Electromagnetic Lock Overview

As applications and security requirements increase, electromagnetic locks are indispensable in many (not all by any means) electronic locking applications.

However, some traditional locksmiths prefer latching hardware over electromagnetic locks. Some also have an aversion towards wiring and electrified systems.

There is a segment of the industry for whom the electromagnetic lock is their first choice, usually because these individuals are not familiar with locksmithing and architectural hardware, and they consider an electromagnetic lock as a quick fix for the majority of applications.

Both of these attitudes are pretty extreme, and the professional security professional is best advised to become better informed about the benefits and shortcomings of maglocks in order to best serve their clients.

Electric locking devices fall under the following two main classifications:

1. Electromagnetic: which includes electromagnetic locks and shear locks
2. Electromechanical: which include latching hardware such as electric strikes and electrified exit devices; electrified bolt type locks, and electrified mortise locks and cylindrical locks.

Maglock History

The first modern direct-pull electromagnetic lock was designed by Irv Saphirstein in 1969. The initial design objective was to develop a lock that would be safe in a fire emergency.

The original technology involved the adaptation of magnetic door holders which were used to hold doors in an open position and released them when power would be interrupted when it was desired they close (in a fire, when doors close and latch to mitigate the spread of fire and products of combustion).

Saphirstein started the Locknetics Company to develop accessories and control circuits for electromagnetic locks.

The founders of many of today’s manufacturers of electromagnetic locks were originally employees of Locknetics. There were several electromagnetic lock factories in Connecticut, but that’s all changed.

Electromagnetic locks use magnetism to create a bond between the two major components of the electromagnetic lock: the electromagnet and the armature plate.Maximum performance is achieved when the mounting surfaces are clean and aligned, providing surface contact over the device’s maximum surface area.

Popular holding ratings are 600 and 1200 lbs. dynamic holding force. The dynamic holding force of a magnetic lock refers to the amount of sudden impact force necessary to defeat the magnetic bond of the electromagnetic with the armature. Normal or Static holding force is the progressive application of force on the door until the bond is overcome.

Another type of electromagnetic lock is the shear lock.

Unlike the electromagnetic lock which is a direct pull arrangement, the shear lock is mounted in such a way that the armature which is mounted facing up in the top of the door is pulled towards the electromagnet which is mounted in the header facing down. The magnetic bond holds the armature and electromagnet interlocked, creating a stronger hold than a similarly sized direct pull electromagnetic lock.

Shear locks can be used on bi-swinging doors, are often concealed in the top rail of the door, and provide the combined hold of an electromagnetic bond and mechanical interlock. Adjustment of the door and the shear lock is more critical than with a direct pull electromagnetic lock.

Since the locking ability of an electromagnetic lock is dependent on power being applied to the electromagnet when the armature is contacting the electromagnet, and removing power immediately relaxes the magnetic bond and unlocks the door, electromagnetic locks are classified as Failsafe.

A noteworthy characteristic of electromagnetic locks is the absence of a means to manually unlock, which is not typical among electronic door hardware. So while the electromagnetic lock is intrinsically safe being non-latching and requiring power to lock, there is a potential life safety hazard if the electromagnetic lock is not installed in a control system which adequately addresses possible failure modes. A failure mode is a way the electromagnetic lock might not unlock when it is necessary to allow emergency egress. Therefore it is important to take into consideration the advantages and the disadvantages of electromagnetic locks.

Electromagnetic Lock Pros:

Easy to install: Electromagnetic locks are generally easier to install than latching mechanical locks which require careful alignment between the latch or bolt and the strike. All electromagnetic locks require auxiliary control stations, power supplies and interfacing with building systems. Note that most electric locking devices require power and wiring, but because of the life safety issues associated with electromagnetic locks, more attention to safety is required.

Fast acting: Electromagnetic locks respond instantly when power is cut or applied. Some locking devices respond slower to lock and unlock signals.

Sturdy: Electromagnetic locks are robust and more immune to abuse and attack than other type locks.

Simple: There are no moving parts in an electromagnetic lock to break. Fewer parts equals fewer failures.

Electromagnetic Lock Cons:

REQUIRES A CONSTANT POWER source in order to be secure. If power is removed the electromagnetic lock will unlock. This is not always desirable, even if a power supply with battery back up is used.

EXPENSIVE An electromagnetic lock may cost more than some electrified mechanical locks; especially when the other required circuit components are taken into consideration.

Bear in mind that maglocks make it possible to create security and life safety solutions not possible with other type locking devices so a direct comparison based on cost is not always appropriate.

UNSAFE (if not properly installed with adequate failsafe measures.) because if there is power to the electromagnetic lock, the door it is mounted to will remain locked and prevent egress.

Installation Options

The magnetic lock is suitable for both in-swinging and out-swinging doors, but not bi-swinging doors. Brackets (L bracket, LZ bracket, U bracket) are used to orient the armature for use with both applications.

Electromagnets are typically mounted on the secured side of the door or on the interior side if the door to protect the electromagnet from attack or exposure to the elements. The cables to the electromagnet should likewise be installed in such a way as to protect them from attack, damage or the environment.

There are, however, attack resistant electromagnetic locks and locks designed for exterior applications such as gates.

Brackets and accessories are available to adapt electromagnetic locks to a variety of mounting scenarios. Some accessories are designed to be adaptable to a variety of locks and armatures, while others are device specific.

The frame and door hosting the electromagnetic lock and armature must provide a rigid and strong mounting environment to reduce the possibility of the bond be broken by door/frame movement or oscillation.

Codes and Approvals

A prerequisite for code compliance with electromagnetic locks is that the lock and associated components are UL Listed for the purpose they are being used. For example a maglock may carry a label indicating it is a “Listed Auxilliary Lock.” A four-letter code may identify the items product category and the types of tests the item was subjected, for example “GWXT.”

Some items used in a locking system must be combined with other items in order for them to operate. These items must be UL recognized which ascertains the context into which the item is used.

Electromagnetic locks are also certified to meet certain performance standards, often an ANSI or BHMA standard.

UL may actually perform the certification testing as a third party for the manufacturer of the equipment. The first ANSI standard for electromagnetic locks was published around 1991, many years after electromagnetic locks were put into service.

Once the electromagnetic locking system is installed, the LAHJ actually approves the installation. Experience is a valuable asset when working with electromagnetic locks, but the LAHJ is the ultimate source for determining if an electromagnetic locking solution may be deployed.

The installer must determine whether a maglock is appropriate for an application by considering factors besides whether it can be physically mounted on the opening.

Electromagnetic locking devices are a dynamic product group with different models and features being introduced, and building Codes undergoing regular revisions as to their suitability for an application or building occupancy. An expansive library of resources is available to the locksmith to guide him or her through the entire process of specification design and installation.

Here are three key considerations:

1. Is the opening suitable for an electromagnetic with regards to functionality, building and life safety codes? Remember: The LAHJ has the final word.
2. Is the door on which you are intending to use the electromagnetic lock robust enough and structurally sound and working properly? If the door flexes due to wear or it does not offer a physical barrier or if the frame is not strong or properly anchored in the surrounding wall, the maglock will not correct these shortcomings. If the maglock is not properly mounted, and all fasteners are not tightened and thread lock used, the maglock may wind up being more a liability than an asset.
3. The electronic control circuits for the electromagnetic lock must be properly designed to ensure a code compliant installation, and safe operation after analysis of possible failure modes that may occur which would impede safe egress from the structure. This means that the control circuit must address more than providing the rated voltage and current. In most building codes, the power to the electromagnetic lock must also under be under control of the premises fire alarm for egress in fire emergencies. Other controls and safeguards should be in place to ensure immediate egress in other situations where the fire alarm may not be in an alarm.

These three things are matters of law and it is your responsibility to be sure your installations are in compliance with the law.