Pump stations have a way of failing at 2 AM, during the storm, with a full sump and nobody on site. Two pumps, one lead and one lag — the lead wears out from all the starts while the lag sits pristine untill the day it is suddenly needed and fails from disuse. That is not bad luck. That is unautomated pumping.
The fix fits on a DIN rail, costs less than one emergency call-out, and can text the duty engineer when something goes wrong.
The Station and the Three Problems
- Alternation: both pumps must share the load, so the station keeps working when one pump fails
- Dry-run protection: running a pump without water destroys the mechanical seal in minutes
- Remote alarm: nobody sits at the station — the alarm has to travel to a phone
The Solution: PR-26DC-DAI-RT-4G
The PR-26DC-DAI-RT-4G is a 26-point Micro PLC with analog inputs and a built-in 4G channel. A 4-20mA level transmitter reads the sump level; the program alternates the lead pump by run time, trips the running pump on low level, and restarts with a delay so it does not short-cycle.
Level logic is where a real PLC earns its keep. Below 4mA on the loop means a broken wire, not an empty tank — the program flags it as a sensor fault instead of dry-running the pump. The comparator blocks set the start/stop thresholds, the run-time counters drive the alternation, and the alarm chain fires on level, pump fault or wire break.
When an alarm trips, the 4G module sends an SMS with the fault code to the duty engineer. No internet connection, no SCADA, no app — just a text message that wakes somebody up. On Ethernet sites the same station reports to EasySCADA or a cloud dashboard over Modbus TCP, so the contractor can watch trends from a laptop.
Commissioning Notes
The station in our test bench: one PR-26DC-DAI-RT-4G, one level transmitter, two contactors. The program — alternation, dry-run, restart delay, SMS alarm — took about fifty blocks and an afternoon. The first simulated storm cycled both pumps, sent one SMS, and nobody had to leave the office. The test report used the word "boring." That is the highest compliment a pump station can earn.
Recommended Models for Pump Groups
| Model | Best for |
| PR-26DC-DAI-RT-4G | Remote sites — alternation + 4G/SMS alarms, no network needed |
| PR-26DC-DAI-RT-2G | Same logic on a 2G network where 4G coverage is patchy |
| PR-26DC-DAI-RT-N | Ethernet sites feeding Modbus TCP to SCADA or BMS |
Related: pump station control deep-dive · EasySCADA setup · Modbus tutorial
