BECKHOFF CU20xx/CU22xx Switch Installation and Troubleshooting

Beckhoff CU20xx/CU22xx Industrial Ethernet Switch Installation, Debugging, and Troubleshooting Guide

In industrial automation networks, Ethernet switches serve as the core nodes for data aggregation and forwarding, and their reliability and performance directly affect the communication stability of the entire system. The Beckhoff CU20xx series (5/8/16 port 100Mbps) and CU22xx series (8-port Gigabit) industrial Ethernet switches are ideal choices for network cabling inside control cabinets due to their compact metal casing, unmanaged plug and play design, automatic cross detection, and wide temperature capability. However, in the face of practical issues such as lack of support for PoE, limitations on macro frame usage, UL power supply standards, and on-site LED diagnostic interpretation, engineers need a clear practical guide. This article is based on official technical documents and presents a systematic engineering practice manual for you, covering model selection, mechanical installation, electrical wiring, functional principles, and troubleshooting.

Product Series Overview and Selection Points

The CU20xx/CU22xx series includes four models, all of which are installed on DIN rails, powered by spring terminals (24V DC), and support adaptive speed and full/half duplex modes:

Model, Port Number, Rate, Typical Current Size (W × H × D), Giant Frame Support

CU2005 5 10/100 Mbit/s 90 mA 73 × 100 × 38 mm No

CU2008 8 10/100 Mbit/s 100 mA 85 × 100 × 38 mm No

CU2016 16 10/100 Mbit/s 150 mA 146.5 × 100 × 38 mm No

CU2208 8 8 10/100/1000 Mbit/s 180 mA 122 × 100 × 38 mm is (≤ 9720 bytes)

Selection decision:

If the network needs to transmit a large amount of video or high-throughput data, choose CU2208 Gigabit Switch, but its macro frame function is only effective on Gigabit link ports, and it supports up to 2 ports using macro frames at full load.

All models do not support PoE (IEEE 802.3), and it is strictly prohibited to connect PSE devices, otherwise it may cause damage.

The ambient temperature range is 0-55 ° C, storage is -25~85 ° C, humidity is 95% without condensation, meeting the basic requirements of industrial sites.

Mechanical installation: DIN rail fixation and space reservation

The CU series switch adopts standard 35mm DIN rail installation (compliant with EN 50022), and installation and disassembly do not require tools:

Installation steps:

Fix the installation guide rail in the designated position of the control cabinet.

Hang the lower side card spring of the switch onto the lower edge of the guide rail.

Push the switch (1) upwards while pressing the upper side (2) towards the guide rail until you hear the locking sound.

Connect the cable.

Disassembly steps:

Remove all cables.

Push the switch (3) upwards to disengage the lower side.

Pull the upper side (4) away from the guide rail and remove the switch.

Space requirements:

The depth varies depending on the RJ45 connector model, and it is recommended to reserve sufficient space for plugging and unplugging.

An additional height of approximately 10mm is required above the guide rail to facilitate the locking action.

The width of each model is shown in the table above. When multiple units are installed side by side, the heat dissipation gap (at least 20mm) should be considered.

Electrical wiring and power requirements

3.1 Power supply terminal (spring type three pin)

Terminal definition:+(24V DC positive), - (0V), PE (protective grounding).

Voltage range: 18~30V DC, with polarity reversal protection.

Current consumption: CU2005 about 90mA, CU2008 about 100mA, CU2016 about 150mA, CU2208 about 180mA.

3.2 UL compliant power supply (key)

According to UL certification requirements (cULus), switches must be powered by one of the following methods:

Isolation power supply, with a maximum 4A fuse connected in series at the front end (compliant with UL248); or

NEC Class 2 power supply (output limited).

It is strictly prohibited to use two NEC Class 2 power supplies in series or parallel.

In addition, the device must not be connected to an unrestricted voltage source, otherwise it does not comply with UL safety regulations.

3.3 Ethernet wiring

The RJ45 interface supports automatic cross detection (Auto MDI/MDIX), which can be connected directly or across Ethernet cables.

The maximum length of twisted pair cables is 100 meters, and switches can be cascaded without restrictions (but attention should be paid to total latency and broadcast storm risks).

The pin definition follows the standard EIA/TIA 568B (1, 2 send, 3, 6 receive).

LED status diagnosis

Each RJ45 port is equipped with two LEDs, providing real-time link and activity status:

Meaning of LED status

Link/ACT (green/yellow) is off and there is no connection

Constant light link established (Link)

Flashing Data Transmission (Activity)

100/1000 (orange/green) extinguishes 10 Mbit/s connection

Constant brightness (CU2005/08/16) 100 Mbit/s connection

Constant brightness (CU2208) 1000 Mbit/s connection

Power LED (green): Constant light indicates normal 24V power supply.

Quick fault location:

If the Link light on a certain port does not light up: check if the network cable is disconnected, if the other end device is powered on, and if the port is disabled (no disabled function for unmanaged switches, which can generally be ruled out).

If the Activity light continues to flash rapidly but communication is abnormal: there may be a broadcast storm or frame conflict, check the network loop or faulty device.

If the 100/1000 light is not on but the Link light is on, it indicates that the negotiation is for 10M, which may be due to poor network cable quality or the other end only supporting 10M.

Functional principles and usage limitations

5.1 Storage and forwarding mechanism

The switch adopts a store and forward mode: after receiving a complete frame, it first checks the CRC, discards erroneous frames (CRC error), frames that are too short (<64 bytes), or frames that are too long (>1536 bytes, in the case of non jumbo frames), and then forwards them to the target port. This ensures that 'junk frames' in the network will not be spread.

5.2 Address Learning and Aging

The switch automatically learns the MAC address of the devices connected to each port and maintains an address table (>1000 addresses per port). If an address is inactive for about 5 minutes (aging time), it will be removed from the table and re learned later. This mechanism allows the switch to connect the entire network segment without affecting performance.

5.3 Throughput

CU series switches can achieve line speed forwarding (148800 frames per second @ 100M, or higher @ Gigabit), ensuring real-time data is unobstructed.

5.4 Mega frame support (proprietary to CU2208)

CU2208 supports frames of up to 9720 bytes, but please note:

Mega frames only take effect on gigabit link ports.

Mega frames require extremely high internal data throughput, with a maximum of 2 ports simultaneously transmitting mega frames at full load, otherwise frame loss may occur.

The macro frame is not standardized, and it needs to be confirmed that the frame format used by the application is compatible with CU2208.

5.5 PoE not supported

CU series switches do not comply with the IEEE 802.3 PoE standard and cannot be used as PSE (power supply equipment) or PD (power receiving equipment). Any PSE device connected to the switch (such as a PoE injector) must not apply voltage, otherwise it may damage the switch or pose a safety hazard.

Common Troubleshooting Ladder Table

Troubleshooting steps for possible causes of fault phenomena

The whole machine has no power (Power LED off). The power supply is not connected or the voltage is insufficient. Measure the voltage of the power supply terminal (18-30V); Check if the polarity is correct; Check if the external fuse is blown

The Link light on a certain port does not light up, the network cable is disconnected, the other end device is not powered on, or the port is faulty. Replace the network cable for testing; Check if the peer device is started; Try connecting to another port to confirm if the port is damaged

Link light on but unable to communicate (Ping timeout) IP address configuration error or switch not learning MAC confirmation that the peer IP is in the same subnet; Check if there is a broadcast storm (Activity light keeps flashing); Try restarting the switch

The network speed is much lower than expected due to poor cable quality, resulting in a speed drop to 10M. Check the 100/1000 LED status; Replace Cat5e or Cat6 cables; Avoid wiring that is too long (>100m)

Giant frame transmission packet loss (CU2208): More than 2 ports are simultaneously using giant frames or the link is limited to 100Mbps. The number of giant frame ports is ≤ 2; Confirm that all macro frame links are gigabit; Attempt to reduce the size of giant frames

After misconnecting a PoE device, the switch does not respond and the PoE voltage is damaged. The internal circuit of the switch is immediately disconnected from the PoE device; Contact Beckhoff Service for repair (not covered by warranty)

After cascading multiple switches, the network is paralyzed and there are network loops (the spanning tree protocol is not enabled). Check the topology to ensure that there are no redundant loops; The CU series does not have STP and requires manual confirmation of ring free operation

The power LED is on but all port Link lights are off. If there is an internal fault or poor grounding in the switch, check if the PE grounding is reliable; Attempt to supply power separately to eliminate interference; If still ineffective, repair

Environmental and UL Compliance Precautions

Working temperature: 0~55 ° C, avoid approaching heating elements to ensure convective heat dissipation.

Storage temperature: -25~85 ° C, avoid severe vibration during transportation (in accordance with EN 60068-2-6).

Protection level: IP20 (only applicable to dry and clean control cabinets), strictly prohibited from use in damp and dusty environments.

UL certification: Switches are only compatible with Beckhoff's UL Listed EtherCAT system and must not be connected to telecommunications circuits (such as telephone lines). When used in the North American market, it is essential to comply with 4A fuses or NEC Class 2 power supply requirements.

Maintenance and scrapping

There are no user replaceable components inside the switch. When cleaning, only wipe the outer shell with a dry soft cloth and do not use solvents.

When disposed of, follow the WEEE directive, the metal casing can be recycled, and the circuit board should be disposed of as electronic waste.