TF140DU Thermal Overload Relays The TF140DU thermal overload relays are protection devices for the main circuit used mainly to protect motors in the event of overload or phase failure. These devices have trip class 10A. Manual or automatic reset selectable Phase loss sensitive Two electrically isolated auxiliary contacts – 1 N.O. + 1 N.C. TEST and STOP function – Trip indication on the front Temperature compensation Suitable for three- and single-phase applications