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  • Supplemental Solar Power In My House

    The other day, I wired in a Reliance Transfer switch to my breaker box. This switch allows you to plug a 30amp power cord from your emergency generator into the switch and run your generator through your household electric circuits, bypassing the grid without any switching dangers. It's intended use was for a 6KW propane generator. After I set it up, I thought "What a great idea for a solar system". I am now considering putting together a 2-3KW solar system which would serve as a supplemental system to my house as well as emergency backup power. I assume I would also need 8-12 L16 batteries, inverter, and controller. This system would basically run all the 20 amp circuits in my house. It would not control the main air unit or the stove, or any 220V stuff. My water heater and heaters are gas. The big electrical stuff would remain on the grid and run only off the power company. If power went but, I would lose them. But I might could run selected window units for air, and a $30 stove top burner to heat food.

    I was wondering if anyone out there has tried something like this and your comments. It is very similar to having a system tied in that sells back to the grid, but you would have total off the grid capacity in the event of a power outage.

    Basically, it would be a Reliance Transfer breaker switch system with a off grid solar system plugged in to run all the house except the heavy 220V stuff.

    Any comments/ pro or con would be appreciated.

  • #2
    re-consider the batteries vs a generator. How often have you lost power in the last 7 years, 7 is about the number of years batteries last before they die and need replacing, where a mid size genset (honda eu3000) can manage a house fairly well.

    Solar is great, but there is also a great cost involved too.
    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

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    • #3
      He is talking about having a hybrid system for the cost of the Reliance switch.

      He would need a hybrid inverter would he not?

      Russ
      [SIGPIC][/SIGPIC]

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      • #4
        Piggyback system

        Thanks for y'alls replies. Russ, I don't know if I would call this a hybrid system, or a dual / piggyback system.

        I realize a generator is a much cheaper way to ensure power compared to solar. No doubt, hands down. But Im not trying to just make a backup system. I also am converting probably 1/4 of my energy usage to solar and getting an emergency backup at the same time. The payout on this system would obviously be many years.

        I am accepting that my central air unit and kitchen stove will only run off the grid when it is up and running. If the grid is down, these units are dead. But the rest of the house keeps on running all the time. My breaker panel has a 60amp 220 for the electric unit and also for the stove. But the rest of the 20 amp breakers are the ones tied into my new reliance switch and they are the circuits I want to run off solar. GRANTED, I must minimize use on all of these circuits. But I mainly run a couple computers, a few lights, and a refrig. and freezer off them. These are pretty low wattage.... the refrigerator is the largest using about 50kw / month. Im guessing that my useage (aside from the central air / stove) would be 100-150KW/month.

        The Reliance switch has 10 breakers. Six are 15 watt and 4 are 20 watt. Each breaker has an independent switch for (1)Grid (2)Off (3)Emergency . So you select if you want that circuit to run on the grid, or off emergency (or solar) power. Very slick and no danger to the electric grid.

        So what I am considering doing is running my entire house off solar through this transfer box and just running the central air and stove off grid.

        If I can size my solar system with enough energy, I also wish to put a 10 or 12K BTU window air unit in a couple rooms to selectively cool what is necessary. When these are running, then the central air unit would obviously be turned off. I might only be able to run one of these at night and only during selected times during the day, but we all will have to adapt to a different lifestyle.

        I believe this system would use a standard type inverter with a L14-30 plug that would go into the transfer switch.

        If energy bills double in 5 years, which wouldn't surprise me, then this system might be a good idea. Solar panels appear cheap right now. Im thinking I should buy them now before the price goes up.

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        • #5
          I'm trying to figure this stuff out too... But I think what the guys are saying that it is still better to go with a grid tied inverter. You could still have a battery backup system for grid outages, but when the solar panels kick in they will immediately supplement, or even push the meter backwards. Also, in normal operation, you won't have to deal with battery issues, which are costly (life-cycle cost) and add the inefficiency of charging & discharging your battery bank.

          However, the advantage of your approach is that you can do the work yourself (no electrician) and don't have to worry about UL listed stuff.

          I have frequent power outages at my house and use a single deep-cycle battery and inverter to run just a few lights, tv and computer. Much like you, I hate to deal with the noise, fumes, and maintenance of a generator.

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          • #6
            Perry, thanks for your post. I think I see much better now. A grid tie would allow me to eliminate the batteries if i wanted. Of course, I would have to keep my generator handy. But the grid tie would utilize ALL of the solar energy I would be collecting, whereas the system I proposed would not utilize all the energy, unless my load just happened to be what the panels were producing.

            I guess I better start studying the grid tie stuff. Do you have any recommendations for equipment for a grid tie system? Panel brand/type, grid-tie? Thanks.

            Comment


            • #7
              Originally posted by tcombest View Post
              Do you have any recommendations for equipment for a grid tie system? Panel brand/type, grid-tie? Thanks.
              No, I'm just learning about the solar stuff and have only looked at off-grid stuff so far.

              Comment


              • #8
                Tc you are still talking about a hybrid system and regardless still requires all UL equipment.

                A hybrid inverter is two inverters in one box. One is the GTI and works like any standard GTI so that when commercial power is up, everything in your house works off commercial power, and the solar panels excess energy is sold back to the utility.

                It also has a battery inverter and it own automatic transfer switch built inside the unit to power emergency loads only. When power goes out, the ATS operates and the battery inverter is turned on and picks up the emergency loads until the emergency GENERATOR comes on and takes over to keep from draining the batteries down.
                MSEE, PE

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                • #9
                  You are talking about a system that I doubt any utility will accept for grid tie. For the utility, insurance and most likely the inspector will want a standard system of some known type with all equipment UL (or equivalent certification agency) approval.

                  If you want to have batteries and grid tie then it is referred to as a hybrid system with a hybrid inverter. The battery side is roughly 50% efficient.

                  For two separate systems, the solar system would have to be 100% separate from anything that was connected to the grid. Different panels and all.
                  [SIGPIC][/SIGPIC]

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                  • #10
                    I think the best way for me to go is for a grid tie system. I checked and there are three electric providers here who buy back. But I assume if you always use more electricity than your system can produce, it doesn't matter how much they pay to buy back electricity?? If so, I can stay with my current provider. Im getting in contact with them to discuss hookup info. Thanks for all your help. I'll be back.

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                    • #11
                      Where are you located? What state?
                      [SIGPIC][/SIGPIC]

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                      • #12
                        Central-West Texas, San Angelo

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                        • #13
                          You have a good start then I suppose - sunny location compared to much of the US.

                          Grid tie is the best choice as you noted - as long as you still buy some quantity from the utility it makes no difference what the feed in tariff would be.

                          To get an idea of what size system you might want you could try this tool from Sharp http://sharpusa.cleanpowerestimator.com/sharpusa.htm

                          Enter your zip code and annual bill amount to start - then you can make adjustments.

                          Choice of panels and inverter - many of the solar companies will probably not be around in a year or two so their guarantee is meaningless. Big companies that have been around for years will be there when you need them most likely. This is especially true if solar is a small part of the companies business. Kyocera, Sanyo, Sharp come to mind.

                          For inverters others can better say.

                          Do you have any shade problems? Do you have a roof facing south? If the roof is not suitable then do you have an open area for ground mount?

                          The most cost effective solar is always conservation. A kWh saved is a lot cheaper than a kWh from solar. Using energy efficient lamps and appliances helps. Insulating and sealing the home can really help.

                          Russ
                          [SIGPIC][/SIGPIC]

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                          • #14
                            San Angelo huh? You had first check on Net Metering as TX has no NET METERING laws.
                            MSEE, PE

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                            • #15
                              Don't think he is talking about net metering - just talking about installing a system smaller than normal use so nothing is exported.
                              [SIGPIC][/SIGPIC]

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