Intermittent low amperage on submersible pump - troubleshooting suggestions.

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Hardyh

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Our setup had been running flawlessly for about 4 years when the pump had to be pulled a few months ago - the installer actually thinks it was as simple as the electrical tape loosening from the connections and either causing a short or getting tangled in the pump. Either way, we had a new 3/4HP pump put in around April and everything worked fine again for a while. Now it has been acting up again and originally I thought it was either the tank or the pressure switch. We had a 30/50 low pressure cut-off pressure switch that I thought might be the culprit and I had been planning on adding a cycle sensor to the system anyway so I order/installed the sensor and switched to a 40/60 (no cut off) pressure switch. The cycle sensor has been helpful in giving me a better picture of what is going on:
It seems like the pump kicks in and floats around 6.5-7 amp, except sometimes when it drops down to about 4.5 amp ( I have the dry sensor set to 5amp right now with a 20min delay). To me that sounds like the well is being run dry, because usually a cycle or two max and the pump is back to normal running a cycle at 6.5amp to full pressure and then shutting off. But today I measured the well depth with some fishing line and a bobber and it was sitting at about 40ft down from the well head and this was within half an hour of a load of laundry and some breakfast dishes. If it really was running dry I think it should have been lower. Also, the cycle sensor shows me that occasionally there is an amp draw when the pump isn't on, usually .06-.08 amp but I have seen .30 amp once too. So what else could this be? We seem to have a well that can hold at least 150gal at a time, and there is no way we're pumping that much out before the sensor notices the amperage drop, which usually happens within 2 minutes of the pump kicking it. Also, can it be a faulty pump if it works correctly 3/4 of the time and then drops amps sporadically? Are there other steps I can take to troubleshoot before we get the installer back out here?
Here is a drawing of the setup;
well-setup.jpg
 

Valveman

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6.5-7 amps is full load for a 3/4HP and without a CSV it should be drawing this much all the time. 4.5 amps sounds like the pump is being restricted, as pumping the well dry will usually cause 3.5 amps or lower. The Cycle Sensor just doesn't go to zero, but your pump is not running when it shows minimal amps.

A pump screen clogged with gravel will cause low amps, and the gravel will fall off when the pump shuts off. A stuck check valve or some other restriction is also possible.
 

Hardyh

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4.5 amps sounds like the pump is being restricted, as pumping the well dry will usually cause 3.5 amps or lower.
Ok thanks, at least it's probably not the well itself.
A pump screen clogged with gravel will cause low amps, and the gravel will fall off when the pump shuts off. A stuck check valve or some other restriction is also possible.
The pump is about 20ft from the bottom of the well, would sediment still be an issue? Could changing the pump this spring have effected the bottom of the well? Is there any troubleshooting that could isolate whether it might be sediment, stuck valves or something else?
 

Reach4

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If sediment, expect sediment to be pumped up. I am not saying this relates to your symptom.
 

Hardyh

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Our water comes out clear and we've never had sediment (is that something the foot valve would block or would that get through?) The well water seems high in minerals (whatever causes that calcium buildup on faucets) but otherwise it is clear.
 

Hardyh

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Does it go back to pumping a good volume after letting the well sit
Yes, it comes back like nothing happened. I was just confused by the depth measurement I took the other day, when I intentionally measured immediately after using water and the water line was still right around where it should be when the well is full. The only thing I haven't been able to do yet is get a measurement from the well when the low amperage situation is actually happening.
 

Reach4

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Watch the current as you approach one of these events. Does the current drop smoothly for a while? I would expect that as the water level drops. Maybe take a movie of the display with your phone for later review. Maybe use 30x time lapse.
 
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Hardyh

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Mine never goes under about 4.4 or so, and it takes about 30seconds or so to get there from 6.5amp.
 

Reach4

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Mine never goes under about 4.4 or so, and it takes about 30seconds or so to get there from 6.5amp.
So in that thirty seconds, the pressure tank does not get filled, does it?

If you turn the Cycle Sensor to a trip lower than 4.4, what happens? Pumping air? Reduced pressure if you are using water? Don't go long that way, but manually cut the pump off after maybe another 30 seconds. I am not a pro.

You don't actually have a foot valve, but you have the equivalent. A foot valve is a check valve plus a screen. You have a check valve at/just above the pump, and the pump has a screen. It is just not called a foot valve.

Also, is that 3/4 HP pump a 5 gpm, 7 gpm, or 10 gpm pump? I am suspecting that the pump may not have the pressure-generating ability to pump water into your pressure tank as the pressure rises.
index.php


A 3/4 hp 10 gpm pump would be much less capable of lifting than a 3/4 hp 7 gpm pump.
 
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Hardyh

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So in that thirty seconds, the pressure tank does not get filled, does it?
No, even under ideal circumstances it takes about a minute to fill the pressure tank/reach the cutoff pressure (60psi).
If you turn the Cycle Sensor to a trip lower than 4.4, what happens?
I have held the Manual button down on the Cycle Sensor (to override the dry cutoff) and it seems to just hover around that 4.4amps and the pressure no longer builds. It also doesn't pump out air but with a faucet open it keeps slowly losing pressure (like the pump suddenly can't produce more than 30 or 40psi). I have not tried this for very long being concerned about burning out or otherwise messing up the newly installed pump. If I were to guess I would say that the pump would probably continue chugging along at whatever small psi it can muster (somewhere between 10psi and 30psi) but again I've been nervous to let it run that low for more than about 30 seconds.
Also, is that 3/4 HP pump a 5 gpm, 7 gpm, or 10 gpm pump?

That's a good question, I'm not sure what exact model the well guy swapped ours out with.
A 3/4 hp 10 gpm pump would be much less capable of lifting than a 3/4 hp 7 gpm pump.
So the higher gpm is not more desirable (just sounds counter-intuitive)?
 

Reach4

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Yes, counterintuitive. Think of climbing a slope on a bicycle in high gear.

5 gpm has more stages than 7 gpm, which has more stages than 10 gpm. So 10 gpm would usually be cheaper.

Nice sketch.
 

Hardyh

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Thanks, so based on the chart you posted @250ft a 5 or 6gpm 3/4 HP pump or a 1HP pump with 5gpm or less would be ideal? I don't quite get the PSI on the vertical axis (is that cut-in PSI?).
 

Reach4

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Thanks, so based on the chart you posted @250ft a 5 or 6gpm 3/4 HP pump or a 1HP pump with 5gpm or less would be ideal? I don't quite get the PSI on the vertical axis (is that cut-in PSI?).
Cut-out and cut-in. Figure a box of squares where the width is the static water level on the left, and almost the pump depth on the right, and the height is cut-in and cut out. I think you would like the pump to be pumping a gpm or two if the water has fallen and the pressure tank is near 60.

index.php
 

Hardyh

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So I was just able to take a depth measurement during an 'event' and I still hit water at around 50ft down. The well had a bit of a gurgling sound and while I had the pump going somewhere around 4.5amp it almost sounded like a trickling as well (couldn't tell but it did sound different than once the pump was off). Note that the pipe down to the pump is a single length of the thick blue poly.
 
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