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January 25, 2023
Class 4 power (CL4) power systems are popping up all over the market with the publication of the new class rating in America’s electrical code (the National Electrical Code, or NEC for short). With the introduction of the Class 4 rating, comes the legitimization of fault-managed power (FMP) systems. This enables higher-voltages to be transmitted over cables without any mechanical protection, makes the installation safer, and means that electrical systems in buildings are becoming more intelligent!
In this article we’ll compare two Class 4 power systems from different manufacturers: Panduit’s Pulse Power (delivered via Pulse Current), and Cence Power’s Digital Current™ Class 4, direct current (DC) power distribution system (Cence HVDC). Let’s start with what a Class 4 power system is.
The NEC recently added a new article to the 2023 edition called Article 726. Article 726 encompasses a new electrical class rating called Class 4. Power systems rated Class 4, safely provide up to 450 volts DC, while making use of low-voltage wiring practices. The other class ratings for power systems (class 1, 2 and 3) are applied to power systems that have power limiting built-in, meaning they are safe from either electrical shock, fire or both, because they can only supply a limited amount of power. Class 4 power systems, on the other hand, are fault-managed. In other words, they don’t need to be power-limited because they intelligently detect specific electrical faults, and then power is shut off if any of these faults occur. This means they can supply higher voltages than power systems with class ratings of either 1, 2, or 3.
These are the faults that Class 4 power systems monitor for:
According to UL 1400-2 (which outlines the requirements for Class 4 cables), the cables used in Class 4 power systems can provide higher voltages over cables that require minimal insulation and no mechanical protection. UL is also expected to publish an outline of the requirements for fault-managed power systems, under UL 1400-1.
The main benefits of a Class 4 power system are most obvious when compared to Class 2 power systems (for example, Power over Ethernet). Power over Ethernet (PoE) is well known for using low-voltage wiring practices, being safe to handle, and delivering both power and data over one cable. However, it’s limited to about 90 W of power, and usually between 44 and 57 volts DC (nominally 48 volts DC). It also only works with PoE enabled devices. Because of these limitations, it’s not usually justifiable for higher-power applications, like lighting. Class 4 power systems, like Pulse Current, Digital Electricity™ and Digital Current™, bring the best of both of these worlds together. Typically Class 4 power systems like these can safely provide higher voltages, can make use of low-voltage wiring practices, don’t need to be used with PoE enabled devices, and have the same (or greater) distance capabilities as alternating current (AC) power.
Both PoE and Class 4 power systems are DC power distribution systems, meaning they distribute DC power rather than AC power. The main benefit of this is to provide DC power to DC powered devices, thus eliminating conversions from AC to DC, that DC powered devices would otherwise have to make. These conversions (executed by converters inside device drivers) are typically very inefficient, wasting between 5% - 20% of energy consumed by a DC powered load. Class 4 power systems can also distribute DC power, so they also eliminate these inefficient conversions from AC to DC by DC powered devices. As a result, DC power distribution saves buildings an increasing amount of energy, especially as an increasing proportion of power loads in buildings require DC power. In fact, currently about 74% of total electrical loads in homes need DC power to operate (if they power electric vehicles and have HVAC equipment with a DC motor). This number is on the rise considering anything “digital” (meaning anything that uses semiconductors, such as cellphones), and anything with a battery, all require DC power. Thus, DC power distribution throughout buildings will save them more energy in correlation with the increase in DC powered devices and systems.
Unlike PoE, Class 4 systems don’t necessarily transfer both power and data over one cable, power is transferred via a cable, and data can be transferred over a wireless mesh network. It’s not necessarily practical to use PoE for lighting or HVAC systems, this is because there’s not enough data generated by these systems to justify a dedicated IP address or Ethernet connection. A wireless connection can be used instead. One might want to directly connect systems via a cable to ensure that they are turned on or off immediately, but there’s actually not a lot of latency when using a wireless connection to switch systems on or off. The delay is practically imperceivable. Additionally, there are many benefits to sending data wirelessly, such as a reduction in cabling and system cost, improved system flexibility, and an easier installation. Another reason you may not see data on Class 4 cables, is because the communication on these cables is reserved for detecting faults. So, rather than asking if Class 4 systems deliver both power and data over one cable, the better question might be: with all the wireless technology we have these days, is it still relevant to deliver both power and data over one cable?
Next, in this article we’ll be defining the difference between Pulse Current and Digital Current™, and we hope this provides a better understanding of Class 4 power systems, applications for them, and options currently available on the market. First, let’s cover Pulse Current.
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Pulse Current is the power delivery method for Pulse Power, which is Panduit’s version of a Class 4 power system. It complies with UL standard 1400, uses low-voltage wiring practices, distributes about 57 volts DC to power loads, and provides up to 30x the power of Class 2 power systems (depending on the diameter of a cable’s gauge). For example, if a Class 2 system provides 20 W, this system can provide up to 600 W. Pulse Current is labeled as such because of how power is delivered; the transmitter in this Class 4 power system sends power in pulses that are about 3 milliseconds long. 2 of these milliseconds are used to supply power, and 1 ms is used to check for faults. This is called the safety check, and a safety check is performed in all Class 4 power systems. Let’s get into more detail onhow this system works.
1) AC power is delivered from the power grid to a building which, in this case, has a Pulse Power Source installed. Power grids usually supply AC power, and there’s a good reason for this. You can read about it in this article on the War of the Currents.
2) The Pulse Power Source then converts the AC power from the grid into Pulse Current. This essentially means that it converts the AC power from the grid into DC power, and then sends the DC power in pulses that include a safety check. It’s converted to DC power because DC power generally has less line losses along cables than AC power. It doesn’t have as many line losses along cables because it only suffers from 1 of the 3 major types of line losses experienced by electrical systems. If you’d like to learn more about line losses along cables, we’ve made an entire video about it, which you can check out here. The Source in this system is located close to a local power source (such as an electrical panel), and can take up to 3 power supply modules in the back, and 9 pulser modules in the front.
3) Pulse Current is then sent along cables of up to 2 km to a Pulse Power converter. These convert Pulse Current into 57 volts DC power.
4) From there, the converter delivers DC power to DC powered loads.
It’s relevant to note that the Pulse Power Source also includes what’s called a “management module”. This connects the pulse power system to the local network, which enables the user to manage the Pulse Power system through a remote desktop.
Pulse Power is not to be confused with pulsed power, which has been around for much longer.
According to Wikipedia, pulsed power is the technology involved in accumulating small amounts of energy over a relatively long period of time, and releasing that energy instantaneously, thus increasing the amount of energy that can be supplied to a load. This technology is used in applications such as food processing, water treatment, and medical applications.
Pulse power, on the other hand, provides power to remote equipment with minimal line losses along cables, it also has built-in fault management. Pulse power is delivered via Pulse Current, and is a Class 4 power system developed by Panduit.
Pulse Current has minimal line losses because, due to its built-in fault management, it can deliver higher voltages (as we discussed before). According to the formula for power (see the image below), when voltage increases, current decreases. Because more current also means more heat along lines (and heat is wasted energy), it’s common knowledge in electrical engineering circles that sending higher voltages reduces line losses along cables for this reason. Class 4 power systems, like Panduit’s, can distribute higher DC voltages along cables, and this is a large part of what makes Class 4 power systems so efficient when distributing power over longer distances.
Digital Current™ is the Cence Class 4 power system (located in Cence HVDC). Like other Class 4 power systems, it combines the benefits of low-voltage wiring practices with the benefits of traditional AC electrical systems. See the image below for an idea of what this means:
A big difference between Pulse Current and Digital Current™ is that Digital Current™ distributes pure DC power continuously, rather than with pulses or packet energy transfer (PET). A safety check is still executed between the transmitter and receiver of the Digital Current™ Class 4 power system, so it’s still fault-managed.
1) The Cence Class 4 transmitter is integrated into our panel in an HVDC (high-voltage DC) compartment, which converts power from AC to DC, and also includes an integrated safety computer. There are two layers of safety to this computer:
2) From the transmitter, up to 450 volts of DC power is sent continuously (rather than discretely) along a 3-wire DC power distribution system. Cables can abide by low-voltage wiring practices.
3) When power arrives at the receiver, the receiver confirms with the transmitter that power is safe to send to loads. Additionally, the receiver senses the power requirements of the load it’s connected to, and steps down power accordingly with a DC to DC converter.
4) DC power is sent to connected loads.
The Cence system is transformer-less, so no energy is wasted with inefficient transformers. Digital Current™ additionally saves a building energy by eliminating individual AC to DC conversions which would have otherwise been made at the load level. These conversions can be very inefficient (as we discussed before).
Another difference between Digital Current™ and Pulse Current is that the Pulse Current system provides a “Management Module'' so building managers can control the Pulse Power system through a remote desktop. The Cence system includes something similar, but it can also control buildings systems (like lighting), as well as the Digital Current system. With the Cence system, this control can be executed via a cloud-app with integrated digital twin software. Meaning, you can control the system, see data collected by sensors, view actionable insights, and control lighting systems and more, anywhere with Wi-Fi, by logging into a secure app. The Cence system eliminates the need for a remote desktop because it is BACnet enabled. Let me explain. Building systems, like lighting and HVAC, communicate via the BACnet protocol. The Cence system includes a “BACnet bridge”, which enables the wireless mesh network (created by the Cence Smart Nodes) to communicate with BACnet devices.
See the Cence cloud-app in action in this video:
Class 4 power systems can be thought of as the next evolution to Class 2 power systems, such as PoE. In comparison to PoE, Class 4 power systems deliver higher voltages, which also reduces line losses along cables, making the distribution of power throughout a building more efficient. Class 4 power systems are also not limited to working purely with PoE enabled devices. Because of this, they are useful in a more broad array of applications, such as LED lighting, and with many HVAC systems. Additionally, Class 4 power systems, like Pulse Current and Direct Current™, both distribute DC power to DC powered loads. This eliminates the need for inefficient conversions from AC to DC power, and saves DC powered loads 5% - 20% on consumed energy. There are essentially two main differences between Pulse Current and Digital Current™:
If you do decide to implement a Class 4 system in your building (regardless of which company’s system to go with), we applaud you for taking the next step to bring your building’s electrical system into the future. Implementing a Class 4, DC power distribution system, will save your building energy, and enable the control and optimization of building systems for convenience, comfort and efficiency.
If you’d like to learn more about the Cence system, feel free to contact us to talk to a specialist, get white papers, or ask a question.
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We improve the value of commercial and multifamily buildings with an intelligent DC power distribution system that's pain-free to install. It combines the benefits of low-voltage wiring practices with voltage capabilities of up to 450 Volts DC.
