What is IEC 60204-1?
IEC 60204-1 is the international basic standard for the safety of the electrical, electronic and programmable electronic equipment of machines, from the point where the supply is connected through to the control system, operator controls, wiring and documentation. Its full title is Safety of machinery β Electrical equipment of machines β Part 1: General requirements, and it is maintained by IEC technical committee TC 44. Europe adopts it as EN 60204-1; in the Netherlands it is published as NEN-EN-IEC 60204-1.
In OT environments, IEC 60204-1 is the standard against which you assess a machine with PLCs, drives, HMIs and a control cabinet when you build, modify or hand it over.
𧱠Which machines and voltages does IEC 60204-1 cover?
The standard applies to machines that are not portable by hand while working, including groups of machines working together in a coordinated way, such as a production line. Its requirements start at the point where the supply connects to the electrical equipment of the machine. Everything upstream, the building installation, falls under IEC 60364 and, in the Netherlands, NEN 1010.
| Characteristic | Limit or boundary |
|---|---|
| Alternating current | Nominal supply voltage up to 1,000 V AC |
| Direct current | Nominal supply voltage up to 1,500 V DC |
| Frequency | Nominal supply frequency up to 200 Hz |
| Higher voltages | IEC 60204-11 (high-voltage equipment) |
| Sewing machines, hoisting machines, semiconductor equipment | Separate parts IEC 60204-31, -32 and -33 |
| Not covered | Additional requirements for open-air use, mines or explosive atmospheres (ATEX, IEC 60079) |
Annex C lists example machines, from machine tools and packaging machines to robots and conveyor systems. Non-electrical hazards, such as guarding and mechanical interlocking, are outside the scope; standards such as ISO 12100 and ISO 14119 deal with those.
π§ What does IEC 60204-1 regulate, clause by clause?
The standard has eighteen clauses and nine annexes. The most important topics for designers and panel builders:
| Clause | Topic | Example requirements |
|---|---|---|
| 5 | Supply terminations and disconnecting device | Lockable main switch that isolates the machine, with a clear OFF position |
| 6 | Protection against electric shock | Enclosures, insulation, residual voltage, automatic disconnection |
| 7 | Protection of equipment | Overcurrent, motor overload, short-circuit current rating (7.10) |
| 8 | Equipotential bonding | Protective conductor and earthing of exposed conductive parts |
| 9 | Control circuits and control functions | Stop categories, interlocks, cableless control, behaviour on failure |
| 10 | Operator interface and control devices | Colours of push buttons and lights, emergency stop, emergency switching off, enabling device |
| 11 | Controlgear and enclosures | Location, accessibility, heat, degree of protection |
| 12β13 | Conductors, cables and wiring | Cross-sections, flexible cables, colour and wire identification |
| 14 | Motors | Motor protection and connection |
| 16β17 | Marking and documentation | Nameplate, warning signs, diagrams, maintenance information |
| 18 | Verification | Tests before commissioning |
The sixth edition of October 2016 added, among other things, requirements for power drive systems such as the variable frequency drive, revised EMC requirements, a mandatory determination of the short-circuit current rating of the complete equipment and a rewritten clause 9 that includes Safe Torque Off. It also made residual current devices of no more than 30 mA mandatory for socket outlets up to 20 A.
π§ What stop categories does IEC 60204-1 define?
Clause 9 defines three ways to stop a machine. The choice follows from the machineβs risk assessment:
- Stop category 0 - an uncontrolled stop by immediately removing power to the machine actuators. In modern drives this is often done with Safe Torque Off (STO) from IEC 61800-5-2 instead of with a contactor.
- Stop category 1 - a controlled stop with power available to the drive, after which power is removed once the machine has stopped. Suitable for heavy axes that would otherwise coast for too long.
- Stop category 2 - a controlled stop with power left available, for example to hold an axis in position.
An emergency stop must function as stop category 0 or 1; category 2 is not permitted for it. The standard also separates emergency stop (stopping a hazardous movement) from emergency switching off (removing electrical energy where there is a risk of electric shock). For the function itself the standard refers to NEN-EN-ISO 13850; you determine the required reliability of the stopping chain with ISO 13849-1 or IEC 62061, implemented with a safety relay or safety PLC.
π¨ Which colours and values does the standard specify?
Part of the requirements can be measured directly. The best-known values from IEC 60204-1:
| Topic | Requirement or recommendation |
|---|---|
| Protective conductor (PE) | Green-and-yellow, mandatory |
| Neutral conductor | Light blue |
| AC and DC power circuits | Black (recommended) |
| AC control circuits | Red (recommended) |
| DC control circuits | Blue (recommended) |
| Interlock circuits supplied from an external source | Orange (recommended); stay live when the main switch is off |
| Residual voltage | Parts above 60 V must discharge to 60 V or less within 5 s, otherwise a warning is required |
| Enclosure degree of protection | At least IP22; in practice often IP54 or higher |
| Insulation resistance | Measured at 500 V DC between power circuits and PE: at least 1 MΞ© |
For choosing the degree of protection, see IP Code. Operator control colours are fixed as well: emergency stop buttons are red on a yellow background, start buttons preferably white, grey, black or green, and stop buttons preferably black, grey or white. North America deviates: green for earth, white or grey for neutral and a maximum control voltage of 120 V AC are among the differences.
π How do you apply IEC 60204-1 in practice?
A common approach for a new machine or a substantial modification of an existing one (brownfield):
- Specify supply and environment - use the enquiry form in Annex B to record the supply system, prospective short-circuit current and ambient conditions. The form also works well as a contract document between the customer and the OEM.
- Carry out the risk assessment - in line with ISO 12100; it determines stop categories, emergency stop locations and required safety levels (PL or SIL).
- Design the schematics and cabinet - draw them in a CAE package such as EPLAN, size protective devices and cables, and keep 400 V power and 24 V DC control physically separated.
- Build and mark - wire numbers, colour codes and reference designations that match the schematics.
- Verify - according to clause 18: continuity of the protective bonding circuit, fault loop impedance, insulation resistance, residual voltage and a functional test of every safety function. Record the results in the FAT and SAT reports.
- Hand over the documentation - diagrams, parts list, installation and maintenance information as required by clause 17.
Common mistakes
Inspections and handovers keep turning up the same shortcomings:
| Mistake in practice | What IEC 60204-1 requires |
|---|---|
| Missing or interrupted PE connection on an HMI panel, door or control cabinet | All exposed conductive parts connected to the protective bonding circuit, checked with a continuity test |
| Emergency stop that does not stop every hazardous movement | Stop category 0 or 1 derived from the risk assessment, with a reliable stopping chain |
| Emergency stop confused with emergency switching off | Emergency stop halts movement; emergency switching off removes electrical energy where there is a shock hazard |
| Wiring without wire numbers or colour coding | Every conductor identifiable and matching the schematics |
| Standard cable in a cable chain or on moving parts | Flexible cable suited to the bending stress |
| 400 V power and 24 V DC control mixed together | Separated conductors, or insulation rated for the highest voltage in the same duct |
The standard contains one Dutch national deviation: in a TT system the resistance of the earth electrode may be no more than 83 Ξ©. Once the machine is in service, safe operation, inspection and maintenance in the Netherlands fall under NEN 3140, with Lock-out Tag-out during maintenance work.
π How does IEC 60204-1 relate to legislation and other standards?
EN 60204-1:2018 is harmonised under the Machinery Directive 2006/42/EC and the Low Voltage Directive 2014/35/EU. Applying it gives a presumption of conformity for the electrical requirements, a key building block of CE marking. Amendment A1:2025 adopts the 2021 IEC amendment and mainly contains editorial changes and updated references. From 20 January 2027 the Machinery Regulation replaces the Machinery Directive, so check which edition is cited in the Official Journal at that point.
| Standard | Relationship with IEC 60204-1 |
|---|---|
| IEC 61439 | Construction of low-voltage switchgear assemblies; applies alongside 60204-1 when the cabinet also distributes power |
| IEC 60947 | Product standard for switchgear such as main switches and motor protection |
| ISO 13849-1 / IEC 62061 | Reliability of safety functions in the control system |
| NEN 1010 | The building installation up to the machineβs point of connection |
| IEC 62443 | Cybersecurity of the control system; outside the scope of 60204-1 |
| NFPA 79 | North American counterpart, closely aligned in content |
π What does IEC 60204-1 mean for IT/OT and cybersecurity?
IEC 60204-1 is about electrical safety, not digital threats. It still touches the IT/OT domain. Clause 9.2.4 sets requirements for cableless control: a lost or disturbed connection must automatically lead to a safe stop. And a main switch that you physically padlock also protects technicians against a start triggered via remote access.
The Machinery Regulation will explicitly require control systems to be protected against malicious corruption. Combine the electrical foundation of IEC 60204-1 with IEC 62443 measures for the PLC and the machine network, so that an attack can never disable a safety function.
β Frequently asked questions
Is IEC 60204-1 mandatory?
IEC 60204-1 is not a law in itself, but its European version EN 60204-1 is harmonised under the Machinery Directive. Following the standard is the easiest way to show that the electrical equipment meets the legal requirements. If you deviate from it, you must demonstrate yourself that your solution is equally safe.
What is the current version of IEC 60204-1?
The current international version is IEC 60204-1:2016 with Amendment 1 from 2021, together edition 6.1. In Europe EN 60204-1:2018 with amendment A1:2025 applies. Where possible, buy and use the consolidated version so you do not have to process the amendment separately.
What is the difference between IEC 60204-1 and IEC 61439?
IEC 60204-1 covers the complete electrical equipment of a machine, including control, operator controls and wiring on the machine. IEC 61439 covers the construction and verification of a low-voltage switchgear assembly as a product. A machine cabinet that also distributes power is often assessed against both standards.
Does every machine need an emergency stop under IEC 60204-1?
Not automatically: the risk assessment decides whether an emergency stop is needed, and the Machinery Directive has exceptions, for example for hand-held machinery. Where an emergency stop is fitted, IEC 60204-1 requires it to function as stop category 0 or 1 and to meet ISO 13850.
Which tests does IEC 60204-1 require at handover?
IEC 60204-1 lists in clause 18 checks of the protective bonding circuit, fault loop impedance, insulation resistance, residual voltage and functional tests, among others. Which tests you carry out also depends on the machine and the agreements with the customer. Record the results in the handover file.
Does IEC 60204-1 apply to an existing machine?
An existing machine that you do not modify does not have to be updated to every new edition: the standard is not retroactive, and the machine is judged against the requirements that applied when it was placed on the market. After a substantial modification, you reassess the changed electrical equipment against the current IEC 60204-1. Safe use and periodic inspection fall under the Dutch Arbowet and NEN 3140.
π In summary
IEC 60204-1 is the basic standard for the electrical safety of machines, from main switch and wiring to stop categories, colour codes, verification and documentation. As a harmonised standard under the Machinery Directive, it is a fixed pillar of CE marking. In OT projects, together with ISO 13849, IEC 61439 and IEC 62443, it forms the framework for a machine that is safe both electrically and digitally.