| Document type | Installation Operation and Maintenance Guide |
|---|---|
| Document number | 150.72-ICOM6 |
| Equipment | YLAA Scroll Chiller |
| Brand | YORK |
| Revised | 2026-02-24 |
| File size | 17.9 MB |
Fault codes in this document
Unit Safeties
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| UNIT FAULT: LOW AMBIENT TEMP | Unit Fault Code 2 – Low Ambient Temperature Cutout | Outdoor ambient temperature falls below the programmable Low Ambient Temp Cutout setpoint. | Chiller shuts down. Auto reset: restart can occur when the temperature rises 2°F above the cutoff. | 144 |
| UNIT FAULT: LOW LIQUID TEMP | Unit Fault Code 4 – Low Leaving Chilled Liquid Temperature Cutout (evaporator freeze-up protection) | Leaving chilled liquid temperature (water or glycol) drops below the cutout point; can occur under low flow conditions or if the micro panel setpoint values are improperly programmed. | Chiller shuts down. Auto reset: restart can occur when chilled liquid temperature rises 2°F above the cutout. | 144 |
| UNIT FAULT: CHECK LIQ TEMP SENS | Check Liquid Temperature Sensor fault (unit fault) | While the unit is running and the control panel is programmed for leaving chilled liquid temperature control, the leaving chilled liquid temperature rises over 2.0°F above the entering chilled liquid temperature for 60 continuous seconds. Disabled if the Entering Chilled Liquid Temperature Sensor is disabled under Unit Setup. | Chiller shuts down; requires a manual reset to restart the unit. | 141 |
| UNIT FAULT: PUMP TRIP | Unit Fault Code 27 – Pump Trip (Hydro Pumps 1 or Hydro Pumps 2) | Single pump: the manual motor starter protecting the pump from short circuit or overload conditions has tripped or been set to OFF. Two pumps (duty and standby): both manual motor starters protecting the pumps have tripped or both have been set to OFF. | Setting the device to ON (at least one of the devices on dual-pump units) resets the trip. Auto per Table 15. | 144 |
| UNIT FAULT: PUMP FAIL MAKE FLOW | Unit Fault Code 28 – Pump Flow Failure (Hydro Pumps 1 or Hydro Pumps 2) | After the 30-second stop-to-start timer the pump is started (Leaving Liquid Temperature Cutout active, any compressor running, or daily schedule not calling for shutdown with unit switch ON and remote stop/start input closed) but the flow switch does not close within 10 seconds. On dual-pump units the running pump is stopped and the standby pump started; if the flow switch still does not close within a further 10 seconds the unit locks out. | Unit locks out and the running pump is stopped. Reset by setting the unit switch to OFF then back to ON. Locks out on the first fault (1x). When attempting to clear this fault, check that one of the manual motor starters protecting the pumps has not tripped. | 141 |
| UNIT FAULT: 115 VAC UNDER VOLTAGE | Under Voltage Safety (unit fault) | The 115 VAC to the micro panel drops below a certain level, where malfunction of the microprocessor could result in system damage. | A unit fault is initiated to safely shut down the unit. Restart is allowed after the unit is fully powered again and the anti-recycle timers have finished counting down. | 141 |
| UNIT FAULT: HIGH MTR CURR | Unit Fault Code 22 – Unit High Motor Current (Current Feedback One Per Unit option) | With the CURRENT FEEDBACK ONE PER UNIT option selected, the voltage exceeds the programmed trip voltage for 5 seconds. The trip voltage is programmed at the factory according to compressor or unit RLA. | Unit shuts down; restart occurs after the anti-recycle timer times out. Auto per Table 15. | 144 |
| FLOW SWITCH OPEN | Unit Fault Code 31 – Flow Switch Open | The flow switch contacts connected to Terminals 13 and 14 of XTBC1 are open. A 3-second delay is built into software to prevent nuisance shutdowns due to erroneous signals from the flow switch. | Auto per Table 15: allows restart once meeting the required conditions. | 137 |
| HIGH AMBIENT TEMPERATURE | Unit Fault Code 29 – High Ambient Temperature | Auto per Table 15/Table 16: allows restart once meeting the required conditions. | 144 |
Unit Warnings
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| !! LOW BATTERY !! CHECK PROG/SETP/OPTN | Low Battery Warning (unit warning; not a unit safety, not logged to the history buffer) | On micro panel power-up the RTC battery is checked and a low battery is found; all programmed setpoints, program values, options, time, schedule, and history buffers are lost and reset to their default values, which may not be the required operating values. | Unit is prevented from running until the PROGRAM key is pressed; pressing PROGRAM sets the anti-recycle timers to the programmed anti-recycle time to allow checking/reprogramming of values and options. Replace the RTC/battery (031-02565-000, located at U5 on the microboard) as soon as possible. Will not auto-restart; operator intervention required. | 145 |
| INCORRECT UNIT TYPE | Incorrect Unit Type warning | The condensing unit jumper is installed between J11-12 and J11-7. | This jumper must be removed to operate the chiller. Will not auto-restart; operator intervention required. | 145 |
System Safeties
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| SYS 1 HIGH DSCH PRES SYS 2 HIGH DSCH PRES | System Fault Code 5 – High Discharge Pressure (software cutout, backed up by the mechanical high pressure cutout switch in the refrigerant circuit) | The programmable discharge pressure cutout is exceeded; discharge transducers must be installed for this function. When an operating envelope is enabled, the effective cutout is set to 10 psig above the discharge pressure unload limit if suction pressure is less than 94.0 psig (standard envelope) or less than 42.0 psig (extended envelope). | System shuts down; restart allowed when the discharge pressure falls 40 psig below the cutout. 3x: automatic restart on the first and second fault with a lockout on the third fault within 90 minutes; clear the lockout by turning the system switch (under OPTIONS key) OFF and then back ON. | 150 |
| SYS 1 LOW SUCT PRESS SYS 2 LOW SUCT PRESS | System Fault Code 7 – Low Suction Pressure cutout (protects the chiller from evaporator freeze-up) | Suction pressure falls below the ramped cutout point: at system start the cutout is set to 10% of the programmed value and ramped up to the programmed point over 3 minutes (completely ignored for the first 30 seconds of run time); after the first 3 minutes, if suction pressure falls below the programmed cutout, a transient protection routine sets the cutout at 10% of the programmed value and ramps it up over the next 30 seconds. Can occur with a low refrigerant charge or a restriction in the refrigerant circuit. | System stops. 3x: automatic restart on the first and second fault with a lockout on the third fault in 90 minutes; clear the lockout via the system switch (under OPTIONS key) OFF then back ON. Repeated starts after resetting a low suction pressure fault will cause evaporator freeze-up – immediate steps should be taken to identify the cause. | 145 |
| SYS 1 SP/ FREEZE WARN SYS 2 SP/ FREEZE WARN | Suction pressure / freeze warning – transient protection routine active | After the first 3 minutes, the suction pressure falls below the programmed cutout setting; the cutout is set at 10% of the programmed value and ramped up over the next 30 seconds. Suction pressure transducers must be enabled for this function to work. | The system will stop if at any time during this 30 seconds the suction pressure falls below the ramped cutout. | 145 |
| SYS 1 MP/HPCO FAULT SYS 2 MP/HPCO FAULT | System Fault Code 18 – Motor Protector / Mechanical High Pressure Cutout fault | CR1 (SYS 1) or CR2 (SYS 2) relays de-energize due to the HP switch or motor protector opening, causing 0 VDC to be read on the microboard input. The internal motor protector opens at 185°F to 248°F (85°C to 120°C); the mechanical HP switch opens at 585 psig plus or minus 10 psig and closes at 330 psig plus or minus 25 psig. The compressor discharge temperature sensor also opens the motor protector circuit when it senses high internal scroll temperature (e.g., low refrigerant charge or superheat too high). Message displayed only after the third fault in 90 minutes. | System is locked out and will not restart; the fault condition is cleared when a 30 VDC signal is restored to the input. During the first two faults the MP/HP INHIBIT message is displayed and the system is not locked out. Whenever the motor protector or discharge sensor shuts down a compressor, the internal compressor contacts open for 30 minutes so motor/scroll temperatures can dissipate before the system is permitted to restart. | 188 |
| SYS 1 HIGH MTR CURR SYS 2 HIGH MTR CURR | System Fault Code 17 – System High Motor Current (System Current Feedback option) | Condition present when CR1 (SYS 1) or CR2 (SYS 2) opens, causing 0 V to be read on the input (motor protector faulted or mechanical high pressure cutout open); only occurs when a system is not running. | Condition cleared and the system allowed to start when a 30 V signal is restored to the input by CR1 or CR2 closing. 3x per Table 15. | 150 |
| SYS 1 LOW SUPERHEAT SYS 2 LOW SUPERHEAT | System Fault Code 23 – Low Suction Superheat cutout (EEV mode only); also displayed as “SYS x LOW SUCT SHE AT” | Protects the compressors from liquid flowing back due to low suction superheat. Triggered when the suction superheat is lower than 2.0°F for 3 seconds, or when the LLSV is closed 10 times in 2 minutes due to low superheat. Ignored for the first 15 seconds of system run time; trips after the programmed trip time has passed. | Fault resets if the superheat rises above 2°F; lockout after three shutdowns in 90 minutes. 3x per Table 15. | 145 |
| SYS 1 SENSOR FAILURE SYS 2 SENSOR FAILURE | System Fault Code 24 – Sensor Failure cutout (EEV mode only) | Prevents the EEV from running when the sensors measuring superheat are not functioning properly; shuts the system down if either the suction temperature or suction pressure sensors read out of range high or low for 3 seconds. Ignored for the first 15 seconds of system run time. | Locks out on the first fault; will not automatically restart. 1x per Table 15. | 145 |
| LOW EVAPORATOR TEMPERATURE (R407c ONLY – N/A HP HEATING MODE) | System Fault Code 19 – Low Evaporator Temperature (R407c only; not applicable in heat pump heating mode) | 3x: automatically restarts on the first and second fault with a lockout on the third fault in 90 minutes. | 144 | |
| DISCHARGE INHIBIT (HEAT PUMP HEATING MODE ONLY) | System Fault Code 25 – Discharge Inhibit (heat pump heating mode only) | 3x: automatically restarts on the first and second fault with a lockout on the third fault in 90 minutes. | 144 |
System Inhibits
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| SYS 1 MP/HPCO INHIB SYS 2 MP/HPCO INHIB | System Inhibit Code 26 – Motor Protector / High Pressure Cutout Inhibit | Prevents the system from trying to start when a motor protector is faulted or the mechanical high pressure cutout is open; condition present when CR1 (SYS 1) or CR2 (SYS 2) opens, causing 0 VDC to be read on the input. Only occurs when a system is not running; also displayed during the 30-minute timeout after a motor protector/discharge-sensor shutdown while the internal compressor contacts are open or the HPCO is open. | Compressors will not be permitted to start while displayed; condition cleared and restart allowed when a 30 VDC signal is restored to the input by CR1 or CR2 closing (contacts close after the 30-minute timeout). Auto per Table 15. | 188 |
| SYS 1 ATV SUCT PRESS SYS 2 ATV SUCT PRESS | System Inhibit Code 30 – Anti-Vacuum Low Pressure Cutout | If the system is running, it shuts down when the suction pressure falls below the anti-vacuum low pressure cutout for longer than the programmed Anti-Vacuum Delay Time; if the system is not running, it is inhibited from starting while the suction pressure is below the anti-vacuum low pressure cutout. | Standard system fault: lockout after 3 occurrences in 90 minutes; the fault cannot be reset until the fault condition is resolved. 3x per Table 15. | 143 |
| LEAVING CHILLED LIQUID TEMPERATURE SENSOR FAULT | System Inhibit Code 32 – Leaving Chilled Liquid Temperature Sensor Fault | 3x: automatically restarts on the first and second fault with a lockout on the third fault in 90 minutes. | 144 | |
| SYS 1 LOW DS CH SHE AT SYS 2 LOW DS CH SHE AT | System Inhibit Code 33 – Low Discharge Superheat | System Discharge Superheat drops below 18°F; trips after 5 minutes have passed. Only active when Discharge Temperature Sensors are enabled. | Fault resets if the superheat rises above 18°F; will lockout after three shutdowns in 90 minutes. Listed as Auto in Table 15 (allows restart once meeting the required conditions). | 145 |
Real Time Error Numbers
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| 0 | All ok | No error present. | 175 | |
| 1 | Datum type ok test failed | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 2 | English text too long | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 3 | Floating point exception | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 4 | Get packet failed | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 5 | Get type failed | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 6 | Invalid unit conversion | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 7 | Invalid hardware selection | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 8 | Real time fault | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 9 | Spanish text too long | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 10 | Thread exited | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 11 | Thread failed | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 12 | Thread stalled | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 13 | IO board reset | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 14 | BRAM invalid | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 | |
| 15 | BACnet setup failed | Reset via the REAL TIME ERROR screen (set RESET = 1/YES); reboot required (cycle power) after settings are changed. | 175 |
Flash Card Update
| Code / display | Meaning | Cause | Action | Page |
|---|---|---|---|---|
| FLASH CARD UPDATE ERROR XXXXX | Flash card operating-software update error (error code shown as XXXXX) | An error occurred during the flash card update: the incorrect Flash Card was used, incorrect chiller software was used, the Flash Card is defective, or the IPU and I/O combo board is bad. | The original program will still be active and no reboot will occur; ensure the correct Flash Card was used. | 168 |
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Manufacturer document, published here as reference material for equipment we supply. The original lives at docs.johnsoncontrols.com. The rights holder may ask us to take it down — we will.