start up load tripping inverter

andy t
andy t Registered Users Posts: 12 ✭✭
in Solar Beginners Corner #1
I have a victron phoenix350 inverter ratad at 350w which victron say has very high start up power peaking at 700w.
I have just bought an undercounter fridge 230v and the specs say 70w and 0.6 amps. If I have done my maths right 0.6ampd at 230v would be around 140w. So from this I assumed thay the fridge draws 70w while running and has a start up load of 140w, which I thought would run fine on the victron inverter.
I was wrong. When I turn it on and watch my bogart tm2030 battery monitor the watts go up to 450w then the inverter trips and shuts down.

How can you tell what start up load an item will need and why is the inverter tripping at 450w not 700w?

As the amps listed in the spec are double from what the watts say I assumed this to be the start up load, as I understand motors to take 2 or 3 times there rated power to start up. But this fridge seems to be drawing 6 times its rated power befor tripping the inverter. I had no other loads running through the inverter and it was only a few seconds before it tripped.

Thanks in advance for any help. I would like to understand why this is. I guess im going to have to return the fridge and continue with out one.
Off grid,
12 x 170w in 6 strings, outback fm80, 600ah 24v in 2v cells, 
Outback gfx1424e. Victron 350w inverter.
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Comments

  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #2
    Re: start up load tripping inverter

    It might be that the inverter is current limiting which is a bit different than "power" limiting.

    A lot of appliances will draw a lot more current at start-up. Inverters can trip off and stop trying
    if the current goes over a certain amount for so long a time.

    One thing you might try is to add an extension cord between the Victron and the appliance
    and see if it helps it not to trip so fast.

    boB
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  • andy t
    andy t Registered Users Posts: 12 ✭✭
    #3
    Re: start up load tripping inverter

    So by having a long cable run it could result in a drop in the current?

    A few times the fridge has run but only if I just click it on and wait for it to settle befor turning the temp down. Other times even doing it like this it trips.

    I will try with an extension lead and see if it makes any difference.

    Thanks for your help.

    The plan is to replace the victron with an outback vfx inverter to work along side the fm80 we use, but this isnt possible for at least 6 months.
    Off grid,
    12 x 170w in 6 strings, outback fm80, 600ah 24v in 2v cells, 
    Outback gfx1424e. Victron 350w inverter.
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  • hemmjo
    hemmjo Solar Expert Posts: 90 ✭✭
    #4
    Re: start up load tripping inverter

    We have a 1000w/2000w surge inverter, It BEEPS with it hits the surge, reminding us to cut back. We have a small fridge draws about 60 watts running. It NOTHING else it running, the fridge starts fine, but if the tiny washing machine is running, it draws 265 watts, the inverter beeps. So, subtracting 265 from 1000, there is 735 watts left for the fridge..... I figure our 60 watt fridge takes more than 735 watts to start-up. If it is running and you unplug it then plug it right back in before the compressor leaks off the back pressure, that load alone will cause our inverter to shut off on over load, so it is over 2000 watts.

    Good Luck,

    John
    Two systems in the Dominican Republic  http://villagemountainmission.org/
    installed Feb 2014 at 19.796189° -70.893594°, Classic 150 + WBJR, KISAE SW1210, MN Battery Monitor, IOTA DLS 55/IQ4,  4- Solar World 275w, 4-6v x 225ah Trace Batteries
    installed Feb 2015 at 19.795733° -70.893372°, same components  as above
    Honda PowerMate PC0497000, 7000/8750w generator - powers the well and chargers maybe once a week






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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: start up load tripping inverter
    andy t wrote: »
    I was wrong. When I turn it on and watch my bogart tm2030 battery monitor the watts go up to 450w then the inverter trips and shuts down.

    How can you tell what start up load an item will need and why is the inverter tripping at 450w not 700w?

    I don't have enough details of your system to know if this is relevant... Another cause for your problems may be the wiring and/or the battery. If there is too much resistance in the wiring between the battery and the inverter, or in the battery itself, then the voltage at the inverter input will sag and the inverter will fault. Your trimetric is reading the battery voltage at the battery... you need to know what voltage the inverter is seeing during the startup surge.

    Bottom line: It may be that the inverter can't handle the fridge, but I wouldn't jump to that conclusion unless you know that the battery cables are thick enough, the connections tight enough, and the battery big enough to give the inverter the power it needs.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    Re: start up load tripping inverter

    A general purpose motor will try to draw, for a short period while starting, up to six times the normal running current.
    If the inverter reduces its output voltage to keep the current down to its hard limit, and that still provides enough torque to start the motor and can hold that current for the few seconds that it takes for the motor to get up to speed, then you are OK.
    Incidentally, if you have another motor load running at the time, reducing the inverter output voltage will cause that motor too to pull more current.
    SMA SB 3000, old BP panels.
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #7
    andy t said:
    I have a victron phoenix350 inverter ratad at 350w which victron say has very high start up power peaking at 700w.
    I have just bought an undercounter fridge 230v and the specs say 70w and 0.6 amps. If I have done my maths right 0.6ampd at 230v would be around 140w. So from this I assumed thay the fridge draws 70w while running and has a start up load of 140w, which I thought would run fine on the victron inverter.
    I was wrong. When I turn it on and watch my bogart tm2030 battery monitor the watts go up to 450w then the inverter trips and shuts down.


    I am in the exact same situation. I realize this post is 3 years old but it's still an issue. 

    How can a 60w fridge shut down a 375w inverter when it's rated to over 700w on a peak surge rating?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #8
    Welcome to the forum 

    There could be a number of reasons such as the battery capacity being too low to support the load due to voltage drop, conductor size too small, again causing voltage to drop, or the refrigerator compressor drawing too much due to poor power factor. Can you describe in detail the entire system, this would enable all to evaluate and provide useful comments
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #9
    Victron inverter 375w
    Victron controller 75/15
    Solar panel input 285w
    Lithium based 24v battery power from 1kw
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #10
    What size conductors are used between the battery and inverter and how long? Do you have a multimeter to read the voltage at the inverter terminals on start up, if it drops below 9.7V the inverter will shut down. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #11
    If yours is a 24 volt battery bank, then roughly below ~21.0 volts on the DC bus will cause the inverter to shut down (you may need to cycle DC input power to restart the inverter).

    In general, to start a typical 120 VAC refrigerator compressor needs a minimum of ~1,000 Watt AC inverter (1,200 to 1,500 Watt recommended). One retired poster here got his to work with a 300 Watt (600 Watt surge rated) AC inverter--But he had to do a fair amount of engineering to get it to work.

    Induction motors on compressors (refrigeration, even air compressors), is a tough job--And requires a lot of surge current to support it.

    My full size refrigerators and freezers typically run ~100-120 Watts (I am on grid, so I cannot address surge current question).

    Induction motors typically have ~5x operating power as surge power/VA. Using a cheap 10-20 foot (or long--like 50-100 foot good quality extension cord) can add enough resistance that the surge current is cut down, but still allows enough current through to reliably start the fridge (always keep a close eye on "marginal" solutions--You don't want the compressor to fail to start a week later when you are not monitoring the system and have the food all spoil).

    By the way, if you are up in the "great white north" (Ottawa or farther north)--Is this a summer system (when you have lots of sun) or something you want to run deeper into winter:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Ottawa
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 45° angle:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    2.63
              		3.66
              		4.48
              		4.74
              		4.75
              		4.92
     
    Jul Aug Sep Oct Nov Dec
    5.04
              		4.83
              		4.23
              		3.19
              		2.30
              		2.09
     
    Just running some numbers/guesstimates (need to use a Kill-a-Watt type meter to get Watt*Hours per day)... Assuming 60 Watts and runs 50% of the time:
    • 60 Watts * 0.50 duty cycle * 24 hours per day = 720 WH per day
    • 720 WH per day * 1/0.52 off grid AC system efficiency * 1/4.0 hours per day sun (non-winter) = 346 Watt minimum array
    • 720 WH per day * 1/0.52 off grid AC system efficiency * 1/285 Watt panel = 4.9 Hours of sun per day (minimum "break even" sun with present solar panel).

    Reality is that you should only count on ~65% to 75% of off grid system energy usage for "base loads"--Allows for a bit of cloudy weather and such. Unless you are there and can run a genset on less than clear (average) days.

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #12
    1) few meters will accurately report on Peak Starting Current. 2) un-important looking bits (cables, bolt torque) can make an adequate system fail
    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

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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #13
    Well as an update, i have now upgraded to a 500w inverter. So far my fridge has started 4 out of 4 times. Yes it does run the inverter into a peak capacity mode but can handle it.

    The 375w inverter would max out at 700w or less. Bear in mind that the fridge did start on occasion with the smaller 375w so it must have been boarderline.
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #14
    Fridge manufacturer replied with pertaining information. The peak draw for this little fridge is 724w. The peak output of the Victron 345w is 700w.

    My updated 500w has a peak output of 900w. More than enough to run the fridge at startup.

    So far so good.
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #15
    7 hours in and i have used 6wh. I dont think i will hit 720wh by tomorrow. Or perhaps i don't understand this stuff.

    If the anual consumption is 200kwh then the daily is 0.55kwh or 55wh. If i recall correctly, the stress test on fridges takes place in 25°C with the door being opened by 4 family members. Therefore I should expect my numbers to be a little less.

    We shall see tomorrow.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #16
    0.55Kwh = 550wh

    The temp of the stuff put in the fridge (eg warm pop vs frozen stuff), and whether the fridge has run defrost cycles makes a difference in consumption as well.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #17
    Oops my bad. You are correct.

    550wh
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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #18
    Just to be clear. My Kill-A-Watt meter is indicating 0.06kwh in 7 hours.
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  • hemmjo
    hemmjo Solar Expert Posts: 90 ✭✭
    #19
    just a comment on keeping things cold.

    We have a small refrigerator at our mission in the Dominican Republic. It is totally off grid.  I try to teach  the staff to keep the empty space in both the freezer and the cold section partially filled with full bottles of water. In reality the freezer is mostly used to make ice anyway. This takes a while to cool down, but reduces the load each time the door is opened.  In the event the batteries get too low, due to 3-4 days with a lot of clouds, they can shut down the inverter to protect the batteries and the 'fridge can stay cool enough for 24 hours, to keep from spoiling things.
    Two systems in the Dominican Republic  http://villagemountainmission.org/
    installed Feb 2014 at 19.796189° -70.893594°, Classic 150 + WBJR, KISAE SW1210, MN Battery Monitor, IOTA DLS 55/IQ4,  4- Solar World 275w, 4-6v x 225ah Trace Batteries
    installed Feb 2015 at 19.795733° -70.893372°, same components  as above
    Honda PowerMate PC0497000, 7000/8750w generator - powers the well and chargers maybe once a week






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  • Wilbour
    Wilbour Registered Users Posts: 8 ✭✭
    #20
    So about 250wh after 24 hours of use.
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