48 volt Air Conditioner Install

jalbers
jalbers Registered Users Posts: 13 ✭
in Off Grid Solar & Battery Systems #1
Well, we did it. We purchased one of the 48 volt air conditioer units. It is a mini split unit and works GREAT. The only issue is.....the manufacturer techs really have no idea how to hook this thing up! We currently have it on 6-275 watt panels, an outback 60 charge controller and 8-T 105 batteries. It works great during the day, but is only good for a couple of hours at night.....and we live in Arizona.

This thing pulls about 25 amps. What is the calculation for the number of batteries and panels needed to allow the unit to run 24 hours per day?

Like always....thanks for your help and replys.

Jerry
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #2
    Re: 48 volt Air Conditioner Install

    It doesn't pull 25 amps constantly, does it? I have an inverter based mini split and it cycles its draw.
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #3
    Re: 48 volt Air Conditioner Install
    jalbers wrote: »
    Well, we did it. We purchased one of the 48 volt air conditioer units. It is a mini split unit and works GREAT.

    Jerry

    sorry if I missed something, but what brand/model is this 48 volt unit?
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #4
    Re: 48 volt Air Conditioner Install
    This thing pulls about 25 amps. What is the calculation for the number of batteries and panels needed to allow the unit to run 24 hours per day?
    That is quite a lot of current at 48 volts approximately 1200 watts. I would guess if it is properly sized, it will run about 1/3 of the time on average, more in the daytime and less at night. SO 8 hours * 25 amps = 200 amp hours each day. You would want your battery capacity at about 3 to 4 times that amount so shoot for 600 amp hour battery minimum To replace the current used would require about 2400 watts of panels in ideal conditions. You may need to oversize depending on where you live. You will also need a good generator to cover cloudy days. Some others may have better input on this question.
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #5
    Re: 48 volt Air Conditioner Install

    Thanks for the replys. The unit is new to the world and my wife hopes to sell them.....as soon as we figure them out. The unit does not turn on and off! It runs 24 hours a day and keeps the room at whatever temp you set it to. That way there is no serge. It will also heat in the winter months. It is good for a small house or....in our case....a master bedroom.....up to about 600 sq feet. It works VERY good...as long as we have enough panels and batts to keep it going. It sounds like more batteries are in order.($$$$$$$$$) I do have two more panels I can attach as well.

    At least now I won't be bored this weekend;) More batts and panels!

    Thanks again,

    Jerry
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: 48 volt Air Conditioner Install

    Oh let's see ...
    25 Amps about 1/3 of a day is 200 Amp hours, so at least 400 Amp hour battery bank, plus allowances for system efficiency losses and your should have sixteen of those T105's at least.

    That's 450 Amp hours @ 48 Volts. And probably something along the lines of 3500 Watts of panel to recharge from (A/C will run while charging, panels will derate due to being hot).

    With 225 Amp hours @ 48 Volts and 1650 Watts of panel it doesn't look like you're on target here.
    That much panel would yield about 4 kW hours daily, whereas your usage looks to be slightly more than 2X that.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #7
    Re: 48 volt Air Conditioner Install
    jalbers wrote: »
    Thanks for the replys. The unit is new to the world and my wife hopes to sell them.....as soon as we figure them out. The unit does not turn on and off! It runs 24 hours a day and keeps the room at whatever temp you set it to. That way there is no serge. It will also heat in the winter months. It is good for a small house or....in our case....a master bedroom.....up to about 600 sq feet. It works VERY good...as long as we have enough panels and batts to keep it going. It sounds like more batteries are in order.($$$$$$$$$) I do have two more panels I can attach as well.

    At least now I won't be bored this weekend;) More batts and panels!

    Thanks again,

    Jerry

    Yes my mini splits have the fan section running 24X7 but the compressor does cycle. At night mine uses about 0.8 kWh per hour on average in AZ, using 2 of the 3 9000 BTU wall units in 500 sq ft. During the day it goes up to 1.2 kWh per hour. The building is very tight and has 6 inch walls with 2 inches of Styrofoam wrap on the exterior. No south or west facing windows and the north and east windows are low E.


    The pink line in this picture clearly shows the compressor cycling.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #8
    Re: 48 volt Air Conditioner Install

    Yeah, the amperage on that 48 volt unit sounds way too high. Many multiples above the other mini splits that have been discussed around here. Heck, at 1200 watt-hr over a full day that's over half what my entire house uses... with 2 old 12 SEER A/C units.

    What is the SEER rating on it?
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #9
    Re: 48 volt Air Conditioner Install
    Re it running 24/7 whether cooling is needed or not - - in my opinion that's a gross waste of energy
    As I understand it this is an inverter AC and can throttle down to a couple hundred watts or less depending on demand. The 1/3 day guess for me was exactly that at 25 amps which would be max draw for 1/3 of the day. The reality is that it may draw much less if the house is well insulated and demand is low. Best bet would be to put a logger on the unit and test over all the seasons for your particular cooling needs. This would give you an understanding of the power requirements. I suspect it to be similar to other inverter AC on the market.
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #10
    Re: 48 volt Air Conditioner Install

    This 48 volt unit is in it's "infant" stage. Even the company we purchased it from is not sure how to reply to questions and concerns I have. It is 48 volt and runs directly off a battery bank. My concerns are that I would need as much or more solar to run one unit, as I am currently using to run my entire house.

    I have installed the air conditioner as a stand alone unit. It is not tied into my house which is 24 volt. The air conditioner works great, but it appears it does need a lot of solar to operate. I'll keep you informed as I play with it more.

    Thanks again for everyones replies

    Jerry in northern Arizona
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
    Re: 48 volt Air Conditioner Install

    so what is the btu capacity and what do they spec for normal or maximum current draws?
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #12
    Re: 48 volt Air Conditioner Install

    It says it runs 23.8 amps per hour. The unit is 18,000 btu and has a seer rating of 18.

    Jerry
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
    Re: 48 volt Air Conditioner Install

    sounds about right and to run that all night and day would require quite a bit of power. if it is drawing over the max current the company specifies it for you could fire off an inquiry to the company to be sure there's nothing to be concerned about.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #14
    Re: 48 volt Air Conditioner Install

    Doesn't sound right to me, still sounds high @ 27 kw per day. That's only a ton and a half unit. I have two 2 ton units @ 13 SEER and my average daily total is 40 kw, including everything in the house.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
    Re: 48 volt Air Conditioner Install
    techntrek wrote: »
    Doesn't sound right to me, still sounds high @ 27 kw per day. That's only a ton and a half unit. I have two 2 ton units @ 13 SEER and my average daily total is 40 kw, including everything in the house.

    hmmm. you're right as that should be far less for 18k btu, but he says they spec it at 23.6a. if so then it is not good on its eer.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #16
    Re: 48 volt Air Conditioner Install

    Are you taking into account that is 23.6a at ~48 volts (~1,100 to 1,200 watts)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #17
    Re: 48 volt Air Conditioner Install
    BB. wrote: »
    Are you taking into account that is 23.6a at ~48 volts (~1,100 to 1,200 watts)?

    -Bill

    Sounds about right,my 17 seer dual 9000 btu units draw about 1200 watts at a 30-50% duty cycle running on super quiet mode.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #18
    Re: 48 volt Air Conditioner Install
    BB. wrote: »
    Are you taking into account that is 23.6a at ~48 volts (~1,100 to 1,200 watts)?

    23.6 amps * 48 volts * 24 hours = 27,187

    I can only believe that isn't taking into account the duty cycle, as dave mentioned. So that number should be 1/3 to 1/2 of 27k, hopefully.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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