Description
- Model: P0926MX
- Brand: Foxboro (Schneider Electric)
- Series: I/A Series / EcoStruxure Foxboro DCS
- Core Function: 16-Channel Discrete Output (Externally Powered)
- Product Type: Fieldbus Module (FBM)
- Key Specs: 16 Isolated Outputs | 24 V DC External Power | DIN Rail Mounted
- Output Channels: 16 Isolated Discrete Outputs
- Output Voltage: 15 to 60 V DC (External Source)
- Maximum Current: 2 A per channel (Current limited by external circuitry/fuses)
- Communication: Redundant 2 Mbps Module Fieldbus
- Isolation: 250 V AC between group and ground; 42 V DC between channels
- Power Consumption: 3 W (Maximum) from the baseplate
- Mounting: Horizontal or Vertical on a modular Baseplate
- Operating Temp: -20 to +70 °C (-4 to +158 °F)
- Environmental: G3 Harsh Environment (Conformal Coated)
FOXBORO P0926MX
Application Scenarios & Pain Points
In large-scale industrial automation, specifically in chemical and oil & gas facilities, the FBM242 (P0926MX) is the muscle of the Foxboro DCS. It is used to drive solenoid valves, motor starters, and indicating lamps that require external power to operate. In my experience, the “externally powered” nature of this module is its greatest strength but also its most common point of failure. If the external 24V supply develops high-frequency noise or if a field solenoid shorts out, it can stress the internal opto-isolators on the P0926MX. Having a spare on hand is vital because a single failed output can mean a critical safety valve won’t move when commanded by the controller.
Typical Application Scenarios:
- Solenoid Valve Control: Operating high-current pneumatic or hydraulic valves in a process plant.
- Motor Control Centers (MCC): Sending start/stop signals to large industrial motors.
- Alarm Annunciation: Driving large visual or audible sirens across a facility.
- Interposing Relays: Triggering heavy-duty relays that handle voltages higher than 60V DC.
Case Study: The “Stuck” Solenoid
Background: A refinery in Southeast Asia noticed that a specific cooling water valve refused to close during a batch sequence. The HMI showed the command was sent, but the field valve remained open.
Problem: The site team checked the field wiring and found the solenoid was fine. However, a local surge had damaged the output transistor on the P0926MX module. The module reported “Healthy” status because the logic side was fine, but the physical output path was blown open.
Solution: We supplied a tested P0926MX from our newplcdcs inventory.
Result: Because the FBM242 is hot-swappable, the technician swapped the module on the live baseplate. Once the new module initialized, the valve responded to the next command. The plant avoided an overflow situation that would have occurred if the cooling sequence had failed again.
FOXBORO P0926MX
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevant to this Module? | Quick Check | Action |
| No Output on all channels | External Power Loss | ✅ High | Measure 24V at the Terminal Assembly | Check field power supply |
| Single Channel Dead | Transistor Failure | ✅ High | Swap with an adjacent unused channel | Replace P0926MX Module |
| “Bus Fail” LED | Fieldbus Communication Error | ⚠️ Medium | Check baseplate connector pins | Reseat module or check cable |
| Erratic Switching | Ground Loop / EMI | ✅ High | Check shielding on external power | Ensure proper grounding |
Technical “Pro-Tips” (Avoiding Common Pitfalls)
Replacing a P0926MX is usually a 2-minute job, but keep these points in mind:
- Terminal Assembly (TA) Match: The P0926MX must be used with the correct Terminal Assembly (like the P0916AQ). If you try to seat it on a TA meant for an FBM201 (Analog Input), it won’t work and you might damage the pins.
- External Fusing: Even though the module has internal protection, I always recommend external fuses for your solenoid loads. It’s much cheaper to replace a 50-cent fuse than a P0926MX module.
- Letter Revision: Foxboro often updates these with suffix letters (e.g., P0926MX-B). Usually, these are backward compatible, but always check your system software version to ensure the new hardware revision is recognized.
❗ Warning: Always verify that the “External Power” is disconnected or that the load is safe to cycle before plugging in the new module. Upon initialization, the module may briefly cycle outputs depending on the controller’s “Fail-Safe” configuration.
Other Foxboro Models in Our Inventory:
- Foxboro FBM217 P0914TR
- Foxboro FBM201 P0914XQ
- Foxboro FBM214B P0922VT
- Foxboro FBM241 P0914TG
- Foxboro FBM237 P0914SY
- Foxboro P0916AA
- Foxboro P0916CP
- Foxboro P0904HK
