terminals. The two push-ons connect one end of the run winding and one end of the start winding to the overload. The overload, in turn, is connected to one side of the power supply. The other side of the run winding is connected to the other side of the power supply at L 2 . Connections to the run winding are now complete because it is connected from one side of the power supply to the other (parallel). Connections for the start winding must include a centrifugal switch to disconnect the winding after start-up. The terminal board contains the electrical switch, which must be connected in series with one side of the start winding and power supply (at L1). Connections are performed at the factory. Terminal board design and connections vary from one manufacturer to another, but the principles remain the same. Contacts on a centrifugal switch are normally closed (NC) when the motor is off (not running). A pair of spring-loaded weights and a connecting linkage are attached to the rotor shaft on the inside of the motor. When the motor starts and achieves 75% of operating speed, centrifugal force causes the weights to swing outward. The move- ment of the weights, transmitted by the linkage, opens the switch, which disconnects the start winding from the circuit. When the motor stops rotating, springs pull the weights back to their normal position and the switch closes, ready for the next start-up. See Figure 25‑20. Reversing Rotation. Most manufacturers bring both wires from the start winding to the accessible part of the terminal board. The wires are different colors (identification is on the cover plate). Motor rotation is reversed by switching (reversing) the two terminal board connections. Switching the connec- tions reverses current flow through the start winding, and the rotor follows the direction of current flow. Hermetic Split-Phase Motor Electrical connections to split-phase motors in hermetic compressors are made in the same way as open-type motors. The factory makes the necessary motor connections internally to three insulated terminals extending through the hermetic shell. The three terminals are: common (one end of each winding), start (other end of start winding), and run (other end of run winding). Because arcing occurs as the contacts open or close, the switch for disconnecting the start winding is located outside motor windings to the terminal board with quick- connect (push-on) connectors. The technician must connect the power supply voltage to the correct terminals on the board. Power supply terminals are typically the threaded-bolt-and-nut-type and labeled L1 and L2. See Figure 25‑19. One power supply wire (L1) is connected to Terminal 1. Terminal 1 of the overload is connected at the factory to L1. Terminal 3 of the overload is factory-connected to a pair of push-on-type Goodheart-Willcox Publisher Figure 25‑18. On open-type motors, the terminal board is located at the lead end. Bolt-and-nut-type connections for the power supply wires are most common. Terminal board Centrifugal switch Push-on connectors Run winding Start winding Overload Bolt and nut connector L1 L2 Goodheart-Willcox Publisher Figure 25‑19. Factory and field connections to the terminal board of an open-type motor. The factory con- nections are made with push-on connectors (the dashed lines represent connections made behind the terminal board). 496 Heating and Cooling Essentials Copyright Goodheart-Willcox Co., Inc.