Float Switch wiring w/DPDT Relay

Thread Starter


Joined Nov 18, 2016
Ok here is my situation. I have a 12v Float Switch wired to my return pump. It goes through a DPDT relay. Pretty standard setup. The purpose of this is so that if the OVERFLOW ever stops working it will prevent my return pump from draining the sump onto the floor of my house. As it works right now when the water in the main aquarium starts to fill up to the point where the tank will overflow the switch breaks the circuit which shuts the pump off. Great, prefect.....but its not. As the water level drops in the tank it turns the pump back on. Then the water will fill and repeat the process. This is where I need to make the change. I want to add in a reset switch (momentary switch maybe) of some type that will HAVE to be reset/pushed to allow the 120v circuit to power up again. This way I come home and can see that something went wrong with the overflow and I can fix it before starting the whole thing up again. I don't want the tank to fill drain fill drain all day until I get home. Any thoughts or help is great. I can supply a wire diagram of how its currently hooked up if needed.

One thing I didn't mention. My experience with electronic circuits is limited, very. Think of a person who took at "Home Electronics 101" online and just passed with 50%...very basic understanding. I am just learning with this project I am on. Lots of forum lurking.

My understanding is this ( bare with me )

120v goes through DPDT relay, normally closed, powering the pump.
12v goes through float switch, which is normally open. When float switch activates it becomes normally closed activating the 12v relay coil which makes the 120v circuit normally open, shutting down the pump.
So, I somehow need to make it so that when the float switch becomes normally open again the 12v circuit stays normally closed preventing the 120v to become normally closed again. Is this the basic idea?

1. I have a momentary NO switch. Would this work in the circuit or would I need a momentary NC switch?

2. Would this switch be in parallel or series?

3. Do I have to either buy a latching relay, or can I just wire my existing DPDT relay to make it latch?

This is the part that I am having trouble figuring out.


Joined Nov 30, 2010
First, That word, "normally" defines the condition when no power is applied. Switches and relays do not become "normally" the other kind of switch when they get activated. Sprinkling that word all over the place makes this hard to read.

So...it's push the button, the tank fills, when it's full it won't start until you push the button...right?


Joined Jun 22, 2012
Sounds like you need the relay to have two sets of contacts, one set powers the pump, the other shorts out the float switch when full, so you just need to have a normally closed push switch in series with the extra relay contacts to act as a reset button.

Like this...


Can you provide a diagram of how its wired, you will get better results.