The FX3U-16MR/ES-A is Mitsubishi Electric’s 16-point relay output base unit for the MELSEC FX3U compact PLC series, providing 8 digital inputs and 8 relay contact outputs in a self-contained AC-powered controller housing — combining the FX3U’s high-speed processing engine with relay output versatility for direct AC and DC load switching without external interface relays. As the smallest relay output model in the FX3U range, the FX3U-16MR/ES-A is the preferred specification for compact machine control applications requiring a small I/O count with the flexibility to control AC solenoids, indicator lamps, and contactors directly from the PLC output terminals. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the FX3U-16MR/ES-A?
The FX3U-16MR/ES-A is a MELSEC FX3U series compact PLC base unit — a self-contained programmable controller integrating CPU, memory, power supply, and I/O in a single housing. The «16» indicates 16 total I/O points (8 inputs + 8 outputs), «M» indicates the main unit (base unit), «R» indicates relay output type, «ES» indicates the AC power supply input (100–240 VAC), and «A» indicates the standard FX3U model generation. The FX3U CPU executes programs at 0.065 µs per basic instruction — the fastest in the FX3U family — with a program memory capacity of 64,000 steps, supporting ladder, SFC, structured text, and function block programming via GX Works2 and GX Works3. The base unit can be expanded with FX3U extension modules (FX3U-xEY/FX3U-xEX) for additional I/O, and with FX3U special adapter modules (FX3U-4AD-ADP, FX3U-4DA-ADP) mounted to the left side of the base unit for analogue, temperature, and high-speed counter functionality.
Key Technical Specifications
- Model: FX3U-16MR/ES-A
- Total I/O Points: 16 (8 inputs + 8 outputs)
- Input Type: 24 VDC sink (X0–X7)
- Output Type: Relay contact (Y0–Y7), 2 A per point, 240 VAC / 30 VDC
- Power Supply: 100–240 VAC, 50/60 Hz
- Program Memory: 64,000 steps
- Execution Speed: 0.065 µs per LD instruction
- Built-in Functions: 6 high-speed counter inputs (100 kHz), 3 pulse outputs (100 kHz)
- Communication: RS-422 (built-in), USB via FX3U-USB-BD option
- Real-Time Clock: Built-in
- Battery Backup: Yes (program and data retention)
- Expansion: Up to 8 extension units, up to 4 special adapter modules
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 90 mm × 90 mm × 87 mm
- Weight: Approx. 0.65 kg
Typical Industrial Applications
The FX3U-16MR/ES-A is deployed in compact standalone machine control applications where AC load switching capability is required and the I/O count is small. Typical installations include small conveyor indexing systems with two or three stations, where the 8 relay outputs control conveyor drive contactors, pneumatic valve solenoids (via relay interface), and warning indicators powered directly from the 240 VAC panel supply without intermediate relay hardware. Pump station controllers in water treatment and irrigation applications use the FX3U-16MR/ES-A to control motor starters, valve actuators, and alarm beacons on 110 VAC or 230 VAC power, with the built-in real-time clock enabling timed automatic operation and the RS-422 port providing SCADA connectivity via Modbus RTU or Mitsubishi communication protocol. In building management and HVAC, the FX3U-16MR/ES-A controls air handling unit damper actuators, fan motor starters, and zone valves — 8 relay outputs are sufficient for most single-zone AHU control applications, and the AC power supply input eliminates the need for a separate 24 VDC power supply in panels already supplied with 230 VAC. Small injection moulding machine controllers for laboratory and educational use also commonly specify the FX3U-16MR/ES-A for its compact size, relay output flexibility, and the FX3U’s extensive built-in function block library for temperature PID control via the FX3U-4LC expansion module.
Replacement & Upgrade Notes
The FX3U-16MR/ES-A is the direct replacement for the legacy FX2N-16MR-ES/UL in most applications — the FX3U provides substantially faster execution (0.065 µs versus 0.08 µs per basic instruction for the FX2N), larger program memory (64,000 steps versus 16,000 steps), and enhanced built-in communication options. FX2N ladder programs can be imported into GX Works2 and re-compiled for the FX3U-16MR/ES-A without modification in most cases — Mitsubishi’s GX Works2 compatibility check function identifies any instructions that differ between the two platforms. The FX3U-16MR/ES-A is also compatible with most FX2N expansion I/O modules (FX2N-xEX, FX2N-xEY) via a passive adapter, allowing existing I/O expansion hardware to be reused when upgrading the base unit. Note that FX2N special function modules (analogue, temperature, positioning) are not compatible with the FX3U — these must be replaced with equivalent FX3U special adapter modules or the newer FX3U-32BL special function module range during an FX2N-to-FX3U migration. For new system designs requiring more than 16 I/O points or advanced communication (Ethernet, CC-Link), the FX5U-32MR/ES or FX5U-64MR/ES from the FX5 series provides a direct upgrade path within the Mitsubishi compact PLC family.
Frequently Asked Questions
Q: Can the FX3U-16MR/ES-A relay outputs directly control a 230 VAC motor contactor coil?
A: Yes. The FX3U-16MR/ES-A relay contacts are rated at 2 A at 240 VAC for resistive loads, which is more than sufficient to control standard 230 VAC contactor coils (typically 50–200 mA inrush at 230 VAC). For contactor coils with high inductive switching energy, fit a varistor or RC snubber across the contactor coil terminals to suppress the voltage spike at coil de-energisation — this protects the relay contact from arc erosion and extends relay service life beyond the rated 200,000 operations for inductive loads.
Q: How many extension modules can be connected to the FX3U-16MR/ES-A?
A: The FX3U-16MR/ES-A supports up to 8 FX3U extension I/O units connected to the right side of the base unit via the extension bus connector, expanding the total I/O to a maximum of 256 points (8 inputs + 8 outputs base + up to 240 extension points). Up to 4 FX3U special adapter modules (analogue, temperature, high-speed counter) can be connected to the left side of the base unit. The total expanded I/O must not exceed the FX3U CPU’s maximum supported I/O address range of 256 points.
Q: Does the FX3U-16MR/ES-A include a built-in Ethernet port?
A: No. The FX3U-16MR/ES-A has a built-in RS-422 port for programming and Modbus RTU or Mitsubishi protocol communication, but does not include Ethernet. Ethernet connectivity requires the FX3U-ENET-L Ethernet adapter module or the FX3U-ENET-ADP adapter, which connects to the left-side special adapter interface. For new designs requiring built-in Ethernet, specify the FX5U-32MR/ES which includes a built-in 100BASE-TX Ethernet port as standard.
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