heat sensor shut off for water pump

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Stevenfyeager

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United States, Indiana
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electrical contractor
a customer is asking me for a solution of a water pump pumping water uphill to his house that keeps pumping even when dry and overheats and burns out the motor. I haven't seen it yet, he is hoping for heat sensor shut off. I called my supply house, no ideas. I'm not sure why it wouldn't have some kind of a float switch like a sump pump turns off the motor when dry...
 
They make a pressure switch that locks out the pump, and has to be manually reset if the pressure drops too far below the cut in pressure. I’ve used them on spring tank systems.
 
If the pump pressure falls below the lowest set point, the lever on the side must be lifted until the pump builds enough pressure to get past the second set point, after that, it can be released, and it will act like a standard pressure switch, until pressure drops too low again. The only flaw, may be the residual pressure if the switch is at the bottom of the hill.
 
hillbilly1 said:
If the pump pressure falls below the lowest set point, the lever on the side must be lifted until the pump builds enough pressure to get past the second set point, after that, it can be released, and it will act like a standard pressure switch, until pressure drops too low again. The only flaw, may be the residual pressure if the switch is at the bottom of the hill.
Click to expand...
I think if the power goes out and then someone opens a faucet or valve to draw some water, then that could require the pressure switch to be reset using the lever?
 
You want a Symcon, now owned by Littelfuse, Pump Saver. It will sense the drop in amperage when the pump runs dry and shut it off for a predetermined amount of time. It will automatically restart after the timeout period, for a predetermined number of times. Then will shut the pump down requiring a manual reset. It will also shut the pump down if it short cycles. Short cycling is caused by a bad pressure tank.

The pressure switch that Hillbilly mentioned will work. It requires a manual reset EVERY time the pump runs dry. I have one of these on my yard irrigation pump, in case it looses prime. I DO NOT recommend these on domestic water systems. Go with an electronic control.
 
hillbilly1 said:
Here is a better picture and explanation of the switch.


Click to expand...
it says in the features that it is "standard action".

I have used "reverse action" switches from that product series which sounds like something that may be useful in OP, though it would need to be used as a sort of lock out means and would need some override to get things started up again. Reverse action closes the switch contacts on pressure rise.

We sort of need more details on what OP is doing. If he is pumping water out of something that is expected to run dry he needs controls that will take that into consideration and have provisions to shut down when that condition is reached. If it naturally fills back up then some sort of restarting control may be needed as well.

If this is something that is not expected to run dry then there is something wrong with the design of it or a malfunction of some sort.
 
A water well with a submersible pump is the normal application for a "pump saver".
The well has two characteristics that determine its water delivery capacity.

The first is the recharge rate. The rate at which water flows into the well from the acquifer that supplies the well. This depends on the diameter of the well, the depth of the acquifer compared to the well depth and the rock characteristics. A well can deliver its recharge rate continuously while maintaining a constant water level, which will be lower than the static water level in the well. It may decrease from the original value when drilled as the water table and demand on thw acquifer change, or as the rock around the well silts up.

The second is the depth of standing water in the well above the pump level. This acts as a storage tank with a capacity of one or more gallons per foot of water.

The critical practical factor is that sensing the water depth in the well above the pump is hard to do reliably over a period of several years, so that is not an answer to the problem of protecting the pump (not just the motor, since the submersible typically includes hydrodynamic bearings that will wear rapidly without water.) The typical pump protector senses the drop in motor current when the load on the centrifugal pump disappears. This is NOT intended to be required regularly since each cycle risks damage to the pump.

A second, rather clever, solution for a low capacity well is a timed motor controller which integrates the pump on time and compares the nominal (maximum in the system) flow rate of the pump minus the recharge rate times the pump on time to the static storage of the well and cycles the pump off before it can run dry and locks out the pump until enough recharge has occurred to prevent short cycling. It is more expensive than a simple pump monitor but is best suited to maximizing the output of a well that is marginal compared to demand. It has the advantage that when it is properly set up the pump will never actually run dry.
 
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