HVACopediaHTP boiler error codes
32 codes (20 faults, 12 normal display and menu codes).
| Code | Meaning | Severity / type |
|---|---|---|
| E03 | System sensor failure (cascade) | Medium |
| E07 | Flue temperature high | High |
| E19 | Line voltage frequency out of range | Medium |
| F00 | Water high temperature (ECO) | Critical |
| F01 | Flue temperature switch / low water | Critical |
| F02 | Supply sensor failure | High |
| F03 | Return sensor failure | High |
| F04 | Flue sensor failure | High |
| F05 | Supply temperature high | Critical |
| F06 | Return temperature high | Critical |
| F09 | No flame on ignition | Critical |
| F10 | Flame loss | Critical |
| F11 | False flame signal | Critical |
| F13 | Fan speed error | High |
| F20 | Condensate full | High |
| F31 | Program error | High |
| CASCADE MASTER READY | Cascade master ready | Normal status |
| CASCADE NO FOLLOWER | Cascade - no follower | Normal status |
| CASCADE NO SENSOR | Cascade - no system sensor | Normal status |
| DHW | Temperature blocking - DHW demand | Normal status |
| FL | Low water flow | Menu / mode display |
| FLU | High flue pressure | High |
| FOU | Outdoor sensor fault | Low |
| GAS VALVE ON / RUN | Ignition then run status | Normal status |
| LOCKOUT | Lockout (display message) | Normal status |
| LOU | 24 volt supply low | Medium |
| MAINTENANCE REQUIRED | Service reminder | Normal status |
| PP | Control programmed | Normal status |
| PRO | Low water pressure | Medium |
| SERVICE PUMP CH / DH / SH | Pump service mode | Menu / mode display |
| SERVICE RUN | Test mode running | Menu / mode display |
| TT | Temperature blocking - thermostat (TT) demand | Normal status |
Models covered
EL-110 LPEL-110 NEL-150 LPEL-150 NEL-220 LPEL-220 NEL-299 LPEL-299 NEL-399 LPEL-399 NEL-80 LPEL-80 N
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.