Lochinvar · Error codes
Lochinvar error codes and alerts
Identical code numbers can mean different things on different controllers, so every entry is tied to the documented series, controller and manual version. A code is never a diagnosis.
If you smell gas
- Stop what you are doing. Do not use phones, switches, matches or anything that can spark inside.
- Go outside and leave the door open behind you.
- Call the FortisBC 24-hour emergency line at 1-800-663-9911 or dial 911.
Only after that, call ROMA about the boiler. Official guidance: FortisBC gas leaks and odour.
Lochinvar Knight fire-tube boilers (KHB floor and WHB wall, SMART SYSTEM control)
Gas Pressure SW
Gas pressure switch contacts are open. The gas pressure switch contacts on the Low Voltage Connection Board are open, so check for a loose o…
Lockout
Flow Switch/LWCO
Flow switch or low water cutoff is not making. Either the optional flow switch or the low water cutoff (LWCO) is not making, so check boiler…
Lockout
Air Pressure SW
Air pressure switch contacts are open. The air pressure switch contacts are open, so check the switch wiring to the common and normally clos…
Lockout
Too Many Recyclings
A limit switch opened more than five times during one call for heat. One or more limit switches has opened more than five times during the l…
Details
Anti-cycling
Burner recently turned off and is waiting to relight. The burner recently turned off, and the control board will release the call for heat a…
Details
Flame Fail Ign
Failed to prove main burner ignition after several attempts. The unit has failed to prove main burner ignition after several attempts, so in…
Lockout
Flame Sequence
Flame signal detected while the gas valve is off. The flame detector circuit is seeing a flame signal while the gas valve is off, so check s…
Lockout
Outlet ARHL
Outlet water temperature exceeded the automatic reset high limit. The outlet water temperature has exceeded the setting of the automatic res…
Details
Outlet MRHL
Outlet water temperature exceeded the manual reset high limit. The outlet water temperature has exceeded the setting of the manual reset hig…
Lockout
Fan Speed
Actual fan RPM is 30% lower or higher than target. The actual fan RPM is 30% lower or higher than the fan speed target, so check vent and ai…
Lockout
Inlet, Outlet, or Flue Sensor Fault
Flue, inlet, or outlet water temperature sensor disconnected or shorted. Either the flue, inlet water, or outlet water temperature sensor ha…
Lockout
AUX Contact Sw
Optional remote proving switch is not making. An optional remote proving switch is not making, so check the function of remote devices and c…
Lockout
Outlet Temp Diff
Temperature difference between the two outlet sensors is too high. The temperature difference between the two outlet sensors is too high, so…
Lockout
Fatal Error
Control module detected corrupted parameter settings. The control module has detected parameter settings that are corrupted, so restore the …
Details
Memory Error
Lockout occurred at the same time as a power outage. A lockout occurs at the same time as a power outage, and the corrective action is to re…
Details
Flue Temp High / Flue Temp Limit
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so clean…
Details
Delta T High / Delta T Limit
Temperature rise across the heat exchanger exceeded set parameters. The temperature rise across the heat exchanger has exceeded the set para…
Details
Outlet Temp High / Outlet Temp Limit
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Low 24 vac
120 vac input to the control board dropped below 80 vac. The 120 vac input to the main control board has dropped below 80 vac, so check the …
Details
Watch Dog Error
Main control board detected an internal fault. The main control board has detected an internal fault, so cycle power to the boiler and repla…
Details
Write EEProm
Main control board detected an internal fault. The main control board has detected an internal fault, so cycle power to the boiler and repla…
Details
CRC Parameters
Main control board detected an internal fault. The main control board has detected an internal fault, so cycle power to the boiler and repla…
Details
No Error Stored
The lockout information for the fault has been lost. The particular lockout information has been lost, so press the RESET button and replace…
Details
Lochinvar Noble fire-tube boilers and combis (NKB, NKC, NCF; SMART CONTROL)
Memory Error
Control module detected corrupted parameter settings. The control module has detected parameter settings that are corrupted, and the correct…
Details
Fan Speed
Actual fan RPM is outside the tolerance of the target RPM. The actual fan RPM is outside of the tolerance of the fan speed RPM target, so ch…
Lockout
LWCO
Low water cutoff is not making. The low water cutoff (LWCO) is not making, so check boiler pump operation on a call for heat, closed valves …
Lockout
Flame Sequence
Flame signal seen while the gas valve is off. The flame detector circuit is seeing a flame signal when the gas valve is OFF, so verify no fl…
Lockout
Outlet ARHL
Outlet water temperature exceeded the automatic reset high limit. The outlet water temperature has exceeded the setting of the automatic res…
Details
Air Pressure Switch
Air pressure switch contacts are open. The air pressure switch contacts are open, so check the switch wiring to the common and normally clos…
Lockout
AUX Limit Fault
Aux limit device is open. The aux limit device is open, so check the wiring to the aux limit device and check the aux limit device itself.…
Details
Flame Fail: Running
Flame signal lost four times during a call for heat. The unit has lost the flame signal four times during a call for heat, so inspect the sp…
Lockout
Flame Fail: Ignition
Failed to prove main burner ignition after several attempts. The unit has failed to prove main burner ignition after several attempts, so ch…
Lockout
Flue Temp Limit
Stack temperature exceeded the Flue Temp Limit setting. The stack temperature has exceeded the Flue Temp Limit set parameters, so clean the …
Details
Flue Temp High
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so clean…
Details
Outlet MRHL
Outlet water temperature exceeded the manual reset high limit. The outlet water temperature has exceeded the setting of the manual reset hig…
Lockout
Outlet Temp High
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Outlet Temp DIFF
Temperature difference between the two outlet sensors is too high. The temperature difference between the two outlet sensors is too high, so…
Lockout
Flue Sensor Fault
One or both flue sensors are open or shorted. One or both of the flue sensors is open or shorted, so inspect the flue sensor and its associa…
Lockout
Outlet Sensor Fault
One or both outlet sensors opened or shorted. One or both of the outlet sensors has opened or shorted, so check the sensor and its associate…
Lockout
Inlet Sensor Fault
Inlet sensor is open. The inlet sensor is open, so check the sensor and its associated wiring and repair or replace the sensor or wiring if …
Lockout
Set Point Met
Temperature reached the set point plus 10°F. The temperature has reached the set point plus 10°F, and the manual lists no corrective action …
Details
Anti-Cycling
Call for heat came too soon after the previous call ended. The main control board has received a call for heat too quickly after the previou…
Details
Delta T High
Temperature rise across the heat exchanger exceeded set parameters. The temperature rise across the heat exchanger has exceeded the set para…
Details
Low Voltage
120 vac input to the control board dropped below 80 vac. The 120 vac input to the main control board has dropped below 80 vac, so check the …
Details
No Flue Temp Change
Flue temperature did not change after the burner started firing. The flue temperature did not change after the burner started firing, so ver…
Details
Combi Sensor Fault (Combi Only)
DHW sensor is not connected (combi only). The DHW sensor is not connected on combi units, so check the DHW sensor and its associated wiring …
Details
Lockout Inlet Sensor Fault
Inlet sensor disconnected or shorted. The inlet sensor has been disconnected or shorted, so check the sensors and their associated wiring, m…
Details
Outdoor Sensor Missing
Outdoor sensor opened or shorted. The outdoor sensor has opened or shorted, so check the sensors and their associated wiring, measure the re…
Details
No Hot Water at Faucets (Combi Only)
No hot water is delivered at the DHW faucets. No hot water at the faucets can occur when the DHW flow switch does not trigger a DHW demand, …
Details
DHW Water is not Hot Enough (Combi Only)
DHW water is delivered below the DHW set point. DHW water that is not hot enough can result from a DHW set point that is too low, an anti-sc…
Details
Combi Boiler is Running but Does Not Supply Heated Water to Space Heating System (Combi Only)
Combi boiler running but not supplying heated water to space heating. A running combi boiler that does not supply heated water to the space …
Details
Space Heating System Heat Emitters Get Hot During a DHW Draw and the Combi Boiler does not Provide Hot Enough Domestic Hot Water (Combi Only)
Space heating emitters heat up during a DHW draw (combi only). Space heating heat emitters that get hot during a DHW draw are caused by the …
Details
Lockout! Water Press Switch
Water pressure switch is open. The water pressure switch is open, so verify the water pressure at the boiler, verify the harness connection …
Details
Lochinvar Knight XL (KBX) commercial boilers (Service Manual Table 3-4 fault codes)
Gas Pressure SW
Optional manual reset low or high gas pressure switch tripped, or gas pressure switch contacts open. Either the optional manual reset low ga…
Lockout
Flow Switch/LWCO
Optional flow switch or low water cutoff is not making. Either the optional flow switch or the optional low water cutoff is not making, so c…
Lockout
Blocked Drain SW/HEX O-Temp SW
Blocked drain switch detected condensate build-up, or burner access door over-temperature switch fault. The blocked drain switch has detecte…
Lockout
APS Open
Air pressure switch contacts are open. The air pressure switch contacts are open, so check the switch wiring (wires should be connected to t…
Lockout
Anti-cycling
Call for heat received too quickly after the previous call ended. The main control board has received a call for heat too quickly after the …
Details
Flame Fail Ign
Failed to prove main burner ignition after four attempts (KBX0400) or two attempts (KBX0500-1000). The unit has failed to prove main burner …
Lockout
Flame Sequence
Flame signal detected while no flame is present. The flame detector circuit is seeing a flame signal while no flame is present, so check the…
Lockout
Outlet ARHL
Outlet water temperature exceeded the automatic reset high limit setting. The outlet water temperature has exceeded the setting of the autom…
Details
Outlet MRHL
Outlet water temperature exceeded the manual reset high limit setting. The outlet water temperature has exceeded the setting of the manual r…
Lockout
Fan Low/High OR Fan Speed Low/High
Actual fan RPM is 30% lower than what is being called for. The actual fan RPM is 30% lower than what is being called for, so check that vent…
Lockout
Sensor Open
Inlet or outlet water temperature sensor disconnected. Either the inlet water or outlet water temperature sensor has been disconnected, so c…
Lockout
Sensor Shorted
Inlet or outlet water temperature sensor shorted. Either the inlet water or outlet water temperature sensor has been shorted, so check the s…
Lockout
Louver Proving Sw
Optional remote proving switch is not making. An optional remote proving switch is not making, so check the function of remote devices and c…
Lockout
Inlet Sensor Fault
Control reads the inlet sensor as open or shorted. The control reads the inlet sensor as open or shorted, so check the wiring to the sensor,…
Lockout
Outlet Sensor Fault
Control reads the outlet sensor as open or shorted. The control reads the inlet sensor as open or shorted, so check the wiring to the sensor…
Lockout
Outlet Temp Diff
Excessive temperature difference between the two outlet sensors. The control module reads an excessive temperature difference between the tw…
Lockout
Flue Sensor Fault
Control reads the flue sensor as open or shorted. The control reads the flue sensor as open or shorted, so check the wiring to the sensor, m…
Lockout
Flue Temp Diff
Excessive temperature difference between the two flue sensors. The control module reads an excessive temperature difference between the two …
Lockout
Flue Temp Limit
Stack temperature exceeded the Flue Temp Limit set parameters. The stack temperature has exceeded the Flue Temp Limit set parameters, so ins…
Lockout
Fatal Error
Control module detected parameter settings that are out of range. The control module has detected parameter settings that are out of range, …
Details
Memory Error
Lockout occurred at the same time as a power outage. A lockout occurs at the same time as a power outage, and the corrective action is to re…
Details
Flue Temp High
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so inspe…
Details
Delta T High
Temperature rise across the heat exchanger exceeded the set parameters. The temperature rise across the heat exchanger has exceeded the set …
Details
Outlet Temp High
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Rem Ctrl Flt
External control is cycling too often. The external control is cycling too often, so check the set point of the external control, check the …
Details
Parameters Progr
After downloading parameters from a laptop the main control board must be reset. After downloading parameters from a laptop the main control…
Lockout
Service Blk
Outlet temperature exceeded 185°F while the unit is in Service Mode. While the unit is in Service Mode the outlet temperature has exceeded 1…
Details
Low 24 vac
120 vac input to the main control board dropped below 80 vac. The 120 vac input to the main control board has dropped below 80 vac, so check…
Details
Watch Dog Error
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
Write EEProm
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
CRC Parameters
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
No Error Stored
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
Lochinvar FTXL commercial fire-tube boilers (Service Manual Table 3-4 fault codes)
Gas Pressure SW
Optional manual reset low or high gas pressure switch tripped, or gas pressure switch contacts open. Either the optional manual reset low ga…
Lockout
Flow Switch/LWCO
Optional flow switch or low water cutoff is not making. Either the optional flow switch or the optional low water cutoff is not making, so c…
Lockout
Blocked Drain SW
Blocked drain switch detected excessive condensate build up inside the unit. The blocked drain switch has detected excessive condensate buil…
Lockout
Anti-cycling
Call for heat received too quickly after the previous call ended. The main control board has received a call for heat too quickly after the …
Details
Flame Fail Ign
Failed to prove main burner ignition after several attempts. The unit has failed to prove main burner ignition after several attempts, so in…
Lockout
Flame Sequence
Flame signal detected while no flame is present. The flame detector circuit is seeing a flame signal while no flame is present, so check the…
Lockout
Outlet ARHL
Outlet water temperature exceeded the automatic reset high limit setting. The outlet water temperature has exceeded the setting of the autom…
Details
Outlet MRHL
Outlet water temperature exceeded the manual reset high limit setting. The outlet water temperature has exceeded the setting of the manual r…
Lockout
Fan Low/High OR Fan Speed Low/High
Actual fan RPM is 30% lower than what is being called for. The actual fan RPM is 30% lower than what is being called for, so check that vent…
Lockout
Sensor Open
Inlet or outlet water temperature sensor disconnected. Either the inlet water or outlet water temperature sensor has been disconnected, so c…
Lockout
Sensor Shorted
Inlet or outlet water temperature sensor shorted. Either the inlet water or outlet water temperature sensor has been shorted, so check the s…
Lockout
Louver Proving Sw
Optional remote proving switch is not making. An optional remote proving switch is not making, so check the function of remote devices and c…
Lockout
Inlet Sensor Fault
Control reads the inlet sensor as open or shorted. The control reads the inlet sensor as open or shorted, so check the wiring to the sensor,…
Lockout
Outlet Sensor Fault
Control reads the outlet sensor as open or shorted. The control reads the outlet sensor as open or shorted, so check the wiring to the senso…
Lockout
Outlet Temp Diff
Excessive temperature difference between the two outlet sensors. The control module reads an excessive temperature difference between the tw…
Lockout
Flue Sensor Fault
Control reads the flue sensor as open or shorted. The control reads the flue sensor as open or shorted, so check the wiring to the sensor, m…
Lockout
Flue Temp Diff
Excessive temperature difference between the two flue sensors. The control module reads an excessive temperature difference between the two …
Lockout
Flue Temp Limit
Stack temperature exceeded the Flue Temp Limit set parameters. The stack temperature has exceeded the Flue Temp Limit set parameters, so ins…
Lockout
Fatal Error
Control module detected parameter settings that are out of range. The control module has detected parameter settings that are out of range, …
Details
Memory Error
Lockout occurred at the same time as a power outage. A lockout occurs at the same time as a power outage, and the corrective action is to re…
Details
Flue Temp High
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so inspe…
Details
Delta T High
Temperature rise across the heat exchanger exceeded the set parameters. The temperature rise across the heat exchanger has exceeded the set …
Details
Outlet Temp High
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Rem Ctrl Flt
External control is cycling too often. The external control is cycling too often, so check the set point of the external control, check the …
Details
Parameters Progr
After downloading parameters from a laptop the main control board must be reset. After downloading parameters from a laptop the main control…
Lockout
Service Blk
Outlet temperature exceeded 185°F while the unit is in Service Mode. While the unit is in Service Mode the outlet temperature has exceeded 1…
Details
Low 24 vac
120 vac input to the main control board dropped below 80 vac. The 120 vac input to the main control board has dropped below 80 vac, so check…
Details
Watch Dog Error
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
Write EEProm
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
CRC Parameters
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
No Error Stored
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
Lochinvar Crest with Hellcat (FCB) commercial boilers (Service Manual Table 3G fault codes)
Gas Pressure SW Open
Low or high gas pressure switch tripped. Either the low gas pressure switch or the high gas pressure switch tripped, so measure the supply g…
Lockout
Low Water Cutoff Open
Low water cutoff is not making. The low water cutoff is not making, so reset the LWCO from the RESET button on the front control panel, veri…
Lockout
Blocked Drain SW Open
Blocked drain switch detected excessive condensate build up inside the unit. The blocked drain switch has detected excessive condensate buil…
Lockout
APS Open
Blocked flue/inlet pressure switch contacts are open. The blocked flue/inlet pressure switch contacts are open, so check that vent and air i…
Lockout
Anti-cycling
Call for heat received too quickly after the previous call ended. The main control board has received a call for heat too quickly after the …
Details
Flame Failure
Failed to prove main burner ignition; requires a manual reset before firing again. The unit has failed to prove main burner ignition and req…
Lockout
Flame Fail Running
Unit was running and lost the flame signal. The unit was running and lost the flame signal, so inspect the flame rods and associated wiring,…
Lockout
Gas Valve / Relay Failure
Main control board did not detect a gas valve. The main control board did not detect a gas valve, so check the wiring harness connection at …
Lockout
Auto Reset High Limit
Outlet water temperature exceeded the setting of the automatic reset high limit. The outlet water temperature has exceeded the setting of th…
Details
Manual Reset High Limit Open
Outlet water temperature exceeded the setting of the high limit. The outlet water temperature has exceeded the setting of the high limit, so…
Lockout
Fan Speed Low
Actual fan RPM is 30% lower than what is being called for. The actual fan RPM is 30% lower than what is being called for, so check that vent…
Lockout
Fan Speed High
Actual fan RPM is 30% higher than what is being called for. The actual fan RPM is 30% higher than what is being called for, so check that ve…
Lockout
Louver Proving Sw Open
Optional remote proving switch is not making. An optional remote proving switch is not making, so check the function of remote devices and c…
Details
Flue Temp High
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so inspe…
Details
Delta T High
Temperature rise across the heat exchanger exceeded the set parameters. The temperature rise across the heat exchanger has exceeded the set …
Details
Outlet Temp High
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Parameter Programming Complete
After downloading parameters from a laptop the main control board must be reset. After downloading parameters from a laptop the main control…
Lockout
Sensor Open
Inlet or outlet water temperature sensor disconnected. Either the inlet water or outlet water temperature sensor has been disconnected, so c…
Lockout
Sensor Shorted
Inlet or outlet water temperature sensor shorted. Either the inlet water or outlet water temperature sensor has been shorted, so check the s…
Lockout
Flue Sensor Open
Flue sensor disconnected or removed from the flue. The flue sensor has been disconnected or removed from the flue, so check the sensor and i…
Lockout
Flue Sensor Shorted
Flue sensor shorted. The flue sensor has been shorted, so check the sensor and its associated wiring, repair or replace the sensor or wiring…
Lockout
Too Many Resets - Try Later
Too many manual resets occurred during a 15 minute period. Too many manual resets have occurred during a 15 minute period, so wait 15 minute…
Details
Internal Fault
Main control board detected an internal fault. The main control board has detected an internal fault, so replace the main control board.…
Details
Flue Temp Shutdown
Stack temperature exceeded the set parameters for the boiler. The stack temperature has exceeded the set parameters for the boiler, so inspe…
Details
Delta T Shutdown
Temperature rise across the heat exchanger exceeded the set parameters. The temperature rise across the heat exchanger has exceeded the set …
Details
Outlet Temp Shutdown
Outlet water temperature exceeded the maximum outlet water temperature. The outlet water temperature has exceeded the maximum outlet water t…
Details
Writing/Programming EEProm Error
Main control board detected an internal fault. The main control board has detected an internal fault, so turn the power off and back on, and…
Details
CRC Parameter Error
Main control board detected an internal fault. The main control board has detected an internal fault, so turn the power off and back on, and…
Details
Wrong Error Code
Main control board detected an internal fault. The main control board has detected an internal fault, so press the RESET button on the SMART…
Details
Flame Sense Out of Sequence 1
Flame Sensor 1 senses a flame while the gas valve is turned off. Flame Sensor 1 senses a flame while the gas valve is turned off, so clean F…
Lockout
Flame Sense Out of Sequence 2
Flame Sensor 2 senses a flame while the gas valve is turned off. Flame Sensor 2 senses a flame while the gas valve is turned off, so clean F…
Lockout
Flue Damper Switch Open
Flue damper proving switch is not closed when the flue damper is energized. The flue damper proving switch is not closed when the flue dampe…
Details
IO Expander Out Error
Control board detected an internal fault. The control board detected an internal fault, so turn the power off, wait 15 seconds, and turn the…
Details
Failure ADC Controller
Problem detected with measuring one or more temperature sensors. A problem was detected with measuring one or more temperature sensors, so c…
Lockout
Outlet Sensor Differential
Readings from the two outlet temperature sensors are too far apart. The readings from the two outlet temperature sensors are too far apart, …
Lockout
Flue Sensor Differential
Readings from the two flue temperature sensors are too far apart. The readings from the two flue temperature sensors are too far apart, so c…
Lockout
Talk to a boiler technician
Describe what the boiler is doing and get a straight answer about the next step.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.