What it means
The controller is reporting excessive differential pressure across the fluid separator.
The STS manual lists this as a warning and also includes it in the troubleshooting table. If the machine has progressed to a fault or shutdown, do not bypass the protection.
Likely causes
- Separator element is restricted or plugged
- Pressure sensor or related wiring is giving an incorrect differential-pressure reading
Operator-safe first checks
- Record the exact displayed message and whether the amber warning or red fault indicator is active.
- Check whether separator service is already overdue in the maintenance history.
- Do not open the separator vessel or any pressurized connection while the package is pressurized.
Trained maintenance / service checks
- After proper isolation, lockout and full depressurization, inspect the separator condition and differential pressure.
- Check the relevant pressure sensor wiring and signal if the separator condition does not explain the reading.
Can the compressor keep running?
Do not treat a warning as permission to ignore the condition. The STS normally allows operation through many warnings, but a red fault leaves the compressor inoperative until corrected.
Source confidence
OEM VERIFIED
Sullair defines High Separator dP as high fluid-separator differential pressure; the troubleshooting table points to separator restriction and pressure-sensor failure.
Source: Sullair STS Controller User Manual, part 02250241-178 R01. Referenced manual page(s): 20, 31, 34.