energy efficient air conditioner

shockmanshockman Solar Expert Posts: 113 ✭✭
Before I run out and buy a window mount AC what should I know?? thinking in the hood of 6000BTU
4x240w panels,Classic 150 CC, 4x380AHR L16's, antique Trace 12V inverter

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,204 admin
    Re: energy efficient air conditioner

    What do you want it to do?

    Run off grid? Have a heat pump mode? Is this a short term (couple of seasons) of use, or a long term installation (i.e., mini-split + heat pump)? Small room, well insulated?

    How much power do you have (grid, off grid, generator, etc.)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,697 ✭✭✭✭✭
    Re: energy efficient air conditioner
    shockman wrote: »
    Before I run out and buy a window mount AC what should I know?? thinking in the hood of 6000BTU

    Well, lets see, how about;

    They are often loud and noisy likely the #1 complaint.

    Don't even think about using the fan fold push out stuff that comes with the A/C, Buy a sheet of insulating poly styreen(?) and be sure you have at least 2" of insulation instead of the thin piece of plastic!

    Mini splits tend to be much more effiecent, quiet, but of course more costly.

    You can check energy star ratings and buy near the most effiecent A/C in your class, basically the most cool for the $ spent.

    Know that they often have high startup requirements, so if your planning on using this with an inverter, you might expect to need 2.5 to 3x the rated wattage to start the thing.

    They use a lot of wattage and unless you have a sizable system you may not be able to run them for long with out drawing your battery down.

    Likely you will want a Midnite classic charge controller and the soon to be released battery module to properly charge your batteries while the A/C is running.

    Most of the new designed ones use the condesation water and splash it onto the cooling fins to make them more effiecent. Them not having a drain hole is not a design flaw.

    If I haven't guessed your question, please ask more a more specific one.
    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.
  • shockmanshockman Solar Expert Posts: 113 ✭✭
    Re: energy efficient air conditioner

    K more details. cabin is 980sq.ft, there are only several days of the summer, 10ish, that it is unbearably warm for sleeping at night. Not sure if I should try to only cool bedroom or if cooling whole house is possible?? I will have about 1000 watts of panel, 760a/hr of batt. on a classic 150. Do have a 1000w honda, and 6500w genset. Do not enjoy running the big genny, noisy and thirsty, 1k honda quite and sippy! imagine Honda would not run AC ??? and could use big gen. for couple of hrs for additional chargeing. What prey tell is Mini split???
    4x240w panels,Classic 150 CC, 4x380AHR L16's, antique Trace 12V inverter
  • BB.BB. Super Moderators, Administrators Posts: 32,204 admin
    Re: energy efficient air conditioner

    A few Mini Split threads:

    Sa
    nyo mini split AC (inverter/variable speed)

    Sanyo Mini-Split AC
    Mitsubishi mini-split 26 SEER
    smallest, most efficient A/C ?
    what's a good window based AC unit?
    Design help needed for off grid air conditioner
    Fedders 5000 BTU A/C test

    A Mini Split is just an Air Conditioner that has (usually) the compressor and heat exchanger outside, and a separate (some times multiple) wall/ceiling unit.

    They are (roughly) 2x as efficient as a typical window unit. Many mini-splits are available as heat pump (winter heating). A few people here will heat when there is snow on the ground (impressive).

    Unfortunately, Sanyo make a really nice mid sized mini split that ran off of 120 VAC--Panasonic bought Sanyo and (apparently) killed the product line.

    Regarding 5k BTU window unit on a Honda eu1000i:
    icarus wrote: »
    Just as an aside, we have had very hot weather (humid too) this summer. I bought a 5000 btu window unit. It will run and start on a EU 1000 Honda. I have run it several nights, with the bedroom closed off and it gets the BR down to an acceptable temp for sleeping. I end up running the genny for about 3 hours and, I n spite of burning a 1/2 litre fuel,, it is a godsend for the few short weeks of really hot nights.

    It draws ~500 watts running. To get it to start, I run it fan only, then turn it on low coo, get it spinning, then switch to high cool, all with the genny with the Eco throttle off. Once it is up and running, I can turn the Eco throttle off, the genny slows down a bunch, and I have enough power to run the paddle fans in the rest of the house off the genny.

    Tony

    I don't know what model/mfg. Tony has, but you do have to be careful and get a "good one"... Many people here have a 5kW unit and it will not even start on an eu2000i genny (1,600 watt continuous).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: energy efficient air conditioner

    Almost 2 years ago got a small Frigidaire mini split. Why Frigidaire? Because that's what our local home building supply outfit carries. So far I have to say it's been awesome, beyond expectations, very happy with it. Incredibly quiet both the inside unit and the outside unit. Compressor is inverter type, running only as fast as required to do the job. In Fall and Spring, as as during milder winter weather, I run it in heap pump mode. When it's really cold, I heat with wood.
    In summer, I get FREE air conditioning! The solar system has no problems running it. There is NO and I mean NO start surge! The compressor gently starts, drawing perhaps a couple hundred watts, then if necessary, it slowly ramps up to 3, 4, 5 or 6 hundred watts. Most times it hangs around 3 or 4 hundred watts in cool mode. So the house never gets hot in Summer, I shut down the unit overnight and the place stays cool. The cooling efficiency is nothing if not incredible compared to the standard, window shakers.
    My mini-split looks similar to this one: http://www.minisplitwarehouse.com/Senville_12000Btu_19_Seer_Inverter_Mini_Split_Heat_Pump_AC_110v___Energy_Star/p315964_6136980.aspx
  • PhotowhitPhotowhit Solar Expert Posts: 5,697 ✭✭✭✭✭
    Re: energy efficient air conditioner

    It sounds like you could run a "window Shaker" with your present system if you have a >2000 watt true sine inverter, It's a motor so a true sine will allow it to run effeicently.
    shockman wrote: »
    I will have about 1000 watts of panel, 760a/hr of batt. on a classic 150.
    I take it this is a 12 volt system? and you have calculated your amp hours correctly, we often have people add the amperage of batteries in a string, but sounds like 4-L16 sized batteries. Your already marginal on Array to battery sizing so I would run the genny to charge the batteries at some point, but a small 500 watt unit should run over night on your battery.

    Note 2; biggest problem with starting a large load on a 12 volt system is the starting surge creating a low voltage fault due to too small of wires, but if you've run a microwave from the battery your likely fine.

    Note 3; If you choose to run the A/C during the day, Midnite should come out with a battery monitor module later this year that will measure the charging current across the shunt so if installed the midnite charge controller should be able to properly charge your batteries while the A/C is running, though it is likely you won't cover the A/C with your solar alone so you might skip it.
    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.
  • solar_davesolar_dave Solar Expert Posts: 2,384 ✭✭✭✭
    Re: energy efficient air conditioner

    Friedrich makes a 22 seer 120V minisplit still
    http://www.appliancesconnection.com/friedrich-m09ch-i182185.html?ref=froogle

    $869 is not a bad price
  • shockmanshockman Solar Expert Posts: 113 ✭✭
    Re: energy efficient air conditioner

    "
    Photowhit wrote: »
    It sounds like you could run a "window Shaker" with your present system if you have a >2000 watt true sine inverter, It's a motor so a true sine will allow it to run effeicently."


    It is an old 2012 Trace MSN ??? is this a problem?

    "I take it this is a 12 volt system? and you have calculated your amp hours correctly, we often have people add the amperage of batteries in a string, but sounds like 4-L16 sized batteries. Your already marginal on Array to battery sizing so I would run the genny to charge the batteries at some point, but a small 500 watt unit should run over night on your battery."


    Correct 4L16's

    Note 2; biggest problem with starting a large load on a 12 volt system is the starting surge creating a low voltage fault due to too small of wires, but if you've run a microwave from the battery your likely fine.

    Too small of wire, where??

    Note 3; If you choose to run the A/C during the day, Midnite should come out with a battery monitor module later this year that will measure the charging current across the shunt so if installed the midnite charge controller should be able to properly charge your batteries while the A/C is running, though it is likely you won't cover the A/C with your solar alone so you might skip it.

    What happens without BMM???
    4x240w panels,Classic 150 CC, 4x380AHR L16's, antique Trace 12V inverter
  • BB.BB. Super Moderators, Administrators Posts: 32,204 admin
    Re: energy efficient air conditioner

    When you get into the details of designing/running a battery bank, you figure out that nothing should work right or last more than a few months before something goes wrong or the battery fails (usually from under charging or taking it "dead", sometimes from over charging/not adding enough distilled water).

    One of the "ideal" methods to recharge a battery bank is to watch the "ending amps" when charging... For example, a 100 AH battery bank will usually end around 1-2 amps--flat line charging. At that point, the charger should cut back from "absorb" (around 14.5 volts) to "float" at ~13.2-13.6 volts. That reduces water usage and can help the battery last a little longer (generating a lots of hydrogen and oxygen gases uses up water, can erode plates, and drive oxygen into the positive plate/grid and cause corrosion).

    So--Knowing when the battery is "full" by monitoring ending amps is a nice way to do the float transition. The problem is that 99.999% of the charge controllers today only know how much current they are outputting, and not how much goes into the battery bank--If there is other DC loads present... So, you may "fix this" with an Absorb timer of 2-4-6 hours, or some other less than ideal charge termination technique.

    What should be coming out of Midnite for use with their Classic controller is the possibility to put a battery shunt (typically on the negative connection between the bus and physical battery posts). This will allow Midnite to directly monitor battery charging/discharging current and controller their output voltage stages more accurately and, hopefully, give the battery a bit better life.

    -Bill "as I understand the issues and I don't work at/for Midnite" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,697 ✭✭✭✭✭
    Re: energy efficient air conditioner
    shockman wrote: »
    It is an old 2012 Trace MSN ??? is this a problem?
    On a Modified Sine Wave inverter, It's likely to run, but it's motor/compressor will run hot and have a shorter life, and the wattage used will be higher.
    shockman wrote: »
    Too small of wire, where??
    Between the Battery and the inverter, Likely you should have 4/0 for anything over 1800 watts, unless they are very close together.
    shockman wrote: »
    What happens without BMM???
    Bill did a great job of discribing this, I think since you have such a small array you will draw enough power for the Charge Controller to never get to Float and Likely start over each time the A/C shuts down on thermostat (Something we haven't discussed is that the 500 watt draw is only while the compressor is running and will cycle on and off)
    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.
  • shockmanshockman Solar Expert Posts: 113 ✭✭
    Re: energy efficient air conditioner

    Thanks guys! great info.
    The other thing I don't really understand is watts dc in/watts ac out. If I have 1000watts coming in from array and 500watts ac being used do I have 500 (less inv. inefficecies) left for charging or is there way more math to be done >:)
    4x240w panels,Classic 150 CC, 4x380AHR L16's, antique Trace 12V inverter
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: energy efficient air conditioner
    shockman wrote: »
    Thanks guys! great info.
    The other thing I don't really understand is watts dc in/watts ac out. If I have 1000watts coming in from array and 500watts ac being used do I have 500 (less inv. inefficecies) left for charging or is there way more math to be done >:)

    Not much more than that. There are inefficiencies in the MPPT conversion, although far less than in most PWM situations. There are inefficiencies in running the inverter, and in charging the battery (power in greater than power out.)

    The biggest loss of potential panel power comes when the inverter is not running (no loads) and the batteries are full (not much charging current.) In that case the potential power output of the panels remains just that, potential. This is one reason that off-gridders spend time planning when to do high energy use opportunity loads (washing machines, A/C, water heating) at times when the full output of the panels would not otherwise be used.
    It is much better in terms of efficiency and wear and tear on the batteries to send power from the panels straight through the inverter to the load whenever possible rather than cycling the batteries by time shifting the loads.
    Some things, like lighting, just have to shift.
    SMA SB 3000, old BP panels.
  • PhotowhitPhotowhit Solar Expert Posts: 5,697 ✭✭✭✭✭
    Re: energy efficient air conditioner
    inetdog wrote: »
    Not much more than that. There are inefficiencies in the MPPT conversion, although far less than in most PWM situations. There are inefficiencies in running the inverter, and in charging the battery (power in greater than power out.)

    There are less, but Far less in a healthy off grid system, to me is just wrong. If you have panels rated for the voltage of your battery bank, I'd guess 10% is a realistic advantage of MPPT over PWM systems. I'm off grid and have and use both, though I'm really just starting with the Midnite classic, which has other features that help utilize the energy when your battery is nearing full. But while in Bulk the MPPT will produce 20-25% more charging current, but in a healthy off grid system you aren't in bulk very much.

    So the basics of your system; (you can post your system in the signature as an option of your profile)

    You have a 1000 watt array, but this only produces 1000 watts under idea situations. If you have newer panels you can find the NOCT (Normal Operating Cell Temperature) values for your panels these tend to be 70-80% of the panel rating. This is what you can expect on most days.

    So your producing 750 watts and this comes into your charge controller and the charge controller uses a little energy and sends the energy to the battery, Batteries Charge at roughly 80-85% efficiency, if your using the energy as it comes in you don't loose as much of this energy, but then you go to your inverter which is likely 80-90% efficient at converting the DC current into AC. Notice these percentages compound, so your inverter running off batteries isn't loosing 15% of the 750 watts that was sent to the battery, but it looses 15% of the 600watts stored by the battery. So if your running the A/C during the day before the energy is stored you don't loose as much. Clear as Mud?

    Since the 500watt load is at the A/C you have to add the inverter inefficientcy, so the inverter is using 575 watts to make the 500watts you want to use, there are other losses, but they are small.

    If your using a Modified Sine wave inverter, it will take more energy yet, to run a motor as the motor will try to create a smooth wave from a choppy one and will release heat. How much depends on how smooth the modified sine wave is.

    So a moment on your Array to battery bank, Most flooded batteries like to be charged ar 5%-13% of their rated capacity, so a 760Amp Hour battery bank would like 38-98 Amps of current In NOCT your 1000 watts of panels should produce @50-55 at charging voltage and as little as 40 during Bulk with a PWM Charge controller. So long as it reach float on a regular basis, you should be fine, just understand where your at in your relationship with the batteries.
    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.
  • VicVic Solar Expert Posts: 3,124 ✭✭✭✭
    Re: energy efficient air conditioner

    shockman,

    To your original question;

    Regarding your stated desire to run a 6,000 BTU Window A/C:

    We use three of them here. Two of them separately cool two different Power Rooms. In the summer, with excess power available, use the third one is allowed to run in a 550-ish SQ Ft cabin. They all are Samsung 6 KBTU models, each consumes about 530 measured AC watts at 120 VAC. These are teriffic little units with an EER of 10.7, which is fairly good, and surprisingly quiet for what they do. Bought one of these for US $100, and the following year two more for $120. Have been running one for six Summers and the other two for about four years on average.

    During Summer days the cabin unit runs TRYING to kinna cool the whole cabin from about 1 PM til about 5:30 PM from excess power available when in Float. At night close the bedroom door to the rest of the cabin and cool just the small 150 SQ Ft bedroom, works great, and uses not more than 1.5 Kwh from the batteries at night because it is cycling. Do keep the fan running constantly to help the noise of the Compressor starting.

    These units will start easily on my Honda EU2000isa in Eco Throttle.

    Unfortunately, Samsung has no models smaller than 10 KBTU the last time I checked.

    Cooling your entire cabin during the day would probably be a struggle for 6K, but if your heat load/gain is not too great, it may do OK. For my cabin, a 6K mounted in the bedroom window, with the BR door open, the afternoon temps stop rising on a full sun summer day. The temp differential twix outside and inside of those days needs to be less than 20 degrees F in oreder to stall the main cabin temp from rising.

    You mentioned only a few days per year that the A/C would be essential. So, even running a small Honda EU1000 EDIT *to directly DC* charge the batteries, with a suitably large TSW Inverter might do the trick, if the A/C you select was unable to start on an EU1000 ... dunno.

    There are the obvious trade offs between permitting the A/C to cycle, vs trying to get it to run constantly during the night vs EU1000 or 2000 and cooling only the BR and so on.

    Am very happy with this "solution" to my cooling needs for now. Probably a Mini-Split is in the future here. Would have gotten such a system last year, but Sanyo being bought up, stalled that project.

    The BMM or similar that photowhit mentioned, believe, is the MidNite battery charge current monitor, which will be able to terminate Absorb based only on the actual battery charging current.

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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