Cycle Sensor Pump Monitor: General Information

The Cycle Sensor is a system monitor that detects Rapid Cycle and Dry Run and reacts to either of these conditions by shutting down the pump. It does not control or prevent rapid cycle or dry run but protects your pump in the event these problems occur. This sensor was designed for a pump that is controlled with a Pump Control Valve such as a Cycle Stop valve and/or is installed with enough pressure tanks to prevent a rapid cycle condition. The pump must also be supplied with enough fluid to prevent dry run which causes the undercurrent condition.

These units continuously display the load characteristics of the motor when it is running. When a fault is detected, the relay will shut off power to the pump and display RCYCL for Rapid Cycle or DRY for a Low Current condition. The unit can be reset by pressing the manual reset button or by shutting off power to the unit and then powering back on.

The "Rapid Cycle" feature of this relay monitors the duration of time the pump is on. If the pump "run time" is shorter than the Cycle Sensor minimum set time, the pump will be shut down before damage from cycling occurs. Length of acceptable minimum pump run time is adjustable and can be set for as little as 0 seconds to as much as 600 seconds. (Rapid cycling can be caused by water logged or improperly sized tanks, improper pressure switch settings, control malfunctions, broken check valves, and chattering contacts.)

This "Rapid Cycle" feature only allows for a manual reset. This means that when a rapid cycle is detected, the pump is turned off and it will remain off until the Cycle Sensor is manually reset. Undetected "short cycling" can lead to multiple problems such as submersible pumps unscrewing themselves from the drop pipe and falling into the well, water hammer, contact failure, stripped splines or couplings, broken pump or motor shafts, and ultimately system failure.

The "Dry Run" feature of the Cycle Sensor, unlike other similar relays that look for dry run conditions, can detect the minute differences between the low current achieved when the pump is restricted by a Cycle Stop Valve (or any other valve that restricts the pump to match a low flow demand), and the slightly lower current that occurs when the pump has actually run dry. (For example, if the inlet to the pump became clogged with debris and low current is not detected at this point, the pump and or motor could be destroyed from a lack of cooling flow. Low current can also be caused by cavitation and broken pump shafts or couplings). After a 10 second delay, the pump will be shut down before damage from running dry can occur.

This "Dry Run" feature allows for either a manual reset or a timed restart. The timed restart is adjustable from 0 minute to 300 minutes to allow low producing wells to recover before the pump automatically restarts. The manual reset option is designed to protect systems where the loss of the water supply would be out of the ordinary but a possibility.

Note: Standard overloads do not detect dry run or rapid cycle conditions until damage has occurred and some part of the electrical system has failed. The Cycle Sensor does not control or monitor overload conditions nor is it meant to replace standard overloads, which normally come in the motor or motor starter.

The cycle sensor works with 230V single phase pumps from 1/3HP to 2HP.


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