I recently had a customer call into our Technical Support team with a unique problem, hoping we could help him devise a solution. After he explained his needs, I was confident that some configuration of our products would solve his problem.
Problem: 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.
Solution: 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.
As always, if you plan to use our products in your installation, make sure our device ratings meet the specifications required.
We’re here to help! Please give us a call or send us an email if you have any questions.