Moxa EDS-308 8-Port Ethernet Unmanaged Switch with Relay Warning

What the EDS-308 does on the plant network

Moxa describes the EDS-308 as unmanaged Ethernet switch with 8 10/100BaseT(X) ports, relay output warning, 0 to 60°C operating temperature. The EDS-308 adds a relay output to an eight-port unmanaged switch, so a loss of power or a link break can be signalled to a PLC or an alarm lamp without any management software.

On the datasheet side, the power input is Redundant dual inputs; 12/24/48 VDC; operating temperature is -10 to 60°C (14 to 140°F); dimensions are 53.6 x 135 x 105 mm (2.11 x 5.31 x 4.13 in); weight is 790 g (1.75 lb); the enclosure is rated IP30.

Standards and approvals printed for this model include hazardous-location listings of ATEX; Class I Division 2; marine approvals (DNV); safety standard UL 508; UL 60950-1; CSA C22.2 No. 60950-1; EN 62368 (LVD). Approvals can differ between variants of a series, so check the one on the exact order code.

Technical specifications

Selection and installation notes

That makes it a sensible choice for remote cabinets, pump houses and packaged plant where you want a hardwired fault signal but not a managed switch. Fiber models in the series allow one or two 100BaseFX uplinks.

On the practical side, mounting is listed as din-rail mounting; wall mounting (with optional kit); the housing is metal; the stated MTBF is 2,972,907 hrs; the warranty period is 5 years. Treat the MTBF as a manufacturer prediction under its stated method, not a guarantee for your site.

Please check the port combination, whether you need the relay alarm wired, and the operating-temperature grade before you place an order. Seven Star LLC supplies as an independent company and prices against the precise code requested.

Related models in the EDS-308 family

Other order codes listed alongside it (14 entries in total): EDS-308, EDS-308-M-SC, EDS-308-M-SC-T, EDS-308-MM-SC, EDS-308-MM-SC-T, EDS-308-MM-ST, EDS-308-MM-ST-T, EDS-308-S-SC, EDS-308-S-SC-80, EDS-308-S-SC-T, EDS-308-SS-SC, EDS-308-SS-SC-80, EDS-308-SS-SC-T, EDS-308-T. Suffixes such as -T generally mark wide-temperature versions and fiber suffixes (M, S, MM, SS with SC or ST) mark the connector and fiber type, but the order code printed on the datasheet governs.

Choosing between the EDS-308 variants

The base EDS-308 is all copper, with eight RJ45 ports, which is enough for most control cabinets in which PLCs, HMIs and drives are a few metres apart. If one link must leave the building or run beside heavy power cables, a fibre version from the family is the better fit: the M and MM codes use multi-mode fibre, the S and SS codes single-mode, and the -80 suffix marks the longer single-mode reach. Two fibre ports allow a cabinet to sit in the middle of a line of connections. For cabinets that can exceed the 60 °C upper limit of the standard version, the -T codes are worth checking against the datasheet. Count the copper ports actually needed, plus some spare, before choosing between copper-only and fibre variants.

Wiring and commissioning

• Mount the switch on a DIN rail with clearance for ventilation around the metal housing; use the optional kit if wall mounting is required.
• Connect two independent 12, 24 or 48 VDC supplies to the removable 6-contact terminal block to use the redundant power inputs.
• Wire the relay output, rated 1 A at 24 VDC, to a PLC input or an alarm lamp so that a power or link fault becomes visible.
• Set the DIP switches for which ports should raise the relay alarm if their link goes down, following Moxa’s manual.
• Connect the devices with shielded industrial cables and check the link and speed LEDs on each port.
• Disconnect one power supply and a monitored link deliberately during commissioning to check that the relay alarm operates.

Troubleshooting a link

Since the switch is unmanaged, most fault finding relies on the LEDs and the relay. A port with no link LED usually points to a cable, connector or device fault; swap the cable before suspecting the port. A port running at the wrong speed or duplex can be caused by a device with fixed settings, while auto-negotiation is used on the switch. If the relay alarm trips without an obvious reason, check both power inputs, since the alarm will report the loss of one supply even when the switch keeps running on the other.

Cabinet conditions in Oman

Outdoor RTU and pump-station cabinets in Oman can become very hot inside during the summer. Measure the cabinet temperature on a summer afternoon before relying on the -10 to 60 °C rating, and add shading, ventilation or cooling where necessary, or choose a -T version. The IP30 rating means the switch relies on the cabinet for protection against dust and moisture, so cabinet seals and filters must be maintained, particularly in desert and sand-prone locations. In coastal plants, humidity must stay non-condensing as the datasheet requires; anti-condensation heaters and sealed cable entries help when cabinets cool at night.

Documents and quotation

The attached file is Moxa’s published datasheet for the family (moxa-eds-308-series-datasheet-v1.4). For a quotation, send the full order code, the quantity required and where the goods are to be delivered.

More products in this range: Industrial Communications.