Elevator shunt trip is one of the most frequently misunderstood elevator and fire alarm interfaces. In simple terms, elevator shunt trip is used to remove operating power from an elevator before sprinkler water can be discharged onto elevator equipment where energized equipment and water could create an unsafe condition.
The important distinction is that elevator recall and elevator shunt trip are not the same function. Elevator recall is normally initiated by smoke detection and sends the elevator to a designated or alternate recall level. Elevator shunt trip is an elevator power shutdown function associated with sprinkler protection in specific elevator spaces.
Where elevator hoistways, machine rooms, control rooms, or control spaces containing elevator equipment are protected by automatic sprinklers and elevator power shutdown is required, the system must be arranged to disconnect elevator power before sprinkler water creates an unsafe condition. NFPA 72 Section 21.4 provides the fire alarm interface requirements for this elevator power shutdown function.
What Is Elevator Shunt Trip?
An elevator shunt trip system automatically opens the elevator's main power disconnect when required by the applicable elevator, building, electrical, and fire alarm codes.
The purpose is not simply to turn off the elevator during a fire. The purpose is to coordinate elevator power shutdown with sprinkler operation so that water is not discharged onto certain energized elevator equipment while the elevator remains capable of movement.
A typical elevator shunt trip sequence may include:
- A heat detector or other approved initiating method operates in a sprinkler-protected elevator space.
- The fire alarm system processes the elevator shutdown signal.
- A listed relay or control interface operates the elevator shunt-trip disconnecting means.
- Main operating power to the affected elevator is disconnected.
- The disconnecting means remains open until it is manually restored in accordance with elevator and electrical system requirements.
The exact sequence must be coordinated between the fire alarm contractor, electrical contractor, elevator contractor, sprinkler contractor, engineer, and Authority Having Jurisdiction (AHJ).
Elevator Recall vs. Elevator Shunt Trip
Elevator recall and elevator shunt trip work together as part of the overall elevator emergency-control strategy, but they perform completely different functions.
| Function | Typical Initiating Device | Primary Purpose |
|---|---|---|
| Elevator Recall | Smoke detection or other permitted automatic detection | Moves the elevator to the designated or alternate recall level |
| Elevator Shunt Trip | Heat detection, pressure/waterflow initiation, or another approved method where applicable | Disconnects elevator operating power before sprinkler discharge creates an unsafe condition |
For a complete explanation of recall operation, see our Elevator Recall and Shunt Trip Explained guide.
When Is Elevator Shunt Trip Required?
Shunt trip is generally associated with elevators where automatic sprinklers are installed in elevator hoistways, machine rooms, control rooms, control spaces, or similar elevator equipment locations and the application of sprinkler water could create an unsafe operating condition.
The International Building Code requires elevator power shutdown where specified elevator spaces containing elevator equipment are protected by automatic sprinklers. The shutdown arrangement is coordinated through NFPA 72 Section 21.4.
This means you should not determine whether shunt trip is required simply by asking whether the building itself is sprinklered.
Instead, determine:
- Whether sprinklers are installed in the applicable elevator space.
- Where the sprinkler is located.
- Whether elevator equipment could be exposed to sprinkler water.
- Whether the elevator is a standard passenger elevator, Fire Service Access Elevator, Occupant Evacuation Elevator, or another elevator type.
- Which editions of the building, fire, elevator, electrical, sprinkler, and fire alarm codes have been adopted by the jurisdiction.
2024 IBC Requirements for Elevator Shunt Trip
IBC Section 3005.5 addresses elevator shunt trip.
Where elevator hoistways, machine rooms, control rooms, and control spaces containing elevator control equipment are protected by automatic sprinklers, the IBC requires a means arranged in accordance with NFPA 72 Section 21.4 to automatically disconnect main-line elevator power before the application of water.
The disconnecting means is also required to be non-self-resetting. In other words, power should not automatically restore when the fire alarm initiating condition clears.
Sprinkler activation elsewhere in the building is not intended to indiscriminately shut down elevator power. The shutdown function is associated with sprinkler protection affecting the elevator equipment areas addressed by the applicable code.
NFPA 72 Section 21.4: Elevator Power Shutdown
NFPA 72 Chapter 21 covers emergency control function interfaces. Section 21.4 specifically addresses Elevator Power Shutdown.
Heat Detectors Used for Shunt Trip
When heat detectors are used to initiate elevator power shutdown, they must be selected and arranged so that elevator power is removed before sprinkler operation.
The heat detection must be coordinated with the sprinkler system so that the detector operates sooner than the sprinkler under the conditions anticipated by the design.
NFPA 72 requires heat detection used for this purpose to have a lower temperature rating and greater response sensitivity than the associated sprinkler.
24-Inch Heat Detector Placement
When spot-type heat detectors are used for elevator power shutdown, NFPA 72 requires them to be located within 24 inches of each sprinkler associated with the shutdown function unless an approved engineering method is used to demonstrate that the required operating sequence will occur.
This is why elevator machine rooms and hoistways may have heat detectors positioned immediately adjacent to sprinkler heads rather than laid out using ordinary area heat-detector spacing.
Waterflow or Pressure Switch Initiation
Where an approved pressure switch or waterflow switch is used to initiate elevator power shutdown, NFPA 72 does not permit the use of a time-delay function in that initiating path.
This is very different from ordinary sprinkler waterflow alarm applications where retard or time-delay arrangements are commonly encountered.
Can Elevator Shunt Trip Be Delayed?
Some elevator shutdown designs using heat detection may incorporate a coordinated delay intended to provide additional opportunity for the elevator to complete recall before power is removed.
However, this is not a universal permission to program an arbitrary shunt-trip delay. The sequence must remain coordinated with the elevator safety requirements so that power is removed before sprinkler water creates the hazardous condition the shutdown function is intended to prevent.
Any proposed delay should therefore be reviewed with the elevator contractor, design engineer, and AHJ.
If a pressure or waterflow switch is being used as the elevator shutdown initiating device, the NFPA 72 restriction on time-delay capability still applies.
Shunt Trip Control Circuit Supervision
This requirement is frequently overlooked in both design and installation.
The control circuit used to operate the elevator disconnecting means must be monitored for the presence of the operating voltage needed to perform the shutdown function.
If that operating voltage is lost, the fire alarm system must indicate the required supervisory condition so building personnel know that the elevator shutdown function may no longer be available.
A typical addressable fire alarm installation may use a monitor module and appropriately listed relay or interface arrangement to supervise the availability of the shunt-trip control voltage.
Smoke Detectors Do Not Normally Initiate Elevator Shunt Trip
One of the most common design mistakes is assuming that the smoke detector used for elevator recall should also operate the shunt-trip breaker.
These are separate functions.
Smoke detection is generally associated with elevator recall.
Heat detection or another approved sprinkler-related initiating method is generally associated with elevator power shutdown.
The final design must follow the adopted elevator, fire alarm, building, sprinkler, and electrical codes for the project.
Fire Service Access Elevators and Occupant Evacuation Elevators
Fire Service Access Elevators and Occupant Evacuation Elevators require special treatment and should not be designed using the ordinary passenger-elevator shunt-trip assumptions.
Under the 2024 IBC:
IBC Section 3007.4 prohibits installing the ordinary elevator shutdown means described by Section 3005.5 on Fire Service Access Elevators.
IBC Section 3008.4 provides the corresponding restriction for Occupant Evacuation Elevators.
The IBC also restricts automatic sprinklers in their associated elevator hoistways and specified elevator equipment spaces.
Always identify the elevator type before designing the fire alarm interfaces.
Elevator Pit Sprinklers and Shunt Trip
Elevator pits create another common area of confusion because the required shutdown arrangement depends on the sprinkler location, elevator configuration, adopted elevator code, and applicable exceptions.
A sprinkler located very low in an elevator pit can be treated differently from a sprinkler located higher in the hoistway because the potential for sprinkler discharge to affect energized elevator equipment is different.
For a detailed explanation, see:
Do You Need a Heat Detector in the Elevator Pit?
California Elevator Shunt Trip Requirements
California deserves special attention because elevator installations are regulated by the California Division of Occupational Safety and Health, commonly known as Cal/OSHA, through its Elevator Unit, in addition to the applicable California Building Standards Code.
Older guidance sometimes stated that elevator shunt-trip equipment had to be located outside the elevator machine room. That is not an accurate blanket statement under current California Elevator Unit guidance.
The California Elevator Unit issued a memorandum clarifying the location of shunt-trip equipment.
California permits shunt-trip devices that are incorporated into the design and function of the listed equipment serving as the single main-line disconnecting means to be located in elevator machine rooms, control rooms, and control spaces.
However, shunt-trip equipment that is not incorporated into that listed single disconnecting means is treated differently and is not permitted by that Elevator Unit policy to be located in those elevator equipment spaces.
See the official California Elevator Unit memorandum here:
California Elevator Unit – Location of Shunt Trip Equipment
California projects should also be reviewed against the current edition of the California Building Standards Code and any local amendments adopted by the AHJ.
Where Should the Elevator Shunt Trip Disconnect Be Located?
There is no universal rule stating that every elevator shunt-trip disconnect or breaker must always be located in one particular location.
Location depends on the electrical code, elevator code, equipment listing, elevator configuration, jurisdiction, and whether the shunt-trip components are incorporated into the elevator's listed main-line disconnecting means.
For California installations, follow the California Elevator Unit guidance described above rather than relying on the older assumption that every shunt-trip device must automatically be located outside the machine room.
Resetting an Elevator Shunt Trip Disconnect
Elevator power shutdown is intended to be a non-self-resetting function.
After the initiating condition has been investigated and the fire alarm and elevator systems are ready to be restored, the elevator disconnect must be manually restored using the proper procedure for the specific listed equipment.
Do not assume that resetting the fire alarm control unit should automatically restore elevator power.
Restoration should be performed by qualified personnel in accordance with the elevator equipment manufacturer's instructions, electrical safety requirements, elevator contractor procedures, and AHJ requirements.
Who Is Responsible for the Elevator Shunt Trip Wiring?
Responsibilities vary by project, but the interface normally involves several trades.
| Trade | Typical Responsibility |
|---|---|
| Fire Alarm Contractor | Initiating devices, monitor modules, control modules, relay interfaces, programming, annunciation, and fire alarm testing |
| Electrical Contractor | Elevator disconnect and shunt-trip power wiring and associated electrical distribution work |
| Elevator Contractor | Elevator controller interface, recall operation, elevator safety functions, and elevator-side testing |
| Sprinkler Contractor | Sprinkler locations, temperature ratings, waterflow or pressure interfaces where applicable, and sprinkler system coordination |
The construction documents should clearly identify responsibility rather than leaving the trades to determine the interface during final testing.
Typical Elevator Shunt Trip Sequence of Operations
A common sequence for a sprinkler-protected elevator equipment space may look like this:
- Smoke detection initiates elevator Phase I recall when required.
- The elevator begins traveling toward the applicable recall level.
- A heat detector associated with the sprinkler operates.
- The fire alarm system initiates the approved elevator power-shutdown sequence.
- The shunt-trip disconnect removes the required elevator operating power before sprinkler discharge creates an unsafe condition.
- The fire alarm system supervises the availability of the shutdown control circuit.
- Elevator power remains disconnected until manually restored by qualified personnel.
This is only a general example. The project-specific sequence must match the elevator type, sprinkler configuration, adopted codes, equipment listings, engineering documents, and AHJ requirements.
Common Elevator Shunt Trip Design Mistakes
- Using the elevator recall smoke detector to initiate shunt trip.
- Installing the shunt-trip heat detector using ordinary room spacing instead of coordinating it with the sprinkler.
- Failing to supervise shunt-trip control voltage.
- Using an improper delay on a waterflow or pressure-switch shutdown circuit.
- Allowing sprinkler operation elsewhere in the building to shut down elevator power.
- Assuming every sprinklered building automatically requires elevator shunt trip.
- Failing to distinguish standard elevators from Fire Service Access Elevators or Occupant Evacuation Elevators.
- Failing to coordinate sprinkler temperature ratings and heat detector response characteristics.
- Failing to coordinate fire alarm, electrical, sprinkler, and elevator contractor responsibilities.
- Using outdated California guidance regarding shunt-trip equipment location.
Elevator Shunt Trip Wiring
This article focuses on the code requirements and operating principles behind elevator shunt trip.
For the actual fire alarm control wiring and relay arrangement, see:
How to Wire Elevator Shunt Trip
If you are looking specifically for a diagram, see:
Elevator Shunt Trip Wiring Diagram
Codes and Standards Commonly Used for Elevator Shunt Trip
Elevator power shutdown is a coordinated function involving several different codes and standards rather than a single fire alarm section.
Common references include:
- NFPA 72 – Section 21.4, Elevator Power Shutdown
- International Building Code – Section 3005.5, Shunt Trip
- ASME A17.1/CSA B44 – Safety Code for Elevators and Escalators
- NFPA 70 / NEC Article 620 – Elevators and associated disconnecting means
- NFPA 13 – Sprinkler protection and sprinkler installation requirements
- California Title 24 and California Elevator Safety Orders for California projects
Always verify the exact code editions adopted by the project jurisdiction. A project designed under an older adopted code cycle may not use the same edition referenced by a newly permitted project.
Final Elevator Shunt Trip Checklist
Before approving an elevator shunt-trip design, confirm:
☐ Is sprinkler protection installed in the applicable elevator space?
☐ Is elevator power shutdown actually required for that location?
☐ Is the elevator type clearly identified?
☐ Are recall and shunt trip being treated as separate functions?
☐ Is heat detection properly coordinated with each applicable sprinkler?
☐ Are heat detector temperature and response characteristics coordinated with the sprinkler?
☐ Is the shutdown control circuit supervised for operating voltage?
☐ Are prohibited time delays avoided?
☐ Is the disconnecting means non-self-resetting?
☐ Have the fire alarm, electrical, elevator, and sprinkler contractors coordinated responsibilities?
☐ Have the applicable adopted codes and local amendments been confirmed?
More Elevator Fire Alarm Resources
Continue learning with these Fire Alarms Online resources:
Elevator Recall & Shunt Trip Explained
Elevator Recall & Shunt Trip Fundamentals
How to Wire Elevator Shunt Trip
Elevator Shunt Trip Wiring Diagram
Is a Heat Detector Required in the Elevator Pit?
