Removed check valve from bilge pump- now it won't stop running

[RaymondR]

Originally Posted by Panacea2183

Had the same problem constant cycling of pump
Install a high and low float switch with a relay
Additional advantage of taking “load” off of the float switch which fail often
My pump is in a sump which only hold about 3 cups of water. Rest of bilge is alway bone dry.
Attachment 237672

Will not work because the lower switch will turn on the pump and only stay on until the water pumps down enough to switch off the lower switch. Then the water will drain back and switch the the pump on and it will cycle as it does now.

You need a latching circuit which requires a second set of contacts which keeps the solenoid current flowing until the lower switch opens breaking the solenoid circuit.

[Marqus]

Originally Posted by RaymondR

Will not work because the lower switch will turn on the pump ....<snip>.

I'm with John's reply her - only the upper float switch can turn the pump on.

The setup achieves what an intelligent float switch (like Water Witch) does by using an electronic delay. Instead of electronic smarts, the setup achieves it by using extra components - two floats and a relay arranged to serve as one "smart" float switch.

That said, it does not negate your explanation above of how a more explicit latching design can deliver the same outcome.

[cal40john]

Originally Posted by RaymondR

Will not work because the lower switch will turn on the pump and only stay on until the water pumps down enough to switch off the lower switch. Then the water will drain back and switch the the pump on and it will cycle as it does now.

You need a latching circuit which requires a second set of contacts which keeps the solenoid current flowing until the lower switch opens breaking the solenoid circuit.

I did the same thing. I wrote an entire post on how it didn't work. I then remembered our lab had two different systems, a waste tank and a rabbit that used a circuit where a second switch that was powered by the closed relay kept the relay coil energized once the first momentary switch was pressed. I then looked at the diagram in this thread more carefully and deleted my post.

[RaymondR]

Originally Posted by Panacea2183

Had the same problem constant cycling of pump
Install a high and low float switch with a relay
Additional advantage of taking “load” off of the float switch which fail often
My pump is in a sump which only hold about 3 cups of water. Rest of bilge is alway bone dry.
Attachment 237672

The upper float switch and the lower float switch are wired in parallel, either one will turn the relay on but since most bilges fill from the bottom up the lower will switch on first. There is no latching circuit in this circuit drawing to hold the relay on when the water level lowers and the float switch turns off.

[EngNate]

Here is a solution for flowback in small, deep bilges. Two float switches, a relay and a diode are wired so that the pump is turned on by the high switch and turned off by the low switch. Then you can make the differential as much as needed to accommodate the flowback. The relay is a standard automotive "Bosch"-type, available at auto parts stores, the terminals are numbered as shown below. You may have to look around for a local supplier of a diode. Just about any kind will do, common part #s - In4000, IN5400. Wire as below:



There may be a simpler solution. Ultra Pumpswitches did sell one of their models in a high differential version that solved this issue in most cases. I didn't find it on the site but maybe they still do. These are the best float switches you can get.

I only just looked at the above posts... This works and is simple, a standard setup for basic tank level control.

[RaymondR]

Originally Posted by EngNate

Here is a solution for flowback in small, deep bilges. Two float switches, a relay and a diode are wired so that the pump is turned on by the high switch and turned off by the low switch. Then you can make the differential as much as needed to accommodate the flowback. The relay is a standard automotive "Bosch"-type, available at auto parts stores, the terminals are numbered as shown below. You may have to look around for a local supplier of a diode. Just about any kind will do, common part #s - In4000, IN5400. Wire as below:

Attachment 237731

There may be a simpler solution. Ultra Pumpswitches did sell one of their models in a high differential version that solved this issue in most cases. I didn't find it on the site but maybe they still do. These are the best float switches you can get.

I only just looked at the above posts... This works and is simple, a standard setup for basic tank level control.

For reasons previously explained one cannot do what is claimed with a common relay such as those sold for auto use. Either a double pole relay with the second set of contacts used to implement a latch on circuit with the lower float switch opening and thereby removing continuity of the holding circuit to turn the relay off or a dedicated holding relay which has two separate solenoid inputs one to toggle on and the second to toggle off.

[Uncle Bob]

Originally Posted by Panacea2183

Had the same problem constant cycling of pump
Install a high and low float switch with a relay
Additional advantage of taking “load” off of the float switch which fail often
My pump is in a sump which only hold about 3 cups of water. Rest of bilge is alway bone dry.
Attachment 237672

Originally Posted by RaymondR

Will not work because the lower switch will turn on the pump and only stay on until the water pumps down enough to switch off the lower switch. Then the water will drain back and switch the the pump on and it will cycle as it does now.

You need a latching circuit which requires a second set of contacts which keeps the solenoid current flowing until the lower switch opens breaking the solenoid circuit.

Raymond, the lower float switch does not turn on the pump, its power is drawn from the relay after the upper float switch turns on powering the pump and lower switch. It's function is to keep the pump running until it lowers and switches off the power, effectively latching on the power until no longer needed.

[Cadence]

I'm not sure how the high and low switch are going to do anything for the water flowing back out of the discharge hose and triggering a cycle. Best solution might be shortening the length of the discharge hose. A valve or a loop with antisiphon might be next. How about a dry bilge or two pumps one pumping to a reservoir, not having enough lift hose to cause cycling and a second doing the same from the reservoir, shower sump might work you're going to be pumping from there over board any way. a little far out but would work.

[RaymondR]

Originally Posted by Uncle Bob

Raymond, the lower float switch does not turn on the pump, its power is drawn from the relay after the upper float switch turns on powering the pump and lower switch. It's function is to keep the pump running until it lowers and switches off the power, effectively latching on the power until no longer needed.

The circuit illustrated shows how to make the requisite latching relay using a double pole relay.

The lower float switch is the one labeled "Push to Break". The rising water will turn it on giving current supply to the B terminal of the relay however since the B terminal will not switch until the relay activates the pump will not start.

The upper float switch will close when the water level gets high enough and supply current to the relay solenoid coil which will then close both the A/B switch and the B/C switch which controls the current to the pump.

The pump is now running and will draw the water level down until the "Push to Make" float switch opens however the pump will keep running because the A/B and "Push to Break" switches are still supplying current to the solenoid.

However when the level drops below the "Push to Break" float switch it will open removing current from the latching circuit and allow the relay to open thereby removing current from both the pump, via the opening of the B/C terminals, and, the latching circuit, via the opening of the A/B terminals.

Functionally there are three circuits involved:

The B/C switch in the relay, the battery and the pump and interconnecting wiring constitute the pump drive circuit.

The A/B switch in the relay, lower "Push to Break" switch in the lower float, the battery and interconnecting wiring constitute the relay latching circuit.

And the Upper "Push to Make" switch in the upper float, battery and interconnecting wiring the switching circuit.

[cal40john]

Originally Posted by RaymondR

The circuit illustrated shows how to make the requisite latching relay using a double pole relay.

The lower float switch is the one labeled "Push to Break". The rising water will turn it on giving current supply to the B terminal of the relay however since the B terminal will not switch until the relay activates the pump will not start.

The upper float switch will close when the water level gets high enough and supply current to the relay solenoid coil which will then close both the A/B switch and the B/C switch which controls the current to the pump.

The pump is now running and will draw the water level down until the "Push to Make" float switch opens however the pump will keep running because the A/B and "Push to Break" switches are still supplying current to the solenoid.

However when the level drops below the "Push to Break" float switch it will open removing current from the latching circuit and allow the relay to open thereby removing current from both the pump, via the opening of the B/C terminals, and, the latching circuit, via the opening of the A/B terminals.

Functionally there are three circuits involved:

The B/C switch in the relay, the battery and the pump and interconnecting wiring constitute the pump drive circuit.

The A/B switch in the relay, lower "Push to Break" switch in the lower float, the battery and interconnecting wiring constitute the relay latching circuit.

And the Upper "Push to Make" switch in the upper float, battery and interconnecting wiring the switching circuit.

Do you mean the B/D switch powers the pump? Yes your diagram will work.

The other diagram works as well. The pump and the relay coil can be powered by the same switch, there is no need for the second pole.

The relay switch and the high switch both are connected to 12 volts.
When the low switch closes on rising water nothing happens.
When the high switch closes the coil is energized.
There is now 12 volts on both sides of the relay switch.
The pump is now running and the water is lowering.
Since the low switch is closed there is 12 volts on both sides of that switch.
When the high switch opens there is still 12 volts to the coil from the low switch.
So the relay switch remains closed. The pump is still on.
The current through the relay switch is powering the pump and the coil.
When the low switch opens, the coil no longer has 12 volts, the relay switch opens, and the pump stops.

Instead of denying it works, work through the circuit and present the specific flaw as to why it doesn't!

[RaymondR]

The circuit I have been commenting on is that illustrated in post 29 which wont work because there's no latching mechanism and whilst that in post 50 might I would class it as potentially unreliable.

The voltage across DC motors does all sorts of things at start up and with varying load and dropping the voltage across the solenoid to say 6 volts plus the addition of the forward voltage drop of the diode may cause it to drop out. It's a suck it and see situation, might or might not work and be reliable or unreliable depending on a number of factors.

[Uncle Bob]

Originally Posted by RaymondR

The circuit I have been commenting on is that illustrated in post 29 which wont work because there's no latching mechanism and whilst that in post 50 might I would class it as potentially unreliable.

The voltage across DC motors does all sorts of things at start up and with varying load and dropping the voltage across the solenoid to say 6 volts plus the addition of the forward voltage drop of the diode may cause it to drop out. It's a suck it and see situation, might or might not work and be reliable or unreliable depending on a number of factors.

Raymond, the circuit that you insist wont work does in fact work, I have tried it long ago, the lower float switch does nothing until the upper switch is activated which provide power to the lower switch to keep the relay latched closed until the lower switch opens eliminating the power to the relay.
Take a deep breath and look at the circuit with an open mind and I am sure that you will see the light.