Lennox Furnace Error Code E 110

E 110 means the furnace control board has detected that the incoming electrical line voltage is lower than the level shown on the unit's nameplate rating. This is a supply-side electrical issue, not an internal furnace failure. The furnace triggers this fault to prevent damage from operating under low-voltage conditions. The alarm will clear on its own approximately 5 seconds after the voltage returns to an acceptable level.

A manual reset alone will not permanently resolve E 110 if the underlying low-voltage condition still exists. The fault is designed to clear itself approximately 5 seconds after the line voltage recovers to an acceptable level. If voltage remains low, the error will return even after a reset.

Cost depends entirely on the root cause. If the issue is simply loose connections, an electrician visit may cost anywhere from $75 to $200. If wiring needs to be replaced or upgraded, costs can range from $150 to $600 or more depending on the length and complexity of the run. If the utility supply is the source of the problem, contacting your utility provider is typically free. No furnace parts are usually required to resolve this error.

Start by measuring the actual line voltage at the furnace with a multimeter and comparing it to the nameplate rating. If voltage is low, check for loose connections at the breaker panel, disconnect switch, and any junction boxes in the circuit. If wiring or the utility supply is the cause, you may need an electrician or your utility provider to resolve the issue. Once voltage is corrected, the fault clears automatically within 5 seconds.

Low line voltage can cause stress on electrical components and motors over time, and the furnace may not operate reliably or efficiently under these conditions. The control board triggers E 110 specifically to prevent the unit from running under potentially damaging voltage levels. While it is not an immediate safety emergency in most cases, persistent low voltage should be investigated and corrected promptly to avoid longer-term component damage.