Green start for my freezer

I am new to the forum and am not sure where to put this post.
I am off-grid at my grass shack and am trying to get my xantrex xpower 1000 watt inverter to run my GE 5 c.f. freezer. The first time I tried (no other load on the inverter) the freezer started but the second time it just hummed, pulled the plug in about two seconds as I did not want to burn out the compressor motor. I run the freezer about 2 hours a day to keep things cold so I have used my Honda 2000IU generator to run the freezer.
I talked to the Wind/Sun people and am looking at a 1500 watt to 2000 watt sine wave inverter to handle the job. The kill-a-watt reading is 1100 watts to start and then 145-155 watts to run the freezer.
My maximum usage (lights, tv, dish receiver, chargers for electronics is 250 watts if I have everything plugged in at one time.
Currently my set up is 12 volt with 400AH of capacity and 2 gauge wire less than 3 feet from the battery bank to the inverter.
So....an engineer that I talked to suggested using a soft start, hard start, green start setup to allow me to use a smaller sine wave inverter for this hard starting application. I tried researching this on the forum but could not seem to find anything to help me. I have googled and followed leads on the internet but really do not get to far. Some say do it, some say it is hard to match up everything, some say while it will work it will shorten the life of the compressor. Needless to say, I am confused. Some say sell the freezer and buy a propane one or get a 12/24 volt freezer. I could do that but those things are expensive. I also can go with the larger inverter but that does not seem to be very efficient when I only need the big power pull for only a second to start the compressor.
What would really help me the most is that if the addition of a hard start kit works one could lead me in the right direction to make the application work.
Thanks, Bob
OBTW, the rest of my little system is 1k of panels and the xantrex xw mppt60 150 controller.:confused:

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: Green start for my freezer

    Assuming the AC compressor is a 3 wire (single phase with external capacitor) induction motor--it is possible a VFD (variable frequency drive) might be an interesting solution to your problem. I have not heard of anyone using it on a refrigerator, and I wonder if the some of the newer high efficiency / energy start compressors would not be a good with a VFD (and how to identify which type of compressor you have in your freezer)...

    People have played with changing the size of the motor start capacitor on some devices (like furnace fans) (assuming this unit has a motor start cap vs a motor run cap)...

    But, in the end, I am not sure there is any solution for your existing freezer. Soft Start/Hard start tend to be just a different motor start capacitor. And they still need that initial surge current to start (just a short pulse of current).

    A VFD may work--but you would be on the cutting edge of the solution--Meaning that it will be your $$$ and time to see if you can get it to work for your inverter. And refrigeration compressors typically already have some sort of load (pressure differential) across their suction/pressure inlet/outlets which make it more difficult to start.

    The other thing to look at--1,100 watts of surge power requires a lot of current from the battery bank. Assuming this is a 12 volt battery bank, the circuit needs to deliver:
    • 1,100 watts * 1/10.5 volts * 1/0.80 inverter eff * 1.25 NEC safety factor = 164 volts
    You wiring should give you about 0.2 volts drop...

    And your 400 AH battery bank should be good for (assuming 12 volt battery bank)--assuming C/2.5 maximum surge current support for a Flooded Cell battery bank):
    • 400 AH * 1/2.5 = 160 amps surge
    So, you are right on the edge of supporting that high of surge current for your AC Freezer.

    If you monitor the input voltage to the inverter, what is the minimum voltage you see?

    In the end, I guess this is a MSW (modified square wave) inverter and the MSW waveform is just not very good for electric motors anyway. They tend to run hot on MSW.

    It is a combination of the surge current and MSW wave form that NAWS is probably recommending a minimum of a 1,500 watt TSW inverter--And it is based on their years of experience from building smaller solar PV systems for use out in the deserts. They want your system to run perfectly and for a generic refrigerator compressor--that is pretty much what it requires.

    You can still setup a small/efficient inverter for your other loads and a larger inverter with search mode or some sort of external on/off line you could control to turn the inverter on when you need to run the pump.

    By the way, for more than ~1,200 watts of load, you should be considering using a 24 volt (or larger) battery bank--that will keep the surge current and your wiring size down.

    Long way around to talking about other options (propane if this is a part time residence, or larger inverter+battery bank, or finding a freezer that has a more efficient pump in it (if there is such a thing out there))...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • petertearaipetertearai Solar Expert Posts: 463 ✭✭✭✭
    Re: Green start for my freezer

    Hi I have a Samsung fridge freezer which runs well on a 1800 watt ps Xantrex inverter.Pulls about 100 watts on run .
    Have i seen people on this site running fridges on morning star 300 watt sine wave inverters?
    Regards Peter
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Green start for my freezer

    145 to 155 watts once it's up and running seems very high! My upright freezer converted to fridge uses approx 100 watts run, my former 5 cu ft chest converted to fridge, more or less 100 watts run and my two large freezers, one 10 cu ft. other 12 cu ft, both more or less 100 watts. In ALL cases, they were not capacitor start, and in all cases, I added capacitor start, which in all cases made a HUGE difference in greatly increasing the speed of the start, and a huge reduction in start power surge. In all (my) cases except for the newest upright which has a capacitor run motor, 200MFD worked best. With the Cap-run unit, it was slightly less, and I'm sorry I can't recall the exact value, and it's fastened in by the compressor where I can't see the value without tearing things apart. (may have been 160 MFD, not sure) Over and above that, I made additional, extensive modifications that allow me to run them all, one at a time of course, on a SureSine 300 inverter and two of them have been so running, totally off grid, for about 3 years now, taking turns, with the "fridge" having priority, shutting off power to the freezer whenever it wants to run. Those modifications are complicated and not likely something that could be done by non technical folks. HOWEVER, you can rather easily add a start capacitor, even with the newer units that have a Varistor to control the start winding, just add the capacitor in series with the varistor and it's done. You'll find the compressor starts far quicker and with far less surge.
    That said, I still wonder about the 150 watts to run yours when everything I have runs at more or less 100 watts once everything settles down. They tend to use a bit more until the pressure builds up over the first minute or so, then the consumption drops. That goes against common sense, yet they all act the same way. Something doesn't seem right with yours sucking back 50% more than any I've checked. My impression is either it's grossly inefficient, or there's something wrong with it. I don't remember having checked any while running on MSW, but certainly wouldn't expect to see 50% more. Up to 20% perhaps, but not 50. And yes, once capacitor start was added, none of mine had any trouble at all starting on the cheap 1000 watt MSW I had.
    One more thing, with Varistor controlled start, if for any reason it doesn't start right away, you MUST let that varistor cool down for perhaps 5 minutes before trying again, otherwise the still hot varistor will block the current to the start winding, preventing the compressor from doing anything other than sitting and humming. In all cases there will be an overload protection that will sooner or later click off for a while if the compressor doesn't start, (assuming your battery doesn't go dead first) and will automatically reset in time, preventing motor burnout. They used to be external of the motor, located in with the start relay. Then when they went varistor start instead of relay start, they began burying the overload breaker in the windings of the motor, so if it didn't start, it sat and hummed for a relatively long time until the motor windings got so hot it would finally click off. The motor would then appear to be dead until it finally cooled off again, which could take almost half an hour. Now most if not all manufactures seem to have moved back to the far faster acting external overload breaker that doesn't need the whole compressor to overheat before it clicks off.
  • System2System2 Posts: 6,290 admin
    Re: Green start for my freezer

    Wayne,
    Thanks for the input. I will recheck the pull on the freezer after it has run for awhile to see if it still pulls the 150 watts. I measured this while it was running off my Honda 2000 IU generator.
    Could you be more specific as to the 200mfd capacitor you wired in? Name of unit, possible website to contact and approx cost?
    I am guessing that this setup is pulling less than the 300 watts that your inverter puts out and it sounds intriguing that you have set these up for separate and priority start up. I really appreciate the help.
    Bob
  • System2System2 Posts: 6,290 admin
    Re: Green start for my freezer

    Peter,
    Thanks for letting me know that an inverter like yours should start my freezer. There also has been a post from Wayne on the 300 watt ps inverter that he uses.
    Bob
  • System2System2 Posts: 6,290 admin
    Re: Green start for my freezer

    BB,
    Thanks for the input. I will have to research VFD technology to learn more about it.
    I appreciate the calculations that you have done as well.
    I have just purchased a bank of agm batteries and will be setting up a 24 volt system with 400AH of capacity. Will need a 24 volt ps inverter and water pump now.
    I also appreciate the other options that you identify as you can never have too many minds working when you are brainstorming.
    Mahalo, Bob
  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: Green start for my freezer

    Bob,

    You are very welcome--As I was researching your question--I read a refrigeration/Air Conditioning forum that had basically the same question (their utility wanted to charge for a new/larger transformer to supply power for their new A/C system).

    And, they did not have any answer either on how to reduce maximum starting current. Soft/Hard start shorten the high starting current, but do not really reduce it.

    Inverter based A/C systems (basically a version of VFD) are starting to become more common (as OEM/upgrade pumps) for larger systems--but they did not have any easy answer either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Green start for my freezer
    erickre wrote: »
    Wayne, Could you be more specific as to the 200mfd capacitor you wired in? Name of unit, possible website to contact and approx cost?
    Bob
    Hey "erickre", I'm lucky to have a friend who owns a motor rewinding and repair business, so I'm able to get the capacitors there. They are just regular MOTOR STARTING capacitors, available at any motor repair shop. 200 MFD value and rated for at least 110 volts. (AC of course. Do NOT use a DC capacitor in such an application, as it will literally create an internal buildup of gas pressure and explode) The cost was about $10.00 .
    I'm also lucky that I was able to try different MFD values to find the one that worked best.
    The following would be typical of what I found to work best with all but one of the freezers I converted:
    http://www.galco.com/scripts/cgiip.exe/wa/wcat/itemdtl.r?listtype=Catalog&pnum=MSC125V189-NTE
    But note: The additional circuits, relays etc, to enable starting on the SureSine 300 are far more extensive and technical.
    Additional note: For your info, the physical size of the capacitor is about 3 inches long X 1 inch diameter. But size does not denote the electrical value of the capacitor, it's just to give you the info that it won't be the size of a gallon jug, or as small as a pencil eraser.
  • Peter_VPeter_V Solar Expert Posts: 226 ✭✭✭
    Re: Green start for my freezer

    You might consider selling your fridge and buying one that runs on DC.

    They tend to be more efficient so they'll use less of your precious power. Plus no need for an inverter or hard start kits, etc.

    They even make ones that use something called a Eutectic holding plate that work by storing the cold in a phase change material. They only have to run perhaps once or twice a day when the sun is out and then will maintain temperature over night, so you don't need to use batteries to power them.
    I've read that ones around 3.5 - 5 cubic foot can run on a single 60 watt panel.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Green start for my freezer

    From the Marine world comes a couple Manufacturer's come the Gas/ AC /DC refrigerators. The gas absorption are so / so to me. It's hard to get them worked on. They have no compressor and use ammonia.

    I have had good luck with the AC/DC models, they have a compressor, the gas do not. Some are free standing ( full cabinet ) and some meant to be built in, be careful if ordering. Most of the Marine / RV discounters can order what you want. You can get a ice maker in some.

    Changed a bad idea, buy a converter ......... No battery taps, bad idea from my aircraft days.

    http://www.thetford.com/home/products/norcoldrefrigerators/tabid/195/default.aspx

    http://www.dometic.com/enus/Americas/USA/RV-Products/refrigerators/
  • mike95490mike95490 Solar Expert Posts: 9,361 ✭✭✭✭✭
    Re: Green start for my freezer
    ......
    There 12 V dc so if you have a 24-48 v bank, you'll have to drop a 12V tap off of it.

    or use a DC-DC converter - lots cheaper than dead batteries from a tap.
    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 ,

  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Green start for my freezer
    mike90045 wrote: »
    or use a DC-DC converter - lots cheaper than dead batteries from a tap.
    guess I never had that problem, thanks for the heads up.
  • Peter_VPeter_V Solar Expert Posts: 226 ✭✭✭
    Re: Green start for my freezer
    I have had good luck with the AC/DC models, they have a compressor, the gas do not. Some are free standing ( full cabinet ) and some meant to be built in, be careful if ordering. Most of the Marine / RV discounters can order what you want. You can get a ice maker in some.

    There 12 V dc so if you have a 24-48 v bank, you'll have to drop a 12V tap off of it.

    Many of the DC ones will run on either 12V or 24V, specifically the ones with a Danfoss compressor

    For example, here is one being sold by our host:
    http://www.solar-electric.com/sundanzer225l.html

    Note: I have zero experience with these refrigerators, so don' t take this as any kind of endorsement.
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Green start for my freezer

    Never tap 12 from a 24v bank of batteries or they will soon die an unhappy death
    I think the Danfos 12/24v compressor is the best available ,it automatically detects which voltage to use. Have been using them for many years
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Green start for my freezer

    The Gas/ AC /DC refrigerators that use the ammonia gas absorption cycle, although practically silent and usually work very well, use heat to drive the cycle, so tend to be quite hard on energy compared to a compressor model. That heat can be useful in winter, but in summer, not so much. Most 8 cu ft models use about 1 pound of propane / 24 hours at normal room temp. More of course if it's hot weather.
Sign In or Register to comment.