Off-Grid water, pump fail safe help

[Old Guy in Tenn]

We got our water running a couple of weeks ago. A 300 gallon tank down by the spring, with a 1HP submersible pump inside the tank to pump the water up 160 feet with a 500 foot run to the house. We have a bladder tank up at the house, which is where it switches the pump on/off as water is used. The switched 220 then powers the pump. It is working very well, so I could leave it alone, but...

I am worried that we could somehow run the tank dry, and damage the pump. I want some simple way to turn off the pump if the water in the tank gets too low. We ran an extra wire pair down to the spring to connect to a float switch or whatever, in case that helps.

Looking forward to hearing your suggestions.

Thanks.

 

[DuckSlayer1017]

Use the float and probably a relay to power the pump. If the float is up pump runs. If the float is down pump won’t run. Use your extra pair of wires to turn on a light at the house if the float is down. Also, make sure you check the float periodically, we’ve burned up plenty of pumps at work because floats stuck.

Maybe one of the electricians or EE’s on here could draw the circuit for you. I’m just a ME and let the pros do the circuit design for me.

 

[Fallon]

Thermal sensor on the pump near the seal & latching relay. Might be hard to tune so it trips in time without to many false positives.

Redundant float switches wired in series. More likely to leave you without water if any one of the float switches failed.

 

[fried1765]

We got our water running a couple of weeks ago. A 300 gallon tank down by the spring, with a 1HP submersible pump inside the tank to pump the water up 160 feet with a 500 foot run to the house. We have a bladder tank up at the house, which is where it switches the pump on/off as water is used. The switched 220 then powers the pump. It is working very well, so I could leave it alone, but...

I am worried that we could somehow run the tank dry, and damage the pump. I want some simple way to turn off the pump if the water in the tank gets too low. We ran an extra wire pair down to the spring to connect to a float switch or whatever, in case that helps.

Looking forward to hearing your suggestions.

Thanks.

You can buy a "PumpTec" or "Pump Saver Plus".
When they sense the pump running out of water, they will shut the pump off, and can be set for automatic time delay, to allow water recovery.
Works great.

 

[gary49]

You can change your pressure switch to a low pressure cut off type switch. Square D makes one. It cuts the pump off if the pressure falls to 12 PSI. That will be the simplest, cheapest way to do it. If the cut off is activated, there is a lever on the switch that you have to use to reset the switch.

 

[Egon]

There are options:
Low level! Low flow, temperature sensor, low discharge pressure, pump run time. Pick one that suits you equipment and situation best.

For awareness a low pressure at the house should be all that is required.

 

[CobyRupert]

You can change your pressure switch to a low pressure cut off type switch. Square D makes one. It cuts the pump off if the pressure falls to 12 PSI. That will be the simplest, cheapest way to do it. If the cut off is activated, there is a lever on the switch that you have to use to reset the switch.

I have the "low pressure cut-off" version of the pressure switch at the input of my ballast tank that controls submersible pump, as I have house, barn and a few apartments on well and always feared somebody would leave a faucet on, or a pipe break, etc.. when not home and pump would burn up. ...
The down side is if the power goes out for an extended period of time and too many people flush toilet etc.. and reduce pressure to below cut-off point. When the power comes back on you're still without water until you manually hold reset lever on switch and pressure builds back up to above the cutout pressure. For me, that means climbing down through an outdoor manhole into a dark cramped underground vault. And if I've been away at work all day or on vacation, nobody has water until I get there.
It's like paying for insurance.

If you go with float switch wired directly in the wire between the pressure switch and pump, make sure it's rated for 220V and horsepower rated for the motor. That is, switch is not just rated for motor's full amps, but can handle motor overload and motor starting amps too. Generally a (general use AC/DC) switch's ampere rating should be twice the motor's full load amp rating if a horsepower rating is not given. [For an AC (only) general use switch, 125% or greater of the motors rating is ok]

If wired directly, float switch should be 2 pole, that is, it interrupts both wires / legs (L1 & L2) of the 220V circuit and not just one leg, which would leave voltage through the motor even when off.
If float switch operates (drops out) a relay whose contacts interrupts pump's power circuit from pressure switch, relay's contacts should be rated for pump hp/amps as mentioned above. Relay (coil) & float switch will then need to operate on the separate 120V circuit.

(Note: there are ways to operate the float/relay off the existing 220V circuit from the pressure switch, but that gets more complicated. That is, you either need a (white) neutral conductor (in addition to (green) ground conductor) run with your 220V so you can get 120V for the relay coil and float switch, or you have a 220v relay coil and float switch. Also in these scenarios, the relay would be starting the pump every time the pressure switch calls for water rather than just stopping the pump in an low water situation.)

 

[mrmikey]

You can change your pressure switch to a low pressure cut off type switch. Square D makes one. It cuts the pump off if the pressure falls to 12 PSI. That will be the simplest, cheapest way to do it. If the cut off is activated, there is a lever on the switch that you have to use to reset the switch.

What he said...works great, no extra moving parts.........Mike

 

[hawkeye08]

You can change your pressure switch to a low pressure cut off type switch. Square D makes one. It cuts the pump off if the pressure falls to 12 PSI. That will be the simplest, cheapest way to do it. If the cut off is activated, there is a lever on the switch that you have to use to reset the switch.

Yep, I accidentally got one of these and the it does shutoff when pressure drops too low and has to manually reset.

https://smile.amazon.com/gp/product/B000FKBY8W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Old Guy in Tenn]

You can change your pressure switch to a low pressure cut off type switch. Square D makes one. It cuts the pump off if the pressure falls to 12 PSI. That will be the simplest, cheapest way to do it. If the cut off is activated, there is a lever on the switch that you have to use to reset the switch.

OK. If this type of switch is installed, and the pump goes dry after the faucet/toilet/whatever is turned off but before the OFF pressure is reached, wouldn't the pump keep running? It seems it would go off only when more water was used and the pressure finally dropped below the low-pressure cutoff.