need well pump advice

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Megunticook
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need well pump advice

Post by Megunticook »

I'd like to replace our conventional well pump which is the biggest load on my system. We're grid-tied with battery backup so hasn't been an issue but if/when we have more extended grid outages I'd like something that won't draw down my 430 amp-hour battery bank too quickly.

We have a deep well, 580 feet. No high-demand water use so 2gpm flow is probably going to be fine. I'm looking at the Grundfos 3 SQF-3 (https://thesolarstore.com/manuals/SQF_B ... SL-010.pdf) which runs about $2400. Made in Denmark, looks to be a high-quality product. Should I be looking at any other products?

Any advice from folks who've already gone through this process?

Current pump runs on a dedicated 240V/15A circuit, probably simplest to continue using that with the new pump (the Grundfos can handle that).

Thanks for any comments/suggestions. Just thought I'd check in before pulling the trigger on this purchase.
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Re: need well pump advice

Post by raysun »

I don't know about the deep well pumps, but my Grundfos MQ3-35 pressure pump is well built, gives trouble-free operation, and is smarter than me (at least when it comes to pumping water.)
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Megunticook
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Re: need well pump advice

Post by Megunticook »

That's your well pump? Does it run on 240AC? How many amps does it draw? Soft start or does it require a lot of amps initially to get started?
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raysun
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Re: need well pump advice

Post by raysun »

Actually, its a pressure pump, rather than a well pump. (Private wells are rare on Hawaii Island.)

I have it wired for 120V. Starting amps = 29. Running amps = 10.

Since its a different pump and application, my comment was just about general build quality.
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Re: need well pump advice

Post by JRHill »

raysun wrote: Fri Sep 10, 2021 9:17 am Actually, its a pressure pump, rather than a well pump. (Private wells are rare on Hawaii Island.)

I have it wired for 120V. Starting amps = 29. Running amps = 10.

Since its a different pump and application, my comment was just about general build quality.
I have an 11SQF2 that was the first improvement as we started this project. It's primarily powered by 48vdc solar but the batteries (old Trojan golf cart units) can be bypassed just by plugging it into the Grundfos CU100 switch box. Its pretty cool. If the box sees 120vac a relay cuts the DC and connects the AC. The pump doesn't care about AC or DC or even polarity. Its a soft start and only 750watts on 48vdc - a little more on 120vac but it pumps harder.

You've got a pretty deep well so the application/depth/gpm charts would be important for selection. Have had no issue for the 14 years its been in service.
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Megunticook
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Re: need well pump advice

Post by Megunticook »

So my primary goal here is to reduce load on the battery bank. Does something like a Grundfos SQF use less power that a conventional pump, or is the soft start the only advantage?
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JRHill
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Re: need well pump advice

Post by JRHill »

Megunticook wrote: Fri Sep 10, 2021 8:00 pm So my primary goal here is to reduce load on the battery bank. Does something like a Grundfos SQF use less power that a conventional pump, or is the soft start the only advantage?
That is a curious question. We use a lot of water in the summer with water tanks for the critters and the gardens. My pump is set at ~170' and I looked up its chart - it only goes to 395'. I don't know how deep your pump is set but I did see this info for the pump you are looking at using: Max Head: 395 ft, Max Flow: 3 gal/min. And if you are filling a pressure tank there is more to the calculation. I'd be a little nervous about this until I spoke with a well guy. You may be past the capabilities of this pump.
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Megunticook
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My RE system: 6.4 kW solar array (21 QCell 305 panels in strings of 3)
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Re: need well pump advice

Post by Megunticook »

Thanks, I'm actually in touch with several solar-oriented pump vendors and will have another chat with my well driller, although he wasn't super helpful last time we talked.

Realized I was making a rookie error too, in that it's the static water level rather than well depth that really matters here. Need to measure that.

Also found some notes where I had done a flow test on my current pump a while back, 7gpm. Probably don't want to go below that.

Still not clear if these Grundfos SQFs use less energy overall in addition to the soft start--the Grundfos brochure claims they do but the spec. just shows maximum power input of 1400 W. I don't believe that's less than the Gould but since my driller couldn't even tell me what pump he had installed (OK it's been 20 years but still, really?) I'm not exactly sure. I know when the well pump kicks in I can see my inverter's load go up well above 1kW, so it has to be at least 800-900W.
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JRHill
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Re: need well pump advice

Post by JRHill »

I'm sure the State of Maine requires a well permit doesn't it? If so the well driller probably had to file a report with some detains of the drilling. Total depth, static level, GPM and maybe even the stata at various depths as drilled. Does the well head have a plate attached to it or any ID numbers stamped in it?
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Megunticook
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My RE system: 6.4 kW solar array (21 QCell 305 panels in strings of 3)
GS8048A FLEXpower Radian (Radian 8048A, 2 FlexMax 80 cc's, Mate 3s, FlexNet DC, Hub)
8x6v Rolls-Surette 550 FLA batteries, 428AH
Location: Maine
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Re: need well pump advice

Post by Megunticook »

I have the well driller's report but it doesn't list static level. When I last talked with him and asked him that he advised me to drop a pebble into the well and count the seconds before the splash. Nice guy but not super professional.
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JRHill
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Re: need well pump advice

Post by JRHill »

Pebble drop - that's kind of funny but I suppose it would get you in the ballpark.

At one time I thought I'd better check my static level after a neighbor had to have his pump lowered (we're in the 8th year of drought and that was 5 years ago.) I used a spool of fishing line with a couple of washers and a chunk on styrofoam big enough that it would float with the washers below by it a foot. It worked great and I could easily tell when the line went slack. When I sensed the water I marked the line with some tape and began pulling the line out 50' at a time. It was accurate and thankfully the static level was almost unchanged.

Since we're on well stories: around that same time I thought I should sanitize the system so I dumped two gallons if clorox down the column. Dumb, dumb. A lot of fine granules of rust got washed off the column. Even though I waited an hour or so when I started opening faucets one by one that crud got sucked up and pushed around the whole system including the pressure tanks. It took months before the aerators, shower head, ect. quit plugging.
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