A 24V power supply for automation may feed a PLC, sensors and solenoid valves, but those loads do not behave as one uniform current demand. A controller can reset during a valve transition even when the arithmetic average looks comfortably below the supply rating. The useful starting point is a branch and operating-state record, not a larger wattage chosen without explanation.
The source-controlled WEHO NDR-120-24 provides the worked product boundary here: 24V, 5A and a documented 120W nominal output. It is a DIN-rail supply, not a complete control system. Its rating does not identify the connected loads, protective devices or acceptance criteria for a particular machine.
Divide the device list into meaningful branches
Record PLC and communication equipment separately from field sensors and actuators. For every device, retain the manufacturer’s current information, acceptable input-voltage range and relevant startup behaviour. Do not use the output-switching capacity of a sensor as if it were the sensor’s own supply current.
Then describe the machine states: power-on, communication establishment, normal production, maximum simultaneous valve operation and fault recovery. Devices that never operate together should not be silently treated as simultaneous; devices that can overlap during transitions should not be excluded because the normal sequence is different.
| Branch | Information to obtain | Acceptance observation |
|---|---|---|
| PLC and communications | Startup current and permitted voltage at the input terminals | Controller and network behaviour during transitions |
| Sensors | Actual supply consumption, polarity and signal-interface requirements | Stable readings during actuator switching |
| Solenoids | Coil voltage, pickup/holding demand and switching arrangement | Pickup without unacceptable shared-rail disturbance |
Check the voltage at the load, not only at the supply
A good terminal reading at the power supply does not prove the same voltage reaches a remote device. Review conductor length, both outgoing and return paths, connections and the actual simultaneous current. Set the measurement points in advance so the test record can be reproduced.
A shared return path can also complicate interpretation. Do not redraw an application with arbitrary wires or imply that a signal reference can be connected anywhere. The equipment designer must define the return, protective earthing and interface arrangement. A product photograph is identity evidence, not an approved wiring diagram.
Use the exact NDR mounting evidence
The controlled mechanical sheet records a 40mm rail-axis width, 125.2mm upright height and 113.5mm front-to-back depth. Those axes matter when allocating panel space. Cable bending room, terminal access and thermal clearance are additional requirements, not included in the body envelope.
The original specimen is a ventilated metal enclosure. Its mounting relationship is rear-to-rail; the front face must not be attached to the rail in a generated scene. Nor should a plastic generic housing or an invented fan be substituted. The surrounding equipment needs enough separation to make the installation and maintenance relationship credible.
Release the ordered revision, not a mixed specification
The physical input label and documentary operating-range text differ in the available sources. The public product page also contains inconsistent case and input descriptions. This guide uses the supported 24V/5A output boundary and does not turn conflicting input language into an installation promise. Obtain a controlled electrical sheet for the ordered unit before energised acceptance.
Built-in protection is not evidence of selective downstream protection. A fault on one branch may affect other loads unless the distribution design and actual protective arrangement have been evaluated. Likewise, an ordinary NDR supply is not automatically a battery charger or UPS because a cabinet contains a battery elsewhere.
A practical procurement release
Attach the branch table, worst-case simultaneous state, input conditions, panel layout and intended restart test to the enquiry. Record the exact model and revision on the drawing and purchase order. During acceptance, compare remote voltage and controller behaviour at the defined points, rather than checking only that the supply indicator lights.
Should actuator demand always be added to PLC demand?
Use the real operating sequence, including overlaps and fault states. Do not invent diversity that the control program cannot guarantee.
Does a 5A label establish transient compatibility?
No. Startup and switching behaviour require exact load information and a controlled system test.
What information should WEHO receive?
The device list and operating states, site input and enclosure conditions. That supports a specific model discussion rather than an unqualified “24V automation” recommendation.
Official NDR-120 product reference; use the exact original and mechanical sheet in this draft for physical comparison.
