NTI boiler troubleshooting

Statistically, about 90% of boiler malfunctions can be revealed through a visual examination of a heating system. Most problems can be eliminated with ease, and few of them require transportation to a service center. The following troubleshooting table will help you find the cause of the problem and deal with it.

NTI Ti100-200 boilers troubleshooting

Problem Detected Solution
ER1 On Display“Water Temperature Excessive” Sentry has sensed a water temperature in excess of 250°F at the water temperature thermister.1. If the boiler is extremely hot check for adequate water pressure and circulation, contact NTI for assistance.
2. If not hot, check for sources of grounding or shorting (i.e. water) at the thermister electrical connections, check wiring from Sensor to Sentry Control.
3. Replace thermister if the resistance is not in the correct range.
ER2 On Display“Water Temperature Thermister Short Circuit” Sentry has sensed a short circuit in the water temperature thermister circuit.See ER1.
ER3 On Display“W ater Sensor Open Circuit” Sentry has sensed an open circuit in the Water Sensor circuit.1. Check wiring to Water Sensor for open circuits or shorting to ground (i.e. water). (Note: ER3 will be displayed if temperature sensed is less then 0°F.)
2. Replace Water Sensor if the resistance is not in the correct range.
ER4 On Display“24V Limit Error” Sentry has sensed a lack of 24V on the outlet of the Sentry burner relay (B1).The error locks the boiler out for one hour before retrying ignition.
1. Reset power, if error goes away the problem is intermittent and was likely caused by a tripped limit that has automatically reset, check for adequate water pressure and flow rate. Allow the boiler to cycle and verify proper operation including outlet water temperature and flue temperature. If operation is unsuccessful and the error reoccurs continue to step 2.
2. Til 00-200’s are equipped with a low water pressure switch on the boiler return that requires a minimum of 10PSI to complete the 24VAC ignition circuit. Ensure there is a minimum of 15PSI on the boiler outlet prior to the primary circulator; ensure the boiler is plumbed in primary- secondary fashion. Rcplace water pressure switch if plumbing and pressure is correct and if it measures an open circuit.
3. Check for continuity through the 24VAC limit wiring and manifold and stack limits, rcplace limits or wiring that are not a elosed circuit.
ER5 On Display“DHW Time-Out” The ER5 option is ON and the Sentry has sensed that the DHW call has lasted longer then 2.5 hours, thus removing priority from the DHW call.Reset the ER5 error by resetting the power or cycling the DHW call. Check for proper operation of the DHW call.
1. Combi’s are equipped with a DHW flow switch; ensure it is not sticking in the closed position when there is no DHW flow. If so, remove it and free it of any debris and check for proper operation, replace if necessary.
2. For non-Combi boilers, operating with an indirect water heater, check for proper boiler water circulation during a DHW call, and check for proper operation of the indirect water heater’s Aqua-stat.
3. For applications with prolonged DHW draws, turn the ER5 option OFF.
ER6“Flame Lock Out” Sentry has sensed a lack of 24V to the gas valve during operation or a Fenwal ignition lockout.There is a problem in the ignition sequence, it could be caused by a faulty igniter, flame sensor, gas valve or improper line pressure or combustion. Check ignition sequence to determine which component is not functioning. (Sentry will retry ignition sequence 1 hour after ER6 code originally occurs or if control is reset)
If a 3-Flash error occurs on the Fenwal controller prior to locking out on an Er6, proceed to “Three Flashes on Fenwal”.
Burner shuts off before set-point temperature is reached (and burner light goes out)Reset calculation being used to lower HI setting.
Thermostat is satisfied1. If the thermostat demand light is turning off, the thermostat has satisfied.
2. If DHW temp light is turning off; the Aqua-stat or call for DHW has been satisfied.
ER9Internal Controller FaultIndicates that the Sentry control has lost communication with an internal processor, contact NTI for assistance.
ASO Indicates that the Air Switch is Open“Air Switch Open'” This is displayed when the boiler is expecting the air switch to be closed by a differential pressure generated when the combustion blower turns on.1. Are the vinyl tubes connected between the air switch and the ports on the inlet pipe? Negative side of switch connects to the port on the 1 - 1/2” PVC elbow.
2. Check for blockage on the intake and exhaust vents.
3. If fan is running the air switch may be faulty, ensure it is set at 0.2”wc.
4. If fan is not running, check 120V wiring to blower, if ok remove low voltage harness from blower, if blower fails to start, replace blower, if blower does start problem may be with blower or Sentry control.
ASC Indicates that the Air Switch is Closed“Air Switch Closed'” This is displayed when the boiler has turned the blower off and is expecting the air switch to be open.1. Is the fan running. If so check for 24V between B and D terminals. If 24V is not present replace transformer.
2. If fan is not running then the Air Switch is stuck closed.
a. Check to ensure switch is set at 0.2”wc.
b. Check vinyl tubes to air switch for moisture, clear if necessary and check venting termination for proper clcarance (moisture in tubes is generally cause by cross-contamination of the exhaust to the air inlet).
c. Remove the white wire from the air switch, if ASC persists replace the Sentry 2100 controller, if an ASO message is display replacc the air switch.
Two Flashes on Fenwal“Flame Fault" The Fenwal controller senses flame prior to ignition sequence.If the combustion sequence is normal, and there is no flame prior to ignition, the Fenwal control is defective, and must be replaced.
Three Flashes on Fenwal“Ignition Lockout”Check the condensate drain for blockage - a blocked condensate drain will flood the combustion chambcr and cause this error, see for further instructions.
Reset and observe ignition sequence:
1. If the burner ignites then goes out within 2-3 seconds:
a. If the boiler is newly installed, check the polarity of the 120VAC power supply - reversed polarity will cause this error.
b. Ensure the cable is connected to the flame sensor.
c. Check for proper sustained gas line pressure.
d. Check venting and combustion chamber for blockage - clean combustion chambcr.
e. Replace flame probe.
f. Replace Fenwal controller.
2. If the igniter glows but the burner does not ignite:
a. Check for proper sustained gas line pressure.
b. Check venting and combustion chamber for blockage - clean combustion chambcr.
c. Replace igniter.
d. Replace Fenwal controller.
3. If the igniter does not glow:
a. Replace igniter.
b. Rcplace Fenwal controller.
Boiler will not stay lit.Indicates lack of a flame signal. In order to stay running the flame signal must be at least 0.7 nAmps1. If the Burner light on the Sentry is going out, go to “Burner shutting ofr.
2. Check the condensate drain for blockage - a blocked condensate drain will flood the combustion chamber and cause this error, see for further instructions.
Boiler bangs or hissesBangs or sounds like a kettle while burner is running indicates insufficient flow1. Ensure the plumbing is installed as per this manual. Check to see if pumps are operating properly and water pressure is above 15psi. This problem can lead to boiler overheating!
2. Boiler may be plugging-up with scale or magnetite, clean with Femox DS-40 Descaler and Cleaner (NTI PN: 83450).
3. If glycol is being used the concentration may be to high, recommend using a concentration lower then 35%. De-ratc unit by reducing the maximum modulation rate (HFS) and/or the maximum water temperature (LO and HI)
Boiler Lights rough or pulsatesTypically an imbalance in the Air to gas ratio1. Ensure the vent lengths are in compliance with Section 4.0.
2. Check venting and combustion chamber for blockage - clean combustion chambcr.
3. Check for proper sustained gas line pressure.
4. Momentarily remove the intake pipe from the boiler during ignition, if unit lights smoothly with intake pipe disconnected reconnect and check for proper combustion,
Fan appears to be creating a noise in the houseSlight vibration can cause noise in the residence (This is not a warranty issue)Use flexible gas line to insolate the vibration noises between the gas valve and the line.
Don’t hang gas lines from floor joists.
Use rubber insulators with gas line supports.
Making a rubbing noise. ((This is not a warranty issue))If gas valve is not held when the gas nipple is connected, the force of tightening the fitting can damage the valve, and warp the fan housing.
If pipe is used, the gas line must not create any forces to the valve, either vertically (weight of line), or horizontally (misaligned conncction)
Display Goes BlankNo power to control, blown control fuse or control failure1. Reset power, if display comes back on contact NTI for assistance.
2. Ensure 120VAC is being supplied to the boiler.
3. Check the internal fuse in the Sentry - to access the internal fuse, remove the front decal to reveal the screws securing the face plate cover. If fuse has blown replace with equivalent.
4. Rcplacc Sentry 2100 controller.

NTI Trinity Lx150 boilers troubleshooting

PROBLEMPOSSIBLE CAUSECORRECTIVE ACTION
Display shows “System Disconnected” constantlyCommunication wire disconnected
Faulty Sola controllerIf 24VAC present at controller terminals J8 1 & 2, check Power LED on controller. Verify that connector J8 is securely plugged into the controller. Recycle power to boiler, if controller does not operate, replace the controller.
Burner not operatingHeat demand satisfied; no call for heatCheck Demand and Set points via Touchscreen. Check thermostat and DHW aquastat (if applicable) setting.
Boiler outlet temperature exceeds “Setpoint - On Hysteresis”Check outlet temperature, setpoint and hysteresis settings via Touchscreen.
Lockout 2 - Waiting for safety data verificationSafety parameter(s) has been adjustedChanging settings that are considered safety parameters require “Safety data verification”.
Lockout 9 - Flame bias out of range4-20mA input being overdriven.If using 4-20mA input, check to ensure current is not greater than 21 mA.
Control malfunctionCycle power, if problem returns replace control.
Hold 27 - Flame rod shorted to ground detectedA flame circuit shorted to ground may show up as a flame circuit timeout. Zero-ohm shorts can display as Hold 27.Check to ensure condensate drain is not blocked. Check to ensure no voltage applied to R & T terminals. If using 4-20mA input, check to ensure current is not greater than 21 mA.
Hold 61 - Anti short-cycleDemand offCheck demand. Delay is to prevent rapid cycling of burner.
Hold 62 - Fan speed not provedNormal Operation (Drive to Lightoff)Hold 62 is momentarily displayed prior to burner ignition during the Drive to Lightoff.
Blown fuseCheck Fuse "A”, blown fuse prevents blower from operating.
Wiring defectInspect blower wiring, ensure connectors at Sola controller and blower are securely attached.
- Faulty Sola controller; - Faulty BlowerIf Hold 62 persists for 15 seconds or more, while the blower is running, check "Fan speed" indicated on display. If "LOW RPM", "HIGH RPM", “0” or rapidly changing RPM value is displayed, try connecting another Sola controller. If problem remains, replace blower.
Hold 63-LCI OFF (Limit control input)Replacement control incorrectly configured.LCI must be set to “enable” on all Lx models, excluding Lxl50/150E units with a serial number of 49351 or lower and Lx200/400 units with a serial number of 48251 or lower.
Lockout or Hold 65 - Interrupted Air Switch OFFNo problem, normal operationHold 65 will normally be displayed momentarily during the drive to light-off.
Blown fuseCheck Fuse "A", blown fuse prevents blower from operating.
Faulty blowerIf Fuse “A” is good and blower remains off, check 120VAC supply to blower, if present replace blower. If blower is on proceed to next step.
Blocked ventingCheck for blockage of the exhaust vent.
Blocked air inletCheck for blockage of the air inlet.
Disconnected, damaged or blocked tubingInspect the clear vinyl tubing connecting the air switch + and - ports to the air metering elbow. Condensation or other foreign matter may be obstructing the tubing, preventing the switch from sensing differential pressure caused by air flow through the metering elbow.
Incorrect air switch settingContact NTI technical support.
Faulty air proving switchIf venting and air inlet are clear, temporarily jumper the air switch. If the unit lights and operates smoothly - replace air switch. If the unit fails to light or lights but runs rough or abruptly shuts down - check boiler internals for blockage. Only jumper the air switch for diagnosing purposes.
Tripped High Vent Pressure Switch (Lx300-400 only)The high vent pressure switch will trip when the combustion chambcr is blocked. Clean combustion chambcr and reset switch.
Tripped Thermal Fuse (Lx300-400 only)Check Thermal Fuse on the back of the heat exchanger (accessed from the rear of the cabinet). If tripped contact NTI.
Tripped Door Reset Safety Switch (Lx300-800 only)The Door Reset Safety Switch will trip with the combustion chamber gets dirty or the door insulation fails. Clean the combustion chamber, inspect the door insulation and reset the switch.
Incorrect air switch wiringCheck that the red and orange wires are connected to quick connect tabs 3 and 1 respectively.
Hold 66 - Interrupted air switch ON (and blower is off)Incorrect air switch settingContact NTI technical support.
Incorrect air switch wiringCheck that the red and orange wires are connected to quick connect tabs 3 and 1 respectively.
Faulty air switchDisconnect red and orange wires from air switch and check for open circuit between terminals 1 & 3. If continuity detected, replace air switch.
Hold 66 - Interrupted air switch ON (and blower is on)- Blower problem - Faulty controllerCheck low voltage wiring from blower to controller. Check VDC signal from red-green and black-green; if not 28-32VDC and 0 VDC respectfully - replace controller. If signal is correct - replace blower.
Lockout or Hold 67 - ILK OFFInsufficient water pressure (Lxl50- 400 only)Ensure at least 15PSI at boiler outlet.
External Limit TrippedIndication that an external limit (wired to “LIM”) is open. Not a problem with boiler, check external limit.
Insufficient flow for Flow Switch (Lx500-800 only)Check plumbing, ensure circulator is operating.
Tripped Thermal Fuse (Lx500-800 only)Check Thermal Fuse on the back of the heat exchanger (accessed from the rear of the cabinet). If tripped contact NTI.
Tripped High Vent Pressure Switch (Lx500-800 only)The high vent pressure switch will trip when the combustion chamber is blocked or venting is too restrictive. Check venting and clean combustion chamber.
Lockout or Hold 79 - Outlet High LimitCH or DHW settingsCheck if CH and/or DHW setpoint temperature plus off hysteresis exceed “High limit” setpoint - factory setting = 210°F (99°C).
CH or DHW pump problem
Incorrect “Outlet high limit” settingIncrease “Outlet high limit” setting; maximum setting = 210°F (99°C).
Incorrect “Outlet high limit response” setting (Lxl 50-400 boiler applications only)Unless deemed unacceptable by local installation codes, the “Outlet high limit response” should be set to “recycle and hold” to prevent lockout.
Lockout or Hold 81 - Delta T limit or Boiler making banging or hissing soundsInsufficient water flow• Check Fuse "A"
• Check boiler pump.
• Ensure plumbing is correct. Check that water pressure is at least 15PSI.
• Boilers Only - Boiler heat transfer surfaces may be fouled with scale or magnetite. Clean with Fernox DS-40 Descaler and Cleanser.
Lockout 82 - Stack limitDirty heat exchangerInspect and if required clean the combustion chamber and/or heat exchanger.
Incorrect “Stack limit setpoint”Unless installed in Canada with PVC exhaust venting, set “Stack limit setpoint” to maximum setting of 220°F (104°C). In Canada PVC exhaust venting is limited to 149°F (65°C).
Faulty sensorCheck resistance of stack sensor and compare to thermistor resistance chart
Lockout or Hold 85 - Inlet/Outlet Inversion LimitPump flowing in the wrong directionEnsure water circulation is flowing into the boiler at the fitting closest to the wall.
Incorrect factory sensor wiringDisconnect flue sensor cable; screen should display “Hold 95 - Stack sensor fault”; if not contact NTI.
Lockout or Hold 88 - Outlet T Rise limitInsufficient water flow
Hold 91- Inlet sensor faultSensor disconnected• Verify that 2-position Molex connector on wiring harness is securely attached to mating connector on inlet sensor.
• Inspect sensor wiring.
Faulty sensorCheck resistance of sensor and compare to thermistor resistance chart
Hold 92 - Outlet sensor faultSensor disconnected• Verify that 4-position Molex connector on wiring harness is securely attached to mating connector on outlet sensor.
• Inspect sensor wiring.
Faulty sensorCheck resistance of sensor and compare to thermistor resistance chart
Hold 95 - Stack sensor faultSensor disconnected• Verify that 4-position Molex connector on wiring harness is securely attached to mating connector on stack sensor.
• Inspect sensor wiring.
Faulty sensorCheck resistance of sensor and compare to thermistor resistance chart
Lockout 109 - Ignition failure occurred (Lx500-800 only) Spark cable disconnectedEnsure that the high voltage spark cable is securely connected to the spark generator and the igniter electrode. Check that the green ground wire is securely attached to the xAyy quick connect tab on the igniter electrode.
Hold 110 - Ignition failure occurred, failure to prove flame after 3 ignition attempts (Lx 150-400 only)Insufficient gas line pressureEnsure the manual gas shutoff valve is open.
Flame rod disconnectedVerify that the flame rod signal wire is securely attached to the flame rod, which is located bottom center of the burner door.
No 120VAC to Spark GeneratorCheck wiring from controller to spark generator. With an AC voltmeter measure voltage across J5- 6 and ground (the controller chassis is connected to the 120VAC supply ground) during trial for ignition.
Faulty Spark GeneratorDuring trial for ignition check for arc on spark electrode via the observation port located next to the spark electrode in the burner door. If the spark generator is receiving 120VAC and no spark is observed, replace the spark generator.
No 24VAC to Gas ValveCheck the wiring harness for loose or interrupted connections of the gas valve wiring. With an AC voltmeter, measure the voltage from controller terminals J5-2 to J4-10. There should be 24VAC present during trial for ignition.
Faulty Gas ValveThe gas valve emits an audible click when it switches on or off. If the controller is providing 24VAC to the gas valve, and the wiring is intact, it should be possible to detect if the valve is responding.
Lockout 113 - Flame circuit timeoutA flame circuit shorted to ground may show up as a flame circuit timeout. High resistance shorts can display as Lockout 113.Check to ensure condensate drain is not blocked. Check to ensure no voltage applied to R & CH terminals. If using 4-20mA input, check to ensure current is not greater than 21 mA.
Lockout 122 - Lightoff rate proving failedBlower is not turning on
Missing or incorrect blower feedback signal
Blower is always on
Alert 128 - Modulation rate was limited due to IAS was open (Air switch open while burner firing)Blockcd ventingCheek for blockage of the exhaust vent.
Blocked air inletCheck for blockage of the air inlet.
Lockout 173 - Pilot relay feedback incorrectExternal Electrical NoiseLook for sources of electrical noise, i.e. a large motor or multiple pieces of equipment starting at the same time.
Lockout 174 - Safety relay feedback incorrectFailing Limit Switch in ILK circuitCheck operation of internal LWCO, and/or external limit (i.e. devise connected between “R” and “LIM”); replace as necessary
Hardware failure of Sola controllerReset power, If problem persists replace Sola controller.
Alert 206 - Lead Lag header temperature was invalidSystem Sensor not connectedIf desired, install System Sensor and wire to sensor input connections “SYSTEM” and “SENSOR COM”. Otherwise ignore Alert 206
Alert 233 - Lead Lag outdoor temperature was invalidSee Alert 248
Alert 248 - CH outdoor temperature was invalidOutdoor sensor not connectedThe Trinity Lx is factory set with Outdoor Reset enabled. Connect outdoor sensor or disable Outdoor Reset.
Outdoor sensor wiringCheck wiring of outdoor sensor. Wires should connect to Low Voltage barrier terminals 11 & 12.
Faulty sensorCheck sensor. Should be free of ice and snow. Check resistance of sensor and compare to thermistor resistance chart
Alert 311 - Run was terminated due to interrupted air flow switch was offBlocked ventingCheck for blockage of the exhaust vent.
Blocked air inletCheck for blockage of the air inlet.
Disconnected, damaged or blocked tubingInspect the clear vinyl tubing connecting the air switch + and - ports to the air metering elbow. Condensation or other foreign matter may be obstructing the tubing, preventing the switch from sensing differential pressure caused by air flow through the metering elbow.
Incorrect air switch settingContact NTI technical support.
Blown fuseCheck Fuse "A".
Inoperative CH and/or DHW pumpBlown fuseCheck Fuse "B".
Faulty controllerIf Fuse “B” not blown, and controller is operating, navigate to pump diagnostic on display. Manually switch pump on, check for 120VAC at pump connection terminal on line voltage barrier strip. If 120VAC not detected, replace controller.
Faulty pumpIf 120VAC supplied to pump, and pump does not operate, replacc pump.
Blower operating at high speed while burner offBlower signal cable disconnected• Verify that the 5-position Molex connector on the wiring harness is securely connected to its mating connector on the blower.
• Check that the 4-position Molex connector on wiring harness is securely connected to its mating connector on the controller.
Blower operating at high speed while burner offNo 24VAC to controller• Check Power LED on controller.
• Check Fuse "C".
• With an AC voltmeter measure voltage at terminals J8 1 & 2, 24VAC should be present.
Blower not operatingBlower power disconnectedVerify that the 3-position Molex connector on the wiring harness is securely connected to its mating connector on the blower.
Blown fuseCheck Fuse "A" using the procedure described above. Fuse "A" protects the blower as well as the ignition spark generator and boiler pump.
Faulty blowerMeasure voltage across pins 1 & 2 (black and white wires) of 3-position connector on wiring harness. If 120VAC detected, replace power connector and remove 5-position signal connector. Blower should rotate at high speed. If blower does not rotate, replace blower.

NTI Trinity TX51 boilers troubleshooting

CodeDescription
Loc 2-4Gas Valve Circuit Fault (Safety) - control has sensed a fault in the gas valve electrical circuit, check for a loose connection in the gas valve wiring harness. Also see “Loc 5”.
Loc 5Limit Circuit Open (Safety) - control has sensed a fault in the safety limit circuit; check the following:
1. External Limit (Purple wire) - if an external limit device (i.e. LWCO) is connected to the purple wire at the field wiring terminal, check to ensure it has not tripped, and that it is wired correctly.
2. Internal Limit (Heat Exchanger Thermal Fuse) - the heat exchanger is equipped with a normally closed thermal fuse; the fuse opens when the heat exchanger gets too hot. If the fuse is open, contact NTI.
Loc 6 & 7Power Supply Electrical Interference - check for poor line, neutral and ground connections in the wiring leading to the boiler. Check the internal ground connections within the boiler. Eliminate sources of electrical noise, i.e. welders, large pump inverters, etc. If power is being supplied by a generator, install an appropriately sized UPS (Uninterruptible Power Supply).
Loc 8-9Controller Malfunction - contact NTI, check field wiring, replace controller.
Loc 10Supply Sensor Fault - controller has sensed an invalid reading at the Supply/Outlet sensor; check cable, then replace sensor
Loc 11Uncorrected Blocking Error - a blocking error (Err) has lasted for 20 consecutive hours.
Loc 12Incorrect Fan Speed - measured fan speed is not reaching target fan speed within 60 seconds. Check wiring to fan, replace fan.
Loc 13-24Controller Malfunction - contact NTI, check field wiring, replace controller.
Loc 25Excessive Supply Temperature Reading - controller has sensed an excessive temperature reading at the Supply/Outlet sensor; verify proper water circulation, check supply sensor cable, then replace sensor.
Loc 26Flue Sensor Fault - controller has sensed an invalid reading at the Flue sensor; check cable, then replace sensor
Loc 27Flame present 10 seconds after closing gas valve - verify flame is going out immediately following the end of a burner demand; check flame sensor (replace); check condensate drain for blockages; increase post purge setting.
Loc 28Flame present before ignition - check flame sensor (replace); check condensate drain for blockages; increase post purge setting.
Loc 29-30Controller Malfunction - contact NTI, check field wiring, replace controller.
Loc 31Flame lost three times during one demand - see Loc 1.
Loc 32 upController Malfunction - contact NTI, check field wiring, replace controller.
Err 45-51
Err 52Incorrect Field Wiring - check electrical connections to field terminal strip; ensure the Thermostat is connected to terminals 7 and 8.
Err 53Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 54Flame detected out of sequence - check/replace flame sensor; check flame sensor wiring; check condensate drain for blockages; replace controller.
Err 55-59Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 60Flue Sensor Error - flue temperature reading exceeds 220°F or the sensor is shorted, check flue sensor connection and wiring. Temporarily disconnect the electrical conncctor from the flue sensor, if problem goes away, replace flue sensor; if problem persists, replace the controller.
Err 61Return Sensor Error - inlet temperature exceeded 203°F; error clears when inlet temperature drops below 190°F: (1) ensure there is water flow through the boiler, (2) check for correct return sensor reading (menu reading 1-09), (3) check wiring to return sensor; replacc sensor.
Err 62-63Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 64Faulty Grounding - check appliance grounding to breaker panel, check internal ground connections.
Err 65Incorrect Polarity - controller has sensed reversed polarity of the 120VAC power supply; check field wiring to L2 NEUTRAL (terminals 12 &13) and LI 120VAC (terminal 14). There should be 120VAC potential between LI 120VAC and ground, and 0VAC potential between L2 NEUTRAL and ground.
CodeDescription
Err 66Incorrect Frequency - the controller accepts a line voltage frequency of 60Hz ± 2%; if outside this range the controller may be damaged or function incorrectly. If using a generator as a power source, install a UPS (uninterruptible power supply) between the generator and boiler.
Err 67Faulty Earth Ground - check grounding of boiler and power supply; replace controller.
Err 68-71Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 72Supply Sensor Open - check wiring to supply sensor; replace sensor
Err 73Supply Sensor Fault - check wiring to supply sensor; replace sensor
Err 74-77Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 78Flue Sensor Open - check wiring to flue sensor; replace sensor
Err 79Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 80Supply Sensor Shorted - check wiring to supply sensor; replace sensor
Err 81
Err 82-85Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 86Flue Sensor Shorted - see Err 60.
Err 87 Err 88-92Reset Button Error - controller has sensed that the “Reset” button is stuck, inspect button, try pressing and releasing it to “unstick” it, if necessary remove plastic overlay from display. Turn power off and on, if problem persists, replace display.
Controller Malfunction - contact NTI, check field wiring, replace controller.
Err 93Appliance Type - the appliance type stored in the display does not match the appliance type stored in the controller. Set the appropriate appliance type using the procedure described under “Controller Replacement Instructions”;
Err 94 & upController Malfunction - contact NTI, check field wiring, replace controller.
Att 2Outdoor Sensor Shorted - controller has sensed a short circuit at the Outdoor sensor; check wiring to terminals 3 and 5 and outdoor sensor.
Att 3DHW Sensor Open - controller has sensed an open circuit at the DHW tank sensor; check wiring to terminals 3 and 6 and tank sensor. If no tank sensor is being used, set DHW Mode (setting 2-08) to the appropriate setting;
Att 4
Att 6Warm Weather Shutdown (WWSD) Active - when the outdoor temperature (menu reading 1-08) exceeds the WWSD setting (menu setting 2-04), “Att 6” is displayed during central heat demands, and the boiler only responds to DHW demands. To avoid this error, increase menu setting 2-04. If the indicated temperature reading does not match the actual outdoor temperature, inspect the outdoor sensor wiring. If wiring is fine, disconnect the outdoor sensor, menu reading 1-08 should indicate “OPEn”, if not, replace the controller, if “OPEn” is indicated replace the outdoor sensor.
Att 7Service Reminder - occurs every 365 days; service the boiler and dear the warning by adjusting menu setting 2-16 to “OFF”.
FILLLow W ater Pressure - increase system water pressure to a minimum of 12 PSI. If water pressure reading at the external pressure gauge exceeds 15 PSI, inspect water pressure sensor and cable - rcplace water pressure sensor