Was The use of High Frequency Grid inverter with battery back up charger a right choice? Pls help...

mozambi
mozambi Registered Users Posts: 4 ✭
in Advanced Solar Electric Technical Forum #1
I recently installed an 8kw solar grid tie system with a 57,6kwh battery back of 48V for a client in West Africa. It is a 3ph installation. The inverter I used is high frequency 10kw unit that has both grid-feed and battery charging capacity. But my client is unable to use his 2.5hp air condition either during the day or at nights. Other low load appliances work fine but would have worked with just a 2kw installation. So I need help on what to do to help the client. Thanks
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2

    "unable to use" when off grid or the grid is down, I assume?

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mozambi
    mozambi Registered Users Posts: 4 ✭
    #3
    yes, both when off-grid and when the grid is down which is frequent. The inverter I use is called 
    InfiniSolar 10KW On-grid Inverter with Energy Storage
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #4
    Have you looked into "hard start" kits for the A/C system? Standard A/C systems assume that the "Grid" has very high capabilities for surge current and do to do much to limit starting surge.

    An alternative--Do you have any "mini-split" type A/C systems available (at least they could run a smaller one when the power is down, or run several). Mini-splits tend to use "inverters" internally to run the compressor--These systems have very low surge current (and can be quite efficient too when compared to traditional central air systems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mozambi
    mozambi Registered Users Posts: 4 ✭
    #5

     "hard start" kits for the A/C system?"

    Thank you. Any suggestion on reliable types of  "hard start" kits for the A/C system? will be helpful.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #6
    Hmmm... I may be wrong here suggesting a hard start kit. If the A/C system uses a three phase motor, then a hard start kit will not be used on it (they are only for single phase compressors).

    For a three phase motor/compressor, a VFD (Variable Frequency Drive) may be the solution:

    http://ecmweb.com/power-quality/basics-variable-frequency-drives

    The VFD is a form of AC inverter that varies the output frequency (and power)--It starts the motor turning by running slower than 50 Hz (your line frequency?) then ramps up to full programmed frequency.

    I am not an A/C expert by any means--VFDs can cause other problems with motors (many output "square waves" instead of pure sine wave power)--Which can cause motors to run hotter (your compressor motor needs to be rated "higher" to ensure it does not over heat).

    Can you find somebody locally that has experience with VFDs and A/C systems?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,907 ✭✭✭✭✭✭
    #7
    I do not "get" why this AC does not work when the grid is up???? It use to correct?
    If you are going thru all of this to be more efficient and the AC is 3 phase,  then you really should just buy a window unit for now and replace the whole forced air cooling with mini-split heat pumps. You will save energy and it will improve your life. As Bill said, find someone local, if you can.  Good Luck and let us know what worked please!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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