PoE Midspan FAQs

A Midspan, also referred to as an injector, is a device used within a network to supply power over an Ethernet cable that does not already carry power. It is typically connected to the output of a switch, router, gateway or similar network device that provides data connectivity but does not deliver power. The Midspan then outputs a second cable that integrates both network data and power, allowing it to be connected directly to an end device.

The most common type of Midspan is a single-port indoor model. However, Midspans are available in a wide range of configurations, including single-port and multi-port options designed for indoor, outdoor and industrial environments. They support various power outputs of up to 90W per port and data rates of up to 10 Gbps.

An Ethernet switch is a network device that connects multiple devices within a Local Area Network (LAN) and manages data traffic by forwarding data packets only to the intended recipient. Some Ethernet switches also have the capability to provide PoE while others do not.

A PoE Midspan is a device that adds power to an existing Ethernet connection. It is typically used in conjunction with a non-PoE switch to enable the delivery of both data and electrical power to compatible devices over the same Ethernet cable.

When selecting the appropriate Midspan, consider the following criteria:

• Number of Ports Required - 1, 6, 12 or 24
• Power Output per Port - 15.4W, 30W, 60W, or 90W
• Deployment Environment - Indoor, Outdoor or Industrial
• Supported Data Rate - 1 Gbps, 2.5 Gbps, 5G bps or 10 Gbps

Many devices are marketed as PoE Midspans; however, not all offer the same level of functionality or protection. It is essential to select Midspans that are fully compliant with IEEE^® 802.3af, 802.3at, or 802.3bt standards to ensure reliable performance and device safety.

A compliant Midspan, adhering to IEEE 802.3af, 802.3at or 802.3bt standards, supplies power only when requested by a compatible device and automatically shuts off when power is no longer needed or if a fault is detected. This approach safeguards connected equipment. In contrast, a compatible or passive Midspan continuously delivers power over the Ethernet cable without any protective features, which can put devices at risk.

While there are numerous cost-effective Midspans available on the market, these options may not be the most reliable or safest choice. Passive units are typically less expensive because they lack the necessary circuitry for proper PoE negotiation and may be constructed with substandard materials, potentially including hazardous substances. It is important to avoid Midspans that do not comply with the latest local government efficiency and safety standards.

Many existing networks are not equipped to provide PoE and not all new switches on the market include PoE capability. Additionally, even when a switch supports PoE, it may not be able to deliver full power to every port simultaneously due to power budget constraints. As a result, when connecting a PoE-powered device to a network that does not support PoE, using a PoE Midspan is often the most efficient and cost-effective solution for delivering power to these devices.

There is significant variation in quality among available Midspans. Because Midspans are typically “plug and play” devices and are often installed in remote locations, it is especially important to choose a high-quality unit—particularly for commercial, industrial, outdoor or harsh environments. When evaluating options, consider selecting a manufacturer that publishes Mean Time Between Failure (MTBF) statistics to help ensure long-term reliability.

Midspans are known for their very low failure rates and are generally not considered a common point of failure within the network infrastructure. PoE Midspans function at layer 1 of the utility infrastructure and also act as data pass-through devices. If a Midspan fails at this level, the network continues to operate. On the other hand, if a PoE switch fails, the entire network goes down. Thus, a PoE switch represents a critical point of failure in the network. In contrast, a Midspan enhances network resilience by isolating the critical Layer 2 and Layer 3 functions from the power supply.

Some organizations choose to purchase non-PoE switches and provide power through Midspans. Since Ethernet switches typically have a shorter lifespan than Midspans and are frequently replaced due to rapid technological advancements, separating the Midspan from the switch can help reduce overall costs over the network’s lifecycle. This approach allows organizations to upgrade switches as needed without having to replace the PoE infrastructure, resulting in greater flexibility and long-term savings.

Power over Ethernet (PoE) is widely regarded as a highly energy-efficient method of power delivery. It supplies power only when requested by a valid device and delivers precisely the amount of power required, making it more efficient than traditional power supplies or passive PoE units that continuously provide power regardless of demand.

However, it is important to note that PoE Midspans typically convert AC power from the utility grid to DC power for end devices. This conversion process inherently results in some energy loss. While AC power is the most efficient form for transmission and distribution, most modern devices in homes and offices operate on DC power. To minimize energy loss from multiple conversions, it is generally more efficient to use multi-port PoE devices, which can serve several endpoints from a single conversion point. This approach helps to further optimize overall energy efficiency in PoE deployments.

While no powering option is 100% energy efficient, PoE offers some unique energy efficiency capabilities including:

• Providing power only when requested
• Delivering only the amount of power requested
• Terminating power delivery when no longer required
• Protecting devices from damage due to surges or other conditions

To further enhance energy efficiency, Microchip Midspans minimize power consumption during periods when they are not delivering power, also known as a no-load condition.

Compliance with energy efficiency standards is essential because PoE Midspans continue to consume electricity even when they are not actively delivering power, a condition known as the “no-load” state. During this time, the device remains operational to monitor for new power requests. Energy efficiency standards specify the maximum allowable power consumption for power supply devices in the “no-load” state, helping to reduce unnecessary energy usage and improve overall system efficiency.

You can be certain that a device complies with local energy efficiency standards when the unit has an applicable logo. In the US it will be a Department of Energy logo (current standard is 6 moving to 7). In the European Union, look for the CE logo. 

Microchip Midspans are engineered to comply with, and often surpass, local energy efficiency standards. As these standards continue to evolve and become more stringent, Microchip is proactively enhancing our product portfolio to ensure ongoing compliance worldwide. We are pleased to announce the launch of our Green Series (GS) indoor single-port Midspans, specifically designed to meet the upcoming U.S. Department of Energy (DoE) Level VII standards, as well as all other relevant local regulations.

An Indoor single port Midspan, also referred to as an Injector, is a device designed with one input port for an Ethernet cable without power and a second output port for an Ethernet cable with power. It also features a third connection for the power supply, which can be either AC or DC. Typically, a single port Midspan is compatible with only one type of power input, either AC or DC.

There are many indoor single port Midspans on the marketplace today offering a wide range of features and varying levels of quality. Below are some of the key differences to consider:

PoE Standards Support – Not all Midspan devices support IEEE 802.3af (PoE), IEEE 802.3at (PoE+) or IEEE 802.3bt (PoE++) standards. Some units may be labeled as compatible, meaning they continuously supply a standard power level without performing a handshake protocol. This constant power delivery can potentially damage connected devices.

Power Supply – Some indoor single port Midspans do not include a built-in power supply. While these units may be smaller and appear cost-effective, they require the separate purchase of an external power supply, which should be considered when evaluating total cost.

Voltages – Input voltage requirements can vary by device. It is recommended to select a device with an input voltage range of 100 Vac to 240 Vac for maximum compatibility. Additionally, always verify that the output voltage complies with IEEE standards, as there are many units on the market with non-standard output voltages.

Form Factor – Indoor single port Midspans are often installed in environments where wall mounting is required. When selecting a unit, ensure it includes features or mounting options that facilitate easy and secure installation.

Data Rate – The most common data rate for PoE devices is 1 Gbps; however, many modern applications require higher data rates. It is important to verify that the selected unit supports the necessary data rate for your specific requirements.

Surge Protection – Surge protection is not typically included as a standard feature on most indoor PoE Midspans. If surge protection is required for your deployment, consider using an external indoor surge protector that can be connected via Ethernet cable. Alternatively, some devices are available with built-in, industry-standard surge protection.

Quality - There is a wide range of quality among indoor single-port Midspans available on the market. Some models use lower-cost materials, particularly for the casing. For commercial applications, it is advisable to select higher-quality units. One indicator of quality is the Mean Time Between Failure (MTBF) rating, which is typically published in hours. Reputable manufacturers will provide the MTBF rating in their product documentation, while lower-quality units may omit this information from their data sheets.

The following criteria should be used to identify the proper indoor single port Midspan:

Environment – Ensure that the Midspan is designed to operate within standard indoor temperature ranges.

Compliance – The Midspan must comply with the IEEE 802.3af (PoE), IEEE 802.3at (PoE+) or IEEE 802.3bt (PoE++) standard, as appropriate for the requirements of the powered device.

Data Rate – The Midspan must support data rates that meet the requirements of the powered device.

Indoor single port Midspans are typically AC-powered and designed for mounting on flat surfaces. In contrast, industrial single port Midspans feature a DIN rail form factor, are powered by DC, and are specifically engineered to withstand the temperature extremes, vibration and electrical conditions commonly found in industrial environments.

An industrial single port Midspan, commonly referred to as an injector, is a device designed with one input port for a non-powered Ethernet cable and one output port for a powered Ethernet cable. It also features a third connection for a DC power supply. The unit is built into the DIN Rail form factor, allowing for easy installation in industrial settings.

This device is specifically engineered for industrial environments and offers the following features:

• Wide operating temperature range
• Enhanced resistance to vibration
• High tolerance to electrical interference, surges and electrostatic discharges

Indoor single port Midspans are typically AC-powered and designed for mounting on flat surfaces. In contrast, industrial single port Midspans feature a DIN rail form factor, are powered by DC, and are specifically engineered to withstand the temperature extremes, vibration and electrical conditions commonly found in industrial environments.

An industrial ingle port Midspan is recommended for deployment in industrial environments, such as shop floors or assembly lines. Its extended operating temperature range also makes it a popular choice for use in construction settings.

A multiport Midspan is a device equipped with more than one port. While some models offer 2 to 4 ports, the most commonly used multiport Midspans are designed for installation in network rooms, typically mounted above an Ethernet switch. These units generally feature 6, 12 or 24 ports. Mounting a multiport Midspan above a switch simplifies the process of connecting devices and integrating power into an existing network infrastructure. 

Most single port Midspans are limited to powering a single device and generally do not offer management features. In contrast, multiport Midspans provide advanced management capabilities, such as enabling or disabling individual ports, scheduling power delivery and setting power limits for each port. 

Rack-mounted multiport Midspans are an ideal solution for adding PoE power to a network. To install, simply mount the multiport Midspan above or below the switch that manages the Ethernet cables. Connect the Ethernet cable previously attached to the switch’s output port to the output port of the multiport Midspan. Then, use a short Ethernet cable to link the switch’s output port to the input port of the multiport Midspan. This setup enables seamless integration of power into your existing network infrastructure.

Multiport Midspans offer a range of user-friendly features that enhance network control and flexibility including:

• Port Control - Enable or disable individual ports as needed
• Power Scheduling - Schedule power delivery to specific ports based on operational requirements
• Power Limiting - Set maximum power limits for each port to optimize energy usage and protect connected devices
• Monitoring - Track power consumption and port status in real time
• Alerts and Notifications - Receive alerts for power faults, overloads or other critical elements

The key features of an outdoor Midspan include:

• Weatherproof Design - Engineered to withstand exposure to rain, dust, humidity and extreme temperatures.
• Corrosion Resistance - Built to withstand damage caused by exposure to moisture, chemicals, salt or other environmental factors that lead to rust or deterioration.
• Rugged Enclosure - Housed in a durable, sealed casing to protect against environmental hazards.
• Extended Temperature Range - Operates reliably in a wide range of outdoor temperatures.
• Surge and Lightning Protection - Built-in safeguards to protect connected devices from electrical surges and lightning strikes.
• UV Resistance - Materials are resistant to ultraviolet radiation, preventing degradation from sunlight.
• Flexible Mounting Options - Supports various mounting configurations for poles, walls or other outdoor structures.
• Sealed Cable Entries - Features watertight cable glands or connectors to prevent moisture ingress.
• Compliance with Outdoor Standards - Meets relevant industry standards for outdoor electrical equipment.

These features ensure reliable and safe operation of PoE devices in challenging outdoor environments.

When an outdoor device is mounted next to a house or building, it is possible to provide power from an indoor location; however, when an outdoor device is mounted more than 100 meters from such a location, it will require power from an outdoor source. Although there are many options for providing PoE power in an outdoor environment, it is best to use a device that is designed for the outdoors. Many attempt to put Ethernet switches designed for an indoor or industrial environment in an outdoor enclosure known as a National Electrical Manufacturers Association (NEMA) box. These installations have extremely high failure rates.

It is best to deploy units designed for outdoor environments that are designed and built specifically to operate outdoors including:

• Tamperproof Enclosure: Sealed unit
• Temperature Range: -40°C to +65°C (-40°F to +149°F)
• Moisture and Dust: IP 67
• Surge Protection: 6 kV
• Corrosion Protection: NEMA 250, Level 4X; ASTM B-117

Many people attempt to reduce costs by placing indoor or industrial equipment in an outdoor or NEMA enclosure. The reason this is done is an attempt to reduce costs since outdoor units are typically more expensive. When deploying these units in a NEMA box, it is important to also ensure that it is properly ventilated without allowing dust or moisture into the unit. It also must include other environmental protections, such as surge protection against lightning strikes. The biggest challenge of this configuration is the buildup of heat within the box. The temperature inside the unit can potentially reach up to twice the ambient temperature outside the enclosure, which may lead to failure.