The 5 S’s of Fault-Managed Power Systems (FMPS) Change the Power Game

Fault-managed power systems (FMPS) are changing the limited-energy delivery game for the better. Although they were only introduced into the National Electrical Code® (NEC) recently—in the 2023 edition—FMPS is already deployed in some intelligent buildings, and its use will continue to grow.

Circa Resort & Casino Las Vegas is an excellent example. Instead of using dedicated AC power, the 35-story building uses Digital Electricity™ (DE)—a form of FMPS—as the backbone power distribution infrastructure instead. It powers everything from lights and switches to in-room climate control and wireless access points.

FMPS is known by many names: Class 4, packet energy transfer (PET), DE and pulsed power, for example.

No matter what you call it, it’s a revolutionary way to distribute limited energy. FMPS offers power distribution that is safe, cost effective, fast to install, energy efficient and supportive of our digital world.

Our friends at VoltServer, the creator of DE, coined a helpful phrase that explains the true impact of FMPS: It offers Safe delivery of Significant power across Significant distance using Small conductors to enable Speed to deployment (they call this the 5 S’s of FMPS).

Let’s break this statement down and look at each “S” individually to see what DE FMPS can offer

1. Safe delivery

A DE FMPS systems are designed to promote safety first and foremost. They do this by limiting energy available during a fault event instead of limiting power source output (how much power the power supply can deliver). The latter is how Class 2 and Class 3 systems operate.

When someone touches exposed Class 4 wires or splashes water onto Class 4 circuits as they operate, the system detects this fault and automatically shuts itself down to prevent hazards. A transmitter and receiver control power delivery and monitor continuously for faults to provide this level of safety. This technology makes FMPS, or Class 4 systems, just as safe as—if not safer than—Class 2 and Class 3 systems.

With our support, UL recently published UL 1400-2 as an Outline of Investigation (the first step toward a standard) to define safety considerations and criteria for evaluating Class 4 circuit cabling. UL 1400-2 encompasses requirements for FMPS cables to ensure their safe installation and operation. UL 1400-1 has also been published to describe the requirements for fault-managed power systems. 

2. Significant power 

Like Power over Ethernet (PoE), which is a limited-energy system, FMPS provides the convenience of a limited-energy system. But that’s where their similarities end. Keep in mind: FMPS is not a replacement for PoE. Both will shine in the right applications. Comparing FMPS to PoE here is done only to compare FMPS to something we're all familiar with (kind of like using a banana for scale in a picture!).  


PoE can only support up to 100W, while FMPS offers nearly 20 times that amount of power. Remember the project we mentioned earlier: It has the capability to serve as the backbone power distribution infrastructure of a 35-story Las Vegas resort (something PoE isn’t able to do).

3. Significant distance

FMPS not only carries more power than PoE, but also carries that power much farther than PoE can—over hundreds of meters instead of a typical maximum of 100 m. (This distance can be increased to 215 m in certain applications with specialized cable, like RemoteIP.) Because PoE is carried by Ethernet cabling, it’s restricted by what Ethernet application standards dictate in terms of resistance limitations of the conductors within the cables. That is why some cables can go beyond the traditional 100 m cabling standard.

Fault-managed power systems are also more efficient and cost-effective than other options that can deliver this amount of power across significant distances.

4. Small conductors 

A DC power supply is a Class 2 device (limited to delivering a maximum of 100W) and typically uses 16 or 18 AWG conductors. If the distance from the power supply to the end device is very long (600 m to 800 m, for example), then multiple cables in parallel or a single cable with a larger gauge would be needed. Because of the way FMPS is designed, more power can be carried using a smaller single cable.

In fact, VoltServer states that DE, which is an FMPS system, can reduce embodied carbon by up to 90% in a typical AC deployment because it dramatically reduces materials by using smaller transformers and cables and eliminating conduit or armored cables.

5. Speed to deployment

Class 2 and Class 4 systems are often used to power communication systems, allowing the possibility to deliver power and data in a single cable run using hybrid cable. This reduces installation costs and time because there’s only one cable to manage and install.

Because they’re inherently safe, the 2023 NEC allows FMPS Class 4 cabling to be installed the same way as other communication systems cabling systems—and using the same pathway. With the right training, FMPS systems can be installed by the same integrators and contractors that install Category and PoE cabling systems, or even by in-house teams.

Whether a hotel is opening its doors for the first time, or an arena is hosting its first sporting event, quick deployment allows critical devices to receive power faster, which accelerates speed to market.

Belden is your FMPS resource

We’re proud that our Fault-Managed Power System (FMPS) Cables are the industry’s first-ever Class 4 cabling system to receive the UL 1400-2 certification. We also recently introduced the industry’s first UL-certified hybrid cable for FMPS installation. These cables feature a copper/fiber construction that transmits power and data over long distances in a single cable run, saving installation time and reducing installation complexity.

We offer a host of other resources on FMPS systems to help you stay in the know. Watch our recent webinar on FMPS and learn about how it will change our industry, . NSCA and Automated Systems Design (ASD) joined us to talk about the impact of Class 4/FMPS on integrators and end-users.

Related resources:

Class-4 Systems

Here Comes Class 4 Power: Differences Between Circuit Classes

Class 4 Systems Change How Technology is Powered