Quincy QGV variable-speed controller
On a QGV, always confirm whether the fault originated in the controller or the drive — the drive keypad carries the detailed code and the fault history the controller does not show.
Manufacturer
Quincy
Display
Backlit graphic LCD with soft keys; drive keypad separately accessible in the cabinet.
Years produced
~2005 – present on QGV variable-speed rotary screws.
Power supply
24 VDC control supply derived from the drive panel.
Ambient range
0 – 46 °C (drive cabinet ventilation is critical).
Protection rating
IP54 front, drive section IP20 internally.
Relay outputs
Drive run/enable, blowdown solenoid, dryer enable, common alarm, remote-run.
Used on
- Quincy QGV 15 – 200 hp variable-speed packages
Features
- Constant-pressure control with a narrow band — typically ±1.5 psi
- Automatic soft start with no inrush penalty on repeated starts
- Minimum and maximum speed limits protecting airend lubrication
- Drive fault mapping into plain-language controller messages
Interfaces
- Modbus RTU (RS-485) to the drive and to a master
- Volt-free contacts
- Remote pressure setpoint (option)
Sensor inputs
- Package discharge pressure
- Sump pressure
- Airend discharge temp (RTD)
- Drive heatsink temperature
- Motor thermal contacts
Fault code lookup
First checks
- Read the raw code on the drive keypad — the controller message is a summary
- Overcurrent: check airend drag and drive tuning
- Overvoltage: check decel ramp and line conditions
First checks
- A/B polarity and termination
- Drive control-source parameter
- Look for VFD carrier noise coupling into the comm run
First checks
- Cabinet filters plugged
- Cabinet fan failed
- Room temperature above rating
First checks
- Fluid level and cooler fouling
- Thermal valve
- Extended low-speed running reduces cooling flow — check minimum speed setting
First checks
- Minimum speed set too low
- Blowdown leaking
- Minimum pressure valve stuck open
First checks
- Loop check at the terminal
- Shielded run kept out of the drive compartment
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
- Motor leads must be shielded VFD cable with the shield landed at both ends per the drive manual — this is the number one source of nuisance sensor faults
- Never run the 4–20 mA transducer loop in the same conduit as the drive output
- Confirm drive input reactor / line conditioning is present on soft plants
Known issues & field notes
- Running a VSD machine at the bottom of its speed range for long periods causes coolant carryover and separator loading — set minimum speed per the manual, not lower
- Drive cabinet filter neglect is the most common cause of repeat over-temperature trips
Controller service level is distributor-set. Drive parameters have their own separate drive-level password.
Manuals & literature
Quincy Compressor — manuals index
Public literature library
Your manuals
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