Phoenix Contact 2744429 Isolated Repeater

1.Basic Model Information

Order No.: 2744429

Full Model: PSM-ME-RS485/RS485-P

Product Type: RS485 Isolated Repeater (Bus Signal Amplifier / Segment Isolator)

Origin: Germany

Mounting: Standard DIN 35 mm rail mounting

Housing Dimensions: W 22.5 mm × H 99 mm × D 114.5 mm, IP20 protection

Housing Material: Flame-retardant PA6.6, Green RAL6021

2. Core Functions
3. 3-way Galvanic Isolation: Power Side ↔ Segment A Bus ↔ Segment B Bus, completely eliminating ground loop interference, surge and common-mode noise.
4. Bus Segmentation & Capacity Expansion: Max. 32 nodes per single RS485 segment; each segment supports independent 32 nodes after repeater connection. Up to 9 units cascaded at low baud rates.
5. Extended Transmission Distance: Standard 1200 m (twisted pair; lower baud rate corresponds to longer transmission distance).
6. Compatible Bus Protocols: Modbus RTU, PROFIBUS-DP, general 2-wire RS485 half-duplex bus.
7. Automatic Direction Control: No external RTS/CTS required; hardware auto transmit/receive switching.
8. Electrical Specifications

3.1 Power Supply

Rated Voltage: 24 V AC/DC ±20%

Typical Power Consumption: 90 mA @ 24 VDC, max. 100 mA

Isolation Withstand Voltage: ≥2.5 kV AC between power supply and buses, and between two bus segments.

3.2 Communication Interface (Dual 2-wire RS485 Half-duplex)

Baud Rate Range: Full coverage from 4.8 kbps to 1500 kbps

4.8 / 9.6 / 19.2 / 38.4 / 57.6 / 75 / 93.75 / 115.2 / 187.5 / 375 / 500 / 1500 kbps

Frame Format: Switchable 10-bit / 11-bit, NRZ UART encoding

Signal Delay: Bit delay ＜ 200 ns, signal distortion ＜ 1.5%

Termination Resistor: Built-in 220 Ω + 390 Ω switchable via DIP switch

Terminal Block: Screw pluggable terminals, cable cross-section 0.2~2.5 mm² (AWG24~14)

3.3 Environmental Parameters

Operating Temperature: -40 ℃ ~ +70 ℃ (Wide-temperature industrial grade)

Storage / Transport Temperature: -40 ℃ ~ +85 ℃

Humidity: 10%~95% non-condensing, max. altitude 5000 m

Vibration / Shock Resistance: 5 g vibration, 25 g shock, compliant with IEC industrial standards.

4. Certifications & Approvals

General Certifications: CE, UL, cUL, RoHS, EAC, DNV GL Marine Approval

Explosion Protection: ATEX II 3G Ex ec IIC T4 Gc (Suitable for hazardous areas)

EMC: Full set of EN61000 anti-interference standards (ESD, surge, RF radiation)

5. Typical Application Scenarios
6. Multi-instrument Modbus networking in factories; segmented isolation when node quantity exceeds 32.
7. Long-distance cross-workshop PROFIBUS-DP wiring to eliminate ground potential difference.
8. Mixed high/low voltage control cabinets; isolate RS485 bus from inverter interference.
9. Signal extension for field bus in chemical & oil/gas hazardous areas.
10. Building automation, long-distance remote PLC RS485 acquisition sub-stations.
11. Alternative Model Reference

Cost-effective non-explosion-proof variant of same series: PSM-ME-RS485/RS485 (without ATEX, different order number)

Fiber-optic isolated version: PSM-ME-RS485/FO, alternative for long-distance heavy electromagnetic interference scenarios.

7. Key Operation Guidelines
8. Termination resistors must be enabled via DIP switches at both physical ends of each bus segment respectively.
9. Use shielded twisted pair for bus wiring; single-point grounding for shield layer.
10. Maximum cascade limit: Up to 9 units at 4.8~93.75 kbps; reduce cascade quantity for high baud rates.
11. Three independent isolation channels allow connection to devices with different ground potentials to avoid communication dropouts.

Official Installation Manual for Phoenix Contact 2744429 (PSM-ME-RS485/RS485-P)

Basic Document Information

Order No.: 2744429

Full Model Name: PSM-ME-RS485/RS485-P

Product Type: 3-way Isolated RS485 Repeater (with ATEX explosion-proof certification)

Mounting Standard: DIN EN 60715 TH35 standard rail

Protection Class: IP20 (Indoor cabinet use only)

Applicable Environment: -40 ℃ ~ +70 ℃, non-condensing, free of dust and water accumulation.

1. Pre-installation Preparation

1.1 Tool List

Flat-blade screwdriver (2.5 mm), torque screwdriver, rail end stop (E/NS35 N, Order No. 0800886), shielded twisted pair cable, multimeter.

1.2 Cable Specifications

Power Terminals: 0.2~2.5 mm² solid / stranded copper wires

RS485 Bus: Dedicated shielded twisted pair (0.5~0.75 mm² recommended)

Terminal Tightening Torque: 0.5~0.6 N·m (5~7 lb-in)

1.3 Installation Environment Prohibitions

1. Do not mount directly under inverters, contactors or high-power transformers (blocked heat dissipation air duct + electromagnetic interference).
2. Reserve ≥25 mm ventilation gap above and below the module.
3. Keep away from 380 V power cables; separate trunking for power and signal cables.
4. Strictly comply with ATEX II 3G Ex ec IIC T4 Gc zoning regulations for hazardous area installations.
5. DIN Rail Mechanical Installation Procedures

2.1 Mount Module onto DIN Rail

1. Fix clean, rust-free standard TH35 DIN rail on cabinet backplate.
2. Hook the upper latches of the module onto the top edge of the rail.
3. Press the bottom of the module forward until a click sound indicates full locking.
4. Install rail end stops on both sides of the module to prevent sliding during operation.

2.2 Module Removal Steps

1. Pry down the bottom locking tab of the module with a flat-blade screwdriver.
2. Gently pull the lower part of the module outward.
3. Lift upward to disengage the upper latches from the rail for removal.

2.3 Mechanical Installation Notes

Do not strike or force plug/unplug the module to prevent damage to internal isolation circuits.

Install shock-absorbing mounting brackets for cabinet rails in high-vibration equipment (stamping, mining).

Only horizontal transverse mounting is permitted; vertical upside-down installation is forbidden.

3.2 Standard Wiring Rules (2-wire Half-duplex Modbus / PROFIBUS)

1. Strictly match bus polarity one-to-one: A1 connects to device A of upstream equipment, B1 connects to device B of upstream equipment; A2 connects to substation A of downstream equipment, B2 connects to substation B of downstream equipment.
2. Shield layer of shielded twisted pair: Single-point grounding at both physical ends of the bus. Unify G1/G2 terminals of intermediate repeaters to FE terminal for central single-point grounding. Strictly prohibit double-ended grounding which forms ground loops.
3. Power wiring: L+ and Lcannot be reversed. Built-in reverse polarity protection exists, yet long-term reverse connection will shorten service life.
4. Do not short-circuit A/B terminals or mix power and bus terminals; short circuits will burn isolation circuits.

3.3 Mandatory Wiring Requirements for Hazardous Areas

1. Use explosion-proof shielded cables with cable glands complying with Ex ec standard.
2. Reliably connect FE earth bar to protective earth of explosion-proof cabinet; ground resistance ＜ 4 Ω.
3. No mid-bus tapping; termination resistors can only be installed at the two physical ends of the bus.
4. DIP Switch Configuration Operation

4.1 DIP Switch Location

Pry open the plastic side cover of the module; two groups of DIP switches are inside:

1. S1: Termination resistor for Segment A bus (220 Ω + 390 Ω voltage divider matched to 120 Ω bus)
2. S2: Termination resistor for Segment B bus

4.2 DIP Switch Application Rules

ON: Enable built-in termination resistor; OFF: Disable termination resistor.

Only set the DIP switch to ON for devices/repeaters at the physical extreme ends of the bus; set all intermediate nodes to OFF.

Typical Scenarios:

1. PLC at the start of Segment A bus, this repeater at Segment A end → S1=ON
2. Last instrument at the end of Segment B bus → S2=ON
3. Repeater only used as intermediate segment divider with other terminals at both ends of two bus segments → S1 and S2 both OFF

4.3 Transmission Rate Adaptation Note

This model features hardware auto-adaptation from 4.8 kbps to 1500 kbps; no baud rate DIP switch required. Hardware auto transmit/receive switching without RTS control signal.

5. Power-on Commissioning Steps
6. After wiring completion, measure voltage between L+/Lwith multimeter: 19.2~28.8 V (24 V ±20%), no short circuit.
7. Power on without load; steady green power indicator light means normal operation. If off, inspect power supply circuit.
8. Bus communication test:

Flashing DATA indicator during data transmission indicates normal signal forwarding.

No flashing: Check reversed A/B polarity, mismatched termination resistor setting or broken bus cable.

4. Communication packet loss troubleshooting: Inspect shield grounding, separation of power & signal cables and termination resistor configuration.
5. Electrical Isolation Safety Instructions (Core)

The module adopts three independent isolation channels: Power ↔ Bus A ↔ Bus B, with isolation withstand voltage of 2.5 kV AC.

1. Supports connection of two bus segments with different ground potentials to eliminate ground potential difference interference.
2. Isolates bus segments connected to inverters and high-power motors, preventing surge breakdown of PLC communication ports.
3. Provides physical isolation between hazardous area bus and control room bus to meet Ex safety clearance requirements.
4. Installation Acceptance Criteria
5. Mechanical: Module fixed without looseness, latches fully engaged, rail end stops installed properly.
6. Wiring: All terminals tightened to 0.5~0.6 N·m, no bare copper exposed, no insulation trapped under terminals.
7. Grounding: FE terminal reliably connected to cabinet protective earth, single-point shield grounding without ground loops.
8. DIP Switch: Termination resistors only enabled at bus two ends, all intermediate nodes disabled.
9. Power-on: Steady power indicator light, normal flashing of communication indicator during data transmit/receive.
10. Environment: Unobstructed ventilation above and below module, kept away from strong electromagnetic interference sources.
11. Installation Fault Troubleshooting Matrix

9. Compliance & Maintenance Requirements
10. Certifications: CE, UL, ATEX, DNV GL, RoHS; retain certification documents for hazardous area projects.
11. Periodic Maintenance (Every 6 Months):

Inspect terminal torque to prevent loosening caused by thermal expansion & contraction.

Clean dust on module surface to guarantee ventilation.

Re-test ground resistance and confirm intact shield grounding.

3. Modification Prohibitions: Do not remove isolation circuits, short isolation terminals or replace with non-original terminal accessories.

Cross-brand Model Comparison Table for Phoenix Contact 2744429 (PSM-ME-RS485/RS485-P)

Core Features of Reference Product (Replacement Matching Criteria)

1. 3-way isolation: Power ↔ Bus A ↔ Bus B, 2.5 kV AC isolation rating
2. 2-wire RS485 half-duplex, auto TX/RX switching, compatible with Modbus / PROFIBUS
3. DIN35 rail mounting, wide temperature range -40~+70 ℃, built-in switchable termination resistors
4. Wide-range 24 V AC/DC power supply, narrow 22.5 mm housing width
5. Factory-certified ATEX II3G explosion protection (Key distinguishing factor)
6. Direct Replacements from Top European Industrial Automation Brands (Preferred for Standardized Projects)

1.1 Weidmüller (Explosion-proof Isolated Repeater with Same Positioning)

1.2 Siemens

1.3 Schneider Electric

1.4 ABB

2. Cost-effective Alternatives from Domestic Industrial Communication Brands (Cost-down Projects)

2.1 Advantech

2.2 Moxa

2.3 Mornsun (DIN Rail Isolated Repeater)

3. Internal Phoenix Contact Replacements (OEM Spare Parts, Zero Rewiring)
4. 2744416 PSM-ME-RS485/RS485 (No P Suffix)

Matching Rate: 99%

Difference: No ATEX explosion-proof certification; terminals, DIP switches, dimensions and electrical performance fully identical

Replacement Suggestion: Direct swap in non-hazardous zones without wiring modification

2. PSI-REP-RS485W2 (Order No. 2313096)

Matching Rate: 85%

Difference: 4-way isolation, wider housing, enhanced surge protection, higher price; suitable for heavy-interference high-power workshops

4. Replacement Selection Grading Recommendations

Grade 1: Fully Seamless Replacement (Priority for Hazardous Area Projects)

Weidmüller 7760054321

3-way isolation + ATEX explosion-proof, narrow 22.5 mm housing, consistent terminal logic; universal wiring, installation and DIP switch rules, only slightly lower max baud rate for high-speed buses.

Grade 2: OEM Equivalent for Non-hazardous Zones (Optimal Cost)

Phoenix Contact 2744416 (Same brand non-explosion-proof variant)

Identical cabinet cutout size, terminal layout and termination resistor DIP switch; plug-and-play replacement without program modification.

Grade 3: Compatible Replacement for Siemens Complete Cabinet Projects

6ES7972-0CB20-0XA0

Supports dual DP & Modbus protocols, 3-way isolation; only wider housing requires reserved cabinet space.

Grade 4: Low-cost General Industrial Replacement (Non-hazardous, Low Interference)

Moxa TCC-80I / Advantech ADAM-4510S

Not recommended for hazardous areas, inverter-dense workshops or sites with large cross-equipment ground potential differences.

5. Replacement Risk Warnings (Key Differentiators)
6. ATEX Explosion Protection: Only Phoenix Contact 2744429 and Weidmüller 7760054321 carry explosion-proof certification; all other models cannot be deployed in Ex zones, causing compliance failure if substituted.
7. Independent 3-way Isolation: Siemens 6ES7972-0AA02 and Advantech ADAM-4510 only provide 2-way isolation, prone to communication dropouts when crossing large ground potential differences.
8. Max Baud Rate: Weidmüller explosion-proof model capped at 500 kbps vs. original 1500 kbps; caution for high-speed Profinet / high-speed Modbus applications.
9. Housing Width: Siemens, ABB and Moxa units mostly 30~45 mm wide; rail layout adjustment required for original 22.5 mm narrow installation slots.