General safety information for PLC, control and control-cabinet components

Important safety information

Unless the specific offer expressly states a different inspection status, used PLC, control and control-cabinet components offered by REHA-Industriekomponenten e.K. are supplied in the condition category “Used, removed from an installation”. In that case, REHA-Industriekomponenten e.K. has not carried out its own electrical inspection or comprehensive operational check.

Before installation and first use, the operator must have appropriately qualified personnel determine, perform and document the required inspections on the basis of the complete component and system identification, the applicable manufacturer documentation, the specific machine or installation and the requirements at the place of use. Installation, release and commissioning may be decided only after this work has been completed.

PLC, control and control-cabinet components may be directly or indirectly connected to lethal voltages, high short-circuit energy and hazardous machine movement.

A cabinet or control system can remain dangerous when the PLC is stopped, indicators are dark, the main switch is off, the network is disconnected, an emergency-stop device is operated or a safety function is shown as active. External supplies, UPS units, auxiliary voltages, externally fed contacts, field devices, other cabinets and stored energy may remain present.

Changes to software, parameters, wiring or modules can energise outputs, operate valves and contactors, start drives or trigger other hazardous machine functions.

This page contains general, non-exhaustive supplementary information only. It is not a work instruction and must never be used as the sole or sufficient basis for selection, connection, installation, inspection, release or commissioning.

Before work begins, the applicable documentation for the complete product version, the documentation for the specific machine or installation and the safety requirements at the place of use must be available, reviewed and followed.

If the exact product version cannot be identified, the applicable manufacturer documentation is unavailable, or there is doubt about condition, assignment, compatibility or connection requirements, the component must not be connected, energised, released or commissioned.

Supplementary manufacturer-independent safety information for business operators and qualified personnel

No connection, wiring, installation, programming, inspection, repair or commissioning instructions

Editorial status: 27 August 2026

For sales through reha-components.com, the product description, order confirmation and the International B2B Terms determine the agreed inspection status and contractual terms.

1. Purpose and limits

This page covers recurring hazards associated with PLCs, motion controllers, standard and safety I/O, bus couplers, HMIs, industrial PCs, power supplies, UPS modules, relays, contactors, protective devices, terminals and industrial network components.

The safe function of a component depends on its selection, enclosure, wiring, software, connected devices and the safety concept of the complete machine or installation.

No terminal or pin assignment, bridge, conductor size, stripping length, fuse rating, tightening torque, earthing measure, output state, software parameter, safety setting or interchangeability statement may be derived from this page.

2. Identify the exact component and project state

Verify the complete manufacturer and order number, hardware and firmware version, supply voltage, module and connector version, safety approval, software and project version, licence and memory media, and all relevant system assignments.

Use the exact manufacturer documentation, current circuit diagrams, I/O lists, network topology, software backups, safety documentation and change history for the specific machine. Similar front labels or mechanical fit do not establish electrical or functional equivalence.

3. Qualified and authorised personnel only

Electrical work, programming, replacement, testing and safety validation must be performed only by personnel qualified and authorised for the specific task. Different parts of the work may require different electrical, software, functional-safety and machine knowledge.

The operator is responsible for the site-specific risk assessment, work authorisation, isolation plan, data backup, protective measures, validation and release under applicable local requirements.

4. Find and isolate every energy source

Trace all normal, auxiliary, UPS, external and back-fed electrical supplies.
Identify stored energy in capacitors, power supplies, drives and connected equipment.
Isolate, lock and label the sources in accordance with the site procedure.
Verify absence of voltage at all relevant potentials and terminals with suitable equipment.
Secure pneumatic, hydraulic, gravitational and other mechanical energy before access.

5. Short-circuit, arc-flash and protective-device hazards

Control cabinets can contain high prospective fault currents even where control voltages are low. Tool slips, incorrect bridges, loose conductors or unsuitable replacement devices can cause arc flash, fire and extensive damage.

Protective-device ratings, selectivity, short-circuit withstand, conductor protection and cabinet classification must be assessed for the complete installation. Never replace a protective device solely because its dimensions or nominal current appear similar.

6. Output states and unexpected machine response

A PLC stop state, download, restart, loss of communication, warm restart, forced variable, diagnostic function or module replacement may change output states. Outputs can also remain energised through separate supplies, hard-wired circuits or retained logic.

Before any software or hardware change, determine the possible effect on actuators and secure the hazard area. Remove forces and temporary bridges after the work and verify the intended normal state.

7. Safety PLCs and safety modules

A safety marking or certified component does not by itself make the machine safety function valid. Hardware assignment, addresses, signatures, program version, wiring, diagnostics, response times and the complete sensor-to-actuator chain must match the approved safety design.

Any replacement, program change, firmware change or altered I/O assignment can require renewed validation. Bypasses and test overrides must be controlled, documented and removed before release.

8. Compatibility, firmware and stored data

A mechanically compatible module may differ in voltage, channel type, signal range, load capability, communication profile, firmware or safety behaviour. Verify the exact replacement route and required migration steps from reliable manufacturer information.

Memory cards, PLC programs, recipes, passwords, licences and process data are included only where expressly stated. Treat any stored data as unverified and potentially confidential; back up required customer data and apply the operator's cybersecurity and data-handling process.

9. Electrostatic discharge, contamination and environment

Open electronic modules can be damaged by electrostatic discharge without visible evidence. Use suitable ESD controls and handle connectors, backplanes and circuit boards only as permitted by the manufacturer.

Check enclosure protection, pollution, conductive dust, humidity, condensation, temperature, ventilation, vibration and corrosive atmosphere. A visually intact component may still be unsafe after moisture, contamination, overheating or surge exposure.

10. Batteries, capacitors and clock or memory retention

Batteries and energy-storage modules can be depleted, damaged, hazardous to handle or subject to transport and disposal rules. Their replacement can erase data or alter the system state.

Follow the exact manufacturer procedure, preserve required backups and prevent short circuit, reverse polarity and uncontrolled loss of retained information.

11. Networks, remote access and cybersecurity

Connecting an unknown component or restored project to an industrial network can create duplicate addresses, unintended communication, unauthorised access or uncontrolled commands. Establish a controlled offline or segmented test environment before connection to the production network.

Change default credentials where applicable, verify authorised firmware and configuration sources, restrict remote access and preserve the operator's logging and change-control requirements.

12. Inspection, test and release

Document identity, physical condition, supply and potential assignments, wiring and software state.
Determine and perform the required electrical and functional inspections before installation and first use.
Use a safeguarded test environment and prevent output-driven movement.
Verify diagnostics, communications, I/O behaviour and every affected safety function.
Record results, remove temporary measures and release only the verified configuration.