| Document type | Installation Guide |
|---|---|
| Document number | 201.21-NM1 |
| Equipment | YCAV Variable Speed Drive Screw Chiller |
| Brand | YORK |
| Revised | 2026-07-09 |
| File size | 11.6 MB |
Fault codes in this document
VSD safeties (faults)
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| UNIT YYYYYYYY PRECHARGE - LOW DC BUS VOLTAGE 4-compressor units: SYS X YYYYYYYY PRECHARGE - LOW DC BUS VOLT | Software fault. Unit fault on 2- and 3-compressor chillers; system fault (Sys 1/3 or 2/4) on 4-compressor chillers. | The DC bus voltage must reach at least 50 VDC within four seconds and 500 VDC within 19 seconds after the pre-charge signal has been asserted. If not, the unit/system will shut down on a fault. | Auto-restart safety: restarts when the fault clears; locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 209 |
| UNIT YYYYYYYY PRECHARGE - DC BUS VOLTAGE IMBALANCE 4-compressor units: SYS X YYYYYYYY PRECHARGE-BUS VOLT IMBAL | Software fault. Unit fault on 2- and 3-compressor chillers; system 1/3 or 2/4 fault on 4-compressor chillers. Locks out on the 1st fault. | The 1/2 DC bus voltage magnitude must remain within +/- 100 VDC of the total DC bus voltage divided by two during the pre-charge interval. If not, the unit/system shall shut down on a fault. | Locks out on the 1st fault; will not restart until the operator clears the fault using the keypad. | 209 |
| UNIT YYYYYYYY HIGH DC BUS VOLTAGE 4-compressor units: SYS X YYYYYYYY HIGH DC BUS VOLTAGE | Hardware fault. Unit fault on 2- and 3-compressor chillers; system 1/3 or 2/4 fault on 4-compressor chillers. Immediate shutdown. | The high DC bus voltage trip level is determined by hardware on the VSD Logic Board and is designed to trip the unit at 766 +/- 30 VDC. If the DC bus exceeds this level, the unit/system will fault and shut down immediately. | Auto-restart safety: restarts when the fault clears; locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 209 |
| UNIT YYYYYYYY LOW DC BUS VOLTAGE 4-compressor units: SYS X YYYYYYYY LOW DC BUS VOLTAGE | Software fault. Unit fault on 2- and 3-compressor chillers; system fault (1/3 or 2/4) on 4-compressor chillers. Immediate shutdown. | The low DC bus voltage trip level is set at 500 VDC. If the DC bus drops below this level the unit/system will fault and immediately shut down. | Auto-restart safety: locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 210 |
| UNIT YYYYYYYY DC BUS VOLTAGE IMBALANCE 4-compressor units: SYS X YYYYYYYY DC BUS VOLTAGE IMBALANCE | Software fault. Unit fault on 2- and 3-compressor chillers; system 1/3 or 2/4 fault on 4-compressor chillers. Locks out on the 1st fault. | The 1/2 DC bus voltage magnitude must remain within +/- 100 VDC of the total DC bus voltage divided by two. If the 1/2 DC bus magnitude exceeds the +/- 100 VDC tolerances, the unit/system will fault and immediately shut down. | Locks out on the 1st fault; will not restart until the operator clears the fault using the keypad. | 210 |
| SYS X YYYYYYYY HIGH MOTOR CURRENT | Hardware fault; individual system/compressor fault for all units. Immediate shutdown. | The three output lines to each phase of the compressor motor are monitored via three current transformers within the VSD and instantaneous output current is compared to a predetermined hardware limit. Nominal peak current trip level is 575.5 Amps (554A min., 597A max.); 380V AC 60 Hz and 400V AC 50 Hz nominal peak current trip level is 649.5 Amps (626 Amps min., 674 Amps max.). The variation in trip point is the result of component tolerances on the VSD Logic Board. If the peak current limit is exceeded, the unit will fault and shut down immediately. | Auto-restart safety: locks out the system on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 210 |
| SYS X YYYYYYYY MOTOR CURRENT OVERLOAD | Software fault; individual system/compressor fault for all systems. Controlled ramped shutdown; locks out on the 1st fault. | Compares the highest of the 3 phases of motor current per compressor to the compressor's 105% FLA ADJUST (overload) potentiometer setting on the VSD Logic Board. If the current exceeds the setting continuously for 20 seconds, the compressor will trip. | Locks out the system on the 1st fault with a controlled ramped shutdown; will not restart until the operator clears the fault using the keypad. | 211 |
| UNIT YYYYYYYY MOTOR CURRENT OVERLOAD | Hardware fault; unit fault that locks out all systems on the first fault. Immediate shutdown. | Compares the highest of the 3 phases of motor current per compressor to the compressor's overload ADJUST potentiometer setting. If the current exceeds the setting continuously for 30 seconds, all compressors will fault and shut down immediately. | Unit fault — locks out all systems on the first fault; will not restart until the operator clears the fault using the keypad. | 211 |
| SYS X YYYYYYYY GATE DRIVER | Hardware fault; system fault for all units. Immediate shutdown. | Each phase bank assembly contains one IGBT gate driver control board per compressor. These boards monitor the saturation voltage drop across each of the six IGBT while gated on. If the IGBT saturation voltage exceeds the prescribed limit, the gate driver determines a short circuit is present, immediately turns off all IGBT in the module and the system shuts down immediately. The same fault is generated if the IGBT Gate Driver board's power supply voltage falls below the permissible limit. | Auto-restart safety: locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 211 |
| SYS X YYYYYYYY HIGH VSD BASEPLATE TEMP | Software fault; system fault for all units. Controlled ramped shutdown. | Each compressor's inverter power module contains an internal temperature sensor (5K ohm at 25 Deg. °C) monitoring baseplate temperature. Limit is 218°F on 2-compressor chillers (each system sensor compared individually); 232°F on 3-compressor chillers (compressors 1 and 3 OR'd together, compressor 2 individual); 218°F on 4-compressor chillers (compressors 1/3 OR'd and 2/4 OR'd). If the limit is exceeded, the unit faults and shuts down with a controlled ramped shutdown. | Auto-restart safety: locks out on the 3rd fault in 90 minutes (lockout cleared by the operator via the keypad). After a fault, the fan(s) and water pump remain energized until the inverter power module base plate temperature(s) fall below 165°F; the system is allowed to restart when the base plate temperatures drop below this value. | 212 |
| UNIT YYYYYYYY HIGH VSD INTERNAL AMBIENT TEMP | Software fault; unit fault for all units. Controlled ramped shutdown; does not cause a lockout. | The VSD Logic board contains a temperature sensor which monitors the unit's internal ambient temperature. If the VSD internal ambient temperature rises above the cutout of 158°F, the unit will fault and shut down with a controlled ramped shutdown. | No lockout. The unit will be allowed to restart when the internal ambient temperature drops 10°F below the cutout. | 212 |
| UNIT YYYYYYYY SINGLE PHASE INPUT VOLTAGE 4-compressor units: SYS X YYYYYYYY SINGLE PHASE INPUT VOLTS | Hardware fault. Unit fault on 2- and 3-compressor units; system fault 1/3 or 2/4 on 4-compressor units. No lockout. | The VSD's SCR Trigger Control board contains circuitry that checks the three phase mains for the presence of all three-line voltages. If any of the line voltages are not present, the system will immediately shut down on a fault. | Does not cause a lockout; the system restarts when the single phase condition clears. | 212 |
| UNIT YYYYYYYY VSD LOGIC BOARD POWER SUPPLY | Hardware fault; unit fault for all units. Immediate shutdown. | Various DC power supplies which power the VSD Logic Board are monitored via hardware located on the logic board. If any of these power supplies fall outside their allowable limits, the unit will immediately shut down on a fault. | Auto-restart safety: restarts after the fault clears; locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 213 |
| SYS X YYYYYYYY VSD RUN RELAY | Software fault. System fault on 2-compressor units; combined as a 1/3 or 2/4 system fault on 3- and 4-compressor units. Controlled ramped shutdown if running. | Upon receipt of either of the two types of run commands (hardware and software) a 5-second timer commences timing. If the missing run signal is not asserted within the 5-second window, the system will fault. In addition, if either run signal is disabled while the VSD is running, the remaining run signal must be disabled within 5 seconds after the VSD is shut down or the system will fault. | Auto-restart safety: autostarts after the 120-second anti-recycle timer times out; locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 213 |
| UNIT YYYYYYYY VSD LOGIC BOARD FAILURE | Software fault; unit fault for all units. All systems shut down immediately if running. | Upon receipt of the voltage and frequency commands, the PWM generator will acknowledge receipt of the command. If the system microprocessor does not receive the handshake within 1.5 seconds of issuing the command, the unit will trip. This safety is only active during precharge and during running of a compressor. | Auto-restart safety: auto restarts after the 120-second anti-recycle timer times out; locks out on the 3rd fault in 90 minutes. | 213 |
| UNIT YYYYYYYY VSD CT PLUG FAULT | Hardware fault; unit fault for all units. Immediate shutdown, or start inhibited if off. | Jumpers are installed in each CT plug on the VSD Logic Board to feed back signals indicating if the plugs are installed or not. If either plug is not installed, a low value is read on the digital input and the unit will immediately shut down on a fault or will not run if off. | Auto-restart safety: restarts after the 120-second anti-recycle timer times out; locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad. | 213 |
Unit warnings
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| UNIT WARNING: !! LOW BATTERY !! CHECK SETPOINTS/PROGRAM/OPTIONS/TIME | Displayed indefinitely when the RTC battery voltage is low; can only occur at unit power-up. | On micropanel power-up the RTC battery is checked. If the battery voltage is determined to be low, all programmed setpoints, program values, time, schedule, and history buffers have been lost and are reset to their default values, which may not be the desired operating values. | Replace the battery as soon as possible. The unit is prevented from running until the MANUAL OVERRIDE key is pressed; pressing it sets the anti-recycle timers to the programmed default anti-recycle time to allow the operator sufficient time to check setpoints, program values, etc. Programmed values will be lost and the unit prevented from running on the next power interruption until the battery is replaced. | 215 |
| Flash Card Update Error XXXXX | Error message displayed if an error occurs during a program/database update from the SD flash card; XXXXX is the error code. | Error codes: 0 Okay; 10 Flash card not found; 11 SOFTWARE.BIN file not found; 14 SOFTWARE.BIN file larger than expected; 15 RAM to IPU Flash transfer of DATABASE.BIN failed; 16 RAM to IPU Flash transfer of SOFTWARE.BIN failed; 17 Could not allocate sufficient memory to read or write file; 99 Internal software error. | 217 | |
| UNIT WARNING: INVALID NUMBER OF COMPRESSORS SELECTED | Start-up of the unit is inhibited; warning displayed indefinitely in the Status display. | Occurs after the VSD has been initialized if no "Number of Compressors Select" jumpers are installed or if more than 1 jumper is installed in the J1 plug wiring harness. | To clear this warning, both the control panel and VSD control voltage must be turned off and the jumpers properly installed in the VSD wiring harness. | 218 |
| UNIT WARNING: INVALID SERIAL NUMBER ENTER UNIT SERIAL NUMBER | May mean the chiller has lost important factory programmed information; an Optimized IPLV chiller will only run in Standard IPLV control mode while this warning is present. | Serial number not programmed into the panel (e.g., after changing a Chiller Control Board or EPROM, or if the chiller was not programmed from the factory). | Immediately contact YORK Product Technical Support. Enter the serial number using the Service Key with the factory-provided password. Optimized IPLV cannot be enabled unless the serial number is programmed into the unit. | 218 |
| UNIT WARNING: OPTIMIZED EFFICIENCY DISABLED - CONTACT YORK REPRESENTATIVE | An optimized (High IPLV) chiller is programmed for standard control. | High IPLV mode is not enabled (e.g., after a Chiller Control Board/EPROM change or loss of factory programming). | Immediately contact YORK Product Technical Support or YORK ES Commercial for a password. Once the password is entered and the option is enabled using the Service Key, the message will disappear. | 218 |
Unit safeties
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| UNIT YYYYYYYY LOW AMBIENT TEMP | Unit fault — controlled ramped shutdown; cannot cause a lockout. Occurs only if the Low Ambient Cutout is ENABLED under the OPTIONS key. | The ambient temperature falls below the programmable Low Ambient Temp Cutout. | Restart can occur, if demand allows, when temperature rises 2°F above the cutout. The unit is also inhibited from starting any time the temperature is below the cutout + 2°F. The fault display is present only while the condition exists. | 219 |
| UNIT YYYYYYYY LOW LEAVING CHILLED LIQUID TEMP | Unit fault — controlled ramped shutdown; cannot cause a lockout. Helps protect the chiller from an evaporator freeze-up. | The leaving chilled liquid temperature (water or brine) drops below the programmable cutout point. This situation could occur under low flow conditions or if the micro panel setpoint values are improperly programmed. | Restart can occur, if demand allows, when chilled liquid temperature rises 4°F above the cutout. The unit is inhibited from starting any time the chilled liquid temperature is below the cutout + 4°F. | 220 |
| UNIT YYYYYYYY VSD COMMUNICATIONS FAILURE | Unit fault — controlled ramped shutdown while operating; prevents the unit from trying to run if communications never initialize. | On power-up the Chiller Control Board attempts to initialize communications with the VSD Logic Board (requesting number of compressors and VSD software version); if the connection fails to occur, the chiller is prevented from operating. During normal operation, if the Chiller Control Board receives no valid response to messages for 8 seconds, the unit shuts down all compressors on a Comms fault. | The unit is inhibited from starting until communications is established. The Chiller Control Board continues to send messages to the VSD while faulted. The fault automatically resets when the Chiller Control Board receives a valid response from the VSD for a data request. | 220 |
System safeties: Faults
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| SYS X YYYYYYYY HIGH DISCHARGE PRESSURE | Software fault — controlled ramped shutdown. X indicates the system; YYYYYYYY indicates FAULT (auto-restart) or LOCKOUT. | The discharge pressure rises above 274 psig for 0.5 seconds. | The system is allowed to restart when the discharge pressure falls to 259 psig; it is also inhibited from starting if the pressure is above 259 psig. System faults are auto-reset: the system restarts when the 120-second anti-recycle timer times out. After any 3 faults on the same system within 90 minutes the system locks out on the last fault — a lockout requires a manual reset by cycling the respective system switch OFF and ON. | 221 |
| SYS X YYYYYYYY HPCO FAULT | Mechanical (hardware) high pressure cutout — protects the system from dangerously high discharge pressure. Immediate shutdown; does not wait the typical 3 seconds. Wired in series with the VSD Run Signal; checked only when the system is running. | The mechanical high pressure cutout contacts open. The cutout opens at 297 +/- 8 psig and closes at 230 +/- 10 psig. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 222 |
| SYS X YYYYYYYY LOW SUCTION PRESSURE | Software fault — controlled ramped shutdown. Secondary back-up for the flow switch; protects against operation with low refrigerant charge and helps protect the chiller from evaporator freeze-up. | Suction pressure falls below the programmable cutout (typically 24 psig for chilled water applications). The cutout is ignored for the first 30 seconds of run time; during the next 3 minutes the cutout point is linearly ramped from 10% of the cutout value up to the programmed cutout. After the first 3 minutes 30 seconds of run time, a transient sets a 30-second timer with a linearly ramped cutout starting at 10% of the programmed cutout; if the suction pressure does not stay above the ramped cutout over the 30 seconds, the system faults. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 222 |
| SYS X YYYYYYYY LOW MOTOR CURRENT | Controlled ramped shutdown when the microprocessor detects the absence of motor current, usually indicating that a compressor is not running. | Motor current detected below 10% FLA. This safety is ignored for the first 10 seconds of operation. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 222 |
| SYS X YYYYYYYY HIGH DIFF OIL PRESSURE | Controlled ramped shutdown; protects the compressor from low oil flow and insufficient lubrication, possibly from a dirty oil filter (measures the pressure drop across the oil filter). | Discharge-to-oil differential pressure rises above the cutout of 65 PSID. This safety is ignored for the first 90 seconds of run time. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 223 |
| SYS X YYYYYYYY LOW DIFF OIL PRESSURE | Controlled ramped shutdown; protects the compressor from low oil flow and insufficient lubrication; assures the compressor is pumping sufficiently to push oil through the oil cooling circuit and internal compressor lubrication system. | Differential between oil and suction pressure falls below the cutout. Ignored for the first 60 seconds of run time; thereafter the cutout is linearly ramped from 0 PSID to 30 PSID in 5 to 10 minutes based on ambient temperature (>50°F: 5 min; >45°F: 6 min; >40°F: 7 min; >35°F: 8 min; >30°F: 9 min; ≤30°F: 10 min). A 30-second safety bypass below 50 Hertz applies during rampdown (e.g., when a running compressor is decelerated to 5 Hz to add an additional compressor). | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 223 |
| SYS X YYYYYYYY HIGH DSCHARGE TEMP | Controlled ramped shutdown; protects the motor and compressor from overheating. | Discharge temperature rises above 250°F. | The system is also inhibited from starting if the discharge temperature is above 200°F. The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 223 |
| SYS X YYYYYYYY HIGH OIL TEMP | Controlled ramped shutdown; protects the compressor from insufficient lubrication. | Oil temperature rises above 225°F. | The system is inhibited from starting if the oil temperature is above 175°F. The system restarts when the fault clears (120-second anti-recycle timer); if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 224 |
| SYS X YYYYYYYY LOW SUCTION SUPERHEAT | Controlled ramped shutdown; helps protect the compressor from liquid floodback due to low suction superheat. Ignored for the first 30 seconds of compressor operation. | Faults when any one of the following occur: after the first 30 seconds of run time, suction superheat < 2.0°F, discharge superheat < 15°F and run time < 5 minutes (safety ignored for the next 30 seconds, then the cutout is set to 0°F and linearly ramped up to 2.0°F over 60 seconds — fault if superheat falls below the ramped cutout); suction superheat < 2°F and discharge superheat < 15°F for 10 seconds with run time ≥ 5 minutes; suction superheat < 0.5°F and discharge superheat > 15°F for 60 seconds with run time ≥ 5 minutes; suction superheat < 5°F for 10 minutes. | The system restarts after the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 224 |
| SYS X YYYYYYYY LOW DISCHARGE SUPERHEAT | Controlled ramped shutdown; helps protect the compressor primarily from liquid floodback through the economizer line due to a high flash tank level, and from liquid floodback through the suction line in conjunction with the low superheat safety. Ignored for the first 5 minutes of compressor operation. | After the first 5 minutes of run time, the discharge superheat falls below 10.0°F for 5 minutes. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 224 |
| SYS X YYYYYYYY SENSOR FAILURE: ZZZZZZZZZZZZ | Prevents the system from running when a critical sensor (transducer, level sensor, or motor winding temp sensor) is not functioning properly and reading out of range. | Checked at start-up and prevents the system from running if one of the sensors has failed; also faults and shuts down a system while in operation if a safety threshold is exceeded or a sensor reads out of range (high or low). ZZZZZZZZZZZZ indicates the failed sensor: SUCT PRESS, OIL PRESS, DSCH PRESS, LEVEL SENSOR, or MOTOR TEMP X. Start-inhibit thresholds: suction/oil/discharge transducers 0.3–4.7 VDC; level sensor 3.0–21.0 mA; motor temp sensor 0–240°F. | YYYYYYYY indicates FAULT (the system restarts when the fault clears) or LOCKOUT after 3 faults — a lockout will not restart until the operator clears the fault using the keypad. The Unit Setup Mode allows a specific motor temperature sensor to be ignored if it fails. | 225 |
| SYS X YYYYYYYY HIGH MOTOR TEMP | Controlled ramped shutdown; prevents a compressor from running when its motor temperature is too high. | Any compressor motor temperature sensor rises above 250°F. | The system is inhibited from starting if its motor temperature sensors indicate temperatures above 240°F. If any single temperature sensor is being ignored under the Unit Set-up Mode, that sensor is not utilized when evaluating motor temperature. The system restarts when the fault clears; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 225 |
| SYS X YYYYYYYY HIGH FLASH TANK LEVEL | Prevents the system from running when the liquid level in the flash tank is too high. Ignored for the first 15 seconds of system operation. | Tank level greater than 85% for 10 seconds. | The system restarts when the 120-second anti-recycle timer times out; if LOCKOUT is indicated, the system will not restart until the operator clears the fault using the keypad. | 226 |
| SYS X YYYYYYYY CONTROL VOLTAGE | Alerts the operator that the 115V AC control voltage to one of the systems is missing; the affected system faults and shuts down immediately. | Could be due to a system fuse that has been removed or is blown. The safety will not shut down a system if the Unit Switch is OFF (which electrically removes the 115V AC to all systems); it only indicates a situation where a single system is missing the 115V AC. | Does not cause a lockout; the system fault resets when power is returned. | 226 |
Troubleshooting guide
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| Chiller Fault: LOW AMBIENT TEMPERATURE | Ambient temperature is lower than the programmed operating limit. Ambient Sensor is defective. | Check the programmed cutout and determine if it is programmed correctly. Check the panel against the thermometer reading of ambient temperature. | 306 | |
| Chiller Fault: HIGH AMBIENT TEMPERATURE | Ambient Temperature is above the maximum operating limit. Ambient Sensor is defective. | Check outside air temperature. Check the Panel Display against thermometer reading of Ambient Temperature at the sensor. | 306 | |
| Chiller Fault: LOW LEAVING CHILLED LIQUID | Leaving chilled liquid temperature drops faster than the unit can unload (restricted flow; rapid flow changes; water loop too small; flow below minimum for chiller). Chilled Water Sensor is defective. | Check for restricted flow. Check for rapid flow changes. Check Sensor against Temp. Gauge in water line. Check Sensor for intermittent operation. Check Wiring for shorts or opens. | 306 | |
| System Fault: CONTROL VOLTAGE | System Fuse is blown. | Check respective system Fuse 20FU or 21FU. | 306 | |
| System Fault: HIGH OIL TEMPERATURE | Oil Temperature Sensor is defective. Condenser Fans NOT operating or running backwards. Coils dirty. | Check Sensor with infrared to determine if reading is reasonable. Check Fans. Check and clean Coils. | 306 | |
| System Fault: HIGH DISCHARGE PRESSURE | Coils dirty. Coils are damaged. Fans NOT operating. System is overcharged. | Check and clean coils. Comb out fins. Check fan fuses; check fan rotation; check fan motor/blade. Remove charge and check subcooling. | 307 | |
| System Fault: HIGH DISCHARGE TEMPERATURE | Discharge Temperature Sensor is defective. Condenser Fans NOT operating or are running backwards. Coils dirty. High Superheat. | Check Sensor. Check Fans. Check and clean Coils. Measure Superheat with gauges and thermocouple; determine cause. | 307 | |
| System Fault: HIGH MOTOR TEMPERATURE | High Motor temperature input from one of the sensors. Refrigerant charge low. Excess charge in system, high discharge pressure. High Superheat — Drain/Feed Valves NOT controlling. Motor Sensor reading incorrectly. Economizer Solenoid energized at low speeds — valve is leaking through. | Check subcooling. Program panel to ignore a single sensor. Isolate cause of Drain/Feed Valves not controlling. | 307 | |
| System Fault: LOW SUCTION PRESSURE | Low charge. Transducer reads incorrectly. Suction Temp. Sensor reads incorrectly. Low flow. Feed or Drain Valve NOT operating. Feed or Drain Valve defective. | Check subcooling. Check transducer against a gauge. Check sensor against a thermocouple. Check flow. Check Feed and Drain Valve operation; check superheat. | 307 | |
| VSD Fault: High Baseplate Temperature | Coolant level low. Glycol Pump is defective. VSD Board is defective. IBGT Module is defective. | Add coolant. Replace Glycol Pump. Replace VSD Logic Board. Check defective IGBT Module. | 308 | |
| VSD Fault: Low DC Bus Voltage | SCR / Diode Module is defective. SCR Trigger Board is defective. | Check SCR / Diode Module. Check SCR Trigger board. | 308 |
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