand (RH), Left Hand Reverse (LHR), and Right Hand Reverse (RHR).

There are removable faceplate electric strikes that can not only accommodate different jamb materials, but they also can accommodate different types of locks. For example, the HES 1006 Series electric strikes are available with 27 different faceplate options.

When choosing an electric strike another consideration is the warranty. Electric strike manufacturers do offer different warranties on their products. Some electric strike manufacturers offer extended warranties if their unit is wired to their power supply and/or other products.

Most models of electric strikes have available options. These depending upon the specific electric strike can include lip extensions, covers, and goof plates. Lip extensions for fixed faceplate models require the extension be ordered when the electric strike is ordered.

Another consideration when installing an electric strike onto an exterior or sensitive outswinging door, would be the installation of a guard plate to protect the electric strike and the latching area on a door that swings out.

Electrical options for electric strikes include LEDs, Piezo/siren, latch monitoring, and door monitoring. An LED can be placed near the door to indicate the condition of the latch. The Piezo/siren can be used to provide notification when the door can be opened. Monitor capabilities permit remote locations to know if the latch is secured and/or if the door is open.

There are many ways to provide power to an electric strike. The cost can range from a few dollars for a door bell transformer to hundreds of dollars to a regulated power supply with backup battery. The electric strike determines the type of power supply. Most electric strikes require that the current be within less than a 10 percent variation of the stated power requirements. For example, a 12-volt electric strike may malfunction if the power source provides more than 13.2 volts or less than 10.8 volts. In addition, the higher quality power sources will maintain a more consistent level of power, and thereby extend the operational life of the electric strike.

Important: Before planning an installation of any electronic locking mechanism, always check with the "Authority Having Jurisdiction" (AHJ).

For more information, contact your local locksmith wholesaler or an electric strike manufacturer. Electric strikes are available from many sources including:

  • Adams Rite , 260 Santa Fe Street, Pomona, CA 91767. Telephone: 800-872-3267. Fax: 800-232-7329. Website: www.adamsrite.com .
  • Folger Adam , 16300 W 103rd St., Lemont, IL 60439. Telephone: 800-966-6739. Fax: 630-739-6957. Website: www.folgeradam.com .
  • HES , 2040 W. Quail Ave., Phoenix, AZ 85027. Telephone: 623-582-4626. Fax: 623-582-4641. Website www.hesinnovations.com .
  • Lee Electric , 309-11 51st Street, West New York, NJ 07093. Telephone: 800-433-3417. Fax: 201-866-0735. Website: www.leeelectric.com .
  • Locknetics Security Engineering , 575 Birch Street, Forestville, CT 06010. Telephone: 860-584-9158. Fax: 860-584-2136. Website: www.locknetics.com .
  • ROFU International Corp , 2004-B 48th Ave. CT. E, Tacoma, WA 98424. Telephone: 253-922-1828. Fax: 253-922-1728. Website: www.ROFU.com .
  • RCI, 2697 International Pkwy , Parkway 5, Suite 100, Virginia Beach VA 23452. Telephone: 800-899-5625. Fax: 757-427-9549 and 210 Shearson Crescent, Cambridge, ON N1T 1J6 Canada. Telephone: 800-265-6630 or 519-621-7651. Fax: 519-621-7939. Website: www.rutherfordcontrols.com.
  • Security Door Controls , P.O. Box 6219, Westlake Village, CA 91359. Telephone: 805-494-0622. Fax: 805-494-8861. Website: www.sdcsecurity.com.
  • Trine Access Technology , 1440 Ferris Place, Bronx, NY 10461. Telephone: 718-829-2332. Fax: 718-829-6405. Website: www.trineonline.com.
  • Von Duprin , 2720 Tobey Dr., Indianapolis, IN 46219. Telephone: 800-999-0408. Fax: 800-999-0328. Website www.vonduprin.com .

Securitron Magnalock Unlatch: Electronic Strike
The Securitron Magnalock Corp. UnLatch models are electronic door lock latch release mechanisms. These patented, motor driven, electronic strikes are designed to remotely unlock cylindrical locksets equipped with up to a 3/4" throw latch bolt, and North American mortise locks. The UnLatch mechanism is designed to operate under pre-load (pressure on the latch). The cylindrical and mortise lock UnLatch are designed to be installed into a 4-7/8” ANSI strike opening.

The Securitron Unlatch are designed to mimic the operation of a door lock through the unlocking and locking processes. They can be installed into hollow metal or wood frames equipped with a 4-7/8" ANSI strike plate opening requiring little or no modifications. When installed and the door closed, the UnLatch is fully concealed, hidden within the frame, only the lip of the strike plate visible.

The cylindrical lock version of the UnLatch is designed for cylindrical locks equipped with a deadlatch pin. The mortise version of the UnLatch has repositionable deadlatch fingers and latch plunger to accommodate the variations in North American mortise lock's positioning of the latch and the deadlatch.

Note: If the mortise lock contains a deadbolt, the deadbolt will not be operable as there is not an accommodating opening.

The Securitron UnLatch is available in a 12 VDC and 24 VDC model, in stainless steel or bright brass finishes. The UnLatch is equipped with an internal sensor that can determine if the door is closed and the latch is secured.

The Unlatch is covered by Securitron Magnalock Magnacare ™ Lifetime Product Replacement Warranty program.

For more information, contact your local locksmith wholesaler or Securitron Magnalock Corp., 550 Vista Blvd. Sparks, NV 89434. Telephone: 775-355-5625 or 800-MAGLOCK. Fax: 775-355-5633. Website www.Securitron.com .