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How would you wire this?

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burleymike

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Feb 25, 2009
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SE Idaho
I have a sprinkler pump that draws from a shallow well. Couple years ago the well casing rusted out about 5' down, the pump lost prime and ran dry for about 30 minuets before I noticed. I don't want to have to buy a new motor again so I am trying to come up with a simple control circuit to shut the pump down if the flow stops.

So far I have a flow switch and a delay on make timer. My original plan was to take 120v off one leg of the contractor step it down to 24VAC and power the delay on make timer with that. The delay on make timer would be connected to the NC flow switch, the flow switch would go to a NC contactor. When water is flowing the flow switch would open, if the pump were to loose prime or a irrigation valve were to fail closed the flow switch would close opening the NC contactor, shutting the pump down.

I cannot find a cheap NC contactor out there. Any ideas on where to find one for about $20?

The other thing that would work would be a relay or something similar that when it gets power, opens and stays open until a manual reset button is pushed, does such a critter exist in the cheap price range?
 
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mrb

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use a NO contactor. If the delay on make timer doesnt have NO and NC outputs use an ice cube relay to get the contact arrangement you need.
 
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walrus

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Maine
The NC contactors I use for Fire Suppression cost about 70 bucks ea. They're rated 30 amps, 120 v coil, Square D and Cutler Hammer make them
 
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nehog

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There are well pressure switches that have this functionality built in already. Don't reinvent the wheel, just buy the right pressure switch and you will be set. Basically, if the pressure drops to zero, they kick off and need to be manually reset.
 
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Aceman

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nehog said:
There are well pressure switches that have this functionality built in already. Don't reinvent the wheel, just buy the right pressure switch and you will be set. Basically, if the pressure drops to zero, they kick off and need to be manually reset.
Click to expand...

I had a Square D one that did this. There was a catch though, you had to manually start the pump until the pressure switch was satisfied allowing the pump to stay running. If your pump is ran automatically(like with a sprinkler controller), you'll need a timer to allow the pump to start and run for a few secs to build up pressure before it switches over to the pressure switch to keep it running.

If they make a pressure switch that works different than this, then I'd love to hear about it. I actually spent countless hours trying to make mine work with the timer, but every time my zones would change the pressure would fluctuate so much, it'd trip the pressure switch and drop the pump out.

Mine now runs off a pressure transmitter and plc. Much better.
 
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smithbd2

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Dec 23, 2010
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TN
I install septic tank pumps from time to time. They come with a float switch that has a molded plug that you plug into a receptacle then the pump plugs into the float plug. On occasion I have cut off both plugs and direct wired everything, which may be the way you would want to procede.
Here is a link for the float switch:
http://www.septictankparts.com/cart/cstep/9/catname/Septic+Tank+Float+Switches

You may be able to find these at your local supply house.
I also install a float switch for a alarm circuit, it comes without the molded plug, so it should be cheaper. I didn't see one at the website I linked above.
 
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Aceman

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Eastern Oregon
smithbd2 said:
I install septic tank pumps from time to time. They come with a float switch that has a molded plug that you plug into a receptacle then the pump plugs into the float plug. On occasion I have cut off both plugs and direct wired everything, which may be the way you would want to procede.
Here is a link for the float switch:
http://www.septictankparts.com/cart/cstep/9/catname/Septic+Tank+Float+Switches

You may be able to find these at your local supply house.
I also install a float switch for a alarm circuit, it comes without the molded plug, so it should be cheaper. I didn't see one at the website I linked above.
Click to expand...

What does a septic tank float system have to do with a pump running on a well?
 
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smithbd2

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Location
TN
Originally Posted by Aceman
What does a septic tank float system have to do with a pump running on a well?
Click to expand...

Maybe I wasn't clear enough. I was trying to say you could use a float to kill the pump before it went dry & lost its prime. It doesn't realy matter what kind of float, it just needs to have normaly open contacts. At work we use what we call "elephant balls", they are made by Flyte.
http://www.flygtus.com/117864.asp
Not sure how much they cost.
Just another way to skin a cat, so to speak.
 
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B

burleymike

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SE Idaho
Here is what I ended up doing. The sprinkler timer now sends 24VAC to a NO relay that then closes and powers a 120VAC to 24VAC transformer. 24VAC from the transformer then goes to a second relay that is NC and on to the pump contactor. 24VAC from the transformer also goes to the delay timer, then on to the flow switch. If there is no flow the flow switch will close and send power to the NC relay opening it, killing power to the pump contactor.

Sorry for the crappy explanation I would draw a diagram if I had the time. It works like a champ and I am happy for $30 in parts. This idea came to me one night when I could not sleep so I wrote it down.
 
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