What’s New in the 2024 Updates to NFPA 79 – Part 2

20 Nov 2025

Machine Supply Circuit & Disconnecting Means

In Part 1, we explored the groundbreaking introduction of cybersecurity requirements in NFPA 79:2024. Now, let’s turn our attention to Section 5.1, which governs the machine supply circuit and disconnecting means – a critical area for both safety and compliance during installation and maintenance.

Why Section 5.1 Matters

The disconnecting means is the first line of defense for anyone working on industrial machinery. Clear identification and proper selection of these devices are essential to prevent accidental energization, ensure safe lockout/tagout (LOTO) procedures, and maintain compliance with U.S. safety regulations.

The 2024 edition introduces clarifications and new requirements in three key clauses: 5.1.9.2, 5.1.9.3, and 5.1.10.

Clause 5.1.9.2 – Clear Identification of Disconnecting Means

Every machine supply circuit disconnecting means must now be legibly marked with the wording:

“Machine Supply Circuit and Disconnecting Means”

This marking must be placed on or adjacent to the device and indicate the equipment it disconnects.

Why this matters: this change eliminates ambiguity during maintenance and emergency interventions, reducing the risk of accidental energization.

Example Label: WARNING – MACHINE SUPPLY CIRCUIT AND DISCONNECTING MEANS. DISCONNECTS ALL ELECTRICAL EQUIPMENT EXCEPT LIGHTING CIRCUIT

Clause 5.1.9.3 – Multiple Supply Circuits

If a machine is powered by more than one supply circuit, each disconnecting means must include an additional marking that identifies the location of all other disconnecting means.

Practical impact: This ensures technicians are aware of all energy sources before starting work, supporting safe LOTO practices.

Clause 5.1.10 – Acceptable Types of Disconnecting Means

The updated standard clarifies which devices are acceptable as the machine supply circuit disconnecting means. These must be listed and certified (e.g., UL 98) and can include:

• Listed molded case circuit breaker
• Listed molded case switch
• Listed general-use switch (rated in amperes and horsepower) – newly emphasized in 2024
• Listed motor-circuit switch (rated in HP)
• Instantaneous trip circuit breaker (as part of a combination motor controller)
• Listed self-protected combination controller
• Attachment plug and receptacle (for cord-connected machines)

Key takeaway: The inclusion of general-use switches expands design flexibility, but only when they meet the required ratings.

Comparison Table – Old vs New Requirements

Clause	2021 Edition	2024 Edition
5.1.9.2	Marking required, but wording and placement were less prescriptive.	Must state “Machine Supply Circuit and Disconnecting Means” on or adjacent to the device, indicating the equipment disconnected.
5.1.9.3	Required marking when multiple supply circuits exist, but without clear guidance on location.	Must include marking on or adjacent to each disconnecting means, showing the location of all others.
5.1.10	Listed disconnecting means required, but general-use switches were not explicitly emphasized.	Expanded list includes general-use switches rated in amperes and HP, plus clarification on UL 98 compliance.

Practical Takeaways for OEMs and System Integrators

• Update your labeling practices: Ensure every main disconnect carries the correct wording and, where applicable, cross-references other disconnecting means.
• Verify device compliance: Confirm that disconnecting means are UL 98 listed or equivalent and meet the new rating requirements.
• Document everything: Include updated schematics and location diagrams in the machine’s technical file.

How Intertek Can Help

Navigating the new NFPA 79 requirements can be challenging, but you don’t have to do it alone. Our experts can:

• Identify compliance gaps in your current designs through a detailed Section 5.1 assessment.
• Train your team on the latest requirements to ensure smooth implementation and avoid costly redesigns.

Ready to take the next step? Contact us today to discuss your project and ensure your machinery meets the 2024 standard with confidence.

Take action now: Partner with Intertek to ensure compliance, safety, and peace of mind for your operations.

Coming Up Next: In Part 3, we’ll explore updates to Chapter 9 – Control Circuits and Protective Devices, including changes that impact functional safety and wiring practices.