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How to Choose PoE Switch for Harsh Environment

As a time/money-saving technology, Power over Ethernet (PoE) delivers both power and data to powered devices on the same Ethernet cable over a 100 m transmission distance, thereby eliminating complicated power wiring. Along with the rapid expansion of Internet of Things (IoT) or network-connected devices, PoE technology has experienced exponential growth in most networking infrastructures. It is widely implemented in applications like VoIP phones, and wireless access points to build a highly integrated network/power system.

Benefits of Using PoE Switches in Harsh Environment

As a crucial part of the entire network system, PoE switch will automatically detect whether the connected devices are PoE-compatible and transmit power to these remotely-powered devices (if positive). Nowadays, it has become a front-runner for applications in hazardous conditions owing to its inherent advantages: user-friendly installation featuring simple plug-and-play design; low voltage (non-hazardous electrical currents of ≤60 volts) with intelligent power detection to avoid overload or underload; improved reliability with uninterrupted and redundant power supplies for continuous operation; great flexibility for relocation without being hardwired to electrical outlets to improve the scalability of network architecture.

How to Choose a PoE Switch for Deployments in Harsh Environments?

PoE switches bring a wide range of benefits to all walks of life, whether for home or business use, but not all switches are created equal. To choose the right PoE switch for deployments in harsh environments, you need to pay attention to the following points:

PoE, PoE+ or PoE++? (power budget)

The power budget is a significant factor to take into consideration in the selection. According to the IEEE standard (power supply protocol), the PoE switches can be roughly classified into three categories: PoE, PoE+ and PoE++ switches. Before purchasing a PoE switch, you need to calculate the power budget of all the powered devices (PDs) you’re gonna connect to the switch, and then choose a corresponding device that suits your specific needs. If the PDs only require a rather low power level, the basic PoE switch will seem adequate, while to build a robust, high-performance network system, PoE+ or PoE++ is clearly a better choice.

PoE switch (IEEE 802.3af standard-Type 1) supports a maximum power supply of up to 15.4W on a per-port basis with a voltage range of 44-57V, utilizing only two out of the four available twisted pairs for power transmission. It is able to deliver a maximum power of 12.95W to PDs like VoIP phones, WiFi and static surveillance cameras. PoE+ switch (Type 2) is the upgraded version of PoE technology (max power per port: 30W; voltage range: 50-57V; two twisted pairs). According to IEEE 802.3at standard, it can provide a steady power source of up to 25.5W to devices that need more wattage, such as Pan-Tilt-Zoom (PTZ) cameras, video IP phones and alarm systems. Contrary to the other standard switches, PoE++ switch (IEEE 802.3bt) delivers power in a copper cable (with two or four twisted pairs) to PoE-compatible devices. Additionally, it can be subdivided into two types: Type 3 and Type 4. They can power some devices that require higher wattage like video conferencing systems and building access control (Type 3: 51W and Type 4: 71W). The maximum power delivered by each port is 60W under Type 3/100W under Type 4 with a voltage range of 50/52-57V.

Switch Ports, Surge Protection, Service Life & Manageability

Apart from the power budget, you’ll should figure out how many PoE power ports are needed according to the number of powered terminals. Nowadays, the available PoE switches offer a wide range of selection from 4, 8, 16 to the maximum 24 Gigabit ports, and sometimes with extra SFP module slots for fiber or copper cable connection. For outdoor deployment, the PoE switch should support surge protection (4-6 kV) for all ports to protect the device from lightning strikes and other electrical surges, offering safe and reliable performance even in the harshest environments. And service life also matters so much. Regular PoE switches only have a service life of 2-3 years (shorter in harsh environments), while hardened/rugged ones could last for up to 10 years.

According to its manageability, PoE switches can be further categorized into managed and unmanaged switches. Unmanaged switches can’t be modified or managed, but they are affordable and user-friendly, featuring a simple setup (plug and play) with no configuration needed. On the contrary, managed switches offer full management capacities with security features, which also makes them more expensive. Authorized users can regulate the voltage coming out of each port and make up a reasonable power plan accordingly. Although they have complicated setup procedures (assistance from professionals is required), they are your best bet for long-distance deployment.

Other Criteria for Consideration

PoE switches are more prone to failures and interference when applied in an outdoor setting or a harsh environment, so effective protection against uncontrollable environmental changes must be designed-in at an early stage. The following are some important factors you should take into consideration to make sure the PoE switch you choose could deliver superb network performance in all circumstances.

1. Wide Operating Temperature Range (-40-75°C)

One of the most common hazards when installing PoE switches in harsh environments is the ambient temperature. Compared with a climate-controlled setting where the temperature is kept within a tolerable range with a comprehensive thermal control system to automatically store and dissipate heat gains, an under-conditioned environment always faces the challenge posed by significant fluctuations in temperatures. In Dubai, one of the hottest cities on the planet, the outdoor temperature hits 43°C (109°F) in summer with humidity averaging over 90%, while Yakutsk, the world’s coldest city, has a yearly average temperature of -8.8°C (16.16°F). The regular/commercial switches can only operate within a limited temperature range of 0-40°C/30-104°F, which will easily break down in extreme temperatures.

Considering the outside temperature is somehow uncontrollable, to ensure the ongoing functionality of powered devices (PDs) in continuous operation, the selected PoE switches must have the ability to operate over a wide temperature range (-40°C/-40°F to 75°C/167°F) to work in places like Alaska that suffer both extremities. Another reason why people should choose a PoE switch with a wide operating temperature range is that building a climate-controlled environment is expensive and time-consuming, and that it’s nearly impossible to transform a specified setting where there is a strict temperature standard. For example, a barn/farmhouse should stay within a proper temperature to maintain the comfort, health, and production of livestock. The optimum living temperatures for dairy cows are between -5°C/23°F to 15°C/59°F to ensure optimum milk production and livestock health. Therefore, in these situations, it’s clearly not advisable to rebuild or transform a setting.

2. Dual/Redundant Power Supply

To ensure the normal operation of the powered devices, the chosen PoE switch should have dual/redundant power supplies to meet the demands of applications in harsh environments. Powering electronic devices in harsh environments is never an easy job. PoE switches placed outdoors are more susceptible to lightning strikes and power surges, which will jeopardize the connection between power sourcing equipment (PSE) and PDs and disable the entire network system. Therefore, it’s highly recommended to select a PoE switch with redundant power supplies (a combination of two or more power supplies for one load) to minimize the chances of power failures and increase the reliability of the PoE system. So when one is powered off, the other will continue to supply full power to the device. Moreover, PoE switches that have redundant power supplies support hot-swapping, meaning that you can replace the defective power supply with a newer one without taking the device offline, which is ultra-convenient especially for outdoor deployments in harsh environments.

3. Heat Dissipation (choose fan-less switches over fan-distributed ones)

Cooling is necessary because the switches will generate a considerable amount of heat during operation. If left untreated, excessive heat would pose great damages to the Ethernet-based network by burning down the under-appreciated hardware and components. Given that PoE switches are usually installed in unconditioned environments without proper temperature control, a well-developed cooling system is highly needed to dissipate the heat from the equipment so as to avoid potential functional failures. Generally, these systems fall into two categories: passive cooling system (fan-less) and active cooling system (fan-distributed).

As a marvelous solution for thermal management, passive cooling aims to prevent external and internal heat gains by dissipating the heat from a heat spreader or heat sink (something that absorbs or dissipates the heat) to the outside with low or no energy consumption. One of the most important advantages of fan-less switches is noise reduction with a natural cooling system. On the contrary, the active cooling system is oftentimes fan-distributed which not only generates unpleasant noises (which will compromise the network performance of the switch) but requires higher power consumption. And the mechanical cooling system is more subject to failures than its passive counterpart. On the one hand, the breakdown of a fan will lead to the collapse of the entire PoE system (overheating threatens the failure of inner components); on the other hand, regular clean-ups and maintenance (at least twice a year) are highly needed when installing a PoE switch in dusty places like basements because dust will stick to the fan blades as they rotate, which will slow down the cooling process.

4. IP or NEMA-rated Outdoor Enclosure

PoE switch installed outdoors or in harsh environments often faces numerous environmental hazards (water submersion, UV radiation and corrosion, ingress from dust, debris or other airborne particles, etc.) which threaten the failure of the device. A solid-constructed enclosure is what everyone needs for outdoor deployments in a hazardous location. Given its prolonged exposure to various outdoor conditions, the enclosure should have a strong resistance to UV radiation and corrosion. A hinged design is highly recommended to offer quick access while discouraging unauthorized entries. Also, it should be made from durable materials that are highly resistant to all kinds of environmental hazards with less interference to WiFi signals (materials like polycarbonate, stainless steel, etc.)

Most importantly, you should choose an IP or NEMA-rated enclosure that provides protection against unintentional contact with moisture, dust or other physical and chemical hazards. Compared with NEMA ratings that are mostly used in the U.S., IP ratings are internationally recognized and focus on the protection against water and dust for all kinds of devices. The first number of IP codes (on a scale of 0-8) represents the resistance to solid particles like dust or airborne debris, while the second number (0-8) describes the protection against liquids like rainwater. The higher the number is, the more protection it provides. IP65, for example, provides full protection against dust, other particulates and water jets from all directions. On the other hand, NEMA ratings are exclusively used for enclosures. They also rate for other factors not included in the IP ratings like corrosive agents. A commonly used standard for outdoor enclosures, NEMA 4X is a strong level of outdoor defense with strong protection against ingress from airborne particulates, splashing or hose-directed water as well as a built-in resistance to corrosion in the ambient air.

For more information, check FASTCABLING to create an effective PoE system.

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