Using a Amtrol WX 350 to improve well efficiency

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Michaelco

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I finally ran a few amperage measurements, and saw very little difference in the current draw for full flow rate, restricted flow and dead headed condition.

I turned off the power to the well pump, and pumped 1500 gallons from the storage tank to irrigate a few rows of trees in the orchard. Having the well pump's power off kept the well's water level at it's highest level, when I measured the pump's current draw.

I set up a video camera to capture the clamp on meter display and flipped the breaker for the well pump.
Full Flow (no restrictor) - 6.6 amps.
Throttled Flow to 3 GPM - no change (still 6.6 amps)
Throttled Flow to 0 GPM ~ 6.5 amps

Looks like the 3/4 HP pump is not the right pump for the job, and the SymCom's most sensitive setting wouldn't have a chance to catch either dead head, or dry well condition. I adjusted the throttling valve to match as closely as I could to what I think the well is capable of sustaining, and plan to change out the pump if and when the pump fails - The biggest downside I can think of with this approach is a pump failure, if it occurs, may not come at a convenient time.

Are there any other potential issues?

Are there any good source for sizing of well pumps?
 

Valveman

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It must be a 10 GPM series Pentair brand of pump. Those particular ones don’t seem to drop in amps at all when the flow is restricted. The fact that the pump doesn’t drop in amperage when restricted is a good thing for the Symcom. This way it doesn’t have to be sensitive enough to know the difference between low flow and dry run. The pump runs at 6.6 amps pretty much no matter what you do, so when it pumps the well dry, any drop in amps will be enough for the Symcom to see the difference.

In this case the Symcom can tell the difference between deadhead and dry run. There is no difference in amps between deadhead and full flow, but the amps will drop lower when the pump runs dry.
 

Michaelco

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The pump runs at 6.6 amps pretty much no matter what you do, so when it pumps the well dry, any drop in amps will be enough for the Symcom to see the difference.

In this case the Symcom can tell the difference between deadhead and dry run. There is no difference in amps between deadhead and full flow, but the amps will drop lower when the pump runs dry.
Unfortunately I don't know what pump was installed. So, if I understand correctly, the current draw when deadheading, on this pump, is significantly different than when it runs dry - is this correct? Then, the SymCom trip point set at 90% should work? To make that work, the pump current would have to drop below ~5.9 amps when the well runs dry. I didn't run it long enough to run the well dry, as I thought the dead head current draw was going to be approximately the same as the "run dry" case. Could remove the flow restriction, monitor the current, and see if the SymCom trips - I did leave the SymCom sensitivity set at 90%.

Right now, it takes roughly 6 hours to replenish 1000 gallons in the storage tank - the pumping costs are around $1.50. Assuming the SymCom would catch the "run dry" case, pumping out at a faster rate would reduce the electricity costs, but would cycle the pump more often. Plus, would reduce the well productivity (if I understand the situation correctly). Not sure how to assess what would be a better way to go.

I would think the best thing would be to have had a smaller pump, which would run at a reduced cost, and more likely to trip the SymCom in both the "dead head" and "run dry" cases - but, at his this point, the cost to swap out the pump isn't trivial - and, would pay for a lot of electricity.

Any recommendations/thoughts?
 

Valveman

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When the amps do not drop when going from full flow to restricted flow, there should be a fairly good drop when the pump runs dry. You should test it as you said to make sure, but the 90% figure should work because I think it will drop from 6 to about 4 amps when running dry.

If it works you can remove the restrictor and let the pump cycle with the Symcom, as long as it runs at least a few minutes at a time. 10 minutes of run time would be good, even if you have to restrict it a little. It is the amount of time before the pump restarts that takes some trial and error to get right.
 

Michaelco

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Thanks - for the info. We're due for some rain, so will hold off running the test until next time I irrigate - There's over 300 gallons in the casing (above the pump) when the well is completely full. So the pump should run for over an hour (ignoring any influx of "new" water into the well). Like you said, figuring the restart time is an "unknown" - at least without a water level measurement. My thought was to draw down the storage tank by 1000 gallons, with the restart timer at the default setting, and measure the time it takes to refill the storage tank. Then repeat that process, increasing the restart timer each time.

I would think the time it takes to refill the storage tank should decrease until I hit a restart timer setting which is longer than needed (e.g. well totally recovers, and pump isn't taking advantage of well being full). Does that seem reasonable, or is there a better way (that is, without use of a level measurement tool).
 

Michaelco

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Thanks for confirmation - wasn't sure if my approach to "zero in" on a good restart timer setting was realistic.
 
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