What it is
The ABB 1SAZ421201R1001 is a thermal overload heater element, the calibrated resistive pack that drops into the matching ABB contactor base to give a motor-starter assembly its overload trip curve. It belongs to the Thermal Overload Heaters for Starters class within Contactors and Starters, and the broader Circuit Breakers, Fuses & Protection grouping, which is where these elements have always been specified and stocked. The heater is the current-sensing stage only; the contactor and the enclosure provide the switching and the IP rating. Specifying the right heater is what aligns the trip band with the motor's full-load current — the rest of the starter is downstream of that choice.
Where the heater class fits
Thermal overload heaters for starters are used to give direct-on-line motor starters an inverse-time trip characteristic calibrated to the motor's full-load amps, so a stalled or mechanically jammed motor opens the contactor before windings overheat.
Sourcing posture
No lifecycle status is logged for the 1SAZ421201R1001; place it on RFQ against the BOM and confirm availability per the channel response for the line's consumption.