Siemens Potentiometer ASZ12.833

This Siemens potentiometer, model ASZ12.833, converts the mechanical position of a burner actuator into a variable electrical resistance. The burner control reads this resistance to determine the actual position of a gas valve, air damper, or fan-speed mechanism. In a modulating burner, the control compares this feedback with the demanded firing rate and adjusts fuel and air delivery. This item is a spare part for burner and boiler control systems.

Potentiometers of this type are selected by matching total resistance, mechanical travel (rotational or linear range), and electrical connection configuration to the existing component. Mounting dimensions, shaft shape, and connector type must also correspond to the actuator or valve linkage. Compare the code marked on the old part with the replacement before ordering. During installation, confirm that the resistance track is not worn and the wiper contacts are clean.

Wear of the resistance track or dirty wiper contacts can alter the position signal received by the burner control. The control may then read an incorrect actuator position, causing unstable modulation or a safety lockout. If the potentiometer is used for manual setpoint adjustment, the knob scale can drift away from the intended control range. Check the resistance track and wiper contacts before suspecting the control.