traditional air conditioning versus inverter air conditioner

animattanimatt Solar Expert Posts: 295 ✭✭✭
I was wondering if the main savings from inverter ac is due to reducing speed to meet reduced demands.

Kind of like the inverter generators are more efficient at lower output, but running full tilt they are not better than most other generators. Just quieter.

I am building off grid house in mexico. It will have alot of thermal mass. Not that thermal mass is great in the climate. So was wondering if i bought a standard ac unit would there be that much of an efficiency hit versus a 1 ton mini split inverter ac.

Or are the compressors and the whole inverter ac setup much more efficient even running at full load.

Having thermal mass i would be running full blast day time hours. Maybe 8am to 5pm. The mass would keep temps from flucating much.

If going with a standard ac unit would be probably looking at something like 3/4 ton. Something that might not keep up on some days but that would be okay. Coming from 95f outside 80f would not feel to bad.

Anyway an thoughts

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Re: traditional air conditioning versus inverter air conditioner

    The inverter-A/C units generally have much softer starting surge current (some are almost zero surge)... Much nicer on off grid power systems.

    Obviously, power * hours of use--You will have to design the battery bank+solar array to provide the needed energy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    I can only say what I see with my mini-splits and my conventional ground mounted heat pumps. Both are 17+ seer.

    The mini starts up soft like Bill said but as it runs it gradually reduces the load because the cooling demand is less, it then sets up a cyclic gradual ramp up and down to hold temps.
    The conventional units ( I have a 2 speed compressor) starts up to half power then pretty much in a minute or so goes full power. Once the temp is reached it shuts off until the demand hits again.

    The conventional units have a really high starting surge even at half power, you can hear it too as they strain to bring the compressor up to speed.
    The mini is virtually silent, no big huge load at start up.

    The mini seems much more effective at cooling for a given amount of power. It is hard to compare because they are really doing 2 different jobs. The mini has much less cubic feet to cool.
  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    Thanks for the responses. I knew about the soft start. I was just wondering efficiency diff. Both running full tilt. I am going to have 2 foot think stone walls which is enough mass to control temp swings and why full tilt could work for me. More out of curiosity to see if efficiency were in the same areas as inverter generators.

    I may end up making a insulated bedroom inside the house to minimize ac needs.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    So, does anyone have a list of CURRENTLY available 120v mini-splits?
    The old thread mentions many which are not available now since it is a rather old thread.
    I might consider going to one, I would need it for only 2 rooms.
    My window units work well now but wouldn't mind it being a bit quieter and more efficient.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • CDN_VTCDN_VT Solar Expert Posts: 492 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29&

    Good info & links with a long read . I bought a few way back & I hope to install the rest as time allows . Some of the links still have similar of what I purchased

    Ya , in two years the systems change !!! Dates matter ? Just waiting for the apple to hover. Edit add
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    CDN_VT wrote: »
    http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29&

    Good info & links with a long read . I bought a few way back & I hope to install the rest as time allows . Some of the links still have similar of what I purchased

    Yeah I have read thru that one, but like I said it is kinda dated. Would be good if someone had a list of some that are available TODAY and how they are working out for people.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    Even if you will not be running the inverter driven compressor at less than full output, you still get the benefit of reduced starting current. That alone may allow you to use a smaller inverter, smaller wiring, and a smaller battery bank to drive the A/C.
    The starting current surge to a compressor can easily be five times the running full load current, which can require you to provide an inverter (or generator) with high surge capability.
    SMA SB 3000, old BP panels.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    inetdog wrote: »
    Even if you will not be running the inverter driven compressor at less than full output, you still get the benefit of reduced starting current. That alone may allow you to use a smaller inverter, smaller wiring, and a smaller battery bank to drive the A/C.
    The starting current surge to a compressor can easily be five times the running full load current, which can require you to provide an inverter (or generator) with high surge capability.
    Yep, you get all that @ 10 times the cost. By the time you figure the ROI, the payback for most will be after their useful life. The biggest issue around me no one within 200 miles will work on them. All the big name A/C people have their own brands and will not fool with them.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    inetdog wrote: »
    Even if you will not be running the inverter driven compressor at less than full output, you still get the benefit of reduced starting current. That alone may allow you to use a smaller inverter, smaller wiring, and a smaller battery bank to drive the A/C.
    The starting current surge to a compressor can easily be five times the running full load current, which can require you to provide an inverter (or generator) with high surge capability.

    I personally, don't have an issue with the startup surge, running a VFX3648 and I am thinking my 5000BTU window units have a pretty high surge to begin with (might even be more than traditional split systems), and As Blackcherry04 mentioned, service would be an issue. Considering you need a 4WD to get 5 miles into the woods where I am, most service companies won't touch it. I was just wondering if overall energy usage would be so much less that it would be worth the investment for myself.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    I put my units on 24 V relays and run them on a thermostat in each room. That way they can be controlled and you don't have the fan as a issue all the time and use overhead fans. I usually will buy one at the end of the season, think I paid $86 at Lowes for the last 5000 btu I bought. If they don't work. pitch them in the garbage.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    jcheil wrote: »
    I personally, don't have an issue with the startup surge, running a VFX3648 and I am thinking my 5000BTU window units have a pretty high surge to begin with (might even be more than traditional split systems), and As Blackcherry04 mentioned, service would be an issue. Considering you need a 4WD to get 5 miles into the woods where I am, most service companies won't touch it. I was just wondering if overall energy usage would be so much less that it would be worth the investment for myself.
    As far as I know, there is not a large energy savings, if any. Other than perhaps that the motors used in the inverter driven motors may be designed more efficiently.

    Another small advantage is that running a longer time at a lower power is more likely to give you proper humidity control and avoid uncomfortable temperature cycles.
    SMA SB 3000, old BP panels.
  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    I get all those points. I was thinking as well that they may use more efficient compressor designs. Kind of my main question. Although not so directly out by me.

    My current power system can run the air conditioners that are in the motor home. Not a problem with surge currently. I believe 9000 btu. When house setup becomes more permenent i guess i could run into problems with various large loads wanting to start at the same time.


    I also get the long run times for humidity control. My situation somewhat unique with lots of thermal mass should keep uncomfortable temp swings to a minimum.

    I living in mexico there are many neighborhoods that all houses are just wired with a 30amp 120v service. If lucky 50amp but still 120v. The consumer market sees this then sells many 120v appliances where in other area 220v would be more common
  • Ken MarshKen Marsh Solar Expert Posts: 114 ✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    Poly-phase motors are in general 10 to 20% more efficient than single phase.
    This is comparing the PSC type motors used in HVAC with the poly-phase.
    Also when you reduce the speed of the HVAC unit the heat exchangers tend to operate
    with less delta temp across them which helps a little with efficiency
    So the mini splits should be a little more efficient.
    Actually I have not had any experience with the mini-splits.

    But I have changed out single phase compressors with 3 phase and run them with VFDs.
    Each one has showed less energy to operate in addition to the soft start.

    We heat/cool our house with a heat pump which also provides all domestic hot water.
    It makes hot water even if we do not need heat or air condx.
    The problem that comes up with the larger HPs in making DHW is that they are too big.
    The newer VFDs solve this problem by providing multiple speeds.
    When it makes DHW it runs at 30 to 40 CPS.
    The Huanyang/Hydria VFDs provide separate inputs to do this which makes the controls easier.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,026 ✭✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    animatt wrote: »
    I get all those points. I was thinking as well that they may use more efficient compressor designs. Kind of my main question. Although not so directly out by me.

    My current power system can run the air conditioners that are in the motor home. Not a problem with surge currently. I believe 9000 btu. When house setup becomes more permenent i guess i could run into problems with various large loads wanting to start at the same time.


    I also get the long run times for humidity control. My situation somewhat unique with lots of thermal mass should keep uncomfortable temp swings to a minimum.

    I living in mexico there are many neighborhoods that all houses are just wired with a 30amp 120v service. If lucky 50amp but still 120v. The consumer market sees this then sells many 120v appliances where in other area 220v would be more common

    With a mini split and the extremely low sound level inside and outside, you will hear the banditos. I did the window AC units for the first half of my 22 years offgrid. If you do not have the money for one I get it! Any other reason for having a window AC and you are seriously kidding yourself.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    It is mini split or mini split inverter. Are my options. Realistically almost definately end up with the invert kind. But was honestly curious if inverter air conditioning systems were similar to inverter generators which show the most promise at lower speeds. Theives down here seem to be very quiet in general unless they are drunk, in which case a dogs barking is all that is need.
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner

    As Ken said - more efficiency comes from better motors and operation at lower speeds. The compressor might also be a better design in a newer, more expensive inverter AC unit. It all shows up in the SEER rating.

    I am available for custom hardware/firmware development

  • Dave AngeliniDave Angelini Solar Expert Posts: 6,026 ✭✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    jonr wrote: »
    As Ken said - more efficiency comes from better motors and operation at lower speeds. The compressor might also be a better design in a newer, more expensive inverter AC unit. It all shows up in the SEER rating.

    Exactly ! Most of the best inverter based split units are now over 25 SEER and several up to 28 SEER with 5 year warranty.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • Dave AngeliniDave Angelini Solar Expert Posts: 6,026 ✭✭✭✭✭
    Re: traditional air conditioning versus inverter air conditioner
    animatt wrote: »
    It is mini split or mini split inverter. Are my options. Realistically almost definately end up with the invert kind. But was honestly curious if inverter air conditioning systems were similar to inverter generators which show the most promise at lower speeds. Theives down here seem to be very quiet in general unless they are drunk, in which case a dogs barking is all that is need.

    I remember one of my window units was so loud that I could not hear someone knocking at the door ! The dog just slept....

    You do understand the low power concept of programming the room temp to no more than 2 degrees lower? By doing this the unit will stay in the lower 1/3 of its max power. As the room cools you can program another 2 degrees lower? With plenty of solar or grid, you can just set the room temp you want and the unit will meter the power automatically ramping very slowly and not really noticeably. Depending on the morning temp the unit could draw more than solar can provide on small systems. Hence the 2 degree rule! The same for heating !

    I think the inverter based split units do show the most efficiency at low power and that is why I use them for my offgrid customers. Some are on tight budgets and can start small and add solar as they can afford to power the good things in life. Some can afford to do it all right the first time and want the best offgrid.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • TBooneTBoone Registered Users Posts: 3
       I am considering using one of these mini-split systems in a large motor home for obvious reasons. I estimate that I will need 20KBtu+
    of capacity and will use 2-3 ceiling cassettes instead of the wall mounted evaporators. The issue is that my coach system has no 220V available. Only 110V albeit a 10Kw diesel genset but only 110V. I see that multiple comments have been made about the relatively small startup current so I wonder if a device such as a 110V to 220V transformer system might handle it. Here's one rated for 5Kw:
    http://tinyurl.com/zh4dzpk.

    I welcome your thoughts and ideas.

    TBoone Fisher 

  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    Hi TBoone and welcome to the forum,

    I have a link to a website that offers a wide variety of mini-splits. Many brands names at good prices. Some 9000 and 12000 BTU units operate at 120 volt. I saw units that offer ceiling cassettes also. Anyway here is the link....
    http://www.thermospace.com/

    Good luck,

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • TBooneTBoone Registered Users Posts: 3
    Thanks Raj. I need at least 20Kbtu+ and because of space limitations, there is barely room for one compressor.

    I look forward to the discussion.

    TBoone
  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    Well, it looks like a 5000 watt transformer would work. A heat pump that size would present a load far less than that.
    But I can't speak as to the legality or safety of using a plug in connection though. As far as I know this unit should be hard wired to it's power source. Maybe there is a mountable hard wired transformer available for this type of installation. Others here may have more information or solutions concerning this.  

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • TBooneTBoone Registered Users Posts: 3
      Thanks. It would be hard wired in the permanent installation. I just want to make sure it works without problems.
    I would like to find a 20KBtu+ unit to test before I go further. Maybe a used unit??

    TBoone / BSEE
  • LucManLucMan Solar Expert Posts: 223 ✭✭✭
    TBoone said:
       I am considering using one of these mini-split systems in a large motor home for obvious reasons. I estimate that I will need 20KBtu+
    of capacity and will use 2-3 ceiling cassettes instead of the wall mounted evaporators. The issue is that my coach system has no 220V available. Only 110V albeit a 10Kw diesel genset but only 110V. I see that multiple comments have been made about the relatively small startup current so I wonder if a device such as a 110V to 220V transformer system might handle it. Here's one rated for 5Kw:
    http://tinyurl.com/zh4dzpk.

    I welcome your thoughts and ideas.



    TBoone Fisher 

    Do a search on Grainger for an Acme 120 to 240v boost buck transformer, that should work well for you. It would be permanently wired into your electrical system.
    I have used many of these in the past for A/C applications. There are some inherent loses when using transformers along with heat generation so be prepared to deal with those issues.

  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    IMO don't even take a chance messing with those cheap transformers.  
    Get the Outback one and you'll have no issues. Has a cooling fan and all the breakers all built in.
    Rated for 6Kva.

    http://www.solar-electric.com/psx-240.html 

    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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