Overload relays are intended to protect motors, controllers, and branch-circuit conductors against excessive heating due to prolonged motor over currents up to and including locked rotor currents. Protection of the motor and the other branch circuit components from higher currents, due to short circuits or grounds, is a function of the branch circuit fuses, circuit breakers, or motor short circuit protectors. The exclusive one piece melting alloy thermal unit is used in these relays to provide protection against overheating of the motor winding insulation due excessive over current. The melting alloy thermal unit to be used is determined by the full load current of the motor to be controlled, number of phases and the enclosure size. This 27A replacement overload relay is for a Type S NEMA size 00 three phase starters with 3 poles. This replacement overload relay can also be used on Type S NEMA size 0 or 1 three phase starters with 3 to 5 poles. When 3 thermal units are properly installed the relay can be reset. Overload relay has a trip free reset mechanism. Relay has a maximum voltage rating of 600 VAC. This overload relay is 4.00 inches tall, 3.50 inches wide and 3.97 inches deep.