Why is separator pressure drop high on my Sullair WS compressor?
Short answer: Separator pressure differential trip. If your Sullair WS Controller is showing Separator dP High, the controller has logged a specific, documented condition. This page covers what it means, what causes it, what you can safely fix yourself, and when — and why — it takes a technician.
What exactly is the machine telling you?
The pressure differential across the air/fluid separator has exceeded the set high limit (warning threshold is 10 psid). Plugged separator elements or a pressure sensor failure are the documented causes.
Which machines show this?
Sullair's mid-range stationary rotary screws fitted with the WS controller — a text-display unit found on many shop and light-industrial packages from the 2010s. The WS names its faults in plain English (High Temperature, Separator dP High, Aux Motor Overload, Power Interruption) and uses staged temperature protection: a warning at 225 °F, a time-delayed fault at 235 °F, and an immediate trip at 255 °F. Faults are reset from the STOP key after the cause is corrected and the unit has cooled. Practical tip: if the auto-restart timer is configured, the machine can start by itself after a power interruption — make sure nobody is working near it before you walk away from a Power Interruption message.
What causes it?
- Separator elements plugged (warning threshold is 10 psid)
- Pressure sensor failure — the other documented cause
Can you fix it yourself?
The homework is in-house: check separator hours against the schedule and arrange the replacement. The swap itself is not.
Step by step — what to try, in order:
- Check separator hours against the maintenance schedule
- Arrange replacement of the separator element
- Visually check sensor wiring connections with power locked out
When do you need a technician — and why?
The separator lives inside the pressurized sump vessel, so the element change goes to a technician.
If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service industrial air compressors — real businesses with verified contact information, none of whom paid to be listed.
Related questions
What does Separator dP High mean on a Sullair WS Controller?
Separator pressure differential trip. The pressure differential across the air/fluid separator has exceeded the set high limit (warning threshold is 10 psid). Plugged separator elements or a pressure sensor failure are the documented causes.
Can I fix Separator dP High on a Sullair WS Controller myself?
The homework is in-house: check separator hours against the schedule and arrange the replacement. The swap itself is not.
When does Separator dP High on a Sullair WS Controller need a technician?
The separator lives inside the pressurized sump vessel, so the element change goes to a technician. Call a technician to replace the separator — it is inside the pressurized sump vessel.
Verified against service documentation: Sullair WS Controller documentation for Separator dP High (best-aire.com)