Lennox heat-pump — XP17 heat pumps with iComfort communicating controls Error Codes Directory
Complete diagnostic reference for Lennox heat-pump — XP17 heat pumps with iComfort communicating controls fault codes. Each code includes official root causes, safety precautions, and affected replacement components.
Lennox XP17 iComfort Critical Alert 411
For the Lennox XP17, Critical Alert 411 records repeated low-pressure-switch events that reached a lockout threshold. It does not prove low refrigerant charge: airflow, outdoor conditions, restriction, switch or wiring faults, and the refrigerant circuit all require operating measurements. Applies to: XP17 heat pumps with iComfort communicating controls This meaning follows the XP17 installation and service procedure cited here. Lennox alert numbers depend on the communicating equipment and control generation, so confirm the outdoor model and alert text together. Owner-safe checks: Save the complete iComfort alert history, operating mode, filter condition, weather, visible outdoor clearance, and recent service without opening equipment. Qualified technician: Pressure-switch, wiring, refrigerant, airflow commissioning, control-log, and live electrical diagnosis require a Lennox-qualified technician.
Lennox XP17 alerts 418 and 419: a W input fault or a miswire
Alert 418 is raised when the heat pump control sees the W output active while a compressor demand is running, which the installation manual describes as a W input fault or a miswire. Five occurrences within a single demand escalate it to a hardware fault lockout and alert 419. Applies to: XP17 heat pumps with iComfort communicating controls These alert numbers and the strike behaviour come from the Lennox XP17 installation and service procedure for the models listed. Lennox uses the same numbering family across several iComfort products, and the sequence a given alert follows belongs to the equipment it was published for. Owner-safe checks: Record the alert number, whether it was 418 or 419, and whether the system was still heating when it appeared. | Note any thermostat replacement, system conversion, or wiring work carried out before the alert started. | Note whether the property has a backup or auxiliary heat source and how it is meant to be controlled. Qualified technician: Low voltage wiring, thermostat configuration, and the field test pins are all inside equipment covers and belong to a qualified technician. | Ask for the wiring and the thermostat configuration to be verified before any part is quoted, since the manual attributes this alert to an input fault or a miswire.