Lennox Furnace Error Code E313

E313 indicates that the Lennox communicating system has detected a capacity mismatch between the indoor unit and the outdoor unit. This is a warning code, not a lockout fault, meaning the system will continue to operate. It typically points to a configuration issue or an incompatible pairing between components. Checking the installation configuration and the capacity ratings of both units is the recommended starting point.

E313 is not a safety-related fault. It does not indicate a gas, electrical, or combustion issue. However, operating with mismatched capacity units over time can affect system efficiency and may lead to premature component wear, so it is worth resolving even if the system appears to be running fine.

If the issue is purely a configuration error from installation, the cost is typically limited to a service call fee, which generally ranges from $75 to $150 depending on your location. If the mismatch is due to an incorrectly installed replacement unit and a new component is required to achieve a proper match, costs can range significantly higher depending on the equipment involved. Getting a diagnosis from a qualified technician will clarify whether any parts are actually needed.

Yes, E313 is classified as a warning and not a system fault, so your furnace and connected system will continue to operate normally. The code is flagging a potential configuration concern for the technician to investigate, but it does not disable heating or cooling functions.

Simply resetting the furnace will likely not permanently clear E313 if the underlying configuration or capacity mismatch has not been corrected. The code will typically return after a reset if the system still detects incompatible unit pairing. The proper fix involves correcting the system configuration or ensuring matched unit capacities.