This display indicates that the line voltage fre-quency is out of range. This could happen if the boiler is being powered from a small gasoline powered generator that is not functioning cor-rectly or overloaded.
Inspect power wiring to boiler and repair as necessary. If connected to line voltage, notify the power company. If connected to an alternate power source such as generator or inverter, make sure the line voltage frequency supplied by the device is 60 Hz.
