Fail-Safe vs Fail-Secure Electric Locks: What Installers Need to Know
Essential Security Supplies
Choosing between fail-safe and fail-secure operation affects access, security, egress, power supply, and emergency release. For installers, the correct choice depends on what the door must do during a power failure, fire alarm condition, access-control fault, or normal credential-controlled entry.
This guide compares electric locking examples from FSH, Lockwood, Trimec, dormakaba, and Securitron, with practical checks for strikes, mortice locks, V-Locks, and gate locks used in commercial access-control installations.
Why power loss is a design decision, not just a lock setting
Fail-safe and fail-secure describe the lock's behaviour when electrical power is removed. They do not describe the strength of the lock, the quality of the access-control system, or whether a door is automatically compliant for every application.
Before selecting the hardware, confirm the required security state, the required exit behaviour, the door construction, the access-control voltage, the fire strategy, and any mechanical override or emergency release requirements.
Fail-safe and fail-secure in plain installer terms
Fail-safe means power to lock
A fail-safe lock is released when power is removed. It is commonly described as power-to-lock, or PTL, because electrical power is used to keep the lock secured.
When power is interrupted, the door may release from the controlled side. This can support applications where maintaining a free release condition during a power failure is important, but it also means security can be reduced while the lock is unpowered.
Fail-safe operation may be appropriate for selected exit routes, some internal doors, areas where automatic release is required during a fire alarm condition, and locations where the risk of people being unable to leave is greater than the risk of unauthorised entry during a power outage.
It is not a substitute for a complete fire and egress design. The lock, door hardware, emergency release equipment, alarm interface, backup power arrangement, and building use must be considered together.
Fail-secure means power to open
A fail-secure lock remains locked from the controlled side when power is removed. It is commonly described as power-to-open, or PTO, because power is applied to release the lock.
This can preserve access security during a power outage, but the door still needs a compliant way to allow authorised exit. Depending on the door, that may involve a mechanical lever, panic hardware, key override, request-to-exit device, or another approved release arrangement.
Fail-secure does not mean that occupants should be trapped behind the door. It means the electrically controlled locking function stays secure when power is lost. The independent exit method must still be available, usable, and appropriate for the installation.
Where each operating mode usually fits
| Requirement | Typical direction to investigate | Installer considerations |
|---|---|---|
| Release on loss of power | Fail-safe, power-to-lock | Confirm that releasing the door during a power failure is acceptable for the area and access-control strategy. |
| Maintain controlled access during a power failure | Fail-secure, power-to-open | Confirm that mechanical exit, key override, panic hardware, or another approved release method remains available. |
| Door connected to a fire alarm or emergency release system | Often fail-safe, but not automatically | Follow the approved fire and egress design. Do not select the lock mode from the alarm interface alone. |
| External or weather-exposed door | Either mode, subject to hardware suitability | Check the lock's IP rating, drainage, mounting position, cable protection, voltage drop, and environmental limits. |
| High-security internal access | Often fail-secure | Check the door's free-exit arrangement, cylinder or key override, monitoring requirements, and emergency procedures. |
| Gate or perimeter access | Either mode, based on the gate's security and emergency-release requirements | Check preload, gate sag, alignment, weather exposure, vehicle or pedestrian use, manual override, and monitoring. |
Match the lock type to the door and use case
Electric strikes for latch-controlled doors
An electric strike is installed in the frame and controls the release of a mechanical latch or lock tongue. This makes it useful where the existing lockcase, lever furniture, or cylinder arrangement should remain part of the door hardware.
Check the frame preparation, latch projection, door handing, keeper depth, preload, voltage, current draw, and whether the strike is designed for fail-safe, fail-secure, or field-selectable operation.
The active FSH FES10M is an ANSI-footprint electric strike with field-selectable fail-safe or fail-secure operation, 12/24VDC input, and a door latch sensor. The dormakaba KES2200 is a heavy-duty monitored strike with interchangeable fail-safe and fail-secure operation, monitored latch, keeper and solenoid status, and solid stainless steel construction.
Electric mortice locks for integrated door control
An electric mortice lock provides a more integrated locking solution inside the door. It can be suitable where the access-control system needs lock, door-position, latch, or request-to-exit feedback in one assembly.
Lockwood 3782ELNZSS and 4782ELNZSS Selector electric mortice locks provide field selection between power-to-lock, or fail-secure, and power-to-open, or fail-safe, operation. The 3782ELNZSS has a 23mm backset, while the 4782ELNZSS has a 25.4mm backset.
The Lockwood range includes monitoring for request to exit, deadlatch, door position, key override, and locked status. The motor-driven design supports lower power usage in power-to-lock applications, and the product record lists reader-in and reader-out functions where the external side can fail securely while the internal side fails safe for free egress.
Mortice-lock installations require accurate preparation and alignment. Check the door thickness, lockcase dimensions, furniture compatibility, cable transfer, latch engagement, cylinder requirements, and any fire-rated door documentation before cutting the door.
V-Locks and drop bolts for alignment-sensitive doors
V-Locks and drop bolts are useful when the locking point needs to secure the door at a different position from a conventional latch. They can be suited to selected glass, aluminium, metal, or heavy-door applications, but alignment and door movement are critical.
The Trimec ES8100 V-Lock provides one-step field selection between fail-safe and fail-secure operation. It uses a motorised bolt and V-shaped strike plate to help pull the door into alignment, with up to 12mm total misalignment correction and unlocking under preload of up to 100kg in the listed configuration.
The ES8100 also includes door-position and lock-status monitoring, IP53 weather resistance, 11.4-26VDC operating voltage, a listed 1,000kg holding force, and vertical or horizontal mounting options. It must not be mounted in the floor.
Gate locks for perimeter and vehicle access
Gate locks need a different installation assessment from standard door strikes. Gate sag, preload, wind loading, vehicle impact, weather exposure, pedestrian movement, and manual release all affect the result.
The active Securitron SGL1 gate-lock range includes fail-secure non-monitored, fail-secure monitored, and fail-safe monitored variants. The product record lists 907kg holding force, operation under preload up to 45kg, automatic dual voltage, a self-aligning receiver with horizontal adjustment, surface mounting, and indoor or outdoor use.
The SGL1-FL is the fail-secure non-monitored variant, SGL1-FLM is fail-secure monitored, and SGL1-FSM is fail-safe monitored. Select the variant only after confirming how the gate must behave during loss of power and how manual release will be handled.
Installation checks that prevent callbacks
Confirm the door or gate's exit behaviour first
Before choosing the lock mode, confirm how a person exits the area during normal operation, a power failure, a fire alarm, a controller fault, and a failed credential reader. A door that is electrically secure from the entry side still needs a reliable exit method.
For New Zealand projects, review the door and access-control arrangement against the current MBIE Building Code fire provisions and the project's approved fire and egress design. The correct lock mode depends on the complete installation, not just the product label.
Verify voltage, current, and cable capacity
Check whether the lock requires 12VDC, 24VDC, AC, or a selectable range. Confirm the start or inrush current, holding current, power-supply capacity, battery support, fuse protection, and voltage at the lock under load.
Long cable runs can create voltage drop that causes intermittent release, incomplete bolt retraction, nuisance alarms, or unreliable monitoring. Size the power supply and cable run from the actual lock data, not from the controller output rating alone.
Lockwood 3782EL models list a variable 9-28VDC supply range and a three-wire control arrangement that can help keep the lock less susceptible to voltage-drop issues across long wiring runs. The Trimec ES8100 lists an 11.4-26VDC operating range, with peak current of 1,000mA and idle current of 35mA at 12VDC with the LED activated.
Check alignment, preload, and door movement
Even a correctly selected lock can fail if the door is sagging, the frame is moving, the latch is under pressure, or the bolt is not aligned with the keeper. Check clearances with the door closed and latched, then test the lock under the real door load.
For V-Locks and drop bolts, confirm that the bolt can extend fully without hitting the strike plate or frame. For electric strikes, check that the latch is not forcing the keeper under preload. For gate locks, test alignment with the gate both closed and under normal operating pressure.
Decide whether monitoring is required
Non-monitored hardware can release the door or gate, but the controller may not know whether the door is closed, whether the latch is engaged, or whether the bolt has reached its locked position.
Monitored hardware can provide valuable status information for alarms, access logs, interlocking, building management, and fault finding. The FSH FES10M includes a door latch sensor, the Lockwood 3782EL provides multiple lock and door status points, the Trimec ES8100 monitors lock status and door position, and the Securitron SGL1-FLM and SGL1-FSM variants provide monitored gate-lock options.
Confirm manual override and emergency release
Check whether the installation requires a key cylinder, mechanical lever, panic device, request-to-exit input, emergency break-glass device, fire alarm interface, or local release button. Confirm how each device behaves when power is lost and whether the release arrangement can be tested without compromising the building's normal security.
Product Specifications
The following examples are drawn from active electric-lock product records in the Essential Security Supplies catalogue. Always confirm the latest manufacturer documentation and the exact model configuration before installation.
| Specification | Detail |
|---|---|
| FSHFES10M, FSH | ANSI-footprint, mortice-mounted electric strike. Field-selectable fail-safe or fail-secure operation, 12/24VDC, listed 200mA at 12VDC, monitored with a door latch sensor, and listed weight of 1.3kg. |
| 3782ELNZSS, Lockwood | Electric mortice primary lock with 23mm backset. Field-selectable power-to-lock, or fail-secure, and power-to-open, or fail-safe, operation. Variable 9-28VDC supply, 15mm stainless steel latch bolts, monitoring for REX, deadlatch, door position, key override, and lock status, 35-50mm metal door thickness, 32-50mm timber door thickness, -15 to 60 degrees Celsius operating environment, and stainless steel finish. |
| 4782ELNZSS, Lockwood | Electric mortice primary lock with 25.4mm backset. Field-selectable fail-safe or fail-secure operation, 9-28VDC supply range, motor-driven operation, 3.6m supplied cable with 12-pin connector, multiple monitoring outputs, and stainless steel finish. |
| ES8100, Trimec | Motorised V-Lock with field-selectable PTL or PTO operation. 11.4-26VDC, up to 1,000kg holding force, IP53, up to 100kg unlocking preload in the listed configuration, up to 12mm total door misalignment correction, door-position and lock-status monitoring, vertical or horizontal mounting, 500,000-cycle durability listing, stainless steel construction, and body dimensions of 210mm by 24mm by 42mm. |
| KES2200, dormakaba | Heavy-duty monitored electric strike with interchangeable fail-safe and fail-secure operation. 12-24VDC listed in the product description, suits latch depth up to 15mm, monitors latch, keeper, and solenoid status, includes mounting tabs for metal frames, supports optional lip extensions, and uses solid stainless steel construction. |
| KES100, dormakaba | ANSI-size electric strike with interchangeable fail-safe and fail-secure operation. Dual-voltage 12/24VDC, 16mm keeper allowing 19mm latch throw, 700kg listed holding force, long faceplate for timber-frame installation, trim plate, and optional lip-extension brackets. |
| SGL1, Securitron | Electromechanical gate-lock platform with SGL1-FL fail-secure non-monitored, SGL1-FLM fail-secure monitored, and SGL1-FSM fail-safe monitored variants. Listed 907kg holding force, operation under preload up to 45kg, automatic dual voltage, self-aligning receiver with plus or minus 12mm horizontal adjustment, surface mounting, black finish, and listed 2.72kg shipping weight. |
| SMUNL, Securitron | Mortise UnLatch electric strike with field-adjustable latch and deadlatch positions, release under preload, latch-status monitoring output, 10-30VDC input, 40mA continuous current with at least 700mA operating current at 12VDC, 680kg listed holding force, and operating temperature of -29 to +52 degrees Celsius. Confirm the required operating mode from the project specification. |
| Product pages and model-specific data | View our product for FSHFES10M, View our product for Lockwood 3782ELNZSS, View our product for Trimec ES8100, View our product for dormakaba KES2200, and View our product for Securitron SGL1. |
Installer decision checklist
- Confirm whether the door or gate must release or remain secure when power is lost.
- Confirm the independent exit method for fail-secure applications.
- Check the door or gate type, frame preparation, latch geometry, handing, and available mounting space.
- Verify voltage, start current, holding current, voltage drop, power-supply capacity, and battery support.
- Decide whether door, latch, bolt, gate, or lock-status monitoring is required.
- Confirm mechanical override, request-to-exit, emergency release, and fire alarm interfaces.
- Check IP rating and environmental suitability for external or weather-exposed locations.
- Check preload, misalignment, sag, and closing pressure before selecting the lock type.
- Test the complete door or gate under real operating conditions, including power loss and emergency release.
- Record the selected operating mode and emergency-release method for the client and future service work.
The short version
Choose fail-safe when the design requires the lock to release on loss of power, and choose fail-secure when the design requires the controlled side to remain secure without power. Then verify the exit path, fire strategy, door hardware, power supply, monitoring, alignment, and emergency release as one complete system.
FSH, Lockwood, Trimec, dormakaba, and Securitron all offer different ways to achieve this, including field-selectable hardware, monitored strikes, integrated mortice locks, motorised V-Locks, and gate-lock variants. The best choice is the one that matches the door, the risk profile, and the approved access and egress design.
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