Keeping a consistent hydraulic head in a drainage pipe

[boredat20]

Hey everyone,

I've got a problem here and I'm looking for a simple solution.

Basically, I need to keep a consistent hydraulic head between two points of a vertical drainage pipe. I have a sump pump and two electronic float valves (that I purchased separately). What I want to do is wire the two float valves such that one is above the pump, and one is right at the base of the pump. Basically, I want the whole system to work as such: when the water level in the drainage pipe reaches the upper sensor, I want the whole pump assembly to turn on, and when the water level reaches the lower sensor, the pump should turn off. Essentially, water activating the top sensor should turn the whole thing ON, but not turn it off when the water level drops below that point. Same thing with the bottom sensor, except it should turn everything OFF.

This would obviously have to use some sort of electronic switch that may or may not exist.

Now, to me this seems like such a simple problem to solve, I just can not for the life of me figure out an effective way to do so. I am currently testing another method to do this that involves much more time and effort, but gets the job done (albeit not that well).

I'm not an engineer by trade, but am more than handy when it comes to stuff like this.

Any help would be much appreciated!

Thanks

 

[boredat20]

Sorry, I re-read my question and realized it sounds a bit confusing. Heres a simpler version.

I have a water pump connected to two water sensors. I want the pump to turn on only when both sensors are activated (immersed in water), and turn off only when both sensors are not activated (so not immersed in water).

Any clever solutions would be appreciated!

 

[EgadsNo]

Quick question- is your problem that the pump is turning off, water rushes back and the pump goes back on and you plan on using the higher sensor as a on delay function?

Odds are the cheaper and easier solution is a check valve (one way valve) located close to the output of the pump that will prevent back flow.

 

[boredat20]

Quick question- is your problem that the pump is turning off, water rushes back and the pump goes back on and you plan on using the higher sensor as a on delay function?

Odds are the cheaper and easier solution is a check valve (one way valve) located close to the output of the pump that will prevent back flow.

That is exactly the problem! Unfortunately, the whole thing is outside and exposed to the elements so a check valve will solve the water rushing back problem, but standing water in a pvc pipe + sub zero temperatures = not good!

 

[EgadsNo]

Hmm, are you at all familiar with relays?

 

[EgadsNo]

I can make you up a schematic using two SPST relays (single pole single throw) , you can use two DPDT but you need two coils for this, at least best i can think of at the moment hehe. If you are familiar with relays the schematic should be enough- if not I can explain to you the operation principle of the schematic and relays.

 

[boredat20]

Wow! I was literally just considering relays. I haven't used them before, but the concept seems simple enough.

I was thinking it would go something like this: the top sensor controls a relay that when activated, switches to a circuit loop that includes only the bottom sensor. The bottom sensor would be reversed (water immersion=OFF). When the water level drops and the bottom sensor switches ON, it controls another relay that switches back to the original loop (the one with the top sensor only).

Does this sound right or am I completely misinformed in my understanding of relays?

A schematic and a quick explanation would be great if it's not too much trouble. I'm currently reading up on relays, so hopefully I won't be too lost. Thanks a lot!

 

[EgadsNo]

http://picasaweb.google.com/lh/photo/0MErmYkIztMNeTkesT2N0N2_0MvXy9JeVCfdQTOfeN0?feat=directlink

:: edit :: ***SLEEP DEPRIVATION IS DANGEROUS, schematic is incorrect lol- but a working one has been added***

 

[boredat20]

http://picasaweb.google.com/lh/photo/0MErmYkIztMNeTkesT2N0N2_0MvXy9JeVCfdQTOfeN0?feat=directlink

Heh, I think I might need that explanation after all

 

[EgadsNo]

Meh I will explain anyway incase others do not. Ok I should have labeled the relays different, but no matter...

Float one is the upper float switch, the power feeding the common will only pass the switch once the high level of water is reached. Once this happens power will goto the sump pump, it will also pull in the right relay coil, which will send power from the relay common out to continue to run the motor after Float 1 drops.

Float 2 at this time is not sending power because it active, once the water is below float 2, power will be sent to the left relay, this will cut off the power feeding the right relay coil and the motor will shut off.

While the motor is shut off- the left relay will be consuming power, luckily the relay is really only consuming a dozen or two watts.

Also I should note all the wires on left side are the Hot common, on the right side of the motor is the neutral

::edit:: *** this description matches the updated newer wiring diagram added but does NOT match the old one***

 

[EgadsNo]

You can also feed this circuit using a lightswitch, providing your sump pump draws less current then the switch is rated for. So you can turn off the left relay when you know water is not going to be an issue

 

[EgadsNo]

And if you have any questions do not hesitate, I pulled an all nighter and went to work today so my schematic could possibly be a little confusing looking particularly to someone who is not used to looking at them.

 

[boredat20]

Thanks so much! I do have a few questions. 1)What state does the schematic show? As in what is going on exactly in the picture?

2) Float 2 is NO until the water level drops below it, at which point it is NC, activating the relay on the left, is that correct?

3) How does the relay on the right switch back after the water has dropped below float 2?

I'm about to step out for a while so I won't be able to reply, but I really appreciate your help and will definitely get back to you tonight or tomorrow.

Thanks again!

 

[EgadsNo]

Here is an example of a typical double pole, double throw relay that I normally use, they cost about 12-15 bucks a piece + 4-6 bucks for the base.

honestly I am not sure the price of single pole double throw, but if your sump burns out the contacts on DP you can use the backup pair of contacts.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PB168-ND

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PB520-ND

The coil is powered through #2 pressure plate screw, the neutral for the coil is #7 (actually you cannot wire it backwards but i'll keep it at that)

 

[EgadsNo]

Thanks so much! I do have a few questions. 1)What state does the schematic show? As in what is going on exactly in the picture?

2) Float 2 is NO until the water level drops below it, at which point it is NC, activating the relay on the left, is that correct?

3) How does the relay on the right switch back after the water has dropped below float 2?

I'm about to step out for a while so I won't be able to reply, but I really appreciate your help and will definitely get back to you tonight or tomorrow.

Thanks again!

1) The state of the schematic is 0 power applied.

2) Correct :)

3) OMG i goofed up my schematic- sorry I must have been rushing

I will have another up and I will assure you it will be correct

 

[EgadsNo]

http://picasaweb.google.com/lh/photo/iwTXyJWHwGLhRLD5k0vn292_0MvXy9JeVCfdQTOfeN0?feat=directlink

I once again really apologize for the error I made before, but I assure you I checked this schematic... Here is the breakdown of wiring:

The Hot feeding the common of the upper float once the water level has raised to engage it will momentarily send power to the coil (#2 of the right relay and the motor)

As that happens power is feeding through (#1) of the left relay and exiting #4 screw because Float 2 (the low level float) is not sending power to the coil controlling that contact. #4 is jumping over to #1 on the right relay, since the coil was momentarily closed that power will feed #3 which constantly supplies power to the coil (to keep itself on) and the pump.

Once the water drops below Float 2, it returns to its normal state and sends power to the coil of the left relay, this opens the #1/#4 contact which drops power feeding the right coil and motor.

 

[EgadsNo]

Here is also a diagram for the relay http://picasaweb.google.com/lh/photo/ngHmt

Be sure to check the diagram printed on the relay, but they almost always are setup this way for 8 pin.

10 AMP is the typical rating on the contacts, over the course of their lifetime if the contact fails before the coil you can alternately use #8 instead of #1 as the common, and #5 is the NC equivalent of #4 for #8.

If you need higher amperage then that you can use a contact block, or motor starter as substitution for the relays, the relays fit a budget a bit better though. But these are all still just an electromagnetic switch operated by applying power to a coil.

The relays should be enclosed in an accessible electrical enclosure (a box) with appropriate fittings to allow the wires in and out- the power source feeding the relay circuit can either be off a light switch, or a plug to a receptacle or just your circuit breaker/fuse The relays do not need to be bonded (grounded)- the sump pump must be bonded, if the enclosure is metal, it too must be bonded- as well as any switches or plugs used to feed power to any part of the circuit.

Even though GFCI protection (ground fault circuit interrupt) can be very prone to tripping from current lag when starting an induction motor I would recommend it- and if this is in your basement local code may require it.

 

[EgadsNo]

Here are some state schematics, the wiring diagram does not really show you the states, but gives you wiring information from which you can trace through and imagine any possible state.

http://picasaweb.google.com/lh/photo/DT6x24WDouhg91UXPYFmeN2_0MvXy9JeVCfdQTOfeN0?feat=directlink
Here you see the water above the high float, float one is tripped so it starts sending power to the normally open contact, which pulls in the right relay and sends power out of its NO contact to feed itself (to stay on) and the motor. The lower float (2) is tripped and not sending power to the left coil.

http://picasaweb.google.com/lh/photo/iPwDvM-lmjH6SxnSVSytl92_0MvXy9JeVCfdQTOfeN0?feat=directlink

Has the water between the floats, the top float is no longer triggered, but the right relay is maintaining power to the motor and its own coil. Float 2 is still tripped and not sending power anywhere.

http://picasaweb.google.com/lh/photo/kxPVaThX0NnhsLv--t7-f92_0MvXy9JeVCfdQTOfeN0?feat=directlink
The water has dropped below float 2. Power is sent to the left relay from float 2, this kills power to the right relay coil and pump by engaging the left relay.

 

[EgadsNo]

Consequently, OFF-Delay or programmable mode relays could let you do this with only 1 relay, and 1 float, but OFF-delay relays can be much more expensive as they incorporate a time function to the circuit. But I would highly suggest not using them for this as they cost about 5-20 times as much while being more prone to fail and would only provide predetermined response (for example, the high float is engaged, wired normally open, it momentarily engages the timing relay which stays on for X time (regardless of the float disengaging).

 

[boredat20]

Thanks so much EgadsNo, I will be trying this sometime next week and will be sure to let you know how it works.