Siemens / Furnas E57 Heater rated at 15.1 AMPS for Class 16AF, 16BF AND 16CF Furnas DP starters. This is for one pole, E Heater is standard trip, Class 20, with green reset for Class 48 overloads. 3 heaters must be purchased to satisfy the requirement for 3 phase protection in all 3 phase starters. The class 20 trip offers tripping in 20 seconds or less in an over current state and prevents nuisance tripping that often occurs in class 10 trips.
Click here to view a PDF file for this Furnas Class 16 Starter E heaters
To determine the trip current rating, which is the value at which the minimum current to trip an overload relay, you would multiply 1.25 times the minimum full load current shown for the thermal unit selection. For example, to calculate the thermal units needed for a magnetic starter that has a service factor of 1.25 and a full load current of 26 AMPS, you would multiply 26 times 1.25 and that would result in a trip current rating of 32.5 AMPS.