Eking by with old pump

HorseflyHorsefly Registered Users Posts: 401 ✭✭✭✭
Some here have probably seen the evolution of our design for Solar power at our very off-grid cabin (discussed here).  Now I'm focused on the well pump, and thought a new thread was appropriate.

Here's the background:

As discussed in the other thread, the cabin has been wired for 110VAC and used a generator for its entire 42 year life. We actually have the same well pump all that time. I think the well was drilled about 90 ft deep, but the water table is only about 40 ft below the surface.  The current pump is a 1/2 hp, 110V, 2-wire pump. The water is pumped into a pressure tank (I would estimate about 40 gallons, 35 psi switch), and under normal use when people visit the cabin the pump has to run nominally about 5 times per day, for about 3-5 minutes each run.

As I designed the solar power system to support the cabin, the well pump was clearly the driver. We do have a small microwave oven, but it is used very seldom. Everything else is either LED lights, phone chargers, or laptop computers.  The problem was we really didn't know how much the inrush current was on the pump, so I didn't know what surge we would need the inverter to support. Without showing all the details, I'll just tell you that I ended up going with the Schneider SW4024, which has a nominal / continuous capacity of 3500W, but can handle 4000W for 30 minutes or 7000 watts for 5 seconds. 

@mike95490 scared me when he posted a table that showed a 1/2 hp, 110V, 2 wire well pump could have as much as 55A inrush surge, which would be bad. The current 7500W generator and the previous 5000W generator seemed to handle the pump fine, so I was hopeful we were still OK. However, I was still worried, and the low amount of snow allowed me an opportunity to take my brand new inrush-capable clamp meter up to the cabin and do some testing. The inrush on the pump turned out to generally be 34A, and as high as 34.5A during my 6-8 tests. I guess that is good news in that it sounds like it would be OK with the inverter (just barely), but it still has me worried.  I'll be drawing something between C and C/2 for a split second, which I'm sure isn't good, even with my AGM batteries.

Before anyone says it: We know the long term solution is to replace the 110VAC 2-wire pump. The darned thing is 42 years old. We know it can't go on forever, but at this point I feel like it is part of the family. I'd rather let it go until it decides it is time to part ways with this earth. I've sketched out several alternatives for the next generation, which range from going with a 230VAC 3-wire (since the SW4024 has a split phase output) or a 24VDC pump, or a low volume DC well pump into a cistern-like tank and a second pump (probably also DC) to keep the pressure tank filled from the cistern.  A know all of the longer-term solutions we are looking at will make my battery bank happy, and probably make my inverter overkill.

What I am looking for now is ways to limp along with what we have until the well pump gives out, assuming it continues well after we have installed the solar.  I think what it comes down to is finding a way to limit the inrush current.  I've determined that I certainly can't use a VFD with our single-phase motor, but I had hoped perhaps I could use a soft-start. However, in searching threads here and elsewhere, I've seen references saying that you can't use a soft start with a single-phase motor. I found this device which sounds like it would work. Are there things that preclude this with a well pump, like maybe a capacitor on the start winding? (can't believe I'm even referencing the capacitor on the start winding, as I didn't know there was such a thing until my Google activity today)

Clearly I'm also interested in other ideas.  Thanks in advance!

Steve

Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.

Comments

  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    I'd just try it with your inverter.  There are some < $100 submersible, 24V well pumps now.   Cheaper than the soft start device and probably OK for a cabin.

    I am available for custom hardware/firmware development

  • mcgivormcgivor Solar Expert Posts: 3,814 ✭✭✭✭✭✭
    I too would try it with the inverter, the inrush is of short duration, my pump is a 1 hp multi stage, has an inrush of 44A @ 220V and the inverter is a 24v 2000W, has no problems starting, run current is 4A. Only use it once  or twice a week whilst the sun is shining to fill a 3000 liter holding tank, then a small 100W demand pump to provide running water.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • AnawaAnawa Solar Expert Posts: 211 ✭✭✭
    Have you looked at the Grunfos SQ Flex line of pumps? They operate either AC or DC. 

    I completely understand your "attachment" to the old pump. However, slipping a brand-new pump down the well pit that will operate with your existing wiring, as well as, anything you decide in the future can be fulfilling experience. Your family can retire the old one with dignity. 

    Maybe be something to consider. 
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • HorseflyHorsefly Registered Users Posts: 401 ✭✭✭✭
    mcgivor said:
    I too would try it with the inverter, the inrush is of short duration, my pump is a 1 hp multi stage, has an inrush of 44A @ 220V and the inverter is a 24v 2000W, has no problems starting, run current is 4A. Only use it once  or twice a week whilst the sun is shining to fill a 3000 liter holding tank, then a small 100W demand pump to provide running water.
    Wow! 44A @ 220V, that's over 9000W! (Well, actually over 9000VA)  If that doesn't bother your 2000W inverter, maybe we are OK.

    Interestingly, your setup is similar to one of the alternatives we are considering: Replace the pump with a relatively low GPM DC pump, which can fill a large cistern-like holding tank, and then use a separate small DC pump to keep the pressure tank filled for house use.
    Anawa said:
    Have you looked at the Grunfos SQ Flex line of pumps? They operate either AC or DC. I completely understand your "attachment" to the old pump. However, slipping a brand-new pump down the well pit that will operate with your existing wiring, as well as, anything you decide in the future can be fulfilling experience. Your family can retire the old one with dignity. Maybe be something to consider.
    Yeah, I did see those. They look pretty sweet. I'm also looking at some of the Sun Pumps, like this one.  I guess I wouldn't say we are attached to the old pump, but our pump guy said he is pretty sure we have the oldest operating well pump in a three county area. It would be a shame to pull it out before it gives up.
    jonr said:
    I'd just try it with your inverter. There are some < $100 submersible, 24V well pumps now. Cheaper than the soft start device and probably OK for a cabin.
    Yep, I think you guys have me convinced. I've book marked the soft start device just in case, but I think we'll just keep our fingers crossed!

    Thanks you guys!

    Steve
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • softdownsoftdown Solar Expert Posts: 3,499 ✭✭✭✭
    There is no scenario that would involve me replacing a working well pump. You got a keeper the first time.

    I bought a spare 1/2hp pump when I bought mine in 2011. Long story that one. You can tell the start up surge is significant...even with the 3648 inverter. My pump is also at 100'.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • HorseflyHorsefly Registered Users Posts: 401 ✭✭✭✭
    softdown said:
    There is no scenario that would involve me replacing a working well pump. You got a keeper the first time.
     
    Yeah, I think that is the point. We should be fine, but WHEN that pump gives up the ghost, we need to have a plan in place that will better fit our solar set-up.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • softdownsoftdown Solar Expert Posts: 3,499 ✭✭✭✭
    Can old pumps be rebuilt? I also get sentimental about old stuff.

    Think I may just slap another 1/2hp pump in it....when/if this one gives up the ghost. I've bought/sold hundreds of various water pumps in my life. Your pump deserves a medal.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Softdown, yes, depending on the quality of the water in the 'hole' , like pumping a bit of sand occasionally, ...  I kept my first 1/2  and 1/3 hp pumps when we deepened the well (4 times) until we got 30 gal/min at 305' and now have a 3/4hp pump. the 1/2 hp pump upon inspection / testing showed it was a bit below spec, so they rebuilt the multi stage pump and it sits waiting to be used in an emergency... or here at the cabin... the motors seem to go on and on and on these days
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • softdownsoftdown Solar Expert Posts: 3,499 ✭✭✭✭
    What is a normal charge to rebuild a 1/2hp well pump?

    My well adviser was an extreme prepper...and I emphasize extreme. He talked me into the backup pump...wrapped in foil...of course. In 2011....people were still a bit skeered. The price was also pretty great.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    I don't remember exact figures but well under 1/2 the cost of a new one at. that time, so I felt it was a good bargain for a back up... needed a couple of 'steps' replaced...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • softdownsoftdown Solar Expert Posts: 3,499 ✭✭✭✭
    You could do an 80 gallon pressure tank. It is amazing that the membrane on the 40 seems to be intact? Must have bought a good one last time...
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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