Controlling Access with Electric Strikes

The ability to keep a door locked and to let specific people pass through means convenience and security.


'Fail-Secure' indicates that the lock is in a locked condition when no power is present. Again depending on the application, exit is accomplished at any time by activating the mechanical hardware. Turning the knob or lever or pushing the exit device withdraws the latch and provides egress.

NOTE: Always verify that you are meeting the state and local fire code life safety code requirements of a given electric strike installation by checking with the Local Authority Having Jurisdiction (LAHJ). In most instances the local fire marshal or fire inspector's office can put you in touch with the proper person.

DUTY

In the case of electric strikes there are two duties: intermittent or continuous. Intermittent duty electric strikes are energized only when power is supplied. The majority of the time they are at rest. An example of an intermittent duty electric strike is a Fail Secure electric strike. Only when power is provided will the electric strike unlock.

Continuous duty strikes have power applied continuously. Some fail-secure, continuous duty strikes are used when a door is kept unlocked during normal business hours. After hours, the power is removed and the strike can only be opened if power is supplied momentarily via a switch. In many installations a programmable timer is used to lock or unlock the strike at a pre-determined time or day.

Both fail-safe and fail-secure strikes are available in either intermittent or continuous duty status. Applying continuous power to an intermittent duty strike will most likely cause solenoid to burn out and the unit to fail.

FACE PLATES

The size and shape of the faceplate will determine how the strike body fits into the frame into which it is installed. By making a variety of different faceplates to fit the same case or body, the same lock can be used in a number of varying applications.

Also, the faceplate of the new strike can be matched to the dimensions of the old strike. So even if the lock body size of the new strike is smaller, the faceplate will fill the old opening eliminating the need for patching, filling or resizing the opening in the frame.

ADJUSTABILITY

Some manufacturers offer uniquely designed strikes that allow vertical, horizontal or lateral adjustment of the strike body or its components after installation. This lets you compensate for door or frame movement as a building settles or moves.

POWER & VOLTAGE

While most electric strikes utilize a simple plug-in transformer, some may require a heavier duty power supply. The voltage requirements for most electric strikes are 12 or 24 volts. Exceptions exist in the 16-18 volt range and some specialty applications may use a higher voltage. You need to know the rating of the power source when replacing an existing strike. If you install a 12 volt strike into a 24 volt power supply it will damage or destroy the strike and may actually cause a fire hazard.

If you install a 24 volt lock into a 12 volt power supply it will either not work properly or not work at all. It may unlock or lock intermittently but will not meet the customers' needs.

The other important piece of the puzzle is current. Alternating current (AC) and direct current (DC) are your two choices. AC strikes provide the familiar 'buzzing' noise that most customers are familiar with. DC strikes will provide a simple 'clunk' when the solenoid is engaged.

GAINING ACCESS

When an electric strike is installed, you need to determine how to release it when entry is desired. Some form of switch is required to break or complete the circuit to allow the strike to perform its intended function.

A simple push button located inside will let someone release the strike to allow access. Another option is installing a keypad or card reader to release the strike from the exterior. Of course using the mechanical key in the lock will allow entry but eliminates the strike from the action.

RECAP

When you are choosing an electric strike to meet your customer's needs, you need to consider whether to use fail-safe, fail-secure, 12 or 24 volts, AC or DC, intermittent or continuous duty etc.

Many electric strike manufacturers allow the locksmith to choose the voltage, current and status of the lock right in the field. By turning a screw, rotating and flipping a part or utilizing a jumper you can change the settings in seconds. The addition of multiple faceplates allows you to stock a minimum number of locks and parts on your service vehicle or in your shop to accomplish a multitude of strike applications.

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