High Sump Pressure — Quincy QSI Series controller Fault Code

Quincy QSI Series controller

QSI controllers share the sensor family with Power$ync packages, which makes transducers easy to source even when a board is not.

Manufacturer

Quincy

Display

Backlit LCD text display with keypad and status LEDs.

Years produced

~2000 – present across QSI-series screw packages.

Power supply

24 VDC from package control transformer (115 VAC control circuit on many builds).

Ambient range

0 – 45 °C.

Protection rating

IP54 front.

Relay outputs

Star/delta or full-voltage contactors, load solenoid, blowdown, common alarm, remote-run.

Used on

Quincy QSI 245 – 1500 rotary screws
QSB / QGS larger frames on some builds

Features

Load/unload, modulation and auto-dual control modes
Adjustable unload timer and minimum run timer
Maintenance hour counters for fluid, filters and separator
Alarm history with running-hour stamps

Interfaces

Modbus RTU (RS-485)
Volt-free run/alarm contacts
Remote start/stop

Sensor inputs

Sump pressure
Package discharge pressure
Airend discharge temperature (RTD)
Separator ΔP (option)
Motor overload contact

Fault code lookup

High Discharge Air Temperature Airend discharge above shutdown (typ. 109 °C).

First checks

Fluid level and cooler fouling
Thermal bypass valve
Verify RTD against an IR reading at the airend

See trigger conditions & affected models →

High Sump Pressure Sump above limit while loaded.

First checks

Separator element plugged
Minimum pressure valve stuck
Inlet valve not modulating

See trigger conditions & affected models →

Low Sump Pressure Sump failed to build after start.

First checks

Blowdown solenoid leaking through
Inlet valve stuck closed
Transducer zero with unit vented

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Motor Overload Overload relay opened.

First checks

Amp draw vs nameplate on all legs
Voltage imbalance under 2 %
Starter contact condition

See trigger conditions & affected models →

Phase / Rotation Fault Reverse rotation or phase loss.

First checks

Swap two incoming legs
Test the phase monitor relay

See trigger conditions & affected models →

High Separator ΔP Separator differential over threshold.

First checks

Confirm with a mechanical gauge
Check fluid condition — wrong fluid foams and plugs elements early

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Sensor Fault Analog input open or shorted.

First checks

Loop check at the terminal
Shield grounded one end only
Substitute a known-good sensor

See trigger conditions & affected models →

Fault list is non-exhaustive and firmware-dependent. Always confirm against the controller’s on-screen help or OEM manual.

Sensor pin resistance & signal values

Pin-level resistance and signal values for the sensor types this controller uses. Works offline. De-energise the panel and lift one lead before ohming any element.

Wiring notes

115 VAC control circuits are common on North American builds — verify the transformer tap matches actual site voltage before chasing 'random reset' complaints
Blowdown solenoid coil needs suppression; unsuppressed coils kill the output driver

Known issues & field notes

Keypad overlay lifts at the edges in humid rooms and lets moisture into the dome switches
Older revisions lose the alarm log on a full power-down when the backup cell is dead

Service parameters are behind a distributor code; no published universal code.

Manuals & literature

Quincy Compressor — manuals index

Public literature library

Direct PDFs

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