HTP · Error codes
HTP 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.
HTP UFT (Universal Fire Tube) boilers (Er:## codes, manual lp-542)
Er:10
Flame Has Extinguished Five Times. The flame has extinguished 5 times. Press the Power button to clear the code (it also automatically reset…
Lockout
Er:11
Ignition Has Failed Five Times. Ignition has failed 5 times. Press the Power button to clear the code (it also automatically resets after on…
Lockout
Er:16
CH Supply Temperature Sensor Detects Water Temperature Greater Than 200°F (Auto Reset). Over-temperature safety: Er:16 displays when the CH …
Lockout
Er:20
Condensate - Closed is Normal, Open is Fault. The condensate drain trap switch is open. Check condensate and main controller connections, co…
Lockout
Er:28
Overheat Sensor Open or Short. The overheat sensor is open or shorted. The error clears when CH temperature decreases; check the overheat te…
Lockout
Er:29
APS - Closed is Normal, Open is Fault. The air pressure switch is open. Check the APS and main controller connections, APS resistance (shoul…
Lockout
Er:30
System Sensor Fault. The system (cascade) temperature sensor is shorted or failed; the boiler setpoint defaults to 20°F higher than the syst…
Details
Er:31
Return Temperature Sensor Open or Short. The return temperature sensor is open or shorted. The error clears when operating temperature decre…
Lockout
Er:32
DHW Sensor Short. The DHW sensor (or aquastat) is shorted. If an aquastat is installed ensure AquA is selected in Installer Mode 39; if a se…
Lockout
Er:33
CH Temperature Sensor Open or Short. The CH temperature sensor is open or shorted. The error clears when CH temperature decreases; check the…
Lockout
Er:35
Exhaust Sensor Open or Short. The exhaust temperature sensor is open or shorted. The error clears when exhaust temperature decreases; check …
Lockout
Er:37
Abnormal Supply Frequency. Supply frequency is too high to operate. The error clears when the supply frequency returns to the normal operati…
Lockout
Er:38
Error Appears When Control Stores Data, but Data Is Not Saved. The control stores data but the data is not saved. Press the Power button to …
Lockout
Er:41
Fan Speed Too High with Flame On. The error clears unless it occurs five times in ten minutes; press the Power button to clear. Check the ve…
Lockout
Er:42
Low Water Cut-Off Circuit Is Open. The LWCO circuit is open. Ensure the LWCO jumper is installed if low water cut-off is not used, the water…
Lockout
Er:43
Burner Overheat Switch Open. The burner overheat switch is open; the fan operates to cool the burner until the switch closes. Check the burn…
Lockout
Er:61
Fan Speed Feedback Signal Abnormal. The fan speed feedback signal is abnormal. The error clears when the condition is remedied; check the fa…
Lockout
Er:70
Register, RAM, ROM, I/O Port, AD Abnormal, Important EPROM Data or Safe Data Abnormal. The control register, RAM, ROM, I/O port, or AD is ab…
Lockout
Er:72
Flame Signal Detected Before Ignition. A flame signal was detected before ignition. Check that the boiler cover is secure (the flame detecti…
Lockout
Er:76
Poor Communication. There is poor communication between the main control and the display panel (the error occurs if there is no communicatio…
Lockout
Er:77
Outdoor Sensor Shorted. The outdoor sensor is shorted. When this error occurs the boiler still operates at the max setting of the Outdoor Re…
Details
Er:78
Cascade Communication Error. Cascade communication error - appears only in a cascaded system. Turn power OFF and ON at the boiler display pa…
Details
Er:80
Low Water Level Sensor (Low Water Level Detected Four Consecutive Times). Low water level was detected four consecutive times. Ensure all va…
Lockout
Er:81
Low Water Level Circuit. Low water level circuit fault. Ensure the system is filled with water and all valves are open with no leaks, check …
Lockout
Er:85
Freeze Protection (Boiler Has Detected Water Temperature Below 34°F [1°C]). Freeze protection activated - the boiler detected water temperat…
Lockout
Er:94
Exhaust NTC Detects Vent Temperature Greater Than 190°F (88°C). The exhaust NTC detects vent temperature greater than 190°F (88°C). Check th…
Lockout
HTP Elite Fire Tube Ultra (EFTU) boilers and combis (group fault codes, manual LP-723)
1 01
CH Circuit Overheat. CH circuit overheat. Press the Reset button to clear the error. Check the correct functioning and positioning of the su…
Details
1 03
Insufficient Circulation or Low Water Pressure: Gradient T Supply > 12.6°F/sec, Three Times. Insufficient circulation or low water pressure …
Details
1 04
Insufficient Circulation or Low Water Pressure: Gradient T Supply > 27°F/sec or Gradient T Return > 27°F/sec. Insufficient circulation or lo…
Details
1 05
Insufficient Circulation or Low Water Pressure: T Supply - T Return > 99°F, Three Times. Insufficient circulation or low water pressure with…
Details
1 06
Insufficient Circulation or Low Water Pressure: T Return - T Supply > 18°F, Three Times. Insufficient circulation or low water pressure with…
Details
1 08
Fill System: No Water in the Primary Circuit (P < Pmin). The boiler shut off due to insufficient water pressure in the heating circuit - fil…
Details
1 10
CH Flow Temp Probe Circuit Open/Short Circuit. The CH flow (supply) temperature probe circuit is open or shorted. The error clears when the …
Details
1 12
CH Return Temp Probe Circuit Open/Short Circuit. The CH return temperature probe circuit is open or shorted. The error clears when the opera…
Details
1 14
External Sensor Circuit Open/Short Circuit. The outdoor (external) sensor circuit is open or shorted. When this error occurs the appliance o…
Details
1 16
Floor Thermostat Contact Open. The floor thermostat contact is open. If parameter 223 is set to 0 and a floor safety thermostat is not prese…
Details
1 P1
Insufficient Circulation or Missing Water: Gradient T Supply > 12.6°F/sec. Warning of insufficient circulation or missing water with a suppl…
Details
1 P2
Insufficient Circulation or Missing Water: T Supply - T Return > 99°F. Warning of insufficient circulation or missing water with supply minu…
Details
1 P3
Inadequate Circulation or Missing Water: T Return - T Supply > 18°F. Warning of inadequate circulation or missing water with return minus su…
Details
2 01
Damaged or Shorted DHW Temperature Probe. Applicable to Combi models only - the DHW outlet temperature probe is damaged or shorted. Check th…
Details
2 03
Storage Temp Probe Circuit Open/Short Circuit. Only applicable to Non-Combi boilers with a DHW tank sensor - the storage tank temperature pr…
Details
2 05
DHW In Probe Open Circuit. The DHW inlet probe circuit is open. Check the DHW inlet probe and wiring. The table classifies it as Blocking (A…
Details
2 09
Storage Overheating (> 176°F = on; < 175°F = off). The storage (DHW tank) temperature exceeded 176°F and switches back off below 175°F. Chec…
Details
2 P2
Anti-Legionella Function Not Completely Finished. The anti-Legionella function did not complete. The table classifies it as Warning.…
Details
3 01
Display Error Eeprom. Display EEPROM error. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens again r…
Details
3 02
Communication Error GP - GIU. Communication error between the main PCB (GP) and the HMI (GIU). Switch the boiler OFF and ON at the main elec…
Details
3 03
PCB Internal Error. PCB internal error. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens again repla…
Details
3 04
Too Many (> 5) Resets in 15 Minutes. More than five resets were attempted in 15 minutes. Switch the boiler OFF and ON at the main electrical…
Details
3 05
PCB Internal Error. PCB internal error. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens again repla…
Details
3 06
PCB Internal Error. PCB internal error. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens again repla…
Details
3 07
PCB Internal Error. PCB internal error. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens again repla…
Details
3 09
Gas Relay Check Failed. The gas relay check failed. Switch the boiler OFF and ON at the main electrical power supply; if the problem happens…
Details
3 P9
Scheduled Maintenance - Call for Service. Scheduled maintenance is due - call for service. Reset the error with parameter 852. The table cla…
Details
4 11
Room Sensor Circuit Open or Short Circuit Zone 1. The Zone 1 room sensor circuit is open or shorted. Check the room sensor and its wiring fo…
Details
4 12
Room Sensor Circuit Open or Short Circuit Zone 2. The Zone 2 room sensor circuit is open or shorted. Check the room sensor and its wiring fo…
Details
4 13
Room Sensor Circuit Open or Short Circuit Zone 3. The Zone 3 room sensor circuit is open or shorted. Check the room sensor and its wiring fo…
Details
4 30
Detected Accessory Wired to BUS Connection. An accessory was detected on the BUS connection. If connecting an NTI zone controller to the BUS…
Details
4 31
BUS Connection. Communication fault on the BUS connection - check accessory wiring on the BUS connection. The table classifies it as Warning…
Details
5 01
No Flame Detected (3 Times). No flame was detected in three attempts. Press the Reset button to clear; monitor the gas pressure (3.5 to 10.5…
Lockout
5 02
Flame Detected with Gas Valve Closed. Flame was detected while the gas valve was closed. The error clears when the condition is remedied; di…
Lockout
5 04
Detection of 10 Flame Lifts in One Operating Cycle. Ten flame lifts were detected in one operating cycle. Press the Reset button to clear; m…
Details
5 P1
1st Ignition Failed. First ignition attempt was unsuccessful. Monitor gas pressure (3.5 to 10.5 in. WC NG, or 8 to 13 in. WC for LP), check …
Lockout
5 P2
2nd Ignition Failed. Second ignition attempt was unsuccessful. Monitor gas pressure (3.5 to 10.5 in. WC NG, or 8 to 13 in. WC for LP), check…
Lockout
5 P3
Detection of Flame Loss During Run. Flame loss was detected during run. Monitor gas pressure (3.5 to 10.5 in. WC NG, or 8 to 13 in. WC for L…
Lockout
5 P6
3rd and 4th Ignition Failed. Third and fourth ignition attempts were unsuccessful. Monitor gas pressure (3.5 to 10.5 in. WC NG, or 8 to 13 i…
Lockout
6 02
Exhaust NTC Detects Vent Temperature Greater Than 204°F (96°C). The exhaust NTC detected vent temperature greater than 204°F (96°C). Press t…
Details
6 03
APS Open. The air pressure switch is open. Press the Reset button to clear; check the APS and main controller connections, APS resistance (s…
Details
6 05
Exhaust NTC Circuit Open or Short Circuit. The exhaust NTC circuit is open or shorted. The error clears when the condition is remedied; chec…
Details
6 12
Insufficient Fan Speed (<500 for 3 Seconds or RPM Min -300 for 3 Minutes). Insufficient fan speed. Press the Reset button to clear; check th…
Lockout
NOAVL
PCB Error. PCB configuration error. Check parameter 046 - if set to UNDEF it must be changed to the boiler's application (b--SIN single boil…
Details
EMERG
Incorrect Wiring to BUS Connection (Emergency Mode). The control sensed a short circuit on the BUS connection - when in Emergency mode the b…
Details
HTP Elite Ultra (ELU) boilers and combis (group fault codes, manual 420010970305)
1 01*
Outlet temperature exceeded 210F. Air in the system (ensure boiler is free of air and pressurized to at least 20 PSI); plugged return filter…
Details
1 01*
Temperature sensor safety test failed. Inlet/outlet sensor fault - swap the inlet and outlet sensors and verify that the sensors read correc…
Details
1 03*
Supply temperature rising faster than 12.6 degrees per second three times in a row. Reset by tapping the reset button. Air in the system (fr…
Details
1 04*
Supply temperature rose faster than 27 degrees per second. Same checklist as 1 03 - reset by tapping the reset button; air in system (min 20…
Details
1 05*
Supply temperature exceeded return temperature by more than 99F three times in a row. Same checklist as 1 03/1 04 - reset by tapping the res…
Details
1 06*
Return temperature is hotter than the supply temperature by 18F. Reset by tapping the reset button. Air in the system (free of air, min 20 P…
Details
1 07
Controller Software problem. Control versions prior to 00.85.00 - reset the error by tapping the reset button. Check menu 8.5.5 - if the sof…
Details
1 08
Water pressure too low. Water pressure too low: raise the system pressure, with the boiler and heating circulators off, to a minimum of 20 P…
Details
1 10
Supply sensor short circuit or open circuit. Temperature sensor disconnected (supply sensor near the top of the heat exchanger is on the two…
Details
1 12
CH Return temp. sensor circuit open / short circuit. Temperature sensor disconnected (return sensor near the bottom of the heat exchanger is…
Details
1 14
Outdoor sensor not connected. Outdoor reset turned on but not used - if not using outdoor reset ensure menu 4.2.1, 5.2.1 and 6.2.1 are set t…
Details
115
System sensor Disconnected. System sensor disconnected - in a cascade the system sensor must be connected to the master boiler using the SYS…
Details
1 16
Floor Thermostat contact open. Incorrect setting - if not using a floor sensor set parameter 223 to 0; if parameter 223 is set to 1 and a fl…
Details
150
System Sensor Overheat. Faulty temperature sensor (check for water damage, check resistance per temperature/resistance chart); damaged senso…
Details
1 P1
Boiler temperature rose faster than 12.6F / second. Normal operation - in systems with high and low temperature zones this error may be disp…
Details
1 P2
Supply temperate exceeded return by 99F or more. Normal operation - may display for several minutes in systems with high and low temperature…
Details
1 P3
The return temperature exceeded the supply temperature by 18 F or more. Normal operation - in systems with high and low temperature zones th…
Details
201
Damaged or shorted DHW temperature probe. DHW sensor disconnected (check the connection to the DHW temperature sensor); failed temperature s…
Details
2 03
Storage temp. probe circuit open / short circuit. Incorrect setting - if using an aquastat or zone control for DHW demand ensure setting 2.2…
Details
2 05
DHW In probe open circuit. Perform a factory reset using menu 2.8.0. The table classifies it as Blocking (Auto Reset).…
Details
2 09
Storage overheating - Tank temperature greater than 175F. Tank sensor wiring damaged (inspect wiring from the tank sensor to the boiler for …
Details
2 P2
Anti - Legionella function not completely finished. Tank sensor improperly installed (ensure fully inserted into the well in the proper loca…
Details
3 01
Display error Eeprom. Power problem / defective PCB - test for proper voltage and grounding on the PCB and at the electrical supply to the b…
Details
3 02
Communication error GP - GIU. Wiring between PCB and display damaged/disconnected (check the wire connection between the PCB and the display…
Details
3 03
PCB internal error. Water pressure sensor wiring damaged or shorted (check the water pressure switch wiring for damage or shorts, test for p…
Details
3 04
Too many (> 5) resets in 15 minutes (1) Turn Off the Power to the Boiler. Normal operation - reset button pushed more than 5 times in 15 min…
Details
3 05
PCB internal error. Power problem/defective PCB - reset the error by tapping the reset button; test for proper voltage and grounding; switch…
Details
3 06
PCB internal error. Incorrect outdoor sensor wiring (disconnect the outdoor sensor from the PCB and reset the error); power problem/defectiv…
Details
3 07
PCB internal error. Power problem/defective PCB - reset the error by tapping the reset button; test for proper voltage and grounding; switch…
Details
3 09
Flame detection while burner is off. Damaged flame probe or flame probe wire (check the flame sensor and wire for damage, replace the flame …
Details
3 P9
Sched. Maintenance - Call for Service. Normal operation - the service reminder has been set and the time expired; service the boiler and res…
Details
4 11
Room sensor circuit open or short circuit Zone 1. Room sensor not present (if not using a room sensor set menu 4.2.1/5.2.1/6.2.1 = 0 or 1 or…
Details
4 12
Room sensor circuit open or short circuit Zone 2. Room sensor not present (set menu 4.2.1/5.2.1/6.2.1 = 0 or 1 or 3); bus wiring damaged (in…
Details
4 13
Room sensor circuit open or short circuit Zone 3. Room sensor not present (set menu 4.2.1/5.2.1/6.2.1 = 0 or 1 or 3); bus wiring damaged (in…
Details
4 30
Detected accessory wired to BUS connection. Restore the factory default menu 2.8.0; if the error persists replace the PCB. The table classif…
Details
4 31
Detected accessory wired to BUS connection. Restore the factory default menu 2.8.0; if the error persists replace the PCB. The table classif…
Details
440
Manager boiler missing from Bus. Single boiler configured as a follower (if this is a stand alone boiler turn 0.46 to B-SIN); manager boiler…
Details
4 41
Follower Boiler Missing from BUS Connection. Single boiler configured as a Master (if this is a stand alone boiler turn 0.46 to B-SIN); foll…
Details
5 01
No flame detected (3 times) - No visible flame. Improper gas pressure (test static gas pressure - must be 3.5-10.5" for natural gas and 8-13…
Lockout
5 02
Flame detected out of sequence. Faulty flame sensor (check the flame sensor and wiring for damage, water or other possible shorts to ground …
Lockout
5 04
Flame lost ten times during run. Improper gas pressure (verify pressure while in operation - between 3.5 and 10.5" WC natural gas, or betwee…
Details
5 P1
1st Ignition Failed. Normal operation - 5P1 may be displayed momentarily if there is a problem; the boiler will lock out - follow the direct…
Lockout
5 P2
2nd ignition attempt failed. See lockout 501. The table classifies it as Warning.…
Lockout
5 P6
3rd ignition attempt failed. See lockout 501. The table classifies it as Warning.…
Lockout
5 P3
Detection of Flame loss during run. Wind (in some circumstances the flame will lift during run due to wind); blocked venting (ensure nothing…
Lockout
6 02
Exhaust Temperature exceeded 204F (the error can only be cleared when the flue temperature drops below 149F). Inadequate water flow (ensure …
Details
6 03
Blocked condensate switch open. Clogged condensate drain (clean the condensate trap, ensure it is draining freely); blocked condensate (ensu…
Details
6 05
Exhaust Temperature sensor circuit open or short circuit. Faulty wiring (inspect the wires from the exhaust sensor to the boiler control, di…
Details
6 12*
Blower did not achieve the proper RPM speed. Faulty wiring between control and blower (check the 4 wire harness between the fan and PCB for …
Details
6 19
Power Limiting Mode. Normal operation on new start up - allow the boiler to operate the burner in heating or hot water mode for 5 minutes wi…
Details
NOAVL
There is a problem with the boiler address settings or EBUS wiring. EBUS wiring (orange connector) (check the EBUS connection and wires for …
Details
EMERG
Cascade boiler lost communication - Emergency Mode. When in Emergency Mode the boiler operates in CH mode with a target boiler temperature =…
Details
CONFL
Cascade boilers share a common address. Incorrect settings (two or more boilers in the cascade have the same address - check menu 0.4.6 and …
Details
HTP Elite FT legacy boilers (926 SIT control, manual LP-387)
E03
System sensor failure (Cascade Master only). The system sensor circuit is open or shorted: no system sensor connected to the Master Boiler, …
Lockout
TT
Temper blocking — supply temperature too high to ignite. There is a demand for heat, the pump is powered on, and the supply sensor temperatu…
Lockout
DHW
Temper blocking — DHW demand, supply temperature too high to ignite. There is a demand from the DHW circuit, the pump is powered on, and the…
Lockout
PRO
Low water pressure. Low water pressure in the boiler. Assure the system pressure is above 10 psig and check for leaks in the system piping; …
Details
FLU
High flue pressure. Excessive flue pressure; resets automatically after the high-pressure condition is resolved. Assure the flue is not bloc…
Details
LOU
24 volt low. The 24-volt power supply on the control is damaged or overloaded; resets automatically if the overload is removed. Check line v…
Details
F00
Water high temperature. The water in the boiler has overheated (red light, LOCKOUT flashing; pump runs to cool the boiler). Check circulator…
Lockout
F01
Flue temperature limit switch tripped / low water level (optional UL353 LWCO). The flue temperature limit switch has tripped or the water le…
Lockout
F02
Supply sensor failure. The supply temperature sensor of the boiler has failed. Check the electrical connection to the thermistor on the outl…
Lockout
F03
Return sensor failure. The return temperature sensor of the boiler has failed. Check circulator pump operation and ensure adequate flow by c…
Lockout
F04
Flue sensor failure. The flue temperature sensor of the boiler has failed. Inspect the flue sensor for physical damage or corrosion and repl…
Lockout
F05
Supply temperature high. The boiler supply temperature is excessive (supply sensor exceeded 199°F when accompanied by the red FAULT light an…
Lockout
F06
Return temperature high. The boiler return temperature is excessive (return sensor exceeded 199°F when accompanied by the red FAULT light an…
Lockout
F09
No flame on ignition. The boiler tried to ignite four times during one heat call and failed. Watch the igniter through the observation windo…
Lockout
F10
Flame loss. The flame was lost 3 times while the boiler was firing during one demand call. Monitor gas pressure while in operation; assure t…
Lockout
F11
False flame signal. There is flame when the control is not telling the boiler to run. Look into the window: if there is flame, turn the gas …
Lockout
F13
Fan speed error. The fan is not running at the speed determined by the control (more than 30% faster or slower than commanded for more than …
Lockout
F20
Condensate full. The condensate trap is full. Check condensate lines for obstructions, check the float switch in the condensate reservoir, a…
Lockout
F31
Program error. An error occurred while programming the control and the memory is corrupt. The control must be reprogrammed; if programming d…
Lockout
PP
Control programmed. The control has been programmed by a technician or the factory and is left in a locked-out mode. Press RESET for at leas…
Lockout
FOU
Outdoor sensor. The outdoor sensor is shorted, damaged, or disconnected from the boiler. Check the outdoor sensor connections and wiring; ch…
Details
E07
Flue temperature high. The flue sensor temperature is excessive (above 210°F). The boiler will not respond to a demand for heat; when the fl…
Details
E19
Line voltage frequency out of range. The line voltage frequency is out of range - this can happen when the boiler is powered from an overloa…
Details
HTP Elite Premier boilers (928 SIT control, manual LP-550)
E03
System sensor failure (Cascade Master only). The system sensor circuit is open or shorted: no system sensor connected to the Master Boiler, …
Lockout
F02
Supply sensor failure. The dual supply sensor contains two sensing elements; one or both halves have failed, or the difference between the d…
Lockout
F03
Return sensor failure. The return temperature sensor has failed. Check circulator pump operation and ensure adequate flow (less than 50°F ri…
Lockout
F04
Flue sensor failure. The dual flue sensor contains two sensing elements; one or both halves have failed, or the difference between the dual …
Lockout
F05
Supply temperature high. The boiler supply temperature is excessive (supply sensor exceeded 210°F with the red FAULT light and LOCKOUT). Che…
Lockout
F06
Return temperature high. The boiler return temperature is excessive (return sensor exceeded 210°F with the red FAULT light and LOCKOUT). Che…
Lockout
F09
No flame on ignition. The boiler tried to ignite four times during one heat call and failed. Watch the igniter through the observation windo…
Lockout
F10
Flame loss. The flame was lost 3 times while the boiler was firing during one demand call. Monitor gas pressure while in operation; assure t…
Lockout
F11
False flame signal. There is flame when the control is not telling the boiler to run. Look into the window: if there is flame, turn the gas …
Lockout
F13
Fan speed error. The fan is not running at the speed determined by the control (more than 30% faster or slower than commanded for more than …
Lockout
F17
Flue limit. The boiler flue temperature is excessive (flue sensor exceeded 210°F with the red FAULT light and LOCKOUT). Check the flue for o…
Lockout
F20
Condensate full. The condensate trap is full. Check condensate lines for obstructions, check the float switch in the condensate reservoir, a…
Lockout
F21
LWCO fault. Water level in the boiler is low. Check the boiler feed water system is supplying make-up water, ensure all air is bled from the…
Lockout
F22
External LWCO. Generated when the External Low Water Cut-Off is installed and the water level is low; the boiler will not respond to a heat …
Lockout
F24
Target wall. The target wall fuse has been disconnected or tripped on boilers 299 kBTU or larger, or the target wall jumper wires are not in…
Lockout
F26
Gas pressure (optional switches). One of the optional gas pressure switches has tripped: the high gas pressure switch (excessive pressure on…
Lockout
F31
Program error. An error occurred while programming the control and the memory is corrupt. The control must be reprogrammed; if programming d…
Lockout
F41
Hard fault — condensate circuit. Internal fault in the circuit within the control connected to the condensate switch. Inspect the ground wir…
Lockout
F42
Hard fault — LWCO circuit. Internal fault in the LWCO circuit. Inspect the ground wires for damage or loose connections, inspect the LWCO wi…
Lockout
F43
AD SAFT fault. The temperature of either the flue or supply sensors has risen nine degrees in 100 milliseconds and not returned to normal wi…
Lockout
PP
Control programmed. The control has been programmed by a technician or the factory and is left in a locked-out mode. Press RESET for at leas…
Lockout
FOU
Outdoor sensor. There is an issue with the outdoor sensor - it is shorted, damaged, or disconnected from the boiler. Check the outdoor senso…
Details
FL
Low water flow. The flow switch is not activated. Ensure the boiler contains water and all valves are open; check the boiler circulator is i…
Details
E07
Flue temperature high. The flue sensor temperature is above 210°F; the boiler will not respond to a heat demand and begins to modulate down …
Details
TT
Temper blocking — supply temperature too high to ignite. There is a demand for heat, the pump is powered on, and the supply sensor temperatu…
Lockout
DHW
Temper blocking — DHW demand, supply temperature too high to ignite. There is a demand from the DHW circuit, the pump is powered on, and the…
Lockout
FLU
High flue pressure. Excessive flue pressure; resets automatically after the high-pressure condition is resolved. Assure the flue is not bloc…
Details
E19
Line voltage frequency out of range. The line voltage frequency is out of range - this can happen when the boiler is powered from an overloa…
Details
HTP Pioneer boilers (926 SIT control, manual LP-325)
Fou
Outdoor sensor shorted or temperature less than -40°F. Inspect the wiring from the outdoor sensor for damage or shorted connections and repa…
Details
E19
Line voltage frequency out of range. Inspect power wiring to the appliance and repair as necessary; if connected to line voltage notify the …
Details
FLU
Blocked vent pressure switch open / condensate cup full or not present. Check the flue vent to ensure it is not blocked or damaged; check th…
Details
LEO
Water level in tank is low. Be sure all air is bled from the system; inspect the low level switch and wiring for damage and repair if necess…
Details
LOU
24 volt low. Check line voltage (must be 100-128 volts); with HTP service software check the 24 V supply display (must be greater than 128, …
Details
E03
System sensor failure (Cascade Master only). Check the wiring to the system sensor and repair as necessary; check the sensor resistance agai…
Details
F00
High temperature switch limit exceeded 194°F. Try reset. If F00 repeats, create a demand for hot water (take care to prevent scald injury); …
Lockout
F01
Vent temperature limit exceeded. Inspect all flue piping for damage or overheating and repair/replace before proceeding; if the flue is inta…
Lockout
F02
Interrupted or shorted upper (supply) temperature sensor. Check the electrical connection to the appropriate temperature sensor; if the conn…
Lockout
F03
Interrupted or shorted lower (return) temperature sensor. Check the electrical connection to the appropriate temperature sensor; if the conn…
Lockout
F05
Upper (supply) temperature sensor exceeds 210°F. If the water in the tank is not greater than 210°F check the wiring and repair if faulty; i…
Lockout
F06
Lower (return) temperature sensor exceeds 210°F. If the water in the tank is not greater than 210°F check the wiring and repair if faulty; i…
Lockout
F09
No flame detected — three ignition attempts failed. Appliance will make three attempts at ignition before the control goes into this lockout…
Lockout
F10
Loss of flame signal. The appliance will relight 4 times before the control goes into this lockout; it will reset in 1 hour. Monitor the gas…
Lockout
F11
False flame signal. The appliance will lock out if it senses a flame signal when there should be none present. Turn the gas off to the unit …
Lockout
F13
Combustion fan speed incorrect. The appliance will lock out if it senses that the fan speed is less than 70% of the expected rate for more t…
Lockout
pp
Parameters programmed. Press {S4} reset for at least 1 second. The table classifies it as Lockout (Manual Reset).…
Lockout
F31
Program parameter error. The control must be re-programmed; if programming does not solve the problem, the control must be replaced. The tab…
Lockout
HTP Versa-Hydro combi units (926 SIT control, manual LP-314)
FOU
Outdoor sensor. The outdoor sensor is defective, shorted or open, or the outdoor temperature is below -40°F. The unit continues to operate b…
Details
E07
CH sensor failure (hydronic heating module). One or both of the clip-on temperature sensors in the hydronic heating module is disconnected. …
Details
E19
Line voltage frequency out of range. The line voltage frequency is out of range - this can happen when the unit is powered from a small gaso…
Details
FLU
High flue pressure. Excessive flue pressure; resets automatically after the high-pressure condition is resolved. Ensure the flue is not bloc…
Details
LEO
Low water level in the main tank. Low water level in the main tank; the unit will not run until the correct water level is restored. Ensure …
Details
LOU
24 volt low. The 24-volt power supply on the control is damaged or overloaded; resets automatically if the overload is removed. Ensure line …
Details
F00
Water high temperature. The water in the tank has overheated (red fault light, LOCKOUT flashing; pump runs to cool the appliance). Check cen…
Lockout
F01
Flue temperature limit switch tripped. The flue temperature limit switch of the unit has tripped. Check the flue for obstructions or heat da…
Lockout
F02
Top temperature sensor failed. The top temperature sensor of the tank has failed. Check the electrical connection to the thermistor on the o…
Lockout
F03
Bottom temperature sensor failed. The bottom temperature sensor of the unit has failed. Check the electrical connection to the thermistor an…
Lockout
F05
Top temperature high. The top temperature of the tank is excessive (top sensor exceeded 230°F with the red fault light and LOCKOUT). Check t…
Lockout
F06
Bottom temperature high. The bottom temperature of the tank is excessive (bottom sensor exceeded 230°F with the red fault light and LOCKOUT)…
Lockout
F09
No flame on ignition. The unit tried to ignite four times during a call for heat and failed all four times. Watch the igniter through the ob…
Lockout
F10
Flame loss. The flame was lost while the unit was lit 3 times during one demand call. Monitor gas pressure while in operation; ensure the fl…
Lockout
F11
False flame signal. The unit senses flame when the control is not telling it to run. Look into the window: if there is flame, turn the gas o…
Lockout
F13
Fan speed error. The fan speed has been more than 30% faster or slower than the control-commanded speed for more than 10 seconds. Check the …
Lockout
F31
Program error. An error occurred while programming the control and its memory could be corrupt. The control must be reprogrammed; if reprogr…
Lockout
PP
Control programmed. The control has been programmed by a technician or the factory and was left in a locked-out mode. Press RESET for at lea…
Lockout
HTP UFT Combi boilers (UFTC control, manual LP-648)
Er:10
Flame has extinguished 5 (five) times. Press the Power button to clear; the code also automatically resets after one hour (up to three times…
Lockout
Er:11
Ignition has failed 5 (five) times. Press the Power button to clear; the code also automatically resets after one hour (up to three times). …
Lockout
Er:16
Operating temperature sensor detects water temperature greater than 203°F (95°C). The error goes away when the DHW temperature decreases; du…
Lockout
Er:20
Condensate (closed is normal, open is fault) — condensate drain trap. Press the Power button to clear. Check the condensate and main control…
Lockout
Er:28
Overheat sensor open or short. The error goes away when the CH temperature decreases. If it happens again: check the overheat temperature se…
Lockout
Er:29
APS (air pressure switch) — closed is normal, open is fault. Press the Power button to clear. WARNING: if Er:29 occurs, turn off the gas val…
Lockout
Er:31
Return temperature sensor open or short. The error goes away when the operating temperature decreases. If it happens again: check the return…
Lockout
Er:32
DHW sensor open or short. The error goes away when the outlet DHW temperature decreases. If it happens again: check the DHW outlet temperatu…
Lockout
Er:33
CH temperature sensor open or short. The error goes away when the CH temperature decreases. If it happens again: check the CH temperature se…
Lockout
Er:35
Exhaust sensor open or short. The error goes away when the exhaust temperature decreases. If it happens again: check the exhaust temperature…
Lockout
Er:36
Abnormal supply voltage. Supply voltage is too high to operate; the code goes away when the supply voltage returns to the normal operating r…
Lockout
Er:37
Abnormal supply frequency. Supply frequency is too high to operate; the code goes away when the supply frequency returns to the normal opera…
Lockout
Er:38
Control stores data, but data is not saved. Error appears when the control stores data but the data is not saved. Press the Power button to …
Lockout
Er:41
Fan speed too high with flame on. The code goes away unless it occurs five times in ten minutes; press the Power button to clear. WARNING: i…
Lockout
Er:42
Jumper wire disconnected. Press the Power button to clear. WARNING: if Er:42 occurs, turn off the gas valve at the manual shutoff and check …
Lockout
Er:43
Burner overheat switch open. Press the Power button to clear; during the error the fan operates to cool the burner until the switch closes. …
Lockout
Er:61
Fan speed feedback signal abnormal. The code goes away when the condition is remedied. If it happens again: check the fan connections are se…
Lockout
Er:66
Mixing valve initial value error (cannot return to initial position). The code goes away when the condition is remedied. If it happens again…
Lockout
Er:68
Mixing valve operation error (stuck in initial position). The code goes away when the condition is remedied. If it happens again: turn power…
Lockout
Er:70
Register, RAM, ROM, I/O port, AD abnormal, important EPROM data or safe data abnormal. The code goes away when the condition is remedied. If…
Lockout
Er:72
Flame signal detected before ignition. The code goes away when the condition is remedied. If it happens again: check the boiler cover is sec…
Lockout
Er:76
Poor communication. The code goes away when the condition is remedied. If it happens again: check the connections from the main control to t…
Lockout
Er:77
Outdoor sensor shorted. The code goes away when the condition is remedied. If it happens again: check the outdoor sensor wiring connections …
Lockout
Er:80
Low water level sensor (detected four consecutive times). The code goes away when the condition is remedied. If it happens again: ensure all…
Lockout
Er:81
Low water level circuit. The code goes away when the condition is remedied. If it happens again: ensure the system is filled with water, all…
Lockout
Er:85
Freeze protection (water temperature below 34°F / 1°C). The code goes away when the freezing condition is remedied. If it happens again: ens…
Lockout
Er:94
Exhaust NTC detects vent temperature greater than 190°F (88°C). The code goes away when the condition is remedied. WARNING: if Er:94 occurs,…
Lockout
HTP UFT Combi legacy boilers manufactured before 1/1/2020 (UFTC control, manual LP-648 Rev. 001)
Er:10
Flame has extinguished 5 (five) times. Press the Power button to clear the Error Code. The Code will also automatically reset after one hour…
Lockout
Er:11
Ignition has failed 5 (five) times. Press the Power button to clear the Error Code. The Code will also automatically reset after one hour (u…
Lockout
Er:16
Operating temperature sensor detects water temperature greater than 203°F (95°C). This Error Code will go away when the DHW temperature decr…
Lockout
Er:20
Condensate - closed is normal, open is fault (condensate drain trap). Press the Power button to clear the Error Code. 1. Check Condensate an…
Lockout
Er:28
Overheat sensor open or short. This Error Code will go away when CH temperature decreases. If Error happens again: 1. Check overheat tempera…
Lockout
Er:29
APS - closed is normal, open is fault. Press the Power button to clear the Error Code. 1. Check APS and main controller connections. Ensure …
Lockout
Er:31
Return temperature sensor open or short. This Error Code will go away when operating temperature decreases. If Error happens again: 1. Check…
Lockout
Er:32
DHW sensor open or short. This Error Code will go away when outlet DHW temperature decreases. If Error happens again: 1. Check DHW outlet te…
Lockout
Er:33
CH temperature sensor open or short. This Error Code will go away when CH temperature decreases. If Error happens again: 1. Check CH tempera…
Lockout
Er:35
Exhaust sensor open or short. This Error Code will go away when exhaust temperature decreases. If Error happens again: 1. Check exhaust temp…
Lockout
Er:36
Abnormal supply voltage. Supply voltage is too high to operate. This Error Code will go away when supply voltage returns to normal operating…
Lockout
Er:37
Abnormal supply frequency. Supply frequency is too high to operate. This Error Code will go away when supply frequency returns to normal ope…
Lockout
Er:38
Error appears when control stores data, but data is not saved. Press the Power button to clear the Error Code. Replace the main control. The…
Lockout
Er:41
Fan speed too high with flame on. The Error Code will go away unless it occurs five (5) times in ten (10) minutes. Press the Power button to…
Lockout
Er:42
Jumped wire disconnected. Press the Power button to clear the Error Code. If Error happens again: 1. Ensure that the jumper wire is installe…
Lockout
Er:43
Burner overheat switch open. Press the Power button to clear the Error Code. If Error happens again: 1. Check burner overheat switch connect…
Lockout
Er:61
Fan speed feedback signal abnormal. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check the connec…
Lockout
Er:66
Mixing valve initial value error (mixing valve cannot return to initial position). This Error Code will go away when the condition is remedi…
Lockout
Er:68
Mixing valve operation error (mixing valve stuck in initial position). This Error Code will go away when the condition is remedied. If Error…
Lockout
Er:70
Register, ram, rom, I/O port, AD abnormal, important EPROM data or safe data abnormal. This Error Code will go away when the condition is re…
Lockout
Er:72
Flame signal detected before ignition. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check the boi…
Lockout
Er:76
Poor communication. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check connections from main cont…
Lockout
Er:77
Outdoor sensor shorted. The Error Code will go away when the condition is remedied. If Error happens again: 1. Check outdoor sensor. Ensure …
Lockout
Er:80
Low water level sensor (low water level detected four [4] consecutive times). This Error Code will go away when the condition is remedied. I…
Lockout
Er:81
Low water level circuit. This Error Code will go away when the condition is remedied. If Error happens again: 1. Ensure the system is filled…
Lockout
Er:85
Freeze protection (boiler has detected water temperature below 34oF [1oC]). This Error Code will go away when the freezing condition is reme…
Lockout
Er:94
Exhaust NTC detects vent temperature is greater than 190oF (88oC). This Error Code will go away when the condition is remedied. If Error hap…
Lockout
HTP EFT Combi boilers (EFTC wall and floor; LP-496 floor table, LP-520 wall prints the same table without Er:30)
Er:10
Flame has extinguished 5 (five) times. Press the Power button to clear the Error Code. If Error happens again: 1. Monitor the gas pressure t…
Lockout
Er:11
Ignition has failed 5 (five) times. Press the Power button to clear the Error Code. If Error happens again: 1. Monitor the gas pressure to t…
Lockout
Er:16
Operating temperature sensor detects water temperature greater than 203°F (95°C). Press the Power button to clear the Error Code. If Error h…
Details
Er:20
Condensate APS – closed is normal, open is fault (condensate drain trap). Press the Power button to clear the Error Code. 1. Check Condensat…
Details
Er:28
Overheat sensor open or short. This Error Code will go away when CH temperature decreases. If Error happens again: 1. Check overheat tempera…
Details
Er:29
Flue APS open - closed is normal, open is fault (intake / exhaust). 1. Check APS and connections. 2. If APS is open, replace the switch. 3. …
Details
Er:30
Storage tank sensor fault. This Error Code will go away when storage tank water temperature decreases. If Error happens again: 1. Check stor…
Details
Er:32
DHW sensor open or short. This Error Code will go away when outlet DHW temperature decreases. If Error happens again: 1. Check DHW outlet te…
Details
Er:33
CH temperature sensor open or short. This Error Code will go away when CH temperature decreases. If Error happens again: 1. Check CH tempera…
Details
Er:35
Exhaust sensor open or short. This Error Code will go away when exhaust temperature decreases. If Error happens again: 1. Check exhaust temp…
Details
Er:36
Abnormal supply voltage. Supply voltage is too low to operate. This Error Code will go away when supply voltage returns to normal operating …
Details
Er:37
Abnormal supply frequency. Supply frequency is too high to operate. This Error Code will go away when supply frequency returns to normal ope…
Details
Er:38
Error appears when control stores data, but data is not saved. Press the Power button to clear the Error Code. Replace the main control. The…
Details
Er:41
Fan speed too high with flame on. Press the Power button to clear the Error Code. If Error happens again: 1. Check the vent connections for …
Details
Er:42
Jumped wire disconnected. Press the Power button to clear the Error Code. If Error happens again: 1. Ensure the jumped wire is properly conn…
Details
Er:43
Burner overheat switch open. Press the Power button to clear the Error Code. If Error happens again: 1. Check burner overheat switch connect…
Details
Er:61
Fan speed feedback signal abnormal. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check the connec…
Lockout
Er:66
Mixing valve initial value error (mixing valve cannot return to initial position). This Error Code will go away when the condition is remedi…
Details
Er:68
Mixing valve operation error (mixing valve stuck in initial position). This Error Code will go away when the condition is remedied. If Error…
Details
Er:70
Register, ram, rom, I/O port, AD abnormal, important EPROM data or safe data abnormal. This Error Code will go away when the condition is re…
Details
Er:72
Flame signal detected before ignition. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check the app…
Lockout
Er:76
Poor communication. This Error Code will go away when the condition is remedied. If Error happens again: 1. Check connections from main cont…
Details
Er:80
Low water level sensor (low water level detected four (4) consecutive times). This Error Code will go away when the condition is remedied. I…
Details
Er:81
Low water level circuit. This Error Code will go away when the condition is remedied. If Error happens again: 1. Ensure all valves are open …
Details
Er:85
Freeze protection (appliance has detected water temperature below 34oF (1oC)). This Error Code will go away when the freezing condition is r…
Details
Er:94
Exhaust sensor detects vent temperature is greater than 190oF (88oC). This Error Code will go away when the condition is remedied. If Error …
Details
Talk to a boiler technician
Describe what the boiler is doing and get a straight answer about the next step.
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