I recently had a customer call into our Technical Support team with a unique fountain pump application problem. After he explained his needs, I was confident that a configuration of our products would solve his issue.
Fountains use pumps to pull water and shoot it up into the air. If the water level gets too low, the pump might not have any water to pull and will start to "run dry". This can damage the pump severely. To protect against this, fountains typically come with a float switch, which monitors the level of the water and will switch the pump off if the water level gets too low.
The customer in this case was working with a parks department which had several old fountains. These fountains were equipped with float switches. However, the department had noticed that on windy days, the water would sometimes get so choppy that the float switch would misread the level and start turning the pump on and off repeatedly. Short cycling a pump in this matter can cause almost as much damage to the pump as running dry. To prevent this, the customer wanted a system in which the float switch could turn the pump off, but not automatically restart it. Instead, it would just give an indication to alert the park maintenance department.
One possible solution involves using the Original Relay in a Box® (RIBU1C), a general purpose latching logic circuit (RIBMNLB-1), a stepdown transformer (TR20VA001), and a prepackaged switch (SIB05S). Fig. 1 is a wiring diagram for this solution.
When the system is running normally, the RIBU1C has power to its coil, keeping its Normally Open (N/O) contact closed. This holds closed the Latch/Fault Input of the RIBMNLB-1, which is powered through a 120 - 24 VAC stepdown transformer (TR20VA001). When the RIBMNLB-1 is powered and the Latch/Fault Input is closed, the on-board DPDT relay is energized. This allows power through one N/O contact to the pump and removes power through one Normally Closed (N/C) contact to the indicator light.
When the water level falls below the threshold for the float, it breaks power to the coil of the RIBU1C and its N/O contact opens. This opens the Latch/Fault Input to the RIBMNLB-1, which de-energizes its relay. The N/O contact feeding the pump opens, and the N/C contact feeding the light closes. Now the pump is locked out until the system is RESET. This can be accomplished by either pressing the RESET pushbutton on the RIBMNLB-1 or by breaking and making power to its input, which the SIB05S can do.
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Functional Devices, Inc., located in the United States of America, has been designing and manufacturing quality electronic devices since 1969. Our mission is to enhance lives in buildings and beyond. We do so by designing and manufacturing reliable, high-quality products for the building automation industry. Our suite of product offerings include RIB relays, current sensors, power controls, power supplies, transformers, lighting controls, and more.
We test 100% of our products, which leads to less than 1 out of every 16,000 products experiencing a failure in the field.
Simply put, we provide users of our various products confidence and peace of mind in every box.