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  • Please critique my cabin/pumping design

    First let me give you a little background. I'm developing a self-sufficient homestead in the foothills of the California Sierra. Our homestead land is on a south-facing ridge at about 5000 feet. Right now our cabin is powered by a meager 400 watt system charging Trojan T105s and powering a 1000 watt Xantrex inverter. It's OK for lights, TV, and occasional power tools. We have extensive garden space and about 110 orchard trees in the ground right now, that must be watered weekly. Our 400 foot deep well has a 1.5hp 240VAC Grunfos pump powered solely by generator power. The static water level of the well is at -100 feet, with the pump down at -380 feet.

    We'll be retiring in the not distant future and I'm in the design phase for a more substantial system that can power the whole cabin and the well pump. I'm looking at this Renogy kit as the heart of the new system.
    http://www.renogy-store.com/3600W-24...cabin3600p.htm

    I'm at a crossroads now, debating whether or not I can successfully power the AC well pump on solar, or if I should install the smaller 2700W system and keep using the generator. Let's assume I build the system with four 3panel strings of Renogy's 300Watt panels. I'd wire them such that each string of three produces 900 watts at 112.5 volts, going into a Midnight solar charge controller. This will charge a bank of 8 L-16 Trojan batteries, wired in series for a 48V battery bank. Perhaps I'll utilize Magnum's 4400 watt 120/240V inverter.

    Assuming these panels are putting out 80% of rated output at local noon, that would give me about 2800-2900 watts of instantaneous power to start the well pump. I think the starting amps of this pump is ~11.6 amps at 240VAC which works out to be 2785 watts. So, if the inverter actually puts out that much power at 240V, I could start the well pump without even drawing any power from the batteries. Is that realistic to think that way? Right now I'm assuming that the rest of the cabin would be satisfied with about 4000-5000 watt-hours per day to power the rest of 21st century living, like a regular refrigerator, satelite connection, TV, and lights.

    I'm going to need about 3000 gallons of water per week, and my pump output is about 275-300 gallons per hour, so that means about 10-11 hours of pumping per week. I have 5000 gallon storage tanks at the top of the hill. I normally pump once a week all day long, fill the tank, then let if fall back by gravity to supply water on demand. I'm assuming I can only pump water for ~3 hours per day, when the panels are producing at least 1100-1200 watts. I'm thinking that if I delay turning on the pump till noon, the morning sun will top off the batteries by noon. By my calculation, the panels might be producing at least 1200 watts till about 2:00-2:30 in the afternoon.

    I'm playing with ideas on how to improve afternoon solar production. Using the sizing program, a Midnight 200 can only handle 4 strings of three 300W Renogy panels. BTW, Renogy is local, so I can buy their panels cheaper because I can pick them up without shipping charges. One idea is to add additional panel strings in directions other than due south. Let's say I took 6 strings of 3 panels, two facing southeast, two facing due south, and two facing southwest. At 9am the southwestern panels would be in the shade, with more or less zero production. The southeast panels would be at full output (~1440 watts from 6-300watt panels) while the south-facing strings might be at about 1/4 output (maybe 360 watts). That level of output should stay about the same as the sun swings over from east to west. By the time the southwest panels start recieving light, the southeastern panels should start shading. I'm assuming that only 4 strings will be producing significant power at any given time.

    By my math, I'd be producing about 1800 watts more evenly from about 9am to 3pm as the sun switches from one string to another. Does an idea like this work in the real world? Don't want to destroy an expensive controller with too much experimentation. The down side of this stratege is the panels won't reach the same highest peak if they were all producing max power at noon, which would be ~2800-2900 watts, so about a kw of power will need to come off the batteries to top off the panels when starting the well pump. Assume that the greatest water needs coinside with maximal insolation rates, in midsummer

    Will this work in the real world?
    Thanks for reading through this!

  • #2
    Welcome.
    Well, that "kit" you linked to, is only the panels, wire and charger. No batteries, mounting racks, or inverter.

    Well pump. My "1/2 hp" pump actually draws 1,000w according to the very good meter on my inverter. That includes the PF losses. Since there is some economy of scale, I suspect your 1.5 hp pump to pull a little under 3Kw, but more than 2Kw. Assume starting surge is 5-10x running power. The starting surge is what you need a $400 peak reading meter to measure, or a friendly electrician to loan you his. Do you know if it is a 2 wire or 3 wire pump - 3 wire start a bit easier off inverters .

    Using arrays in different orientation is often an excellent way to provide virtual tracking, more than 3 facets and you start having 0 contribution from some of your expensive panels.

    I too, pump to elevated storage for use anytime, and have a simple lawn sprinkler timer in the pump relay circuit (old style AC clockwork motor and mechanical trip levers) I did install a manual off switch for winter use so I can not worry about a week of rain and the pump running the battery down. I'm planning to add a manual ON to override the float switch at the tank, so I can test things easier.

    I've found with my Classic 200, more than 2x battery voltage, puts you into a lower efficiency situation, as it works much harder to down-convert to battery voltage.

    I have heard good and bad stories about different brands of inverters working well with generators, I have my XW working well with any of my 3 gensets.

    Plan on at least one more genset to use alternately and as a spare. (last year I had 2 fail on me)
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      If it were me I would just plan the stand alone system for the house and leave the big pump on generator.

      This way you can have a smaller system, and not be worried about weather and if you can pump etc, or need to start the generator anyway, less chance of stressing batteries.

      I have a gravity feed tank and have one pump that runs off generator to fill it but another smaller one that runs off solar. The small one does not pump fast but can runs for hours on end and I have it set to run on a timer during the day when where not home.

      Comment


      • #4
        Originally posted by Mike90250 View Post
        Welcome.
        Well, that "kit" you linked to, is only the panels, wire and charger. No batteries, mounting racks, or inverter.
        That's right. I was planning on buying L-16s at the sample supplier that I got my T-105s at. Got those for 125$ each, so I think I can get a good deal there for the L-16s. I am planning on making my own mounting racks out of perforated angle iron. I have a little MIG welder that I love to use. Sometimes I think I break things just so I can weld them back together. To make the frames supporting my DM solars I welded metal sheetrock edging together. As flimsy as that is, when welding into a truss-like pattern (like an overhead highway spanning truss) it is surprisingly strong. The winds on my ridge have knocked down 18" oaks, but my frames have supported my panels well. I'm designing the new frames such that they'll be seasonal adjustable. As for the inverter, I mentioned the Magnum, because it uses two out of phase 120V circuits to make the 240V one. I was hoping it would be adequate to power the rest of my house loads while the pump was running. I was thinking about maybe shutting the frig off whenever I'd want to start the pump so the two wouldn't ever try to both kick on at exactly the same time.

        Originally posted by Mike90250 View Post
        Well pump. My "1/2 hp" pump actually draws 1,000w according to the very good meter on my inverter. That includes the PF losses. Since there is some economy of scale, I suspect your 1.5 hp pump to pull a little under 3Kw, but more than 2Kw. Assume starting surge is 5-10x running power. The starting surge is what you need a $400 peak reading meter to measure, or a friendly electrician to loan you his. Do you know if it is a 2 wire or 3 wire pump - 3 wire start a bit easier off inverters .
        Doing the math, assuming 1/2 hp is 380 watts, that 1000W starting surge would be 2.6X it's rated consumption, which is in line with what I was expecting. If you read the specs for my Grunfos pump, it's documented starting amps is 11.6, which at 240V comes out to be 2785 watts. That works out to be about 2.5X. My pump is three-wire, single-phase 240VAC

        The other big-ticket item that I've not decided upon yet is the power center. I'm a very good flea-market scrounger, and I think I can gradually build up the parts that I need to build a power center piece by piece, though I may need to buy breakers and surge protector's retail. I can read basic wiring diagrams, so I'm not afraid of that, though I may decide to spend the money on that in case a code inspector ever finds my place.

        Comment


        • #5
          Originally posted by MichaelK! View Post
          .......Doing the math, assuming 1/2 hp is 380 watts, that 1000W starting surge would be 2.6X it's rated consumption,....
          Maybe I wasn't clear, the 1,000w is the running power, on a 1/2 hp pump. There are many types of losses, the 750W = 1hp is the theoretical power, not real life where there are losses. You will need to actually measure the pump when running. And also look up the Locked Rotor current, that's what the inverter, cables, and batteries need to supply to start the motor.
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Originally posted by Mike90250 View Post
            And also look up the Locked Rotor current, that's what the inverter, cables, and batteries need to supply to start the motor.
            I did look up the specifications, and it did not specify "Locked Rotor Current", it documented "Maximum Current" which I stated above is 11.6 amps at 240V. Are they the same?

            Comment


            • #7
              Not sure if this helps but I just had a well dug. 130' and I believe the pump is at 116'. They installed a Grundfos 3/4 horse 230v pump. Model 10SQ07-200. Rated 8.4a. Grundfos recommends a 2,500 watt generator for my pump.

              My builders are currently getting water from the pump using a Honda EG3500 generator. It's 3,500 watts max and 3,000w continuous. They say it doesn't even break a sweat starting the pump.

              My plan is to eventually run the pump with a Schneider Conext SW4048 inverter with a 208ah 48v battery bank. I will have a pretty large pressure tank but no holding tanks. Vacation place for now and my water usage is nowhere near yours.
              Conext XW5548
              Conext MPPT60-150

              Comment


              • #8
                Originally posted by MichaelK! View Post
                I'm at a crossroads now, debating whether or not I can successfully power the AC well pump on solar, or if I should install the smaller 2700W system and keep using the generator.

                I'm going to need about 3000 gallons of water per week, and my pump output is about 275-300 gallons per hour, so that means about 10-11 hours of pumping per week. I have 5000 gallon storage tanks at the top of the hill.

                I'm playing with ideas on how to improve afternoon solar production. Using the sizing program, a Midnight 200 can only handle 4 strings of three 300W Renogy panels. BTW, Renogy is local, so I can buy their panels cheaper because I can pick them up without shipping charges. One idea is to add additional panel strings in directions other than due south. Let's say I took 6 strings of 3 panels, two facing southeast, two facing due south, and two facing southwest. At 9am the southwestern panels would be in the shade, with more or less zero production. The southeast panels would be at full output (~1440 watts from 6-300watt panels) while the south-facing strings might be at about 1/4 output (maybe 360 watts). That level of output should stay about the same as the sun swings over from east to west. By the time the southwest panels start recieving light, the southeastern panels should start shading. I'm assuming that only 4 strings will be producing significant power at any given time.

                By my math, I'd be producing about 1800 watts more evenly from about 9am to 3pm as the sun switches from one string to another. Does an idea like this work in the real world?
                Yes it actually works. This power curve was produced by this 3 orientation system
                in March; it would be even broader in June, and if all the surrounding shade was
                removed. Some careful simulation could improve on this initial effort regarding
                the size & orientation of panel groups.

                All strings are the same voltage (same number of cells), so the power is handed
                off smoothly as the sun moves. It has the additional benefit of considerably
                increasing output on a cloudy day, when light is dispersed and orientation doesn't
                matter so much. In allowing the rest of the system to be smaller, the less efficient
                use of panels is justified here. I use the cheapest panels, mostly the generic 60
                cell "grid tie" type.

                I would just keep the generator-well pump you have. The big tank makes it an
                efficient operation. A huge expansion of your solar system initial + ongoing costs
                will be needed to cover a big well. Bruce Roe
                Attached Files

                Comment


                • #9
                  Originally posted by MichaelK! View Post
                  I did look up the specifications, and it did not specify "Locked Rotor Current", it documented "Maximum Current" which I stated above is 11.6 amps at 240V. Are they the same?
                  Well, if that's all they give you, let's try it. 11.6A x 240V = 2784watts Assuming a standard AC motor, and no plain $90control box, I'd guess the PF of the pump to be .7 which may give a load of 3619 watts. (via a rough seat of the pants calculation)
                  https://en.wikipedia.org/wiki/Power_factor

                  BUT 2784 watts does not look like a good "Max" number for a 1.5HP water pump.

                  My 1/2 hp = 1,000W 3x that would be 3Kw

                  " They installed a Grundfos 3/4 horse 230v pump. Model 10SQ07-200. Rated 8.4a. Grundfos recommends a 2,500 watt generator for my pump."

                  So, a guess for 1.5hp (two times 3/4hp) would be a 5Kw generator or inverter . MAYBE a little less at 4500W BUT THOSE numbers are running, not starting. So I don't get how they say Max 11.6A.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by bcroe View Post
                    I would just keep the generator-well pump you have. The big tank makes it an
                    efficient operation. A huge expansion of your solar system initial + ongoing costs
                    will be needed to cover a big well. Bruce Roe
                    Hi Bruce, thanks for the response. Actually, I got my idea of SE, S, and SW orientation from looking at your pics. I'm starting to give up on powering my 1.5 hp pump via solar. I will though still be expanding my system, and most likely will incorporate the three orientations. What I'm more inclined to do now is wait till my existing pump fails in X years, and replace it at that point with a DC-solar pump. I most likely would select a high capacity deep well pump that needs 800-1000 watts of power and pumps about 500-1000 gallons per day.

                    I'm thinking of all sorts of schemes for water collection. I'm in the market for additional 5000 gallon tanks (now have two) that I can plumb to my cabin's roof. I calculated that in a average winter, about 10-12 thousand gallons of water falls on the roof. That's enough water to get me through about June or July. At that point, I can divert a string of panels (3X300W) to power the DC well-pump. After slowly pumping water all week into the tank, I can pressurize my irrigation system with a 120VAC surface pump that can produce ~80psi and 20 gallons per minute. That only needs to run for about 90 minutes to irrigate everything I have. I should have enough capacity to power that.

                    In the winter, when irrigation demands drop to zero, the power from the pump string can be diverted back into the cabin's power system, when solar capacity is dropping anyway. That seems to be a better option, which seems to naturally complement each other.

                    Comment


                    • #11
                      Even though my pump is a 3/4 horse pump it doesn't say that in the spec sheet. Spec sheet says P2 rated power is 1.54 horsepower.

                      Here is link to my pump: http://www.amazon.com/Grundfos-10SQ0.../dp/B002NJSEBS

                      Note the description of "generator and inverter friendly".

                      Is your pump the SQ series?
                      Conext XW5548
                      Conext MPPT60-150

                      Comment


                      • #12
                        Studying the Magnum MS4448SPAE owner's manual, on page 31 they document running the inverter in "Standby Mode". Here is the reference from the manual.

                        ""3.2 Standby Mode
                        The MS-PAE Series uses an automatic transfer relay and an internal battery charger when operating in Standby mode. Standby mode begins whenever AC power (utility or generator) is connected to the inverter’s AC input. Once the AC voltage and frequency of the incoming AC power is within the AC input limits, the automatic AC transfer relay is activated. This transfer relay passes the incoming AC power through the inverter to power the AC loads on the inverter’s output. This incoming power is also used to activate a powerful internal battery charger to keep the battery bank charged in case of a power failure. Refer to Figure 3-2 to see the flow of power from the AC input to the DC and AC output while in Standby mode.""

                        Here's the link to the manual. http://magnumenergy.com/wp-content/u...WebVersion.pdf

                        So, I start up my generator at noon, warm it up for 5 minutes, then switch on the well-pump. I think that the surge wattage required (5-6kw?) would come from the generator, then, when pumping stabilizes, 100 % of the power could come from the panels. After a minute, I could shut off the generator, and leave the pump running solely on panel/inverter output.

                        Is this a stratege that will work in the real world? Has anyone here heard of that actually being done? I'd much rather run my generator for a couple of minutes per day, rather than a couple of hours per day. On the other hand, switching on and off that many watts might be really hard on either the inverter or the pump electronics.
                        Modify message
                        « Last Edit: Today at 02:53:22 PM by MichaelK »

                        Comment


                        • #13
                          No. The relay glitch when the inverter switches (transfer switch) trips my pump protector every time. Just let the inverter start the pump and run it. The hit on the batteries for starting is nothing, as long as the batteries are good, and starting up a genset daily for a 10 minute run, will wear it out. Make the runs at least 1 hour.

                          Running the generator early morning to BULK the batteries is good, then the solar can do the absorb portion of the cycle.
                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #14
                            OK, here's an update. My Grunfos pump is a three-wire single phase 230VAC pump. It's controlled by a Franklin Electric Model 2823008110 control box. I've measured the "running" amperage off the black wire in the control box at 10.66 amps. The generator was running at 253VAC when it was drawing 10.66 amps of current. That works out to be ~2700 watts, continuous. The "locked rotor" amperage of my pump is listed as 51amps. That works out to be >12kw of power. The maximum amps listed in the the on-line documentation indicated that the maximum running amperage was 11.5. What would happen if I adjusted the AVR to put out exactly 240VAC under load? Would the pump slow down slightly, or would the amperage go up to 11.5 to maintain the same wattage?

                            To put things into perspective, when I first bought our property, the previous owner left us on old Onan 4kw generator made back in the 1960's. This generator was barely adequate for starting the pump, and as it got older, starting the well-pump would stall it. I found I could keep it running if I opened the throttle by hand, just a second before turning on the pump. But, I finally replaced it with a 6KW AC-Delco generator (6500 surge watts). So, does that give you a sense of what the starting watts actually is? Assuming the Onan was a 4kw generator, and it would sometimes stall at startup, might the starting wattage be around 4000W?

                            Comment


                            • #15
                              Now you know why I use a 6KW inverter to run a 1/2 hp pump. The starting surge is insane. You just figured the starting wattage is about 12Kw which is why the 4Kw genset was having trouble. Look up the power factor for the pump - that is going to also cause heating issues with the generator and the pump control box. Older alternators were more robust, new ones have cut every corner possible, my new 3Kw genset (3.3 peak) can manage about 2.2Kw cont before the waveform goes wonky and power factor sucks.

                              Well Pump Motor Specs.jpg
                              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister

                              Comment

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