The Wilkerson Instruments DR1920 duplex lift station back-up pump controller is a compact DIN rail mounted unit used to monitor a backup level alarm in a tank or wet well and start up to two pumps when a high alarm switch closes. The DR1920 is used as a backup to normal tank and well level controls and is wired to the High-High Alarm switch to prevent overflows in situations where the primary level control system fails.

When the level switch in the tank or well closes, Wilkerson Instruments DR1920 duplex lift stations back-up pump controller closes a relay that starts Pump 1 and starts an internal Timer 1. When Timer 1 reaches its set time, and the level alarm switch is still closed, Pump 2 is started. Pump 1 and Pump 2 will run until the level alarm switch opens. When the level switch contact opens, Timer 2 is started and both pumps continue to run until Timer 2 reaches its set time.

If the alarm switch opens during the Timer 1 interval, Timer 2 is started when the switch opens. Pump 2 is not started and Pump 1 will run until Timer 2 reaches its set time. The DR1920 also has provisions to alarm on a switch opening.

Alarm Switch Monitor: The Wilkerson Instruments DR1920 monitors the open or closed status of a switch contact that is already wired into a control system. This switch may have any of several voltages that are used to control the pump system. In addition, if the primary control system fails, the normal voltages may not be present.