Heater displays E18; may indicate internal memory or configuration fault.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Corrupted control firmware, Power surge damage, Incorrect configuration settings

Safety: Disconnect power before handling the control board.

Steps:

Power reset: Turn off power for several minutes, then restore to see if the error clears.
Check dip switches/jumpers: Verify that any configuration switches on the control board match the heater model and gas type per the installation manual.
Surge protection: If you experienced a recent storm or power event, consider adding surge protection to the heater circuit.

EEPROM or firmware faults typically require control board replacement by a Lochinvar-authorized technician.

Professional Required 5/5

Main Control Board

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