Pump run dry protection ideas?

[burleymike]

I am trying to come up with a simple circuit to protect my sprinkler pump if it looses prime or if the well were to run dry.

A buddy gave me a delay on make timer and a flow switch. The best I can come up with is to take 120v off the contactor and run that through the delay timer then into a transformer that will give me 12vdc. Run the 12vdc through the flow switch which when there is flow will be open. If it closes the 12vdc will go to a NC relay which will then open and cut power to the pump.

After the sprinkler timer finishes it's cycle it will then cut power to the pump contactor which will reset the whole thing. I don't like this setup it seems like a mess to me. Anybody got any ideas on a more simple setup?

The reason I don't plan to use the 24vac control voltage the sprinkler timer puts out is because it is powering the pump contactor and two sprinkler valves at once which puts the sprinkler timer power supply at it's limit.

 

[nate379]

Is it common for the well to dry up?

Pump shouldn't be loosing prime. Maybe need a check valve at the bottom?

 

[supertooljunkie]

There are companies that make low pressure cut off switches for the discharge side of your pump. I use to sell them to manufacturers of portable concrete batch plants to shut the pump off if the water tank emptied or became interrupted. It has been 15 years or so, I would have to do some research, but they are out there. I will take a look.

 

[CUSTOMMANCAVES.COM]

Grainger, McMaster-Carr, etc. all sell such switches in their catalogs. No need to "invent" something.

 

[burleymike]

The check valve failed once two years ago lucky I was home and noticed the sprinklers were not on after about 20 min of dry running. The pump actually survived that. This is a sand point well so the only option is a check valve at the pump suction line.

No the well has never run dry and I seriously doubt that would happen the water table stays between 10-6'

A pressure switch with a 5 second delay would be perfect. When the pump first starts it takes a couple seconds for the pressure to build.

I did find a controller that you wire in the line to the pump that monitors how much current the pump is using and can shut it down if it is using too little or too much. It costs a over $100 so I was hoping I could put something together for less with the flow switch and delay timer my friend gave me. I should probably just get the current monitor.

 

[supertooljunkie]

I "Googled" low pressure cut off switches and got numerous hits. It looks like any well pump supplier can get you a "ready made" item for cheap. Or, as above post, Grainger, MSC, etc.
Good luck!

 

[nate379]

Gotcha. Was not doubting your need for it, but I was just curious mainly.

The check valve failed once two years ago lucky I was home and noticed the sprinklers were not on after about 20 min of dry running. The pump actually survived that. This is a sand point well so the only option is a check valve at the pump suction line.

No the well has never run dry and I seriously doubt that would happen the water table stays between 10-6'

A pressure switch with a 5 second delay would be perfect. When the pump first starts it takes a couple seconds for the pressure to build.

I did find a controller that you wire in the line to the pump that monitors how much current the pump is using and can shut it down if it is using too little or too much. It costs a over $100 so I was hoping I could put something together for less with the flow switch and delay timer my friend gave me. I should probably just get the current monitor.

 

[nehog]

Pump pressure switches with a low pressure cutout are common, Grainger carries them, Sears (at one time, maybe even now) has them. Most are made by Furnas IIRC. If you have too much trouble finding one, let me know, I have one on the shelf somewhere.

 

[larry_g]

I take it this pump is not a well pump that provides the sprinkler system full time pressure. Rather when the sprinkler control calls it turns on the pump and the system starts to work. Can you put the flow switch and the timer contacts in parallel on the 24v control line. Call for rain and the delay timer is NC and the flow switch is NO. Once the flow is established the timer could be dropped out and the flow switch holds the circuit in. You may have to invest in some different switches to make the wireing simpler.

lg
no neat sig line

 

[burleymike]

You got it Larry G. If I could find a pressure switch with a 10-20 sec delay that would work but I can't seem to find one. When the sprinkler controller switches circuits the sprinkler valves have some lag so the pressure drops quite low for up to 8 seconds.

 

[antolod]

If you can replace the pump contactor with a pressure switch with low-pressure cut-off, (like this one) and add a small bladder tank, your system would be protected and pressurized all the time.

As long as there are no leaks, the pump will only run when the sprinkler valves open, and if something causes the pressure to drop below the built-in low cut-off pressure the pump will shut off. The bladder tank is needed to hold a reserve of pressure to give a cushion for the lag between the valves opening and the pump coming to pressure and to keep the switch at shut off pressure when the valves close. The only caveat with a switch like this is the bladder tank has to hold enough water to keep the pressure up while waiting for the pump to pressure up. The air pressure in the bladder must be a few pounds less than the cut-in pressure of the pump to prevent the low-pressure feature from turning the pump off.

 

[mrb]

You got it Larry G. If I could find a pressure switch with a 10-20 sec delay that would work but I can't seem to find one. When the sprinkler controller switches circuits the sprinkler valves have some lag so the pressure drops quite low for up to 8 seconds.

can you use pressure switch in conjunction with a time delay relay to accomplish pressure switch with 10-20 sec delay?