DC Ceiling Fan - will it work?

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kansas
kansas Solar Expert Posts: 100 ✭✭
in Solar Beginners Corner #1
I have a cabin with a 300 watt solar system.  Will I be able to start and operate a DC motor ceiling fan that requires 30 watts at high speed?  I don't want to purchase one, install it from my 16' ceiling and then find out it won't work.
Two 140 watt Kyocera panels, wired in parallel; Ironridge top of pole mount; two 6 volt, 242 AH US batteries, wired in series; Morningstar ProStar 30 charge controller and SureSine 300 inverter; Trimetric 2025-A meter; IOTA DLS-45 charger, Honda EG3500X generator; Aermotor 702 water pumping windmill.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    edited July 2017 #2
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    erase bogus equation and below had 300 Watt fan. All wrong. :s

    Different DC Fan Mfg... One vendor/model suggested used 18 Watts on maximum--That would be a much nicer fit for your system (although, these fans are not cheap):

    http://forum.solar-electric.com/discussion/350028/ceiling-fans

    You did not let us know the size of your battery bank and other loads--That is also important in this set of questions (and your feelings about using a genset to "help").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    edited July 2017 #3
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    Bill - 30watts ÷ 12v = 2.5a

    I have a 12vdc ceiling fan. I'm not sure of the draw but it's about 30" wide, and 2.5a seems about right.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    #4
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    A fan from a 16' ceiling will have too long a down rod to be used most likely.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
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    BB. wrote a typo:
    30 Watts * 12 volts = 360 Watts
    If your fan is 30 watts, it would run fine with 300w of solar behind  it.   Nighttime and battery size become the important questions
    Powerfab top of pole PV mount | 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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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
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    In my city house I have a couple of ac ceiling fans in a sunroom with ~16' ceilings. The rods are ~3' and they work fine. They wobble slightly at top speed, but we rarely use them on full.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #7
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    On post #2, I had a really bogus equation. Nothing correct or useful.

    Erased.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #8
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    And I read too  quickly and mixed the 30 watt fan.

    Not my day today.

    -Bill :s
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #9
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    > @BB. said:
    > And I read too  quickly and mixed the 30 watt fan.
    >
    > Not my day today.
    >
    > -Bill :s

    I take some (possibly pathetic) comfort that it happens to the best of us
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • kansas
    kansas Solar Expert Posts: 100 ✭✭
    #10
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    So, Bill are you saying my 300 watt system could power a 30 watt fan?  My system is for occasional use, lighting and computer, small fans. I have a battery "bank" (two golf cart type batteries) but when I run low on power I just do without until the sun shines.  The cabin is wired for a ceiling fan, which until now I've done without.  Prices on DC motor fans seem to have come down and the price of a hanging light fixtures is almost as much as a fan with a light built in.  Thanks all for your help.
    Two 140 watt Kyocera panels, wired in parallel; Ironridge top of pole mount; two 6 volt, 242 AH US batteries, wired in series; Morningstar ProStar 30 charge controller and SureSine 300 inverter; Trimetric 2025-A meter; IOTA DLS-45 charger, Honda EG3500X generator; Aermotor 702 water pumping windmill.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #11
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    At the risk of putting words in Bill's mouth, yes. A 30w fan shouldn't be a problem for a couple of golf cart batteries. I run a DC fridge on my boat on a couple of GCs.

    The main issue is run time. Running it 24x7 plus running computer, other fans, and lighting might be a problem, especially if you're running on solar alone. For good battery life, try to avoid running the batteries down much below 50% full (~12.2v with no big loads or charge sources) and never leave batteries sitting at a low state of charge for more than a day or so.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    edited August 2017 #12
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    I put words (and feet) into my own mouth--Thank you very much Estragon. :D

    Anyway, there are several ways to approach a system. The "best" is to estimate you loads (and how many days of "no sun"/generator usage are acceptable, and such) then define your battery bank. Next, define the solar array to both "keep the battery bank happy" and keep up with your daily loads (two different calculations).

    Or, we start with your system and see how much useful energy we can get out of it. Since you have 2x golf cart batteries and 300 Watts of panel...

    With your battery bank, the usual "optimum" is 2 days of stored energy and 50% maximum discharge. For a "golf cart" bank, that would be around:
    • 200 AH * 12 volts * 1/2 days storage * 0.50 maximum discharge = 600 Watts of stored energy per day
    So, your 30 watt fan would run about 20 hours on the battery bank for two days.

    Or, if you have other loads... Say (just throwing some generic numbers out there):
    • 30 Watt fan * 10 hours = 300 WH per day
    • 20 Watts lights * 5 hours = 100 WH
    • 30 Watt laptop computer * 6 hours per day = 180 Watts
    • Total = ~580 WH per day from your GC battery bank
    And for the solar panels... We suggest around 5% to 13% rate of charge. 5% can work for a weekend/summer cabin. And 10%+ works well for a full time cabin/home (~9 months per year solar + backup genset for winter weather):
    • 200 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 188 Watt array minimum
    • 200 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 377 Watt array nominal
    • 200 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 490 Watt array "cost effective" maximum
    Your 300 Watt array is not bad for a seasonal cabin. And based on hours of sun per day for a fixed array near Lawrence Kansas:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Topeka
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 51° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.57
              		3.75
              		4.66
              		4.89
              		5.16
              		5.41
     
    Jul Aug Sep Oct Nov Dec
    5.70
              		5.36
              		5.33
              		4.64
              		3.61
              		3.36
     
    Toss out the bottom three months (generator assist), you can expect (long term average) solar power per day of:
    • 300 Watt array * 0.52 off grid AC system eff * 3.75 hours of sun (February break even month) = 585 Watt*Hours of solar (February average)
    If you use the cabin  mostly during "summer", a minimum of 5.0 hours of sun would give you:
    • 300 Watt array * 0.52 off grid AC system eff * 5.0 hours of sun = 780 WH per day from solar (May-September)
    500 WH per day is sort of the minimum that would work for a cabin... And 1,000 WH per day works very well (unless you add a refrigerator, well pump, washing machine).

    Does this look like such a system can meet your needs?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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