Grundfos SQ submersible internal switch problem

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StephenCanner

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Hello,
Background:
I am off-grid and running off an inverter (Magnum MS4448PAE) and batteries. For decades we've run "off-the-shelf" 240V pumps directly off the generator but over the years we've gradually upgraded the solar electrical system and finally this weekend I was ready to switch to a Grundfos 10 SQ07200 and run it off the inverter. I don't know the exact specs but the well is about 100' deep, the static water level is about 30', the pump sits about 80' down. At the time it was drilled, it supposedly produced about 3 gpm. We've always had to be careful not to run too much water at a time to let it refill. We have an 86 gallon pressure tank and typically only have to fill it about once per day. The well can be a little bit sandy, but over the years it doesn't seem to have caused much of a problem.
I installed the new Grundfos SQ pump yesterday. The new pump ran fine at first. I shock chlorinated the well and let it sit over night and this morning I was pumping the bleach water out. I alternated emptying out the system and pumping up the pressure tank with what I thought was ample time for the well to refill in between. At one point during the pumping up cycle the pressure stopped increasing so I wondered if the water level had gotten too low, and cut the generator off.
I emptied out that (still bleach-smelling) water from the system, figuring I would only need to let the water rise again and would be fine.
The next time I ran the pump about an hour later it sputtered a bit but did not produce much water, so again I shut it off.
Now when I run it it doesn't come on at all. (The pressure gauge doesn't jiggle, and there is no noise when I listen down the well). There is definitely voltage to it. There is no evidence of a short to ground. The resistance across the two wires is infinite. I didn't test the resistance before I installed it, but the old pump (which still worked fine when I took it out) has a resistance of 3 ohms. So I assume one of the internal protection switches inside the pump has switched off and won't come back on again. Presumably either due to low water or some other blockage. The manual is a little vague on exactly how the dry run protection works and whether it also has other protective switches besides the dry run protection (e.g. protection against running with some blockage). I've read somewhere that the SQ may be particularly sensitive to sand.

Supposedly it will come back on after 5 minutes, or you can reset it by cutting the power for 1 minute. It has had the power off virtually all day except for my occasional retries. I've tried leaving the power on for 5 minutes and that didn't help. The pump is out of warranty because I optimistically bought it 3 years ago and only now am getting it installed. There is not a local official dealer or serviceperson.
I guess I'm going to haul it out of the well and if I can't find anything to fix, I'll put the old one back in. I think the inverter can handle that one too but it will be a little harder on everything because it is definitely NOT a soft start. I would really welcome any ideas on this. Thanks in advance.

EDIT: the cause has been found, it is a wiring issue, not a pump issue.
 
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Valveman

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The slow 5 second ramp up of the SQ pump is good for running on generators, but I don't think it will take a lot of sand. You need a clip around AC amp meter. If 230V is going down to the pump yet there is zero amps, the overload has tripped or a wire is broken. Bound up by sand would cause high amps for a few seconds before the overload trips, then zero amps.
 

Reach4

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I think you are saying that the pump now produces no water, even after the power to the pump has been off for an extended time.

Infinite resistance could also be a bad splice or a broken power wire. But yes, it could be the motor.

To be sure, are you measuring the voltage across two hots at the output of the pressure switch, rather than reading 120 volts to ground on each wire? You might be offended by the question, but it happens sometimes.

Assuming your voltage across the two hot pressure switch outputs measures about 240 volts, you could try taking a voltage reading closer to the pump. If that still shows 240 volts, pull the pump and measure at splices at the pump.

I would have chosen a 5SQ05 pump instead of a 10SQ07. I also would have added a flow inducer if you had room.
 

StephenCanner

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Thank you so much for your responses. I feel like an idiot, but I made a wiring mistake and the pump was not getting any voltage (even though I was measuring 240V at the output of the pressure switch). Long story. The mistake itself was understandable but I feel idiotic for not diagnosing it sooner. I was thrown off by the fact that it worked initially and then stopped when it (presumably) started to run dry. I made a change to the wiring while I was waiting for the well to refill and that's when the problem was introduced.

Didn't figure it out until I had gone through the work of putting the old pump back in and it didn't work either. A non-contact voltage tester would have helped a lot, since I didn't want to expose any splices to measure voltage. I actually considered running into town to get one at one point but instead I continued with my folly.

Apologies for wasting your time. I'm curious about Reach4's suggestion about getting a different pump. I'll look into that in case I ever try buying another one. Thank you.
 

Valveman

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At 100' deep there is nothing wrong with the 10SQ07. But you may want to check into how the dry run feature works on the SQ. A lot of people still use a Cycle Sensor to protect the pump as it can be adjusted to say off as long as needed.

 

Reach4

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I'm curious about Reach4's suggestion about getting a different pump. I'll look into that in case I ever try buying another one. Thank you.
My point was that a 1/2 hp SQ pump was easier to run from a generator than a 3/4 HP. If your current generator powers the 3/4 HP pump nicely then that is not a problem.

But since you are switching to a battery-powered system, maybe using more amps for a shorter time to pump the 28 gallons into the 86 gallon tank would use less energy (Wh) per fill, despite using more power (W) while the pump is on.

Next time you sanitize, you might consider my well and plumbing sanitizing write-up. Sanitizing can reduce H2S and iron slime, and if you kill more completely, you can increase the time for colonies of SRB or IRB to re-establish. https://terrylove.com/forums/index....izing-extra-attention-to-4-inch-casing.65845/
 
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