Electrified Locksets: Fail-Safe, Fail-Secure, and Free Egress

How It Works

In a standard storeroom or entry lock, a key or button sets whether the outside lever retracts the latch. In an electrified lockset, a small electrical device inside the lock body does that job. When the lock gets the signal, the outside lever is either connected to the latch or freed so it turns without retracting it.

Schlage's ND Series electrified cylindrical lock shows how this is described in practice:

• Powered state: depending on the mode, the outside lever is "continuously locked" or "continuously unlocked" while power is applied.
• Key override: the outside key "retracts latch but cannot change the normal locked or unlocked state of the outside lever."
• Egress: the "inside lever always free for immediate egress."

Schlage also offers electrified versions of its mortise and multipoint locks. Electrified locksets are made in the same main body types as mechanical locks; see cylindrical locks and mortise locks.

Fail-Safe and Fail-Secure

The most important choice in an electrified lock is what happens when power is lost. An NIH technical bulletin defines the terms simply: "Fail safe means when no power is applied the door is unlocked; fail secure means when no power is applied the door is locked."

Manufacturers often use their own labels. Schlage's ND Series uses:

• EL, electrically locked (fail-safe): the lever "will lock when power is applied. In the event of power failure, the opening will be unlocked."
• EU, electrically unlocked (fail-secure): the lever "will unlock when power is applied. In the event of power failure, the opening will be locked."

On the ND Series, the mode can be changed with a switch on the chassis. Other products are ordered in one mode or the other.

The NIH bulletin notes that fail-secure "items use less power because they only require power to unlock the door," while "fail safe products require continual power consumption." It recommends fail-secure for most doors "except where quick entrance is needed in emergency situations." This is one agency's guidance for its own facilities. Which mode suits a specific opening is a design decision, and code questions go to the authority having jurisdiction (AHJ).

Fail-Safe Does Not Mean Unlatched

A fail-safe lockset is different from a fail-safe electromagnetic lock. When a fail-safe lockset loses power, its outside lever is freed, but the latchbolt still projects and latches the door each time it closes. A fail-safe mag-lock, by contrast, simply stops holding.

This matters on fire doors, which must latch. Schlage lists its ND Series electrified lock as "UL listed for 3-hour fire door." Requirements for a particular fire door assembly depend on its listing and labels; see fire-rated door hardware.

Free Egress From the Inside

Most electrified locksets control only the outside lever. The inside lever stays mechanical and always opens the door. I Dig Hardware, quoting the 2021 IBC Commentary, describes this as "the most common application for electrified hardware": an access control reader on the ingress side, "and the door hardware on the egress side allows free egress at all times." Such a door is treated like any door with a mechanical lock controlling entry.

Because of this, an electrified lockset with free egress generally does not fall under the special locking arrangements that apply to electromagnetic locks released by sensors or switches. Some functions lock both levers, and those are a different case for code purposes. See request to exit.

Request-to-Exit Switches

Many electrified locksets can report when the inside lever is used. Schlage's ND Series offers a modular Request to Exit (RX) switch, field-installable with a kit, with normally open and normally closed contacts. On a lockset with mechanical egress, the RX switch tells the access control system that the door was opened from inside. It does not release the lock.

Power and Wiring

Electrified locksets need low-voltage DC power and a wire path into the door. Schlage's ND instructions call for "DC power only. DO NOT USE AC POWER" and list 12 or 24 V DC. Wiring usually crosses the hinge edge through an electrified hinge or electric power transfer device (EPT). Schlage's instructions show connections to "an electrified hinge/EPT."

Exact voltages, current draw, and wiring belong to each product's instructions.

Standards

ANSI/BHMA A156.25 covers electrified locking systems. BHMA summarizes its tests as including under-voltage and over-voltage checks followed by "a slam cycle test of 10,000 cycles," along with selections from UL 1034, the standard for burglary-resistant electric locking mechanisms. The mechanical lock is graded under its own product standard. Schlage says its ND electrified lock exceeds ANSI A156.2 Grade 1 requirements. For reference, the Grade 1 cycle test in ANSI/BHMA A156.2-2022 is 1,000,000 cycles; see ANSI/BHMA lock grades.

Electrified Lockset vs. Electric Strike vs. Mag-Lock

Related Topics

• Cylindrical locks
• Mortise locks
• Lock functions: storeroom, entry, and classroom functions
• Electric strikes
• Electromagnetic locks
• Access control
• ANSI/BHMA lock grades
• Door hinges

Sources