Patent ID: 7020543

Claim:
A controller for controlling a fuel fired heating appliance, the controller comprising: a microprocessor for controlling the operation of the appliance, the microprocessor being capable of detecting an interruption in power and responsively storing diagnostic information in a non-volatile memory such that the microprocessor is able to retrieve the stored diagnostic information upon restoration of power; a low voltage power supply in connection with a power source for the appliance, the low voltage power supply being in connection with the microprocessor; a fuse in connection with the power source for the appliance, wherein the fuse is connected in parallel with the low voltage power supply such that the appliance is connected to the power source though the fuse but the low voltage power supply and microprocessor are not connected to the power supply through the fuse; and wherein the microprocessor is connected across the fuse in a manner such that an open fuse state does not interrupt power to the microprocessor, and the microprocessor is capable of detecting the open fuse state.