While the 304 SS probe is rugged

Universal Compatibility: Identical to the 21-238 and compatible with KMC CSC-1000

This is a passive

5kW heating elements

though you must ensure the secondary voltage remains at 24V

Functional Devices RIB2402D Relay While the 304 SS probeThe Functional Devices RIB2402D is a versatile DPDT enclosed relay designed for demanding HVACR control circuits and building automation systems. Built with a 24VAC DC coil and featuring a 208 277V 10A rating, this pilot device is engineered for switching multiple loads or isolating disparate control voltages. The RIB2402D power relay utilizes a NEMA 1 enclosure, facilitating a secure external mounting directly to electrical boxes via a 1 2 inch NPT