Navien furnace frequently trips the household breaker

Safety: This involves line voltage. If you are not comfortable working with electricity, contact a qualified technician. Always turn off the breaker before inspection.

• Inspect wiring: Look for obvious signs of damage, such as melted insulation, burn marks, or pinched wires inside the furnace cabinet.
• Isolate components: Disconnect the circulator pump and attempt to power the unit. If the breaker no longer trips, the pump is likely shorted and should be replaced. Repeat with the fan motor if necessary.
• Check for water intrusion: Water leaks onto electrical components can cause shorts. Repair any leaks and dry components thoroughly.
• PCB evaluation: If all loads test good but the breaker still trips when the PCB is connected, the board may be internally shorted and require replacement.