Sequencers

Sequencers are one of several relay-type switches. Generally (but not always) a lower voltage activates one or more higher-voltage switches. The switch is activated with a delay and possibly multiple delays. For example, a thermostat calling for heat will send 24V to the sequencer which then closes one or more 240V switches to start the heating elements. If all the elements started at once, the surge would probably blow breakers; therefore, a sequencer is employed to start the elements in stages. Contactors and relays are similiar to sequencers. Contactors are generally more heavy-duty and do not incorporate a delay.