Last Updated: September 27, 2026
Respuesta rápida: For a 24V elevator or escalator control panel, the WEHO NDR-120-24 provides a documented 24V/5A output, or 120W. It can be a practical 24V DIN-rail power supply when the verified simultaneous control load, pickup current, ambient derating, cable drop, and fault strategy all fit within that envelope. It must not be selected from wattage alone, and it is not the motor or drive supply.
Elevator and escalator projects contain several electrical layers. The traction motor or escalator drive has its own engineered power path. A separate 24VDC bus may serve the controller, safety chain interfaces, door devices, relays, indicators, communication modules, sensors, and service equipment. This article addresses that low-voltage control bus only.
That distinction is important for procurement. A request for “a 120W elevator power supply” is incomplete unless it states the AC input, DC output, simultaneous load, transient behavior, panel temperature, required mounting format, branch protection, and the exact product revision. The NDR-120-24 is a slim DIN-rail model, but a correct mechanical fit does not prove that it will support every operating state.
Start with the control architecture
Draw a clear boundary around the loads connected to the 24V supply. Typical groups may include:
- controller and remote I/O;
- landing or car-interface electronics;
- door-position sensors and light curtains;
- relays, contactors, and brake or lock interfaces;
- status lamps, buzzers, and service indicators;
- communication gateways and monitoring devices.
Do not add the traction motor, variable-frequency drive, or other high-power actuator to this calculation. Also do not assume every elevator or escalator uses the same control architecture. Obtain the electrical design and the selected component datasheets for the actual project.
For a first engineering screen, build a state matrix rather than adding only normal-running currents. Relevant states can include standby, startup after a power interruption, door opening, door closing, safety-chain reset, emergency communication, inspection mode, and fault indication. For an escalator, review startup control, normal travel, comb-plate or skirt-safety activation, maintenance mode, and emergency stop recovery.
Convert each operating state into current
The NDR-120-24 specification lists a 24V output up to 5A. The arithmetic ceiling is therefore 120W, but that is not a recommended continuous project load under every condition. A realistic schedule should identify which devices can be active together and which loads have a higher pickup current than holding current.
An illustrative elevator-control state might look like this:
| 24V load group | Example simultaneous current | Power at 24V |
|---|---|---|
| Main controller and I/O | 1.10A | 26.4W |
| Door sensors and safety interfaces | 0.55A | 13.2W |
| Relay and contactor coils | 0.80A | 19.2W |
| Door lock or brake-release interface | 0.65A | 15,6W |
| Indicators and communications | 0.45A | 10.8W |
| Service allowance in the defined state | 0.35A | 8.4W |
| Illustrative total | 3.90A | 93.6W |
These are worked-example values, not ratings for a particular lift. At 3.90A, the simple nameplate comparison leaves 1.10A before considering pickup peaks, temperature, cable drop, tolerances, or later changes. Replace every row with the approved project BOM and prove the credible maximum overlap.
Verify the exact NDR-120-24 revision
The current WEHO specification identifies the NDR-120-24 as a 24V, 5A model. It lists an 85–264VAC or 120–370VDC input range, 47–63Hz for AC input, and 88% efficiency for the 24V variant. The official NDR-120 product page also identifies the 24V/5A model.
The enterprise-drive product photograph has a front label reading NDR-120-24, INPUT 100–240VAC 2.6A 50/60Hz, and OUTPUT 24V 5.0A. Because a photographed label and a family specification can represent different documentation or product revisions, procurement should confirm the ordered unit. Do not silently replace label values with the widest value found in another source.
The specification-controlled exterior dimensions are 40 × 125.2 × 113.5mm. This is the product envelope only. Allow additional room for DIN-rail engagement, conductor bends, terminal access, ventilation, adjacent heat sources, and service removal.
Use the machine-room context to test the real duty
This illustrative elevator machine-room scene visibly places the source-controlled NDR-120-24 in an open control cabinet beside traction equipment. Its narrow 40 × 125.2 mm front and 113.5 mm depth remain consistent with the source, while the adjacent DIN rail and two-pole breaker provide physical scale. The image is not commissioning evidence. An elevator machine room can combine changing ambient temperature, drive heat, restricted cabinet space, electrical noise, and long wiring paths to field devices.
For this environment, confirm the cabinet temperature after the drive and control equipment reach steady operation. Review free-air convection, mounting orientation, separation from heat-producing components, and the derating information for the exact revision. If the panel is sealed or densely populated, the air around the supply may be much warmer than the room.
Electrical disturbances also matter. Verify the input source, protective device, earthing, surge environment, and conducted or radiated compatibility required by the complete control system. A supply can meet its own specification while the assembled panel still fails a system-level test.
Treat pickup current separately from steady current
Relay coils, contactor coils, locks, brake interfaces, communication equipment, and controllers can create a transient demand during startup or state changes. Obtain peak magnitude, duration, and repetition rate. Determine whether multiple peaks can overlap after a mains interruption or safety reset.
If the data is incomplete, measure a representative panel. Monitor the 24V bus at the supply and at the most sensitive remote load while the system moves through the worst credible state. A 3.90A steady calculation does not prove that the output stays within the devices’ minimum-voltage limits during pickup.
Separate an escalator service case from the elevator case
The second illustrative application is deliberately different: a shopping-mall escalator service cabinet during maintenance. The source-controlled NDR-120-24 is shown near-frontally with an approximately 3.1 height-to-width face ratio, while an adjacent two-pole breaker and visible rail provide scale. One negative output position remains unused, so the image must not be read as showing four connected output conductors. It is not commissioning evidence and does not imply that the supply belongs in a public floor opening.
Escalator control loads can include safety switches, skirt or comb-plate interfaces, speed or direction sensing, relays, status indicators, and monitoring equipment. Their operating-state matrix differs from an elevator machine-room panel. Select the product from the actual system schedule rather than transferring the elevator example unchanged.
Calculate cable voltage drop
The supply may be near the controller while sensors, locks, indicators, or communication modules are many metres away. Calculate voltage drop over the complete outgoing-and-return path at the highest credible branch current. Include conductor resistance, connectors, terminals, flexible sections, and expected temperature.
Measure the far-end voltage during the demanding state, not just at no load. Do not use the V-ADJ control to conceal an undersized cable. Raising the source voltage can place nearby devices above their limit while the remote branch still behaves poorly.
Coordinate branch protection and fault behavior
Divide the 24V distribution into documented branches where the design requires it. Select conductors and protection together so a branch fault does not overheat wiring or unnecessarily remove unrelated safety or control functions. Review inductive-load suppression, return-current paths, earthing and bonding, polarity, and the behavior of the controller after a brief DC interruption.
The NDR-120 diagram in the specification shows four upper DC positions—two negative and two positive—and three lower AC positions for protective earth, neutral, and line. These duplicated DC terminals assist distribution but do not provide independent internally protected outputs.
The drawing is a terminal and mechanical reference, not a project wiring diagram. Final wiring, conductor sizing, torque, protection, isolation, and required clearances must follow the approved panel design, the exact ordered unit, and applicable local requirements.
Commission before release
Test the assembled system through the worst credible sequence. For an elevator, this can include mains restoration, controller startup, door movement, safety-chain reset, inspection operation, alarm, and communication activity. For an escalator, include startup, normal travel, maintenance operation, emergency stop, safety-device actuation, and reset.
Record input condition, output voltage at the supply, voltage at the farthest load, steady current, peak current, cabinet temperature, and recovery after transients. Repeat relevant tests after the panel reaches its expected thermal condition. A procurement approval should reference this evidence, not only the 120W family name.
Conclusiones clave
- The NDR-120-24 is documented at 24V/5A, or 120W, but final capacity depends on the actual operating states and installation conditions.
- Keep traction motors and drives outside the 24V control-bus calculation.
- Confirm the exact ordered revision because the source photograph and family specification use different input-range wording.
- Use 40 × 125.2 × 113.5mm only as the exterior envelope; add rail, cable, ventilation, and service clearances.
- Elevator and escalator applications require separate load-state reviews rather than a copied example.
- Verify pickup current, ambient derating, voltage drop, branch protection, and system behavior by measurement before release.
Conclusión
The NDR-120-24 is a credible 24V DIN-rail power supply candidate for elevator or escalator control equipment when a verified project load fits within its 5A output and all dynamic, thermal, wiring, and protection checks pass. Its value is the combination of a compact DIN-rail format and a documented 24V operating point—not a promise that one model suits every vertical-transportation panel. Build the state matrix, confirm the exact revision, and commission the completed system before approving production.
Preguntas frecuentes
Can the NDR-120-24 power an elevator traction motor?
No. This selection example covers a 24V control bus for controllers, sensors, relays, indicators, and related devices. The traction motor and drive require their own engineered power path.
What is the rated output of the NDR-120-24?
The current WEHO NDR-120 specification lists the 24V model at up to 5A, equivalent to 120W by multiplication. Apply the exact revision’s derating and installation limits.
What enclosure size should panel designers reserve?
The documented product envelope is 40 × 125.2 × 113.5mm. DIN-rail engagement, conductor bend radius, terminal access, ventilation, and service removal need additional space.
Why does the product photo show a different input range from the family sheet?
Photographs and specification files can represent different documentation or product revisions. Confirm the exact ordered unit and do not combine the most favorable values from different sources.
Can one load calculation be reused for both elevators and escalators?
No. Their safety devices, operating states, cable paths, and transient loads differ. Build and verify a separate state-based load schedule for the actual system.
What tests should be completed before production release?
Measure supply and far-end voltage, steady and peak current, cabinet temperature, transient recovery, and fault behavior through the system’s worst credible operating sequence.
