Fridge is surge overloading inverter

flighthouseflighthouse Registered Users Posts: 18 ✭✭
Yeah, just like it says, when the fridge kicks on, my inverter sometimes goes into an errored state and needs to be turned off in order to recover. The inverter is rated at a constant 1000w and can surge to 2000w. The load on it when the fridge is running is only at 200w, so I'm guessing it's surging over 1800w to cause the tripped inverter.

I need to come up with a plan around this error. What I have in mind is getting a UPS for a computer which has a battery backup in it good for 30 mins. When the fridge first kicks on, I want it to utilize the juice inside the UPS for its surge instead of the inverter. Anyone have any suggestions on which ones do this? I know not all UPS's allow you take a pull off the batteries if it has power coming in. Or maybe there's a better idea someone has to work around this issue?
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Comments

  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Fridge is surge overloading inverter

    A UPS is nothing but an inverter + a battery, so not sure what you would gain there, since that is what you already have.

    The problem with many of the cheap inverters is that they cannot take much of a surge with anything where the power factor is less than 1.0, and most motors fall into that category.
  • flighthouseflighthouse Registered Users Posts: 18 ✭✭
    Re: Fridge is surge overloading inverter

    My inverter is the Xantrex Prowatt 1000w.

    It clearly says in the users manual of my inverter that it can take surge loads when starting up a refrigerator. But every time it does start, the inverter makes a loud beep indicates load overload and recommends to reduce the continuous load on the inverter. This sometimes happens only for 1/2 second, it sometimes tips the inverter over all the way and shuts down, and it sometimes causes problem to the other equipment plugged into the inverter. I had a computer just shut down at the same time the inverter beeped for 1/2 second.

    In my mind it makes sense that if I had a big capacitor filled with electricity, and when the fridge kicks on, instead of surging the grid it just empties the capacitor this would remove the stress on the inverter. Isn't this what a kvar energy controller does? I just think that it has to be possible with certain types of UPS's, unless the UPS can't dump a big load that quick. I essentially want to drain the entire UPS battery in the 1 second the fridge is using to start up.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Fridge is surge overloading inverter

    Most UPS have very little to no surge capacity. What will happen is the inverter will stay on but the UPS will shut down. I tried this already. I ended up getting a better inverter.

    Two things to look at:
    1: The battery wires. Are they sized correctly?

    2: The battery bank. Is it fully charged and sized correctly? Does the voltage stay above 11 volts?

    I have a 1100 watt inverter and can run a fridge/plus more and start the dehumidifier. If the above battery questions are fine, could the inverter be defective?
  • mike95490mike95490 Solar Expert Posts: 8,193 ✭✭✭✭✭
    Re: Fridge is surge overloading inverter

    Are you sure the battery & cables are able to supply the starting surge, and you are not getting a low DC condition ?
    Notice any difference between low battery state, float in the afternoon @ 14V when it starts ?
    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 ||
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  • flighthouseflighthouse Registered Users Posts: 18 ✭✭
    Re: Fridge is surge overloading inverter

    Thank you for your suggestions.

    The wire between the inverter and the batteries is 4 AWG which is indicated in the users manual as permissible. The run is only about 1 foot of wire between inverter and batteries.

    I just tried another test. This time I unplugged everything from the inverter. When I plugged in the refrigerator and only the refrigerator it still went into an error state indicating "over load shutdown". I tried it again, same thing, but on the third try it only beeped for a moment then went back to being ok and is now powering the refrigerator. I conducted this in the afternoon when the batteries indicated a 13.1V charge.

    Could it really be that the initial load of turning on a refrigerator is over 2000w?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fridge is surge overloading inverter

    Possible, but unlikely. Have you got any specs on the 'frige's power consumption? Best if measured with a Kill-A-Watt but the manufacturer's data (Amps @ Volts) is close enough.

    It is more likely that the Inverter's surge rating is "optimistic" or that the battery isn't capable of supplying the sudden high current draw.

    If anyone is planning on running an "unknown" load that plugs into a standard 120 VAC outlet, just remember that those outlets are rated for 15 A - i.e. 1800 Watts. If you get a 2000 Watt inverter it should handle just about anything that a standard outlet will (cumulative loading not withstanding). Don't count on the surge rating of inverters or generators. In my experience they are all a bit "optimistic".
  • BB.BB. Super Moderators, Administrators Posts: 28,768 admin
    Re: Fridge is surge overloading inverter

    A kill-a-watt meter will not be fast enough to measure peak amps... In the olden days--we had equipment (huge 500 MByte Disk Drives) that would pull 40+ amps for a few AC cycles on 120 VAC 15 amp outlets.

    The fridge is probably pulling a lot of Amps which is not Power--so the electronics or any inductors/transformers in the UPS may be saturating, even though there is enough battery power.

    Many UPS (and inverters) are rated not as 2,000 watt, but as 2,000 VA maximum (it is only 2,000 watts if the power factor is equal 1.0). If your starting load is exceeding the VA limit of the inverter--no matter how well the battery is wired and charged--it will just not output enough current to start the motor.

    In your case--2000 VA would seem like it should be enough to power the fridge (and it sometimes does start)...

    Is this a "frost free" fridge--maybe it is going into a defrost cycle and the heaters are on at the same time the motor tries to start... The heaters have been reported to be on the order of 500 watts.

    There is no storage device that can be connected to an AC line to help an inverter ride through a surge. If the fridge has a really poor power factor (use the PF setting on the k-a-watt meter), adding a motor run cap across the lines will bring the power factor back closer to 1.0 and may reduce the starting load current some. But that is just a guess.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Fridge is surge overloading inverter

    what everyone fails to understand about inverters(the readily available ones) is while the output is 120/240v the output impedance is high compared to the very low impedance of a grid supplied outlet..
    I give a not so technical answer ,, it not 100% correct but it gives example
    I f you had a car that weighed 2 ton and then powered it with a 1litre turbocharged motor that had 200 hp it would have trouble getting that weight off the line but would have say top speed 100mph now if you had a v8 6litre with 200 hp it would get that weight off the starting line ok but stil only have top speed of 100 mph..so cruising both about equal
    inverters are like the 1litre engine.
    THE PROBLEM IS A DESIGN ONE .tHEY USE VERY SMALL TRANSFORMERS AT VERY HIGH FREQUENCY TO KEEP SIZE AND COST LOW..
    You can buy low frequency inverters at a cost usually double of high frequency ones..
  • flighthouseflighthouse Registered Users Posts: 18 ✭✭
    Re: Fridge is surge overloading inverter

    alright alright , i solved the problem, not going to use the fridge on solar energy.

    kill-a-watt indicates it uses 120watts, and while it's running it seems to be doing just fine on the inverter. I tried a lot of different load combinations today, at one point i thought i had it just fine, no problems reported for hours then a fuse blew. so i'm going to put the solar energy to a different use instead.
  • westomwestom Solar Expert Posts: 28
    Re: Fridge is surge overloading inverter
    I need to come up with a plan around this error. What I have in mind is getting a UPS for a computer which has a battery backup in it good for 30 mins. When the fridge first kicks on, I want it to utilize the juice inside the UPS for its surge instead of the inverter.
    You are trying to do an analysis assuming concepts of DC electricity. Even the reason behind that capacitor idea is bogus because you are thinking only in DC terms.

    Your electricity is AC. Consider other problems such as harmonics and power factor. For example, power factor of a starting motor is different from one that is running constant. To better appreciate these concepts, learn about capacitor start motors.

    That UPS may be outputting harmonic sine waves - ie square waves. Therefore the motor can only use lower frequency power. Higher frequency power gets dissipated in the motor uselessly (or destructively) as heat. You would be getting less power than you think if thinking only in DC current terms.

    Learn about power factor, harmonics, and how these parameters vary between high torque startup verses low torque operation. Stop thinking only in terms of power consumption.

    Finally, many UPSes output power from the battery so 'dirty' as to be harmful to small electric motors. 'Dirty' power that is also ideal for electronics. Yes, electronics are so robust as to make UPS power more than acceptable - when that same UPS power can be harmful to motorized appliances. To understand this, learn AC electric parameters - not in simpler terms associated only with DC electric.
  • peterakopeterako Solar Expert Posts: 144 ✭✭✭✭✭
    Re: Fridge is surge overloading inverter

    John p is right this type of inverter is using a high freq. transformer and then small capacitors to store before making a sinus shape voltage. the surge from 2000W is only for 30 to 50 ms. even the 1000W it needs time to built up this power. a motor needs a high current to start up and a compressor motor ( fridge) needs the full power instant otherwise the motor stalls and needs 10x the running power that is 2000W 2x your inverter.

    it is also not wise to run inverters against max. starting capacity in your case a real 3000 w inverter will do the work and is avoiding heat loss.

    plus a fridge or A/C on battery power is always a big energy consumer .

    Greetings from Greece
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Fridge is surge overloading inverter

    Flighthouse,

    How big is your 12 V battery bank (in Ah)? I suspect the surge load is causing the battery voltage to drop low enough (the "coup de fouet", or "crack of the whip") to trigger the inverter's low (DC) voltage alarm.

    IOW, rather then the fridge overloading the inverter, the fridge and inverter may be overloading the battery bank.

    Regards,
    Jim / crewzer
  • BrockBrock Solar Expert Posts: 632 ✭✭✭✭
    Re: Fridge is surge overloading inverter

    My first guess would be the battery is dropping to below 11vdc while the fridge is trying to start causing the inverter to shut down. My second guess is the starting cap on the fridge motor is going because you’re trying to run it on a MSW inverter or it is old and failing or a combination.

    If you can try putting a voltmeter on the battery and watch it very closely while the fridge tries to start. My bet would be its falling below 11.0vdc.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭✭✭✭✭
    Re: Fridge is surge overloading inverter
    john p wrote: »
    I give a not so technical answer ,, it not 100% correct but it gives example
    I f you had a car that weighed 2 ton and then powered it with a 1litre turbocharged motor that had 200 hp it would have trouble getting that weight off the line but would have say top speed 100mph now if you had a v8 6litre with 200 hp it would get that weight off the starting line ok but stil only have top speed of 100 mph..so cruising both about equal
    inverters are like the 1litre engine.
    THE PROBLEM IS A DESIGN ONE .tHEY USE VERY SMALL TRANSFORMERS AT VERY HIGH FREQUENCY TO KEEP SIZE AND COST LOW..
    You can buy low frequency inverters at a cost usually double of high frequency ones..

    LOL!

    The example is completely wrong, but only for people who know why that 1L motor with a blower can't move the car off the line the same as the V8. The answer is torque at the drive shaft, not torque at the crank shaft. Re-gear both so they are the same and you get the same results, by definition.

    BB had the best answer --

    The maximum amount of power is limited by the inverter. A cheap MSW inverter that can output 3000VA should be able to start that fridge, if the cabling is correct. A 1000VA won't -- regardless of the cabling.
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Fridge is surge overloading inverter

    The answer is torque at the drive shaft, not torque at the crank shaft. Re-gear both so they are the same and you get the same results, by definition. really?? you trying to say if I put the 1l motor in the car that had the v8 then the v8 in the car that had the 1l so now the 1l car will out accellerate the v8??


    And on something completely different.. A 1000VA won't -- regardless of the cabling.
    But I have a 8cft fridge running of a 400w inverter on 240v has been for nearly 4 years now..
  • westomwestom Solar Expert Posts: 28
    Re: Fridge is surge overloading inverter
    Could it really be that the initial load of turning on a refrigerator is over 2000w?
    Apparently you did not understand my previous post. An inverter could output 2000 watts. Due to those relevant factors, maybe 1200w can be used by the refrigerator. The rest may be lost as heat. To understand this, understand the difference between AC and DC electricity.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Fridge is surge overloading inverter

    "The rest may be lost as heat. To understand this, understand the difference between AC and DC electricity."

    i'm all ears as i'd like to hear about this from you.
  • westomwestom Solar Expert Posts: 28
    Re: Fridge is surge overloading inverter
    niel wrote: »
    i'm all ears as i'd like to hear about this from you.
    I'm not going to teach introductory circuit theory. However to be having this discussion - to make numbers relevant - the OP needs to understand basic AC electrical concepts (not DC concepts) starting with power factor. Why a capacitor start motor is used. How much current a stalled motor consumes (manufacturer specs). Harmonics - energy output by an inverter in frequencies that a motor cannot use. Numerous simple concepts that one should understand to appreciate why he is having problems.

    Most damning is a popular belief that some electrical sources are 'cleaner'. Without specific numbers (ie THD) or literally view waveforms on an oscilloscope, then (my observation) the 'dirtiest' electricity gets declared by a majority as the 'cleanest'. The majority are too often taught only by retail store salesmen - even forget the science taugh in school. Too many know what is 'clean' and 'dirty' electricity using the exact same logic that (edited by niel as having no place here, is political, and is not factual). My observation: those who are most adamant - post subjectively while posting no technical details and ignoring numbers - are most often posting urban myths promoted by sales propaganda.

    Whereas some tried to use quantitative reasoning (ie "size wave"?), still, where are the numbers? What is described in a sales brochure as a sine wave output can be square waves and spikes. The sales brochure did not lie. But again, those who only learn subjectively (ignore the numbers) would not understand - are the easiest to scam. Simple mathematics (ie Fourier Series) explains that. And still, a majority ignore what was taught in school to believe what a salesman preaches.

    To understand the OP's problem means learning simple electrical concepts starting with power factor, harmonics, and how much current for a stalled motor. Unfortunately, too many are posting as if the electricity was DC - therefore are missing what must be considered or measured. Provided are terms to learn from introductory discussions on electricity.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fridge is surge overloading inverter

    I like my simple rule-of-thumb better: never rely on "surge" ratings to handle any load; even a motor "start-up".
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Fridge is surge overloading inverter

    westom,
    nobody wanted an indepth electronics lesson and none should be needed to explain why you think there's a difference between ac and dc and what it has to do with heat loss as either will cause heat. maybe we have a misunderstanding as to your meaning on the original statement, i don't know. now if you are saying about the harmonics causing the heat in a refrig then i agree with you, but any electricity dc or ac will dissipate some power as heat in a load. harmonics will add to the heat normally in an ac inductive load.
    was i confused as to your meaning?
  • westomwestom Solar Expert Posts: 28
    Re: Fridge is surge overloading inverter
    niel wrote: »
    now if you are saying about the harmonics causing the heat in a refrig then i agree with you, but any electricity dc or ac will dissipate some power as heat in a load.
    Harmonics were only one factor mentioned. Many factors were provided - not just harmonics. That means power output by the inverter only creates heat in the electric motor. Potentially destructive to a motor. Does not contribute to moving the motor's shaft.

    Irrelevant is AC or DC normally dissipated as heat in a motor. AC parameters can cause significantly more heat dissipated harmfully. Confusion could be due to discussing electricity only in DC terms when power is AC electricity. Knowledge of AC parameters should be included in an analysis and solution.

    Meanwhile, OP apparently solved the problem. He disconnected the refrigerator. That also eliminates harmful parameters. Relocating a refrigerator on a 'cleaner' electric source (AC mains) is another solution.
  • WillHapgoodWillHapgood Registered Users Posts: 1
    Re: Fridge is surge overloading inverter

    Would an ultracapacitor (or supercapacitor) help, by adding surge capability to the battery bank?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fridge is surge overloading inverter
    Would an ultracapacitor (or supercapacitor) help, by adding surge capability to the battery bank?

    Welcome to the forum.

    No. Ultra or super capacitors will not help this situation. The question comes up quite often. Capacitors do not have power, they borrow it. They work for surges on high-power audio in vehicles because they borrow the power from the alternator and release it to the amplifier when needed.

    When you figure in the cost of such components you see it is a poor substitute for proper wiring and battery capacity. And if the surge problem is one where the inverter can't meet the AC demand no changes to the DC side will help.
  • BB.BB. Super Moderators, Administrators Posts: 28,768 admin
    Re: Fridge is surge overloading inverter

    Interestingly, "bad wiring" [on ac side] between a "marginal" AC inverter and refrigerator can help (bad wiring as in long wire run with smaller gauge copper wire). The wire adds a bit of electrical resistance that limits surge current and can prevent the inverter from "faulting" during starting.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Fridge is surge overloading inverter
    BB. wrote: »
    Interestingly, "bad wiring" between a "marginal" AC inverter and refrigerator can help (bad wiring as in long wire run with smaller gauge copper wire). The wire adds a bit of electrical resistance that limits surge current and can prevent the inverter from "faulting" during starting.

    -Bill

    Note that this is on the AC side: on the DC side it makes things worse.
  • Dragonlady5Dragonlady5 Registered Users Posts: 19 ✭✭
    Re: Fridge is surge overloading inverter

    There was a thread a while ago where I posted surge current for a consumer based bar fridge. One screen shot from the scope showed the 1/4 second surge 9 times the continuous rating. Now this is one of the worst cases on a cheap bar fridge, but older fridges (due to mechanical wear and tear, e.g. bearings) will typically have 6-8 times surges. Newer fridges are more in the range of 4-6 times.
    So yes you need and inverter with surge, but how much is the question. Since no consumer fridge manufacture publishes surge specs you are left with over sizing the inverter for the surge, or invest in a AC fridge built for off grid use (little or no surge.

    IMHO
  • jonrjonr Solar Expert Posts: 1,257 ✭✭✭✭
    Re: Fridge is surge overloading inverter

    As motors get more efficient, the start/run ratio is increasing. My refrigerator measures at 11 times typical load.

    Startup measurement is easy with a current clamp fed into the audio input of a laptop.

    I am available for custom hardware/firmware development

  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Fridge is surge overloading inverter
    Since no consumer fridge manufacture publishes surge specs you are left with over sizing the inverter for the surge, or invest in a AC fridge built for off grid use ...

    Yes. The double-whammy of oversizing is that huge new inverter is drawing more power and running less efficiently than one sized without the surge. I crack up when I see guys charging cell-phones with wall warts from a 2Kw inverter.. :)
  • TaslimTaslim Registered Users Posts: 9 ✭✭

    I have inverter 700watts countinous and power surge with 1400watts. It does not start refrigerator. I have experienced to run it with main grid and then run it on inverter and it run perfectly. How can i start this by inveter.???? Can i use 200 watt 500 watt bulb in series to run it by inverter???

  • 706jim706jim Solar Expert Posts: 238 ✭✭✭

    When I bought my inverter I got one with 1500 watts capacity. I figured that it should be able to run any appliance that would be plugged into a standard outlet. When you get an inverter smaller than 1500 watts, the first thing you do is compile a list of things it WON'T run.

    In this case a refrigerator

    My old Trace was expensive and has 4400 watt surge capacity. This sort of ratio is no longer common from what I can see..

    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 26th year.
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