Calculations for Mini-Split

ryan112ryan
ryan112ryan Registered Users Posts: 11 ✭✭
in Off Grid Solar & Battery Systems #1
I am having trouble calculating my off grid solar panel/battery system requirements for my mini split.

I live in an area where (for me at least) not having AC for the summer months isn't an option (I'm also going to use it for heating). My confusion is around the peak loads (how long does it peak and how often), running loads and how often it will be on and how all that translates to how many amp hours? I need to run the thing for most of the day, generally on "medium" setting.

Minisplit:
-model: Fujitsu 9rls2 9,000 btu
-220V

Cooling:
-peak: 2050 watts
-running: 560 watts

Heating:
-peak:2390 watts
-running: 800 watts

So questions would be:
-How long does it run peak loads typically? and How often will it peak?
-How does one account for the peaks and running loads?
-How many amp hours should I plan for using this most of the day and night?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Calculations for Mini-Split

    Trained HVAC techs can't figure this out, too many variables, How well insulated is your space, how much space, cubic feet, How much air intrusion, how much solar gain, from windows, how much heat gain from outside(did you build in the shade?)

    There are some calculators on line that may help, but it is always a very rough estimate.

    Cooling(and heating) with solar is a tough task! you are looking at a very sizable system, I use my window air nearly 24 hours a day on my 4000watt array, cooling a single room in a reasonable poorly insulated 'Tin Can'(mobile home)
    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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  • KozmoK
    KozmoK Solar Expert Posts: 42 ✭
    #3
    Re: Calculations for Mini-Split

    Did you already buy your minisplit? They make a solar DC 48v AC Unit google: Specs-DC48VRF.pdf I don't want to get into any linking violations.
    I am thinking I will get one of these next month myself.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #4
    Re: Calculations for Mini-Split

    There is software that attempts to predict the btu gain/loss of a room or building. But an actual measurement is much more accurate. Then scale it according to the delta between room temp and peak outdoor temp. For example, if inside temp is 75F and on an 85F day you average 600 watts, then a 95F day will use pretty close to twice that.

    I am available for custom hardware/firmware development

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #5
    Re: Calculations for Mini-Split

    It is a challenge to do this correctly offgrid in places that do not cool off at night. But with the new High SEER units (25+) things are improving. I would read the forum thread I wrote again. Many of the links are not working but the concept is there. http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-(inverter-variable-speed)/page56#top


    ryan112ryan wrote: »
    I am having trouble calculating my off grid solar panel/bathttp://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-(inverter-variable-speed)/page56tery system requirements for my mini split.

    I live in an area where (for me at least) not having AC for the summer months isn't an option (I'm also going to use it for heating). My confusion is around the peak loads (how long does it peak and how often), running loads and how often it will be on and how all that translates to how many amp hours? I need to run the thing for most of the day, generally on "medium" setting.

    Minisplit:
    -model: Fujitsu 9rls2 9,000 btu
    -220V

    Cooling:
    -peak: 2050 watts
    -running: 560 watts

    Heating:
    -peak:2390 watts
    -running: 800 watts

    So questions would be:
    -How long does it run peak loads typically? and How often will it peak?
    -How does one account for the peaks and running loads?
    -How many amp hours should I plan for using this most of the day and night?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • ryan112ryan
    ryan112ryan Registered Users Posts: 11 ✭✭
    #6
    I wanted to just do an update for others looking for this type of info.  I now have been using my mini split for over a year now.  It's the fujitsu 9rls2 and when it first ramps up it uses about 1000 watts for about 1-3 minutes then settles down to 250 watts when its blowing.  I have 2.25 kw system with 8 6v 370 ah trojans L16's setup in a 24 volts system and for most of the year this handles it like a champ.  Really only run into issues with long stints of cloudy days of over a week.
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  • Wheelman55
    Wheelman55 Registered Users Posts: 244 ✭✭✭
    #7
    Ryan...how many cubic feet are you cooling?  And what's your r-value for both walls and ceiling?
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #8
    Clouds are always a challenge. I have been working on that for the wi-fi PCB for the Fujitsu. There is now a 9RLS3 series that is 33 SEER. Probably not that much better than your 27 SEER but going the right way.  Where do you live Ryan?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • WaterWheel
    WaterWheel Registered Users Posts: 385 ✭✭✭
    #9

    FYI.     12,000 btu is roughly equal to a 1 ton AC system.       The Fujitsu 9rls2 is 9,000 btu or roughly equivalent to a 3/4 ton central air system in cooling capacity.       If your average sized home in a fairly warm state requires a 3 or 4 ton system you'd need several of these units to cool the entire house.

     Fujitsu makes these mini split units in several sizes including 12,000 btu and 15,000 btu although the 9,000 btu unit is more efficient than the larger units.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

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