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Oxygen concentrators · EDOCS family

Pacific Consolidated Industries EDOCS-120: troubleshooting and error codes

The ServiceForge knowledge base holds 203 documented symptoms for the Pacific Consolidated Industries EDOCS-120, with 553 ranked causes, 330 diagnostic checks with test points and expected values, and 0 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

No electrical power high voltage

Unit receives no power; no indicator lights or motor operation.

Ranked causes

  1. 1. Electrical power feed cable not connected or connector disconnected (common)
  2. 2. Facility or generator power feed is off (common)
  3. 3. Main Circuit Breaker CB-1 is off or tripped (common)
  4. 4. Electrical power feed is out of phase (occasional)
  5. 5. Emergency Stop Pushbutton Switch actuated (occasional)
  6. 6. Control Transformer input fuse FU-1A or FU-1B blown (occasional)
  7. 7. Control Transformer output fuse FU-2 blown (occasional)
  8. 8. Faulty electrical power feed cable (rare)
  9. 9. Faulty electrical power feed connector (rare)
  10. 10. Faulty or disconnected internal electrical wiring (rare)
  11. 11. Faulty Power Filter PF-1 (rare)
  12. 12. Faulty Main Circuit Breaker CB-1 (rare)
  13. 13. Faulty Reverse Phase Relay PD-1 (rare)
  14. 14. Faulty Control Transformer TR-1 (rare)
  15. 15. Faulty Emergency Stop Pushbutton Switch PB-8 or PB-9 (rare)
  16. 16. Faulty System Shutdown Control Relay CR-4 (rare)

16 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Scroll compressor stops for no apparent reason patient safety

Compressor unexpectedly shuts down; inlet pressure below 0.5 psig triggers safety shutdown

Ranked causes

  1. 1. Leaking from piping, tubing and/or fittings (common)
  2. 2. Leaking from components (common)
  3. 3. Incorrectly adjusted Buffer Tank Back Pressure Regulator (BPR-1) (occasional)
  4. 4. Faulty Buffer Tank Back Pressure Regulator (BPR-1) (rare)
  5. 5. Incorrectly adjusted Scroll Out Back Pressure Regulator (BPR-2) (occasional)
  6. 6. Faulty Scroll Out Back Pressure Regulator (BPR-2) (rare)
  7. 7. Vacuum/pressure problems with VSA process (occasional)
  8. 8. VSA Switching Valve not moving or stuck (occasional)
  9. 9. Lack of sufficient blower output flow (occasional)
  10. 10. Low inlet pressure (PI-3) on scroll compressor (common)
  11. 11. Excessive oxygen product usage (common)
  12. 12. Faulty PLC analog input module (rare)
  13. 13. Faulty PLC (rare)
  14. 14. Faulty or disconnected signal cable wiring for Scroll In Pressure Transducer (XT-2) (occasional)
  15. 15. Faulty Scroll In Pressure Transducer (XT-2) (rare)

15 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Booster compressor fails to start and run high voltage

High Pressure Booster Pushbutton Switch (PB-2/PB-3) pulled but compressor does not start or operate

Ranked causes

  1. 1. RIX Inlet Pressure Switch (PSIL) incorrectly adjusted (common)
  2. 2. Faulty or disconnected electrical wiring (common)
  3. 3. Faulty HP Compressor Motor Starter (M-6/M-7) (occasional)
  4. 4. Faulty Time Delay Relay (TDR-1/TDR-2) (occasional)
  5. 5. Faulty High Pressure Booster Pushbutton Switch (PB-2/PB-3) (occasional)
  6. 6. Faulty RIX Inlet Pressure Switch (PSIL) (occasional)
  7. 7. Faulty RIX In Solenoid Valve (SV-3) (occasional)
  8. 8. Faulty Off-Spec Solenoid Valve (SV-2) (occasional)
  9. 9. Faulty PLC relay output module (rare)
  10. 10. Faulty PLC (rare)
  11. 11. Slipping or broken HP Compressor drive belt (occasional)
  12. 12. Faulty HP Compressor drive pulley and/or shaft key (rare)
  13. 13. Faulty or shorted HP Compressor Motor (MTR-6/MTR-7) (occasional)
  14. 14. Faulty or seized HP Compressor (C-2/C-2A) (occasional)

14 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low discharge pressure (PI-4) from scroll compressor

Discharge pressure below acceptable level

Ranked causes

  1. 1. Excessive oxygen product usage (common)
  2. 2. Scroll compressor drive belt slipping or excessively worn (occasional)
  3. 3. Scroll compressor drive belt broken (occasional)
  4. 4. Incorrect parameters programmed into VFD-2 (occasional)
  5. 5. Faulty Scroll Compressor VFD-2 (rare)
  6. 6. Faulty PLC analog output module with no command signal to VFD (rare)
  7. 7. Faulty PLC (rare)
  8. 8. Incorrectly adjusted Scroll Out Back Pressure Regulator (BPR-2) (occasional)
  9. 9. Faulty Scroll Out Back Pressure Regulator (BPR-2) (rare)
  10. 10. Vacuum/pressure problems with VSA process (occasional)
  11. 11. VSA Switching Valve not moving or stuck (occasional)
  12. 12. Lack of sufficient blower output flow (occasional)
  13. 13. Low inlet pressure (PI-3) on scroll compressor (common)
  14. 14. Worn scroll compressor seals with high internal leakage (rare)

14 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low oxygen purity patient safety

Oxygen output does not meet specification purity levels

Ranked causes

  1. 1. Faulty Off-Spec Control Solenoid Valve (SV-2) with burnt-out coil (occasional)
  2. 2. VSA Switching Valve (V-1) misaligned (occasional)
  3. 3. Oxygen Sensor (AE-1) not properly calibrated (common)
  4. 4. Faulty or disconnected signal wiring to Oxygen Sensor (AE-1) (occasional)
  5. 5. Faulty Oxygen Sensor (AE-1) (occasional)
  6. 6. Faulty PLC analog input module (rare)
  7. 7. Faulty PLC analog output module causing incorrect command signal to VFD-2 (rare)
  8. 8. Faulty PLC (rare)
  9. 9. Incorrect parameters in Scroll Compressor VFD-2 (occasional)
  10. 10. Faulty Scroll Compressor VFD-2 (rare)
  11. 11. Faulty Sample Selector Solenoid Valve (SV-5) stuck in calibrate position (occasional)
  12. 12. Incorrectly adjusted Scroll Outlet Relief Valve (PSV-2) (occasional)
  13. 13. Faulty Scroll Outlet Relief Valve (PSV-2) (rare)
  14. 14. Scroll Compressor drive belt slipping (occasional)

14 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Scroll compressor does not start

Scroll Compressor (C-1) fails to operate

Ranked causes

  1. 1. Blower not running (common)
  2. 2. Scroll Compressor Motor Circuit Breaker (CB-2) is Off or tripped (common)
  3. 3. Scroll Compressor Motor VFD-2 is tripped or in fault mode (common)
  4. 4. Faulty or disconnected electrical wiring (occasional)
  5. 5. Faulty Scroll Start Control Relay (CR-3) (rare)
  6. 6. Faulty PLC relay output module (rare)
  7. 7. No command signal to VFD-2 due to faulty PLC analog output module (rare)
  8. 8. Faulty PLC (rare)
  9. 9. Faulty Scroll Compressor Motor Circuit Breaker (CB-2) (rare)
  10. 10. Faulty Scroll Compressor Motor (MTR-8) (rare)
  11. 11. Incorrect parameters programmed into VFD-2 (occasional)
  12. 12. Faulty Scroll Compressor VFD-2 (rare)

12 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blower fails to start when pushbutton pulled

VSA Blower Pushbutton Switch PB-1 is pulled but blower motor does not start or run.

Ranked causes

  1. 1. No electrical power (common)
  2. 2. No control power due to system shutdown (common)
  3. 3. VSA Blower Electrical Starter Disconnect M-1 is off or tripped (common)
  4. 4. Power Frequency Variable Frequency Drive VFD-1 tripped or in fault mode (occasional)
  5. 5. Faulty or disconnected electrical wiring (occasional)
  6. 6. Faulty VSA Blower Pushbutton Switch PB-1 (occasional)
  7. 7. Faulty VSA Blower Contactor CON-1 (occasional)
  8. 8. Faulty VSA Blower Electrical Starter Disconnect M-1 (rare)
  9. 9. Faulty VSA Blower Motor MTR-1 (rare)
  10. 10. Incorrect parameters programmed into VFD-1 (rare)
  11. 11. Faulty Power Frequency Variable Frequency Drive VFD-1 (rare)

11 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

VSA Switching Valve not moving or stuck

VSA Switching Valve V-1 remains stationary or does not reach correct position during operation.

Ranked causes

  1. 1. Faulty or disconnected electrical wiring (common)
  2. 2. VSA Valve Motor Starter M-2 is off or tripped (common)
  3. 3. VSA Valve Motor Starter M-2 overload set too low (occasional)
  4. 4. Power Frequency Variable Frequency Drive VFD-1 tripped or in fault mode (occasional)
  5. 5. Faulty VSA Valve Motor Starter M-2 (rare)
  6. 6. Faulty VSA Valve Motor MTR-2 (rare)
  7. 7. Incorrect parameters programmed into VFD-1 (rare)
  8. 8. Faulty Power Frequency Variable Frequency Drive VFD-1 (rare)
  9. 9. Faulty PLC analog input module (rare)
  10. 10. Faulty PLC input output module (rare)
  11. 11. Faulty PLC relay output module (rare)

11 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

HP compressor does not stop running high voltage

HP compressor continues to run continuously when it should stop or cycles abnormally

Ranked causes

  1. 1. Backup Cylinders Vent Valve (V-5) in VENT position (common)
  2. 2. Yoke cylinder valve not fully closed (common)
  3. 3. Leaking or improperly seated yoke cylinder connection (common)
  4. 4. Oxygen product usage exceeds compressor output capability (occasional)
  5. 5. RIX Outlet Pressure Switch (PSR) incorrectly adjusted (occasional)
  6. 6. Faulty RIX Outlet Pressure Switch (PSR) (occasional)
  7. 7. Improperly set relief valve (PSV-3) pressure set-point (occasional)
  8. 8. Faulty relief valve (PSV-3) (occasional)
  9. 9. Faulty Time Delay Relay (TDR-1/TDR-2) (occasional)
  10. 10. Line and/or fitting leaks (common)

10 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Vacuum pump fails to start and run high voltage

Vacuum Pump Pushbutton Switch (PB-4) pulled but pump does not start or operate

Ranked causes

  1. 1. No electrical power (common)
  2. 2. No control power due to System Shutdown (common)
  3. 3. Vacuum Pump Motor Starter Circuit Breaker (M-5) off or tripped (common)
  4. 4. Power Frequency Variable Frequency Drive (VFD-1) tripped or in fault mode (occasional)
  5. 5. Faulty or disconnected electrical wiring (occasional)
  6. 6. Faulty Vacuum Pump Pushbutton Switch (PB-4) (occasional)
  7. 7. Faulty Vacuum Pump Motor Starter (M-5) (occasional)
  8. 8. Faulty Vacuum Pump Motor (MTR-5) (occasional)
  9. 9. Incorrect parameters programmed into Power Frequency VFD (VFD-1) (occasional)
  10. 10. Faulty Power Frequency Variable Frequency Drive (VFD-1) (occasional)

10 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Booster compressor fails to start high voltage

Booster compressor does not start when control switch SW-2 is activated

Ranked causes

  1. 1. Discharge pressure above restart set point (approximately 1900 psig) (common)
  2. 2. Booster control selector switch HOA is off (common)
  3. 3. Inlet pressure on booster compressor is below 30 psig (common)
  4. 4. Booster compressor inlet solenoid SV-3 is malfunctioning (occasional)
  5. 5. Motor contactor overload relay OL is tripped or defective (occasional)
  6. 6. Coil on motor contactor M-2 is defective (rare)
  7. 7. Booster motor M is shorted out (rare)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Booster compressor fails to start when High Pressure Booster Pushbutton switch pulled

HP Booster Compressor (C-2) does not run on demand

Ranked causes

  1. 1. Discharge pressure above restart set-point of approximately 1900 psig (common)
  2. 2. RIX Supply Shutoff Valve (V-3) is closed (common)
  3. 3. Scroll Compressor (C-1) not running (common)
  4. 4. Inlet pressure on booster compressor below 70 psig (occasional)
  5. 5. Clogged and dirty Oxygen Product Filter (F-1) (occasional)
  6. 6. HP Compressor Motor Starter branch circuit breaker is tripped (occasional)
  7. 7. HP Compressor Motor Starter Overload Relay (OL) is tripped (occasional)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Hard vacuum cannot be obtained

Vacuum pump fails to achieve required vacuum level during operation

Ranked causes

  1. 1. Yoke cylinder valve (V-10 through V-13) not fully closed (common)
  2. 2. Leaking or improperly seated yoke cylinder connection (CC-1 through CC-4) (common)
  3. 3. Obstructed vacuum pump inlet (occasional)
  4. 4. Leak or faulty Vacuum Gauge Vent Check Valve (CV-7) or Vacuum Pump In Vent Check Valve (CV-8) (occasional)
  5. 5. Leak in vacuum lines, hose, or quick connect (QC-4) (occasional)
  6. 6. Faulty or worn vacuum pump (rare)
  7. 7. Faulty Vacuum Pump Compound Gauge (PI-13) (rare)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Lack of sufficient blower output flow

Blower produces reduced air flow below normal operating specifications

Ranked causes

  1. 1. Slipping drive belt (common)
  2. 2. Damaged or excessively worn blower drive belt (common)
  3. 3. Clogged or excessively dirty Blower In Filter (F-4) (common)
  4. 4. VSA Switching Valve (V-1) not in correct position (occasional)
  5. 5. Obstruction in piping (occasional)
  6. 6. Worn internal gear lobe clearances (occasional)
  7. 7. Faulty Blower (BL-100) (occasional)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low discharge pressure on scroll compressor

Scroll compressor discharge pressure PI-4 lower than normal

Ranked causes

  1. 1. Excessive oxygen product off-take (common)
  2. 2. Variable speed drive VSD misadjusted (occasional)
  3. 3. Scroll compressor drive belt slipping (occasional)
  4. 4. Defective or misadjusted maximum discharge pressure regulator BPR-2 (occasional)
  5. 5. Defective or misadjusted minimum discharge pressure regulator BPR-4 (occasional)
  6. 6. Flow and pressure problems with blower, VSA or valve V-1 (occasional)
  7. 7. Worn scroll seals (rare)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Adsorber pressure does not reach specified levels

Pressure PI-8 on adsorber vessel does not reach 15.5 in Hg vacuum and 9 psig

Ranked causes

  1. 1. Leaks in piping (common)
  2. 2. Analog input module operating voltage jumpers improperly set (occasional)
  3. 3. Faulty adsorber vessel pressure transducer XT-1 (occasional)
  4. 4. Faulty analog input module AI (occasional)
  5. 5. Faulty EEPROM program (rare)
  6. 6. Switching valve V-1 misaligned (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Adsorber vessel does not reach specified vacuum/pressure levels

Vessel fails to achieve 15.5 in. Hg vacuum and 9 psig pressure during operation

Ranked causes

  1. 1. Leaks in the piping (common)
  2. 2. Faulty PLC analog input module (occasional)
  3. 3. Faulty PLC (occasional)
  4. 4. Faulty or disconnected signal cable for XT-1 (common)
  5. 5. Faulty Adsorber Vessel Pressure Transducer (XT-1) (occasional)
  6. 6. The VSA Switching Valve (V-1) is misaligned (occasional)

7 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blower motor does not start

System turned on but blower motor fails to begin operation

Ranked causes

  1. 1. No power supply from mains input (common)
  2. 2. Incorrect phase rotation direction (occasional)
  3. 3. Input fuses open or tripped (common)
  4. 4. Internal fuses open or circuit breakers tripped (common)
  5. 5. Power supply to blower motor fails (occasional)
  6. 6. 110 Volt transformer output defective (occasional)
First check

Verify 3-phase mains input power

Test point
Terminals L1, L2, L3
Expected
3-phase power present

5 more checks with pass and fail actions, 6 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blower vibration caution

Excessive vibration during blower operation

Ranked causes

  1. 1. Drive belt pulleys misaligned (common)
  2. 2. Blower lobes rubbing (occasional)
  3. 3. Worn bearings or gears (occasional)
  4. 4. Unbalanced or rubbing lobes (occasional)
  5. 5. Motor or blower mounting bolts loose (common)
  6. 6. Piping resonance (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

EDOCS-120B in Low Purity Override without indicator light illuminated

Unit is in Low Purity Override condition but indicator light is not lit or not responding

Ranked causes

  1. 1. Indicator light is burnt-out (common)
  2. 2. Faulty or disconnected electrical wiring (common)
  3. 3. Faulty indicator light (PB-6) (occasional)
  4. 4. Faulty Lamp Test Pushbutton Switch (PB-7) (occasional)
  5. 5. Faulty PLC relay output module (occasional)
  6. 6. Faulty PLC (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Excessive high temperature on HP compressor heads and discharge lines caution

Temperature measured on HP compressor head and discharge lines is excessively high

Ranked causes

  1. 1. HP compressor cooling fans not operational (common)
  2. 2. Restriction in lines caused by damage (occasional)
  3. 3. Faulty compressor valves (occasional)
  4. 4. EDOCS-120B unit running without access panels installed (common)
  5. 5. Excessive high ambient air temperature (occasional)
  6. 6. Excessive contact and wear of compressor piston and sleeve (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Excessive or harmonic vibration caution

Blower or system exhibits abnormal vibration or resonance during operation

Ranked causes

  1. 1. Drive belt pulleys are misaligned (common)
  2. 2. Blower lobes are rubbing (occasional)
  3. 3. Worn bearings or gears (occasional)
  4. 4. Unbalanced or rubbing lobes (occasional)
  5. 5. Blower motor or blower mounting bolts are loose (common)
  6. 6. Piping resonance (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No control power due to system shutdown

Unit powered but control circuit de-energized; no device response to controls.

Ranked causes

  1. 1. PLC commanded system shutdown (common)
  2. 2. Faulty System Shutdown Control Relay CR-4 (occasional)
  3. 3. Faulty transducer or sensor (occasional)
  4. 4. Faulty PLC analog input module (rare)
  5. 5. Faulty PLC relay output module (rare)
  6. 6. Faulty PLC (rare)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Scroll compressor does not start after five valve cycles

After 5 complete valve cycles, scroll compressor fails to begin operation

Ranked causes

  1. 1. No power input to scroll VSD (common)
  2. 2. VSD inputs SC, S1 not receiving control signal (occasional)
  3. 3. Inlet pressure to scroll below 2 psig (common)
  4. 4. VSD output failure or motor wiring issue (occasional)
  5. 5. Scroll motor belt drive defective (occasional)
  6. 6. Downstream compressor malfunction (occasional)
First check

Verify 3-phase power to VSD

Test point
VSD terminals L1B, L2B, L3B
Expected
3-phase power present

5 more checks with pass and fail actions, 6 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Vibration from blower caution

Excessive vibration during blower operation

Ranked causes

  1. 1. Drive belt pulleys are misaligned (common)
  2. 2. Blower lobes are rubbing (occasional)
  3. 3. Worn bearings or gears (occasional)
  4. 4. Unbalanced or rubbing lobes (occasional)
  5. 5. Motor or blower mounting bolts are loose (common)
  6. 6. Piping resonance (rare)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

VSA pressure does not reach specified levels

Adsorber vessel pressure fails to reach 15.5 in Hg vacuum and 9 psig

Ranked causes

  1. 1. Leaks in the piping (common)
  2. 2. Analog input module operating voltage jumpers improperly set (occasional)
  3. 3. Faulty adsorber vessel pressure transducer XT-1 (occasional)
  4. 4. Faulty analog input module AI (occasional)
  5. 5. Faulty EEPROM program (rare)
  6. 6. Switching valve V-1 is misaligned (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blower not rotating

Blower remains stationary and does not turn during operation

Ranked causes

  1. 1. Damaged, slipping or broken drive belt (common)
  2. 2. VSA Blower Motor (MTR-1) not running (common)
  3. 3. Pulley shaft key sheared (occasional)
  4. 4. Faulty or seized bearing (occasional)
  5. 5. Faulty or seized internal gear lobes (occasional)

5 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blower starts but shuts down soon after

Blower starts then stops shortly after operation begins

Ranked causes

  1. 1. CR-124 overload set too low (common)
  2. 2. Switching valve V-1 stuck in pressure position (occasional)
  3. 3. Overload relay on motor contactor CR-145 tripped or faulty (occasional)
  4. 4. Analog input module AI faulty (occasional)
  5. 5. Pressure transducer XT-1 faulty (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Compressor output is reduced

HP compressor is producing less air/oxygen flow output than expected

Ranked causes

  1. 1. Suction pressure to compressor too high (common)
  2. 2. HP compressor drive belt slipping (common)
  3. 3. Relief valve on 1st stage popping off (occasional)
  4. 4. Low pressure on HP Compressor 1st stage (occasional)
  5. 5. Line and/or fitting leaks (common)

5 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Excessive blower temperature caution

Blower operating at higher than normal temperature

Ranked causes

  1. 1. Too much or too little oil in gear reservoir (common)
  2. 2. Clogged filter or silencer (common)
  3. 3. Excessive pressure differential (occasional)
  4. 4. Elevated inlet temperature (occasional)
  5. 5. Worn lobe clearances (occasional)

5 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Excessive HP compressor discharge pressure high voltage

Discharge pressure from HP compressor is higher than normal or relief valve on 2nd stage is popping off

Ranked causes

  1. 1. RIX Outlet Pressure Switch (PSR) incorrectly adjusted (common)
  2. 2. Faulty RIX Outlet Pressure Switch (PSR) (occasional)
  3. 3. Improperly set relief valve (PSV-3) pressure set-point (common)
  4. 4. Faulty relief valve (PSV-3) (occasional)
  5. 5. Faulty Time Delay Relay (TDR-1/TDR-2) (occasional)

5 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Scroll compressor not starting after 5 valve cycles caution

Scroll compressor does not start within 5 complete cycles of four-way valve V1. Indicated by lack of blower noise change or pressure rise on gauge PI 4.

Ranked causes

  1. 1. No power input to scroll VSD or improper VSD inputs (common)
  2. 2. Insufficient inlet pressure to scroll compressor (common)
  3. 3. No or low frequency output from VSD to scroll motor (occasional)
  4. 4. Belt slip, motor failure, or downstream obstruction (occasional)
  5. 5. Scroll compressor seal leakage or piston damage (rare)
First check

Measure VSD power input voltage

Test point
Terminals L1B, L2B, L3B
Expected
Proper 3-phase voltage present

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System pressures out of range

Pressures on PI 8 gauge fall outside normal operating range of 8-10 psig pressure and 15-17 inches of vacuum. System has been running at least 1 hour from startup.

Ranked causes

  1. 1. Drive belt slipping or low blower oil (common)
  2. 2. Leaks in blower or air cooler pipework (occasional)
  3. 3. Four-way valve V1 bypass or misalignment (occasional)
  4. 4. Oxygen demand not present; system pressure rise (occasional)
  5. 5. Pressure regulation downstream of B1 & B2 vessels (occasional)
First check

Verify PI 3 and PI 4 pressure readings

Test point
PI 3 pressure gauge
Expected
PI 3 below 5 psig and PI 4 above 60 psig

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System pressures out of range after one hour running caution

Pressure readings on PI 8 are out of specification: not 8-10 psig on pressure side or not 15-17 inches on vacuum side after at least 1 hour of operation.

Ranked causes

  1. 1. Oxygen demand (hospital or cylinder fill) consuming all system output (common)
  2. 2. Blower belt slipping or blower mechanical wear (common)
  3. 3. Leaks in blower, cooler, or vessel piping (common)
  4. 4. High inlet pressure or back-relief valve (BR-1) not sealing (occasional)
  5. 5. Four-way valve V1 bypass or improper seating (occasional)
First check

Verify oxygen demand flows are open and active

Test point
Hospital oxygen flow outlet and cylinder fill line
Expected
Flows are open and demand is present

5 more checks with pass and fail actions, 5 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

VSA switch does not transition from vacuum to pressure

After 30-second delay, vacuum-to-pressure switch fails to change state

Ranked causes

  1. 1. Four-way valve V1 not operating correctly (common)
  2. 2. Valve V1 mechanical blockage or misalignment (occasional)
  3. 3. Limit switch misalignment or malfunction (occasional)
  4. 4. PLC output #2 not energizing after 30 seconds (occasional)
  5. 5. Contactor CR 145 not energizing (occasional)
First check

Test valve V1 movement via motor M200

Test point
PLC input card slot #0 inputs #0&1
Expected
Input status changes when motor M200 activated

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Blower audible knocking

Abnormal knocking or noise heard from blower during operation

Ranked causes

  1. 1. Blower out of time (occasional)
  2. 2. Pipe strain and distortion due to improper blower mounting (occasional)
  3. 3. Excessive pressure differential (occasional)
  4. 4. Worn blower timing gears (occasional)

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Blower fails to start

Blower does not start when control switch SW-3 is turned on

Ranked causes

  1. 1. Main circuit breaker CB-1 is off (common)
  2. 2. Power input is out of phase (occasional)
  3. 3. Overload relay on CR-124 motor contactor is tripped or defective (common)
  4. 4. Coil on motor contactor CR-124 is defective (occasional)

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Blower fails to start when control switch turned on high voltage

Blower does not start when SW-3 is activated

Ranked causes

  1. 1. Main circuit breaker CB-1 is off (common)
  2. 2. Power input is out of phase (occasional)
  3. 3. Overload relay on CR-124 motor contactor is tripped or defective (common)
  4. 4. Coil on motor contactor CR-124 is defective (occasional)
First check

Verify main circuit breaker CB-1 status

Test point
CB-1
Expected
On

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Blower not starting caution

Blower motor does not start when system power switch turned on. Electrical startup circuit failure.

Ranked causes

  1. 1. No mains power supply to system (common)
  2. 2. Input fuses blown or phase protector tripped (common)
  3. 3. Low or no output from 110 Volt transformer (occasional)
  4. 4. No power supply to blower motor (occasional)
First check

Measure mains power supply voltage

Test point
Terminals L1, L2, L3 and CR-124 terminals 1, 3, 5
Expected
Mains voltage present (typically 3-phase)

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Blower running but pushbutton indicator not illuminated

Blower motor operates normally; integral indicator light on PB-1 does not glow.

Ranked causes

  1. 1. Indicator light burnt out (common)
  2. 2. Faulty or disconnected electrical wiring (occasional)
  3. 3. Faulty indicator light pushbutton switch PB-1 (occasional)
  4. 4. Faulty Lamp Test Pushbutton Switch PB-7 (rare)

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Booster compressor fails to start when control switch (SW-2) is switched on

Compressor does not start despite control switch activation

Ranked causes

  1. 1. Booster compressor inlet solenoid (SV-3) is malfunctioning (common)
  2. 2. Motor contactor overload relay (OL) is tripped or defective (common)
  3. 3. Coil on motor contactor (M-2) is defective (occasional)
  4. 4. Booster motor (M) is shorted out (occasional)
First check

Check if motor overload relay has tripped

Test point
Motor contactor overload relay (OL)
Expected
Relay not tripped

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Booster compressor overheats caution

Booster compressor or discharge lines reach excessive temperature

Ranked causes

  1. 1. Fans are inoperative (common)
  2. 2. Restriction in piping caused by damage (common)
  3. 3. Faulty compressor valves (occasional)
  4. 4. High ambient temperature (occasional)

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HP Compressor Motor Starter Overload relay tripped high voltage

Overload (OL) relay on HP Compressor Motor Starter has tripped, preventing compressor start

Ranked causes

  1. 1. Electrical power feed input voltage too low (common)
  2. 2. Suction pressure to compressor too high (common)
  3. 3. Faulty or shorted HP Compressor Motor (MTR-6/MTR-7) (occasional)
  4. 4. Faulty or seized HP Compressor (C-2/C-2A) (occasional)

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Knocking noise caution

Blower produces knocking noise during operation

Ranked causes

  1. 1. Unit out of time (occasional)
  2. 2. Distortion due to improper mounting pipe strains (occasional)
  3. 3. Excessive pressure differential (occasional)
  4. 4. Worn gears (rare)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Knocking noise from blower caution

Audible knocking or clunking sounds during blower operation

Ranked causes

  1. 1. Unit out of time (occasional)
  2. 2. Distortion due to improper mounting pipe strains (occasional)
  3. 3. Excessive pressure differential (common)
  4. 4. Worn gears (rare)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Longer than normal time to fill backup cylinders

High pressure backup cylinders or H cylinder fill time exceeds normal duration

Ranked causes

  1. 1. Leaks in piping, cylinder heads, heat exchangers or seals (common)
  2. 2. Compressor drive belt is slipping (common)
  3. 3. Valves in 1st stage are leaking (occasional)
  4. 4. Worn piston rings (occasional)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Longer than normal time to fill backup system cylinders

Backup system cylinders or H cylinder takes significantly longer than normal to fill to required pressure

Ranked causes

  1. 1. Leaks in lines, fittings, cylinder heads, heat exchangers or seals (common)
  2. 2. HP compressor drive belt slipping (occasional)
  3. 3. Valves in 1st stage leaking (occasional)
  4. 4. Worn or broken rings in 1st stage (occasional)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Longer than normal time to fill the backup system cylinders or H cylinder

Cylinder fill rate is slower than expected

Ranked causes

  1. 1. Leaks in piping, cylinder heads, heat exchangers or seals (common)
  2. 2. Compressor drive belt is slipping (common)
  3. 3. The valves in the 1st stage are leaking (occasional)
  4. 4. Worn piston rings (occasional)

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Low pressure on 1st stage

First stage pressure gauge reading below normal range

Ranked causes

  1. 1. Worn or broken rings in the 1st stage (common)
  2. 2. Blown O-ring on the 1st stage valve (occasional)
  3. 3. Suction or discharge valve on the 1st stage is leaking (common)
  4. 4. Piping leaks (common)

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Low pressure on 1st stage booster

1st stage pressure is below normal operating range

Ranked causes

  1. 1. Worn or broken rings in 1st stage (occasional)
  2. 2. Blown O-ring on 1st stage valve (occasional)
  3. 3. Suction or discharge valve on 1st stage is leaking (occasional)
  4. 4. Piping leaks (occasional)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low pressure on first stage compressor caution

First stage discharge pressure below normal operating range. Compressor can continue running; monitor pressures and shut down when convenient.

Ranked causes

  1. 1. Worn or broken rings in first stage (common)
  2. 2. Blown valve O-ring in first stage (common)
  3. 3. Suction or discharge valve on first stage is leaking (common)
  4. 4. Piping leaks (occasional)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low pressure on HP Compressor 1st stage high voltage

Pressure reading on first stage of compressor is lower than normal

Ranked causes

  1. 1. Worn or broken rings in 1st stage (common)
  2. 2. Blown O-ring on 1st stage valve (occasional)
  3. 3. Suction or discharge valve on 1st stage leaking (occasional)
  4. 4. Line and/or fitting leaks (common)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Scroll compressor stops unexpectedly

Scroll compressor stops for no apparent reason during operation

Ranked causes

  1. 1. Scroll inlet pressure below 0.5 psig (common)
  2. 2. Low inlet pressure PI-3 on scroll compressor (common)
  3. 3. Flow and pressure problems with blower, VSA or valve V-1 (occasional)
  4. 4. Excessive oxygen product off-take (common)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

System pressure troubleshooting: Low pressure on PI-8

System pressure gauge PI-8 reading below 8 psig during pressure cycle

Ranked causes

  1. 1. Drive belts on main blower are slipping (common)
  2. 2. Blower oil level low or bearings need greasing (common)
  3. 3. Air inlet filter is clogged (common)
  4. 4. Leaks in blower, cooler piping, vessels or check valves (occasional)
First check

Verify system has been running at least 1 hour from startup

Test point
System runtime
Expected
Greater than 1 hour

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2nd stage valve leakage

Radial lines or streaks extending outward from the circular seal impression on reed valves or streaked marks on valve seat

Ranked causes

  1. 1. Reed valve cracking or pitting (common)
  2. 2. Valve seat cracks or pits (common)
  3. 3. Deposits on reed valves (occasional)
First check

Inspect reed valves for cracking or pitting

Test point
2nd stage inlet and outlet reed valves (3)
Expected
No cracks or pits visible; thin circular impression where reed seals over valve seat ports

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Blower starts but soon shuts down

Blower motor starts then de-energizes and stops within seconds or minutes of operation.

Ranked causes

  1. 1. VSA Blower Electrical Starter Disconnect M-1 overload set too low (common)
  2. 2. Power Frequency Variable Frequency Drive VFD-1 tripped or in fault mode (occasional)
  3. 3. VSA Switching Valve V-1 stuck in pressure position (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Booster compressor does not start

Cylinder filling booster compressor C2 (Rix) fails to initiate; no pressurization of fill system

Ranked causes

  1. 1. System not running long enough or pressures/purity not normal (common)
  2. 2. Pressure on PI 4 below 35 psig (common)
  3. 3. No power to booster compressor or start circuit (occasional)
First check

Verify system has been running at least 1 hour and pressures/purity normal

Test point
System operation time and PI gauges
Expected
Running ≥1 hour; pressures and purity normal

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Excessive bearing or internal gear lobe wear

Premature wear detected on bearings or internal gear lobes during inspection or operation

Ranked causes

  1. 1. Improper lubrication (common)
  2. 2. Excessive belt tension (occasional)
  3. 3. Pulley misalignment (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Fittings or tubing leaking caution

Visible moisture, oil residue or audible hissing from fittings or tubing connections

Ranked causes

  1. 1. Fitting or connection not tightened (common)
  2. 2. Seal or gasket degraded in fitting (occasional)
  3. 3. Tubing cracked or punctured (rare)
First check

Visually inspect all fittings and tubing for leaks

Test point
All fittings and tubing connections
Expected
No visible moisture, oil residue or hissing

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High pressure on 2nd stage (PI-7, PI-9) caution

Second stage pressure gauge reading exceeds normal limits

Ranked causes

  1. 1. Pressure switch (PSR) is misadjusted or inoperative (common)
  2. 2. Discharge lines or back pressure valve is restricted (common)
  3. 3. Defective relief valve (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

More symptoms

  • High pressure on 2nd stage booster
  • High pressure on second stage compressor
  • HP Compressor overheats
  • Insufficient blower output flow
  • Lack of sufficient output flow
  • Loss of oil
  • Loss of oil from gear housing
  • Loss of oil or oil leaking
  • Motor overload relay tripped on booster
  • Oxygen purity below specification
  • Oxygen purity troubleshooting: Low purity light is on
  • Startup troubleshooting: Scroll compressor does not start after 5 cycles
  • VSA switch does not change from vacuum to pressure after 30 seconds
  • 1st stage piston rings worn or damaged
  • Blower drive belt condition degraded
  • Blower gear case oil level low
  • Booster compressor drive belt degraded
  • Connecting rod bearings require replacement
  • Connecting rod bearings worn or damaged
  • Cylinder filling troubleshooting: Booster compressor does not start
  • Cylinder head leaking or not sealing
  • Entire compressor vibrates
  • Excessive bearing or gear wear
  • Fire or oxygen contamination hazard during compressor servicing
  • High pressure on 1st stage booster
  • High pressure on first stage compressor
  • Piston rings worn or damaged
  • Relief valve on 1st stage popping off
  • Rotor end or tip drag
  • Scroll compressor drive belt degraded
  • 1st stage piston rings worn
  • 1st stage piston rings worn or damaged
  • 1st stage piston rings worn or leaking
  • 2nd stage piston seal leaking or worn
  • 2nd stage piston seal worn
  • 2nd stage piston seal worn or damaged
  • 2nd stage valve installation
  • Bearing and shaft lubrication
  • Blower assembly rotor clearances out of specification
  • Blower assembly rotor timing
  • Blower drive belt misalignment
  • Blower drive belt pulleys loose or misaligned
  • Blower drive belt tension incorrect
  • Blower drive belt tension incorrect
  • Blower drive belt worn or damaged
  • Blower gear case oil level incorrect
  • Blower inlet and outlet fittings reversed on replacement
  • Blower inlet filter clogged or contaminated
  • Blower pulley misalignment
  • Blower pulley misalignment during installation
  • Blower shaft contact with housing after mounting
  • Blower shaft distortion during mounting
  • Cabinet access panel reinstallation
  • Calibration: 1st stage piston clearance
  • Calibration: 2nd stage piston clearance
  • Calibration: Blower assembly rotor clearances
  • Calibration: Booster Compressor Discharge Pressure Switch
  • Calibration: Booster compressor discharge pressure switch (PSR)
  • Calibration: Booster Compressor Drive Belt Tension
  • Calibration: Booster Compressor Filter Cleaning
  • Calibration: Booster compressor inlet pressure switch (PSIL)
  • Calibration: Disconnect oxygen sensor calibration kit
  • Calibration: Interlobe clearances
  • Calibration: Lobe to end plate clearances
  • Calibration: Oxygen sensor output signal
  • Calibration: Oxygen sensor output voltage
  • Calibration: Pressure relief valve set-points
  • Calibration: Pressure switch set-points
  • Calibration: Relief valve pressure set-point
  • Calibration: Spring adjuster torque
  • Calibration: Spring adjusters
  • Calibration: Tip seal orientation
  • Chemical and cleaner exposure hazard
  • Chemical/cleaner exposure hazard
  • Clacking noises coming from one of the cylinder heads
  • Clacking noises from cylinder head
  • Clacking noises in cylinder head
  • Clacking noises in cylinder head
  • Compressed air hazard during component removal
  • Compressed air injury hazard during component removal
  • Contamination of gas stream during maintenance
  • Cylinder filling troubleshooting: Booster compressor starts but PI-6 pressure is low
  • Cylinder filling troubleshooting: Booster outlet pressure (PI-9) below 2250 psig
  • Cylinder head leakage or poor sealing
  • Cylinder head or liner wear
  • Cylinder liner wear exceeds limits
  • Cylinder liner wear or damage
  • Cylinder requires service
  • Drive shaft seal installation
  • Excessive blower bearing grease during preparation
  • Excessive operating pressure
  • Excessive operating temperature
  • Fastener looseness found
  • Filter element replacement procedure
  • Flat slapping sound at compressor start and stop
  • Flat slapping sound during compressor start/stop
  • Flat, slapping sound when the compressor starts and stops
  • Gauge damage or misalignment
  • High pressure on 1st stage
  • Higher than normal 1st stage pressure
  • Higher than normal 1st stage pressure
  • Higher than normal 1st stage pressures
  • Higher than normal pressures on 1st stage
  • Improper head torque after 2nd stage reassembly
  • Install inlet adapter plate with gasket
  • Install outlet tube to scroll compressor
  • Install scroll compressor to frame
  • Install tube to flow control valve (FCV-1)
  • Loss of flow
  • Loss of flow from compressor
  • Loss of flow in compressor outlet
  • Loss of oxygen flow
  • Loud metallic knock
  • Loud metallic knock from booster
  • Low pressure condition detected
  • Maintenance: Booster Compressor Condition Assessment
  • Oxygen sensor excitation voltage out of range
  • Oxygen sensor output voltage out of range
  • Oxygen sensor requires calibration
  • Oxygen sensor voltage out of range
  • Parts binding during 1st stage piston assembly replacement
  • Piston rings making metal-to-metal contact with cylinder wall
  • Piston rings wear out of tolerance
  • Radial lines or streaks on valve sealing surfaces
  • Reed valve cracking or pitting
  • Scroll compressor drive belt misalignment
  • Scroll compressor drive belt tension incorrect
  • Scroll compressor starts and stops often
  • Securing spring adjusters with sealing bolts
  • Startup troubleshooting: Blower does not start
  • Startup troubleshooting: VSA switch does not change from vacuum to pressure
  • Structural damage present
  • Suction pressure to compressor is too high
  • System pressure troubleshooting: High pressure on PI-8
  • The motor overload relay (OL) tripped due to low voltage
  • Tip seal replacement procedure
  • Tip seal replacement required
  • Valve operation impaired
  • Valve seat cracking, pitting, or leakage
  • Valve seat damage (grinding or lapping required)
  • Valve seat erosion or damage
  • Valve seat worn or damaged (1st stage)
  • Wrist pin clearance excessive

143 more symptoms with ranked causes and checks are in ServiceForge. Connect ServiceForge to your AI

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ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.