shared well control

[electrofelon]

I have a friend who has a shared well. He wants each person to be able to power it (with a single pump) from their respective power supply. I am thinking that the simplest way to do it would be to use a DPDT with center position and two coil contactor, however I dont think such a thing exists. One could do it with 4 DPST relays, two that are NO and two that are NC, so a pressure switch would connect power and disconnect the other persons power at the same time. Any ideas? Note that he doesnt care about it being 100% accurate to cover both parties using it as the same time. That would involve much more complexity.

 

[Jraef]

What turns on the pump and where is it pumping into?

 

[electrofelon]

Each house would have its own pressure tank, pressure switch, and power supply out to the well.

 

[GoldDigger]

Each house would have its own pressure tank, pressure switch, and power supply out to the well.

So each house would also have a check valve so that it maintained pressure independently?
If so, you still would not be able to parallel the two pressure switches.
If they want to independently power the pump from the appropriate metered service when running you would have to have two NO relays with an electrical or mechanical lockout to prevent both from closing at the same time, or else one on/off relay and one transfer relay to select the power source.
One setup would run the pump from the first side to call for service whenever both were active, the other would always default to one supply when both were on.
In either case there would probably be a transient when the first call for pressure dropped out.

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[Jraef]

So each house would also have a check valve so that it maintained pressure independently?
If so, you still would not be able to parallel the two pressure switches.
If they want to independently power the pump from the appropriate metered service when running you would have to have two NO relays with an electrical or mechanical lockout to prevent both from closing at the same time, or else one on/off relay and one transfer relay to select the power source.
One setup would run the pump from the first side to call for service whenever both were active, the other would always default to one supply when both were on.
In either case there would probably be a transient when the first call for pressure dropped out.

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Yeah, almost like an alternator in reverse in that you have two control sources and power sources, but one motor being fed by them. There would need to be more to it though, because simply alternating between them could prevent one from getting water if the other one has not called for it. I personally would so this with a little "smart relay" / micro PLC, that way you can add or change the operating conditions as conflicts arise.

I think mechanically interlocked contactors at the well head is going to be an absolute must, because you don't want ANY possibility of the two systems "mixing" power sources.

 

[GoldDigger]

One set of Form C contacts would do just as well as two interlocked contactors. But you would not want one contact pole to stick. Same could happen with two contactors though.

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[kwired]

I have hooked up wells for portable generator connection before using a double pole double throw relay with 240 volt coil.

Common terminals of the switch of course are connected to the load. You could select one of the sources as the default supply so to speak, and connect it straight to the normally closed side. You connect the "alternate" supply to the normally open contact as well as the contactor coil. Whenever there is voltage on the alternate supply the coil pulls in and the load runs from that supply regardless of whether or not the default supply has voltage or not.

I have done this at swine finishing barns a few times. Two most important things in such a place are ventilation and water, they can get by for a lot longer without feed. Many have a mechanical device that automatically drops ventilation curtains when power is lost or temp gets too high - this takes care of ventilation. Then all they need to do is bring a portable generator and plug in the well with this setup and they are good for a while until they can decide how long the power may be out and what actions to take next.

 

[steve66]

It seems like you basically just need a transfer switch. Same principle: One load, two separate sources.

 

[kwired]

It seems like you basically just need a transfer switch. Same principle: One load, two separate sources.

What gets more complicated is code compliant ways to disconnect things. Probably need a disconnect from both sources wherever you do this. Manual transfer switch is not what OP is after, he wants it to automatically distribute power usage to both sources to some extent. Auto transfer switch is essentially a double pole double throw relay, usually with controls set up for a fairly specific set of circumstances, and you don't really find one only rated for less then 100 amps all that easily. Many domestic wells only need a 15 amp 240 volt circuit, occasionally maybe a 20 amp circuit is needed.

I'd probably still go with a 30 amp C form power relay and and wire it as I described earlier - with a disconnect from both sources close by.

 

[Jraef]

I don't think it's quite as simple as that. The tricky part of it will be the "pump call" portion. Neighbor #1's pressure switch called for it first, he's pumping, neighbor 2 waits until #1 is satisfied; fine, no problem. But then #2 is running, but #1 pressure switch calls for it again before #2 is satisfied. #1 has to then wait, but how do you implement that logically? What if #1 has a leak and the well never shuts off for hours and hours, making #2 wait and wait? What if that draws down the well too far, then when it recovers, #1 never "let go" of the pump call? It's going to take some logic.

 

[ActionDave]

I don't think it's quite as simple as that. The tricky part of it will be the "pump call" portion. Neighbor #1's pressure switch called for it first, he's pumping, neighbor 2 waits until #1 is satisfied; fine, no problem. But then #2 is running, but #1 pressure switch calls for it again before #2 is satisfied. #1 has to then wait, but how do you implement that logically? What if #1 has a leak and the well never shuts off for hours and hours, making #2 wait and wait? What if that draws down the well too far, then when it recovers, #1 never "let go" of the pump call? It's going to take some logic.

Most of these shared wells have cisterns at each house.

 

[GoldDigger]

I don't think it's quite as simple as that. The tricky part of it will be the "pump call" portion. Neighbor #1's pressure switch called for it first, he's pumping, neighbor 2 waits until #1 is satisfied; fine, no problem. But then #2 is running, but #1 pressure switch calls for it again before #2 is satisfied. #1 has to then wait, but how do you implement that logically? What if #1 has a leak and the well never shuts off for hours and hours, making #2 wait and wait? What if that draws down the well too far, then when it recovers, #1 never "let go" of the pump call? It's going to take some logic.

I think the fallacy in your analysis is thinking that the pump can only supply one home at a time.
More likely you can analyze the situation as a current limited supply charging two capacitors through a diode. As a practical matter neither capacitor can reach full charge while the other is at a lower voltage, but nevertheless neither capacitor will get pulled down below the switch threshold.

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[drcampbell]

A reversing contactor would probably serve the purpose -- either house can command the pump to turn on and supply power to it, but if the second coil is energized while the first one's already on, the mechanical interlock will prevent the two sources from being connected to each other. (at least, until the contacts get old & welded)

But the bigger question is WHY? What purpose would this serve? The two houses are probably fed by the same branch of the same utility, probably the same transformer, and will suffer outages at the same times for the same reasons.

If it's about billing, install two water meters and reconcile accounts at the end of each month.

 

[electrofelon]

Yes there are multiple options. I think the DPDT contactor would work per Kwired's description. There would be 2 forms of inaccuracy: one is when both users are drawing at the same time and the one who initiated the pump could be pumping for the second party. The other is each party cannot avoid charging the other's pressure tank (perhaps it would "average out"?) I also think that considering typical residential usage and typical pumps, both houses could be supplied at the same time without issue.

I suggested he just install a watt meter on one of the lines and they could just split the bill. I dont think we are talking much energy, unless one of them has a bunch of teenage girls

Another idea would be to put a flow meter on each person's line and measure and compute the energy per unit volume, then it could be split proportionate to usage and one party could supply the pump and get reimbursed.

 

[ptonsparky]

Yes there are multiple options. I think the DPDT contactor would work per Kwired's description. There would be 2 forms of inaccuracy: one is when both users are drawing at the same time and the one who initiated the pump could be pumping for the second party. The other is each party cannot avoid charging the other's pressure tank (perhaps it would "average out"?) I also think that considering typical residential usage and typical pumps, both houses could be supplied at the same time without issue.

I suggested he just install a watt meter on one of the lines and they could just split the bill. I dont think we are talking much energy, unless one of them has a bunch of teenage girls

Another idea would be to put a flow meter on each person's line and measure and compute the energy per unit volume, then it could be split proportionate to usage and one party could supply the pump and get reimbursed.

Very much like any village,town or city. The person using the most gets billed the most.

 

[Ultrafault]

Get a plc, two binary flow sensors, and a interlocked contactor. Track on time for each water line out and if time flow is less then time on then that is the power source chosen. You will have to pick one as priority in the case both have a greater or less time on than flow on.

 

[growler]

Another idea would be to put a flow meter on each person's line and measure and compute the energy per unit volume, then it could be split proportionate to usage and one party could supply the pump and get reimbursed.

Very much like any village,town or city. The person using the most gets billed the most.

Who owns the well? It's on someone's property and they will be responsible for the well and any maintenance of the equipment.

Get a water flow meter for the other house and come up with a reasonable rate to charge for water. Not only the cost of power but also maintenance cost (which may end up being more than power cost).

 

[kwired]

Yes there are multiple options. I think the DPDT contactor would work per Kwired's description. There would be 2 forms of inaccuracy: one is when both users are drawing at the same time and the one who initiated the pump could be pumping for the second party. The other is each party cannot avoid charging the other's pressure tank (perhaps it would "average out"?) I also think that considering typical residential usage and typical pumps, both houses could be supplied at the same time without issue.

I suggested he just install a watt meter on one of the lines and they could just split the bill. I dont think we are talking much energy, unless one of them has a bunch of teenage girls

Another idea would be to put a flow meter on each person's line and measure and compute the energy per unit volume, then it could be split proportionate to usage and one party could supply the pump and get reimbursed.

Unless one place definitely uses a lot more water then the other most suggestions have been too cost prohibitive for what is gained in the end.

I assume all you are after is a little splitting of the energy that powers the well, but without needing much user interaction or spending a lot on monitoring equipment that won't pay back on purchase and installation cost in any reasonable time. Most of these wells only use maybe $5-10 max per month of electric energy, likely even less if no lawn watering or other similar activity happens much.

The actual owner of the well is likely better off just to ask the other user for $15 a month or make some other agreement on any other shared resources, Like maybe - I'll let you put your trash in my dumpster if you let me use water from your water system. Unless I happen to use the majority of the water pumped, is probably a good deal to the well owner. What is bad about this is if the well owner for whatever reason moves, dies, or somehow leaves the property uninhabited and with no electric utilities, then the other person is without water. The DPDT relay I suggested would still run the pump if the primary supply is taken out of service.

This arrangement still has all kinds of potential holes in it for disputes on who is responsible for what though.

Where I sometimes see such a shared well is at adjacent vacation homes out at a lake, river, etc. In those cases the energy usage is maybe only a couple days a week most of the year, making any metering setup pretty expensive for what you are trying to recover.

 

[Jraef]

I think the fallacy in your analysis is thinking that the pump can only supply one home at a time.
More likely you can analyze the situation as a current limited supply charging two capacitors through a diode. As a practical matter neither capacitor can reach full charge while the other is at a lower voltage, but nevertheless neither capacitor will get pulled down below the switch threshold.

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Ok, but in this case it's about who is PAYING for the electricity to run the pump, right? If I'm paying to run the pump, I'm thinking I only pay to run it into MY tank. If my neighbor has a pot farm in his basement, I don't want to pay to run his drip irrigation...

 

[kwired]

Ok, but in this case it's about who is PAYING for the electricity to run the pump, right? If I'm paying to run the pump, I'm thinking I only pay to run it into MY tank. If my neighbor has a pot farm in his basement, I don't want to pay to run his drip irrigation...

Unless his basement is a 30,000 square foot warehouse, he probably isn't using enough water to make enough significance in energy used to pump water for that kind of purpose.