A/c for solar

tattoodrntattoodrn Posts: 1Registered Users
Hello, I am new here. I am building my home soon and need some help. I live in western Ok. and get lots of sun and wind so plan on using solar and a wind turbine. What will be the best heat and a/c unit for my off grid plans? I have looked on heat and cool .com and they have split minis and splits but I am so new at this I haven't a clue. Can someone direct me to where I can figure out my needs? The house will be 770 square feet and basically 2 rooms with a bath/laundry room. I plan on triple pane windows, foam insulation on the roof and the floors and walls. The plan is to keep the inverter, main fuse panel and batteries outside in a shed. Thanks for any help.

Comments

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: A/c for solar

    Welcome to the forum.

    The mini-splits are probably your best bet for A/C because of their being easy on start-up and quite efficient running. Whole long thread about them here: http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29 Yes, it's a lot to read through.

    Be advised that air conditioning still takes a significant amount of power. That power has to come from somewhere, and that means your system will need to be sized to supply it. What that means is that when you don't need it you will have extra capacity. You'll want to think about ways to make use of that too.
  • bill von novakbill von novak Posts: 731Solar Expert ✭✭✭✭
    Re: A/c for solar
    tattoodrn wrote: »
    The plan is to keep the inverter, main fuse panel and batteries outside in a shed. Thanks for any help.

    FYI - your batteries have to be kept at least somewhat warm and cool; they don't tolerate temperature extremes very well. At the upper end they lose water and at the lower end their resistance goes up (and thus their available power goes down.) Depending on state of charge they'll even freeze solid if you're not careful. Take into account energy needed to keep the battery shed at a reasonable temperature (40-100F is a somewhat reasonable range.)
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: A/c for solar

    A fully charged battery won't freeze until -40! Even a partially charged battery will live quite nicely at 0f. I don't beleive it gets to -40 very often in OK!

    Icarus
  • WillBkoolWillBkool Posts: 35Solar Expert ✭✭
    Re: A/c for solar

    Is that -40 f or c? I guess it doesn't matter as that is the only temp that the scales are the same.:D

    It's good to know that charged batteries are ok at cold temps. It's not heated where I keep mine for now, and the temperature in the utility room got down into the 40's a couple weeks back when we got temps in the teens. I was a little worried, but if I keep a 60 watt bulb burning, it stays in the mid to upper 50's.
    670 Watts, 4 Evergreen 120 watt, 1 Eoplly 190 watt; M-Star 15A MPPT; 6 105 AH AGM Configured to [email protected]
    Cotek 1500 watt/24v
  • mike95490mike95490 Posts: 7,642Solar Expert ✭✭✭✭
    Re: A/c for solar

    in a cold area, the heat caused by charging and discharging a battery bank, will warm it a bit, that 80% recharge efficiency ends up as about 20% heat.
    hot days are a different matter, batteries age faster, the hotter they are, so you want to keep them from getting too warm. Shaded, earth shelter, something. They don't care about humidity.
    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
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  • peakbaggerpeakbagger Posts: 341Solar Expert ✭✭✭
    Re: A/c for solar

    AC and solar can match pretty well as the cooling demand roughly lines up with the times of high sun. There are 12 v mini splits on the market but they are from unknown manufacturers, I would recommend sticking to a 120 or 240 volt unit (note a 240 volt unit requires an inverter or stacked inverters that can output 240 volt). You want to buy the most efficient unit you can buy and make sure the outdoor unit is in a shady spot with good air circulation. Mitsubishi's are generally regarded as the most efficient but they do cost more and there are several other brands that seem reliable. Most minisplits can be used for heating but in that case, the heat is normally needed when the sun isn't out so its poor match for solar (but might line up with your wind resource). If that is something you want to explore, you need to look for cold weather heat pump like a Mitsubishi Hyper heat which is designed for cold weather (most regular split heat pumps shut off at around 40 F while a hyper heat works down to -10). The trade off is the optimum place for the outdoor unit for summer cooling it the opposite of the optimum spot for winter heating (lots of sun and low wind are ideal for winter). Planting shade trees can help this tradeoff.

    When building the home, thermal mass and shading is important, every dollar you spend on insulation and shading will allow you to go with a smaller AC unit and more importantly a smaller battery bank.

    By the way, look carefully at your wind resource, 90% of the folks who install small windmills wish they hadn't as the wind speed is not as high as they thought or they are unwilling to maintain the wind mill which requires at least annual major maintenance.
  • Blackcherry04Blackcherry04 Posts: 2,486Solar Expert ✭✭✭
    Re: A/c for solar

    As always the devil is in the details. If you read the below you'd think that this is something very special, in the description detail they leave out that in the heating mode they are using a heat strip to get the heating numbers they show. The specifications only shows 5 ° F and the unit is using 6,370 watts, At 17 ° F , 5,600 watts . That you can do with a hair dryer. Do your homework.

    "Even at -13˚ F outdoor temperature the H2i system can
    provide 100˚ F discharge air temperature from the indoor
    unit. And at 5˚ F outdoor temperature and above, the
    discharge temperature reaches an impressive 110˚ F
    with a 40˚ F temperature rise."

    www.mitsubishipro.com/media/226460/h2i_brochure.pdf‎
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: A/c for solar
    WillBkool wrote: »
    It's good to know that charged batteries are ok at cold temps. It's not heated where I keep mine for now, and the temperature in the utility room got down into the 40's a couple weeks back when we got temps in the teens. I was a little worried, but if I keep a 60 watt bulb burning, it stays in the mid to upper 50's.

    Cold is OK for batetries if they are not used. If they are in use, because of their reduced capacity, higher internal resistance and higher Peukert factor, they will be depleted to a lower SOC for a given load. Your cold batteries will use up their cycle life sooner. Of course if you are using battery power for that 60 watt bulb, you will lose even more cycle life than just running them cold.

    As long as you plan for the reduced capacity there is no real problem with batteries being cold. In summer you will have more capacity and probably shallower cycles... try to avoid shallow cycles in the summer... that's not good for batteries either.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • peakbaggerpeakbagger Posts: 341Solar Expert ✭✭✭
    Re: A/c for solar

    I am not advocating an air source heat pump for full time heating with off grid solar. It works quite well for supplemental heating when on grid. Do note given your house size the previously linked brochure is for a family of much larger units than you would buy, the efficiency goes up on the smaller splits that only run one interior unit. Given your house description I expect you would be looking at the 9000 btu unit.
  • Blackcherry04Blackcherry04 Posts: 2,486Solar Expert ✭✭✭
    Re: A/c for solar

    Mitsubishi 9,000 BTU 26 SEER Ductless Hyper Heat Pump Model# MUZFE09NA. As you can see they don't give anything below 17 degrees.

    47 ° F , 710 watts

    17 ° F , 1730 watts

    Attachment not found.
  • techntrektechntrek Posts: 1,366Solar Expert ✭✭✭
    Re: A/c for solar
    FYI - your batteries have to be kept at least somewhat warm and cool; they don't tolerate temperature extremes very well. At the upper end they lose water and at the lower end their resistance goes up (and thus their available power goes down.) ...

    Partially true. Capacity goes down in the cold (and up in the heat), but battery life goes up in the cold and down in the heat. On the camper forum I run I always advise people to leave their batteries - charged - outside in the cold over the winter and not in their warm garage or basement.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • H2SO4_guyH2SO4_guy Posts: 212Solar Expert ✭✭✭
    Re: A/c for solar

    I use a Mitsubishi 9000 BTU mini split that is 26 SEER rated and also a heat pump. I use used batteries that cost $1300 plus lead trade in and they are rated at 2080 AH @ 48 volts. (2 strings) They have worked 9 months for me running AC in the summer and heating this winter. I love the Mitsubishi, but there are a couple of things I don't like. It never shuts off, so it is drawing power all of the time. I often set the timer so it shuts itself off when I go to bed. I do wish the remote was back lit so I wouldn't have to have a light on to run it, but other than that, it is wonderful.

    Good luck and let us know!

    Skip
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • peakbaggerpeakbagger Posts: 341Solar Expert ✭✭✭
    Re: A/c for solar

    Ditto on lack of backlight and the lack of shutdown. It doesnt draw much when its just blowing air but to an offgridder I expect its a PITA. Mine does fine down to 10 degrees F especially if its dry out. Add in snow or humidity and it cycles through defrost more often. My 12K unit has cut way back on my wood usage and the power hit hasn't been bad (I am grdi tied with net metering so I am burning up last summers surplus.
  • Blackcherry04Blackcherry04 Posts: 2,486Solar Expert ✭✭✭
    Re: A/c for solar

    Good to see some posting specifics about your systems and how you use them. I like Mini-splits, but readers should see how they are used and what they should expect if they get one. Mini's have made great strides nibbling around the edges of the physics of the refrigeration cycle and reducing power consumption, but they have not changed the facts. Wading through their sales brochure is like a mine field and is filled with " Yes, but's " it's hard for a novice to try to understand.

    It's not always easy to find a servicing dealer close, if you get one it should be a consideration. I my area it's a 200 mile service call. Technological advances come at a cost, you have to have someone that understands their logic to work on them. I talked a friend into putting one in a new addition on his house, it's been nothing but a headache and I have wished 100 times I'd of kept my mouth shut.
  • Ralph DayRalph Day Posts: 873Solar Expert ✭✭✭
    Re: A/c for solar

    I can't recall what my Mits standby power consumption is, measured it once, but it's not important. I shut the breaker off when it's not in use...no consumption.

    Ralph

    Tare loads: 120-240 autotransformer 8watts, Mits system on but not running another 41watts...total tare load system not running bounces between 50 and 49 watts on the Kill a Watt.
  • H2SO4_guyH2SO4_guy Posts: 212Solar Expert ✭✭✭
    Re: A/c for solar

    My Mitsubishi 9000 BTU with the Outback 220v transformer is 30 - 32 watts when the unit is off. Heating can be all over the place when it is cold out depending on the temperature. My 'Outdoor' unit is actually 10' high sitting on a pallet rack in a barn, so it does have the advantage of not being on the ground where the most cold would reside, but it is in an unheated space. I can measure it this weekend to see what kind of consumption is typical. Last Sunday I made 23.7 KWH so I was running everything! Ran out of inverter overhead on the Outback so had to cut back.

    Good luck and let us know,

    Skip
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • techntrektechntrek Posts: 1,366Solar Expert ✭✭✭
    Re: A/c for solar
    Ralph Day wrote: »
    I can't recall what my Mits standby power consumption is, measured it once, but it's not important. I shut the breaker off when it's not in use...no consumption.

    I believe they have a crankcase heater like larger units do, you could be damaging yours unless you turn it on 24 hours before use.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • Ralph DayRalph Day Posts: 873Solar Expert ✭✭✭
    Re: A/c for solar

    I will check that out, but the control systems are so advanced I doubt it will run unless everything is within specs.

    Ralph
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