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  Johnson Ultima Switch for Sump Pump Control

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Author Topic:   Johnson Ultima Switch for Sump Pump Control
jimh posted 06-29-2008 08:47 PM ET (US)   Profile for jimh   Send Email to jimh  
The Johnson Ultima Switch device was brought up in the context of another discussion on float switches for controlling a sump or bilge pump. Questions about this device can be answered by consulting the manufacturer's literature and website:

http://www.johnson-pump.com/JPMarine/products/bilge/ultimaswitch.html

The Johnson Ultima Switch is remarkable in that it consists of two detectors. An ON-detector is positioned about 2-inches above the base of the unit. When water in the sump reaches that level the switch activates the pump it is controlling. An OFF-detector is position about 0.75-inch above the base of the unit. When the water drops below that level the switch deactivates the pump it is controlling. This hysteresis or dead-band in the control system prevents the pump system from going into rapid oscillation of cycling on and off. In addition, there is a three-second time ON-delay to further avoid false starts.

The sensor is electrical in nature so it consumes some electrical current all the time to operate the detectors, but the current drawn is rated at a miniscule 16-microAmperes. If attached to a 40-A-hour battery, it would take over a two million hours to discharge the battery. That's over 100 years, so for all practical purposes you can consider that the device does not drain the battery.

The Johnson Ultima Switch has only two leads, which are used both to power the device and to control the attached pump. The device is wired into the positive lead supplying the pump.

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