What is the appropriate inverter?

Discussion in 'Alternative Energy' started by Allan Mistler, Apr 18, 2006.

  1. Allan Mistler

    Allan Mistler Just a simple man

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    Ok, I did a search and realized that either the question and answer session rolled out of the history file or I'm the only fool who can't decide based upon the specifications issued by manufacturers. So here goes....
    My solar/battery backup capacity is designed to run my freezers (2 at an estimated 760 Watts/Day each) and well pump (1/3 HP). Since all are motor loads and run intermittently, there's a pretty high surge frequency of startups. Everyone must have noticed that modified squarewave inverters cost far less than pure sinewave jobs, but I read that the modified squarewave units don't handle motor startup surges as well as pure sinewave units.
    Is there anyone who has some experience in this area who could recommend both type and size since i'm in the market to purchase one inverter to 'do-it-all' rather than have a collection of small individual units.
    Did I mention that I'm basically uh... frugal (Ya that's it.... Frugal!)?

    Thanks!
     
  2. Jim-mi

    Jim-mi Well-Known Member

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    To "do it all"
    Sinewave
    Big
    Such as a Zantrex 4024
    Or better yet a Outback VFX3524

    If you go small (as in "just enough") you will soon regret it.

    Better to let the big guy ease along rather than push the little guy to the limits.
     

  3. JAK

    JAK Well-Known Member

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    Don't be ashamed. My mother was born in Edinburgh and so I also carry that same frugality gene. They should really have a frugality pride march or something. Nothing to be ashamed of. :)

    Interesting question. When there is room in your freezers you can make them stay on longer and therefore startup few times per day by adding some blocks of ice on the bottom. A layer of foam on the bottom might even work better. You will have less space but you won't have to dig down as far. As for the well pump, perhaps you could reduce the air pressure in your pressure tank. This might increase capacity and reduce work and reduce leakage. If you move the tank up from the basement you could reduce the air pressure and increase capacity further. You would still get the same pressure at the taps, but the pump will stay on longer and therefore startup less frequently.

    Other than that I am not sure. Perhaps there is a way to modify an electric motor slightly to make it less powerful but just as effcient. That would also make them run longer, but less peaky, and so you will get more efficiency out of your batteries and need a smaller inverter, so perhaps you could afford a more efficient one. Replacing one of the motors with a DC motor might be an option also. Perhaps if you are handy you could build one or salvage something.
     
  4. mightybooboo

    mightybooboo Well-Known Member

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    My heart 458(modified sinewave) will start my freezer and refer,but they sound different when they are running.That said,i would be pure sinewave all the way if it was my inverted source of homepower fulltime.

    I think that outback is a nice design,how are they holding up? I really like them.
     
  5. mightybooboo

    mightybooboo Well-Known Member

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    Yup,if you want to use on grid appliances,those will do it.

    BooBoo
     
  6. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    I think I would take a different approach. 1/3 HP well pump is small so I would look into replacing it with a DC pump and then you wouldn't have to worry about an inverter for that. Sureflo's 9300 can be found for around $650.

    I'd then put the freezers on timers that only let them operate for 1/2 of the hour. That would insure only 1 freezer was running at a time. Maybe even look into having startup capacitors added to them to cut down the surge load.

    Then you should be able to get by with a small capacity inverter. Would need to know the amp rating on the freezers to tell you how small.
     
  7. Allan Mistler

    Allan Mistler Just a simple man

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    Yes, the thought (or more correctly - the desire) to replace the well pump with a DC pump would be an ideal solution but I ran into the situation where the well is about three hundred feet from the house and the wire currently running to it is 14 gauge.... the voltage drop at 4 Amp would be over six volts and I'm too cheap to replace it with six hundred feet (round trip) of #1 or 1-0 copper.
    The cycle timers on the freezers is a great idea though and should be able to be implemented with a small amount of electronics! I'm still researching the capabilities of the Xantrex UX series and the Vector SST technology offerings. Though they are modified sinewave inverters, they seem to have overcome the surge requirements for motor starting and they are far less expensive than Outback etc. The solar system may be designed for full-time continuous use, but it is only intended to maintain what I consider critical loads, not the everyday household power consumers such as microwave, clothes washer/dryer, refrigerator etc. At this early stage of my transition to power independence it's in my best interest to keep the budget within a range acceptable to my spouse!
    I appreciate the great suggestions and ideas as well as potential pitfalls that each of you has offered and should be able to reciprocate once this learning curve has flattened out. I spent alot of time researching and developing the production end of the system but seem to have overlooked the distribution aspect!
     
  8. mightybooboo

    mightybooboo Well-Known Member

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    You must already be at
    www.homepower.com

    Since I read you as on grid,then the mod sine wave should meet your needs for now.It works as our backup power just fine,except for anything with a digital clock like a micro or stereo(our sony wont run).

    Computers/sat dish,lights,refers,tvs(most) all will run just fine in the backup capacity with mod sine wave.Long term though, its claimed they shorten motors lifes,I believe that,you can hear the difference as they are running.

    BooBoo
     
  9. mightybooboo

    mightybooboo Well-Known Member

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    Are you planning offgrid?

    If so,as refer and freezer die,replace with super efficient 12 volt ones,wont even need an inverter for them.Some dont even need a battery,run straight from the panel(s).
    Replace the washer with a Staber.

    Homepower claims every dollar in efficiency investment saves 3 dollars in solar panels.

    Or if you can afford it,go crazy with panels,and can run efficient regular refer like a couple guys at homepower do.

    BooBoo
     
  10. Allan Mistler

    Allan Mistler Just a simple man

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    Am I planning off grid?... to tell you the truth, I haven't thought that far ahead. This whole thing started when I decided to try to capture some of the wasted energy going over my waterfall every Spring. When I dug a shallow well and placed a few 15 watt panels with a diaphragm pump up in the pasture last year I was amazed how well it performed in keeping both cattle and pigs in fresh water all Summer. That has evolved into taking advantage of the Federal Tax Credits available this year and next. This all coupled with the fact that I lose power at least twice each month and feel quite paranoid about my two freezers full of home raised meat and the electric fencing around my cattle pasture.
    Hopefully, as resources permit, I'll eventually be 'off grid'. In the mean time I'm having one heck of alot of fun getting there!
     
  11. mightybooboo

    mightybooboo Well-Known Member

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    Then you are doing home backup.
    OK,i have 8 trojan L-16s with a Heart 458 inverter/charger.Keep the batts charged,should get you a few days of refer/freezer protection.Thats what we do at home.
    Point being,you need a charger too,may as well get an inverter that has one.

    BooBoo
     
  12. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    Have you thought about a 2 pump system with a cistern? One pump at the well ran solar direct (with panels at well) filling a cistern at the house. Second pump supplying house pressure as needed. Both could be small dc pumps. If you could mount the cistern high enough you wouldn't need a second pump to pressure the house.
     
  13. Allan Mistler

    Allan Mistler Just a simple man

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    W W W... I do like the way you think! Truly 'outside the box' style! I'm going to give that idea some serious consideration since the well is located in a very convenient place for my next set of panels. Thanks for the great ideas!
     
  14. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    This system here otherpower works like I descibed. He has to pump 45' vertical and 480' horizontal. He used float switches to turn the pump off when the cistern was full. I've seen other system not use float switches just have a dependable overflow and place for the excess water to go.
     
  15. Allan Mistler

    Allan Mistler Just a simple man

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    The well issue aside for the time being, I just put my money down on a Magnum MS2812 inverter. From everything I could see, it was $1450 well spent for 2800 continuous watts of pure sinewave power with all the bells and whistles (available) for reprogramming, autostart of generator etc. This is probably the first time I've felt so comfortable parting with so much money since it came with a three year warranty.
    I sized my purchase based upon the results derived from Homepower Magazine's load analysis spreadsheet, so there's comfort in the knowledge that someone else's calculations aligned with mine. Anyone have any experience (good or bad) with the Magnum? I'll keep you up to speed on any issues I experience with it.
    Thanks for all your help in this matter!
     
  16. mightybooboo

    mightybooboo Well-Known Member

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    WTG,looks like you getting into it.

    BooBoo
     
  17. Jim-mi

    Jim-mi Well-Known Member

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    No experience with the Magnum yet.
    But I'm glad to see that you've been doing a lot of thinking about it and did NOT go with the $79.95 kind of junk.

    Like it or not folks the good stuff can get pricey, ...But...your far better off buying the good stuff up front.