What You Need to Know About New Fault-Managed Power Systems

This latest edition of the NEC, set for release in Fall 2022, contains New Article 726, which was created for Class 4 circuits.

The new Class 4 classification standardizes an improved format of electricity. As you hear more about Class 4, you’ll realize it has many names: fault-managed power systems, packet energy transfer (PET), Digital Electricity™ (DE), pulsed power or smart transfer systems. These terms are used interchangeably, but they all refer to Class 4 circuits.

Fault-managed power systems are already in use in some intelligent buildings, but a task group within the NEC recognized that these systems are unique and specialized enough that they need their own code section.

What Are Fault-Managed Power Systems?

To understand Class 4, it’s important to also understand Class 2 and Class 3 circuits.

Class 2 circuits can support lower power (up to 100VA) in many types of environments. They consider safety from a fire initiation standpoint and offer protection from electric shock. Class 2 power loads are often delivered through Power over Ethernet (PoE) cables.

Class 3 circuits function similarly to Class 2 circuits, but they support higher voltage and power limitations. Class 3 power loads can also be delivered through PoE cables.

But while Class 2 and Class 3 systems are power-limited systems with ratings of up to 300 volts, Class 4 is a new standard dedicated to fault-managed power systems with voltage ratings of up to 450 volts.

These fault-managed power systems provide up to 20 times the amount of power or 20 times the distance of PoE and offer a cost-effective alternative to AC power.

What Does “Fault-Managed Power” Mean?

Unlike Class 2 and Class 3 power-limited circuits, Class 4 systems don’t limit power source output.

Instead, they constantly monitor for faults and control the delivery of power current available during an abnormal condition. This mitigates the risk of shock or fire by limiting the amount of energy that can go into a fault.

This technology makes Class 4 systems just as safe as—if not safer than—Class 2 and Class 3 systems. As a result, Class 4 systems can be installed by the same integrators and contractors that also install Category and PoE cabling.

How Do They Work?

Fault-managed power systems can limit available power in a variety of ways.

Let’s use Digital Electricity, created by VoltServer, as a real example. When using Digital Electricity, AC or DC analog electricity comes in from the grid, battery plant or uninterruptible power supply (UPS). A transmitter converts the incoming analog AC or DC power to Digital Electricity.

This Digital Electricity is then split into packetized units that combine power and data so both can be sent via the same structured cable. A receiver converts the Digital Electricity back into analog AC or DC.

Every second, nearly 500 of these packets—each containing a very small amount of energy—move from a transmitter to a receiver.  

The steady stream of hundreds of packets per second is continuously monitoring for faults. The transmitter is able to recognize a fault condition within a fraction of a second—improper wiring, short circuit or someone touching transmission lines—and stop packet transmission. This halts the flow of electricity immediately and makes the conductors safe to touch.

In addition to prioritizing safety, Class 4 is also said to be more efficient and cost-effective than the alternatives available to deliver this amount of power across long distances. Because Class 4 uses small conductors, less copper material is required.

How Will Fault-Managed Power Change the Future?

It will take time, but many industry experts anticipate that Class 4 could someday serve as the primary power backbone infrastructure within facilities. It’s already happening in projects like Texas’ Sinclair Hotel and Las Vegas’ Circa Casino & Resort.

As buildings become more intelligent and need more devices, power and connectivity, Class 4 will be a viable option in venues like airports, Class-A offices, stadiums and arenas, and industrial plants to support mission-critical systems like 5G radios and small cells, power distribution infrastructure, distributed antenna systems (DASs), passive optical networks (PONs) and systems that use PoE switches.

Learn more about Class 4 circuits and how they work.

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