Submersible pump: When to use relay vs contactor?

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Rx1559

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Hello! I would like to learn when to use a relay and when to use a contactor, for controlling power to my submersible well pump. I am replacing the old system, which uses a pressure switch to signal the pump to come on and off, with a fancy new 12V DC SmartWater pump controller.

My water system has power coming in as two legs of a single-phase 230v (and a yellow wire which I assume is a ground, need to get on-site to confirm) running to a SquareD 230V pressure switch. The load side of the pressure switch then runs to a PumpSaver 233P, and in turn to a CentiPro Pump Controller box CB15412CR, and then runs down the wellhead as 3 wires (plus ground) to the pump. I am pretty sure the pump is something like a CentiPro 1.5hp 230v 10A 3450RPM pump.

My well guy said I could just replace the SquareD pressure switch with relay instead of using a contactor; specifically, this one:

Medium-Current Relay DPDT, 8 Terminals, 12V DC Input

I just want to understand this decision because I like to know how this stuff works: When is it appropriate to use a contactor, and when is it appropriate to use a relay, for this application? Does the capacitor-start / capacitor-run, and relay in the Pump Controller box have anything to do with this decision?
 

Reach4

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Contactor means bigger power relay.
 

Rx1559

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So, you are doing away with the pressure tank and going straight to a cistern or storage tank?

I was trying to keep my post focused just on the well pump electrical, to avoid distracting from the main point. But since you asked I'm happy to describe, the system has always had a 5000 gallon cistern, and used a pressure switch to activate / de-activate the well pump which fills it up.

This pressure switch system has been the source of typically-twice-a-year failures that are expensive and time-consuming to fix... the most typical behaviors are non-stop pump thrashing on/off caused by failure of Component X, where Component X can be any of: leaky solenoid valve, calcified leaky horse trough float valve, failing check valve, micro-cracks in PVC pipe, and so forth.

So I am replacing the pressure-switching system with a SmartWater tank monitor, which sends a radio signal to the SmartWater pump controller, and in doing so I am getting rid of the pressure switch and related components. Hopefully this reduces the failure points.
 

Rx1559

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Contactor means bigger power relay.
That's my understanding as well. My well guy mentioned something like "well if the system needs to hold the power, you want a contactor, but yours doesn't so a relay should be fine." This didn't really make sense to me. I figure you buy whatever component is rated to handle the load, in my case a 230v 10A submersible pump.

I wondered if there was some minutia I hadn't considered relating to the pump, perhaps start-up amperage or something like that.
 

Valveman

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I looked up that Smartwater thing. I couldn't get much info on specs and wiring. But they make a 230V version, which should not need a relay unless if cannot handle the 10 amps from your 1HP pump. I think the 12VDC ones will require a 12V relay that can handle 10 amps at 230V.

Sounds like nearly all of your problems were caused by the pump cycling on and off, which could have easily been solved by adding a Cycle Stop Valve.

If you have power from the cistern to the well pump a simple 'Pump up" float switch is all you need. Radio controls are becoming more dependable, but I have had more problems with those than the simple float switch systems.

LOW YIELD WELL_and storage with two PK1A one pipe.jpg
 

Rx1559

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Gosh, I don't really want to add another water tank and pressure-switched valve to the system. Every well company that comes up and looks at our water system has some pressure-switched gadget or another damned valve they think will fix the problem. Oh it's the check valve on the pump. Oh it's the check valve above ground. Oh the pump saver is on the fritz. Oh let's replace the float valve on the cistern with a horse trough valve. Oh this solenoid must be bad. Oh there must be micro-cracks in the 500 feet of pipe between your pump and your water tank, let's dig it up. Over the course of five years and three well companies, something always breaks after 5-8 months and I have to drive 5 hours down to fix it.

The radio-based SmartWater system looks beautifully simple to use. The 5000 gallon water gets down to 3000 gallons and the sender radios the pump to come on, until the tank is back to 5000 gallons. I want to try this and see if it reduces my frustrations a bit.
 

John Gayewski

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Gosh, I don't really want to add another water tank and pressure-switched valve to the system. Every well company that comes up and looks at our water system has some pressure-switched gadget or another damned valve they think will fix the problem. Oh it's the check valve on the pump. Oh it's the check valve above ground. Oh the pump saver is on the fritz. Oh let's replace the float valve on the cistern with a horse trough valve. Oh this solenoid must be bad. Oh there must be micro-cracks in the 500 feet of pipe between your pump and your water tank, let's dig it up. Over the course of five years and three well companies, something always breaks after 5-8 months and I have to drive 5 hours down to fix it.

The radio-based SmartWater system looks beautifully simple to use. The 5000 gallon water gets down to 3000 gallons and the sender radios the pump to come on, until the tank is back to 5000 gallons. I want to try this and see if it reduces my frustrations a bit.
I would suggest, just generally, don't switch companies that often. It can take some time for a person or company to get "intuition" (I say that in quotes because it's not really intuition) for a system. Sometimes things can be systematically fixed with great results although you may think someone is just guessing their way through a problem or could be that any one of these companies would have made found a great solution to your issues if given enough of a chance. As long as they are being fair and honest switching companies will probably only draw out the final confluence of events that get your system working better.
 

Reach4

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SJE Rhombus 30PMPU2WP comes with a 230 volt piggyback plug. That means that you can install the pump with a plug and receptacle controlled with a switch. Then insert the piggyback in line to control the pump with the float switch

I presume the plugs/receptacles are NEMA 6-15P and NEMA 6-15R, but I think you would want to be sure. I don't find that actually specified in the literature.

Ignore "psi" number in description; I am thinking they meant amps.
 

Valveman

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Gosh, I don't really want to add another water tank and pressure-switched valve to the system. Every well company that comes up and looks at our water system has some pressure-switched gadget or another damned valve they think will fix the problem. Oh it's the check valve on the pump. Oh it's the check valve above ground. Oh the pump saver is on the fritz. Oh let's replace the float valve on the cistern with a horse trough valve. Oh this solenoid must be bad. Oh there must be micro-cracks in the 500 feet of pipe between your pump and your water tank, let's dig it up. Over the course of five years and three well companies, something always breaks after 5-8 months and I have to drive 5 hours down to fix it.

The radio-based SmartWater system looks beautifully simple to use. The 5000 gallon water gets down to 3000 gallons and the sender radios the pump to come on, until the tank is back to 5000 gallons. I want to try this and see if it reduces my frustrations a bit.
After re-reading your posts I am thinking you do not even have a pressure tank with the pressure switch that is controlling the well pump? If that is correct, I can see why you are having endless troubles. As Reach said, the simplest way and most dependable is to use a simple flat switch to control the well pump. However, if you are unable to run power from the float switch in the cistern to the pump, a solenoid valve operated by the float switch at the cistern is the next best option. But, you cannot run a well pump with a pressure switch and not at least have a pressure tank. Even with a pressure tank, filling a cistern can take long periods of time like filling a swimming pool. In these cases adding a Cycle Stop Valve stops the cycling for the long periods of time, saving the pump and everything in the system. Plus, with a CSV you don't need more than a little 4.5 gallon size pressure tank.
 

Rockwind1

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Hello! I would like to learn when to use a relay and when to use a contactor, for controlling power to my submersible well pump. I am replacing the old system, which uses a pressure switch to signal the pump to come on and off, with a fancy new 12V DC SmartWater pump controller.

My water system has power coming in as two legs of a single-phase 230v (and a yellow wire which I assume is a ground, need to get on-site to confirm) running to a SquareD 230V pressure switch. The load side of the pressure switch then runs to a PumpSaver 233P, and in turn to a CentiPro Pump Controller box CB15412CR, and then runs down the wellhead as 3 wires (plus ground) to the pump. I am pretty sure the pump is something like a CentiPro 1.5hp 230v 10A 3450RPM pump.

My well guy said I could just replace the SquareD pressure switch with relay instead of using a contactor; specifically, this one:

Medium-Current Relay DPDT, 8 Terminals, 12V DC Input

I just want to understand this decision because I like to know how this stuff works: When is it appropriate to use a contactor, and when is it appropriate to use a relay, for this application? Does the capacitor-start / capacitor-run, and relay in the Pump Controller box have anything to do with this decision?
maybe you could draw a picture of your system and that way cary or reach can visualize it,,,, i have a system similiar to yours, with a 5000 gallon tank. i do not understand how a pressure switch tells your pump to turn off when the cistern is full
 

Rx1559

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There is 500 feet of PVC pipe running underground between the 5000 gallon cistern, which is way the hell off in the deep forest (it's a long story), and the well pump that is near the house.

At the well pump, there is a simple SquareD pressure switch (and a small pressure tank which I believe is to smooth out the rapid pressurization and depressurization that can occur in the PVC line) that monitors the water pressure in this PVC line. When the pressure in the line drops below 40 PSI, the pressure switch turns the pump on. When the pressure in the line builds up to 60 PSI, the pressure switch turns the pump off.

At the cistern, this PVC pipe terminates in a cattle trough float valve that is situated inside the cistern, near the top. When the water level in the cistern drops a bit, the float valve drops and opens its valve, causing a rapid drop in the pressure in the PVC. This signals the well pump 500 feet away to come on, via the pressure switch sensing the pressure drop below 40 PSI. Once on, the pump will fill the cistern until the water level floats the float valve high enough to close its valve. When this happens, since well pump is still running, pressure rapidly builds up in the PVC pipe, until the pressure switch sees 60 PSI and switches the pump off.

Therefore, the cistern uses water pressure created by the well pump, to switch the pump on and off. This may appear as a simple system on paper, but in the real world, where rodents short out contacts and nibble on wires, and float valves calcify and permanently trickle, and check valves 300 feet underground get grains of sand stuck in them and fail, and pressurizing 500 feet of pipe isn't a smooth linear operation that a pressure switch expects... it's not simple.

(Originally, there was no cattle trough float valve in the cistern, and instead there was an electric water level switch hanging, suspended by a knot in its cord, which operated a nearby solenoid valve to open/depressurize and close/re-pressurize the PVC pipe)

Sigh. So that's the water system. It's the first water system I've ever had to depend upon and maintain, and it's been quite a challenge in so many ways.

My plan is to remove the cattle trough valve, and try out the SmartWater system to use radio frequency to turn the pump on when its water tank sender says it's low (how low is configurable), and to turn it off when it's full again. Rather than using water pressure to make these signals.
 

Valveman

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I am sure they are making radio controlled systems more dependable than in the past. But my experience has been they lose signal and either do not turn the pump on, or fail to turn it off and overflow the cistern.

Every problem you mentioned except for the rodents, could be caused by the pump cycling on and off. I prefer the electric solenoid valve over the float valve. But "non-modulating" float valves work ok. Electric valves are also "non-modulating", which means they are either fully open or fully closed. Modulating float valves, which I think you have now, flow less water as the float gets closer to the upper position. These modulating float valves can cause the pump to cycle on and off many times as the last inch or so of water is pumped into the cistern. The smaller the pressure tank, the more times and the more rapid the cycles. Even just the 500' of line can be enough restriction to cause the pump to cycle on and off.

Simply adding a Cycle Stop Valve can solve those problems. The CSV makes the pump start and stop with a "smooth linear operation", regardless of the length or size of the line. The CSV prevents the failure of the pressure switch points, control box, check valve, tank bladder, and even the pump, as there is no more cycling on and off as the cistern fills or bouncing when the pump starts. The CSV can even prevent sand in the check valve, as water is being drawn smoothly from the well instead of surging as it does when the pump cycles on and off continually or rapidly.

Even with the radio control there will be tremendous pressure build up in the 500' of line when the pump starts. It is hard to get 500' of water moving as quickly as the pump starts, so it is kind of like a cannon effect when the pump starts. Is is much easier on the line when the water is drawn from a pressure tank as the float/solenoid valve opens before the pump starts, which is the way the CSV does it.
 

Fitter30

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Relays normally are for resistance loads. General purpose contactors have ratings for resistance and inductive loads often rated in hp. Pick one rated at a larger hp it will last longer.
 
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