Hertz Screw Compressor Controller (HSC / HSC-D / HGS panel)
Hertz does not publish a public, firmware-specific fault-code table. The alarms listed above are the standard protection set documented in the HSC and HSC-D brochures and confirmed by field practice on these packages — treat the exact wording, code numbers and setpoints on YOUR panel as authoritative. Request the unit manual from Hertz or your distributor using the serial number.
Manufacturer
Hertz Kompressoren
Display
Backlit alphanumeric LCD control panel with membrane keypad and status LEDs. Larger frames ship with the graphic touch-style panel. Exact panel varies by frame, build year and region — confirm against the panel label.
Used on
- Hertz HSC Series (belt-driven, 90–160 kW)
- Hertz HSC-D Series (direct-coupled, 22–315 kW)
- Hertz HGS-HSC Series (2.2–75 kW)
- Hertz Impetus / Frecon Plus (VSD builds — controller works alongside the drive)
- Hertz Laser high-pressure screw packages
On AirCompDX
Features
- Load / unload and automatic stop-start control with weekly scheduler
- Alarm history — last 20 alarms retained (per HSC / HSC-D brochures)
- Maintenance-hour counters with pre-warning and service history log
- Phase-sequence / phase-loss protection built into the package
- Star-delta start management on fixed-speed frames; drive handshake on VSD frames
- Master/slave synchronized operation on HSC-D
Interfaces
- Built-in Modbus (RS-485) as standard per Hertz brochures
- Master/slave sequencing for up to two compressors without an external sequencer
- Digital inputs for remote start/stop and remote load/unload
- Volt-free common alarm / run output for BMS
- Optional Hertz SmartBox remote monitoring gateway
Fault code lookup
High discharge / airend temperatureAirend or package discharge temperature above the shutdown setpoint (commonly ~110 °C / 230 °F on oil-injected screw packages — confirm the setpoint on the panel).
First checks
- Check oil level at running temperature
- Clean cooler core and confirm cabinet airflow / ambient
- Verify thermostatic (mixing) valve is opening
- Test the PT100/PT1000 temperature probe against a reference
First checks
- Reset the overload in the starter cabinet and read the trip setting vs nameplate FLA
- Measure running amps on all three phases for imbalance
- Check star-delta transition timing
- Look for a separator or minimum-pressure valve restriction loading the motor
Phase sequence / phase failureIncoming supply phase missing or rotation reversed — the package phase monitor blocks start.
First checks
- Verify all three phases at the disconnect
- Confirm rotation arrow on the airend/motor
- Swap two line phases if rotation is reversed
- Test the phase monitor relay
First checks
- Release and twist out the local E-stop
- Check remote E-stop loop / jumper
- Confirm control voltage at the safety input
First checks
- Check unload solenoid and blowdown operation
- Verify pressure transducer calibration against a gauge
- Inspect the minimum-pressure valve
- Check that the load/unload setpoints are not above the package rating
Sensor fault (pressure / temperature)Transducer or RTD reading outside the valid range (open, shorted, or out of the 4–20 mA window).
First checks
- Inspect the sensor plug for water and corrosion
- Ohm the RTD and compare to a resistance table
- Check the 4–20 mA loop for polarity and supply
- Substitute a known-good sensor
Service due / maintenance warningOne of the maintenance-hour counters has expired (air filter, oil filter, separator, oil, belts).
First checks
- Perform the service that is due
- Reset only that counter in the service menu
- Confirm the interval matches the fluid and duty actually in use
Dryer / drain fault (integrated packages)Integrated refrigerated dryer or electronic drain reporting a fault back to the panel.
First checks
- Test the drain manually
- Check the dryer's own display for its fault
- Clean the dryer condenser
- Verify drain strainer is clear
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
- Control voltage is supplied by the package control transformer — confirm the actual voltage on the transformer tag before probing
- Star-delta contactor coils are switched from the panel relay outputs on fixed-speed frames
- RS-485 Modbus pair must be daisy-chained with 120 Ω termination at the two physical ends only
- Master/slave link between two compressors uses the built-in comms port — do not mix it with a third-party sequencer on the same pair
- Shielded sensor cable: bond the shield at one end only, at the panel
Known issues & field notes
- Panel hardware changed across build years and regions — screen shots and menu paths in older manuals may not match your unit
- Alarm text is translated per region; the same condition can read differently on two units in the same plant
Service and factory menus are PIN-protected and the PINs are issued by Hertz or the regional distributor. AirCompDX does not publish them. Ask your distributor for the service PIN tied to your serial number.
Manuals & literature
Your manuals
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