Codes are often neglected with electromagnetic locks

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Thursday, July 1, 2004

When employing electromagnetic locks, doors generally do not have a door-mounted manual latch release. Because of the absence of a manual latch release, the NFPA has established The Life Safety Code 7.2.1.6.2 , otherwise known as “Access-Controlled Egress Doors.” The intention of these codes is to ensure safe egress through an access-controlled door during a fire, even when vital electronic components of an access control system fail to respond.

A quick overview

The first section of the code requires that a device be added to the opening that unlocks the electromagnetic lock during normal times of egress. The code specifies that this device can either be a PIR detector or a listed panic hardware device that when operated, de-energizes the electromagnetic lock. The PIR sensor is often used because it may be less complicated to install. It is normally mounted above the door and is configured to unlock the door when a person approaches.

The second part of the code specifies that loss of power to the access control system should automatically unlock the door. Many access control systems use a power supply that is common to the electromagnetic lock. In this case, if power is lost at the access control, the power will similarly be lost at the lock. Since an electromagnetic lock is inherently fail-safe, the code is met.

Sections three, four and five of the code are unbeknownst to many professionals and are regularly ignored. However, these codes are extremely important. They describe a manual release device that must be used in conjunction with the electromagnetic lock. Considering that the PIR sensor is directly connected to the access control system, there is no way to de-energize the lock if the control system fails. Since there is no door mounted manual release with electromagnetic locks, a pneumatic push switch is used to directly cut the power to the lock.

A pneumatic switch is a timer that operates using the internal flow of air. This switch has a valve that when adjusted can keep the switch activated for a set amount of time. Section five of the code states that when operated, the manual release device shall result in the direct interruption of power to the lock, independent of the access control system electronics, for a time not less than 30 seconds in length. The pneumatic switch is used because it is the only device that can perform the timing, according to the NFPA, independent of the access control system electronics. When this type of switch is installed with an electromagnetic lock, all of the access control electronics can fail, but a user can still rely on the pneumatic switch as a backup.

Sections three and four specify that the manual release device must be installed between 40 and 48 inches above the floor and can be no more than 60 inches from the secured doors. It must also be labeled with the words “push to exit.”

Sections six and seven of the code are applicable when the building has a fire protection system. The fire or sprinkler alarm must be interfaced to the power supply of the electromagnetic lock. During a fire alarm, the power to the electromagnetic lock is cut, allowing all doors to unlock automatically. This unlocked condition is maintained until the fire signaling system is manually reset.

Don’t go it alone

I urge you to consult with the Life Safety Code and your local AHJ if there are questions concerning the safe operation of the locking system you are specifying. A small amount of research is likely to ensure that the lock system you install is safe rather than a tragedy waiting to happen. Using electromagnetic locks can be safe, reliable and can facilitate convenient egress.

Daniel DeMerchant is the vice president of Highpower Security Products. DeMerchant can be reached via email at hpsp@mindspring.com.