HP LaserJet Enterprise M552 - Fuser heater protection; Fuser unit life detection; Fuser identification

Fuser heater protection
Fuser heater protection is a feature that detects excessive temperatures in the fuser and interrupts the power
supply to the fuser heater.
The following three protective components prevent the fuser heater from excessive rising temperature:
●
DC controller: When a thermistor or sub-thermistor detects a temperature above a certain threshold,
the DC controller interrupts power to the specic heater.
●
Fuser-heater safety circuit: The fuser heater safety circuit monitors the detected temperature of the
sub-thermistors.
●
Thermoswitch: If the temperature in the heaters is abnormally high, and the temperature in the
thermoswitch exceeds a specied value, the contact to the thermoswitch breaks.
Fuser unit life detection
The fuser life is tracked by fuser rotations, and not by the number of pages printed. This is a more accurate
tracking method since the fuser rotates for every print job. There will be variations in fuser life depending on
customer usage. Customers who are running one- and two-page intermittent jobs with long pauses between
each job might reach the fuser low message sooner due to the fuser rotating more times per page than it
would for larger print jobs.
Fuser identication
The printer detects the type and presence of the fuser. The DC controller noties the formatter when it fails to
detect the type or presence of the fuser.
NOTE: This printer detects if a fuser of the correct voltage for the printer is installed. If a fuser of the
incorrect voltage is installed, the DC controller noties the formatter and an error message is displayed on the
control panel.
26 Chapter 1 Theory of operation ENWW