Auto-Topoff System

[55G NewB]

I posted this over on that other reef board, and thought I would post it here also for anyone who may benefit:

Here is a simple diagram using two relays that will automatically top-off your display, and shut down when your RO/DI is low to prevent burning out the pump. Here is a quick explanation of the system operation: - First note that all relay diagrams normally show the contacts in the de-energized position - This is important to understand how this works - The diagram shows the system with both float switches up (each tank has plenty of water) - As the level in the main tank falls, the float switch for the relay on the left side makes contact energizing the relay coil. This causes the contacts to switch position (picking up contacts 3 & 6 and dropping out contacts 1 & 2). - As long as there is sufficient water in the RO/DI supply tank, the right hand relay stays de-energized and the contacts are as shown. This completes the current path and the pump turns-on. - If water level in the RO/DI supply falls so that the float switch closes, the right side relay will energize, opening the supply to the pump. This will prevent burning out the pump when there is no water in the supply tank. - When the water level in the display rises sufficiently, the float switch opens, the left relay de-energizes and the system is back to a static condition. A couple of things to keep in mind: - You need to make sure that the contacts for your relay can handle the current your pump is trying to draw. - Any electrical connections that may be exposed to water/moisture needs to be properly sealed. - Ensure that your DC power supply is the proper voltage and can handle the current from both relays continuously. - Ensure that your float switches are open when the water level is high (if you can not find this type of float, then you should be able to just switch the wiring on both relay contacts (left side connected to 3 & 4 instead of 1 & 2, and vice-versa for the right relay - I think this would work - I haven't thought it out). If anyone has any questions, please feel free to PM me. Forgot to mention that the relay's are available at Radio Shack for < $5 each. You want a relay that uses 12 VDC across the coil, and can handle 120 VAC through the contacts. Just make sure that the contacts are rated for whatever your pump is trying to draw.

[Geoff]

thanks.

G~