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Wilbour
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# Posted: 13 Apr 2018 04:41pm
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Have people tested their mini fridges with a Kilowatt unit to see what the initial power draw is on a mini fridge?
Even finding documentation on the running wattages is elusive.
My library lets you borrow a Kilowatt device so I guess I could purchase a fridge from a store with good return policy and try it at home.
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darz5150
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# Posted: 13 Apr 2018 05:05pm
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Read your post so I went out and checked for you. Its a Haier with the freezer. Watts went to 471 for a fraction of a second.
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Wilbour
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# Posted: 13 Apr 2018 07:32pm
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Thanks darz5150.
I'm looking into an inverter that allows for a peak voltage of 700W and a linear of 300W (if I read the data sheet correctly)
Now to find a mini fridge like your Haier that stays below 700W
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darz5150
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# Posted: 13 Apr 2018 08:02pm
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Your welcome wilbour. I got ours at wally world on sale for $79 bucks I think. I just looked on amazon, and they have one very similar for $99.98. Free shipping if u have prime.
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creeky
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# Posted: 13 Apr 2018 08:44pm
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Don't forget that any good inverter these days will support 3x non linear load. Surge in other words. A 350w should start and run most fridges. 2x linear for a few seconds. 1.5 for minutes. 1 24/7.
If you're looking at lower cost inverters watch for "soft start." Lots of the new DSP inverters have soft start built in now.
A "toroidal" should have the grunt anyway.
And to beat the drum. Your inverter is the heart of your system. And, along with batteries, the weak link in the chain. Money spent here pays off in longevity and efficiency.
I recommend looking for at least 92% efficient. A small pure sine should not draw more than 6-10w on idle.
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morock
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# Posted: 14 Apr 2018 10:36am
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I want to run a septic pump which runs at 800 watts. Not sure what the startup spike would be? So what size of pure sine inverter do I need? I have looking but haven’t found an answer.
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creeky
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# Posted: 14 Apr 2018 03:09pm
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The answer is "it depends."
The quality and age of the pump makes a real difference. I recently had someone use a 1/4 hp pump and it wouldn't start on an 800w inverter. They replaced it with a 1/2 hp pump of higher quality. And the pump started.
Good luck.
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Wilbour
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# Posted: 20 May 2018 07:27pm
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Quoting: darz5150 Haier with the freezer. Watts went to 471 for a fraction of a second.
Revisiting older posts. I too plugged mine into a Kill-A-Watt meter and had similar or slightly larger numbers. The problem with peak start measurements is that the time of need is so small that these meters may not capture the true peak requirement. They essentially take a snapshot of the demand and specific intervals. If it peaks for a millisecond and the meter captures the data as it is descending then the display will not be entirely accurate.
As I posted elsewhere, the company mentioned that this little fridge will demand over 723w for a split second, then taper back to less than 124w while running (although the Kill-A-Watt device shows less than 50w at this point)
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ICC
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# Posted: 20 May 2018 07:58pm
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Quoting: Wilbour The problem with peak start measurements is that the time of need is so small that these meters may not capture the true peak requirement.
Yes, these meters are not capable of accurately measuring the start surge.
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Bancroft bound
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# Posted: 21 May 2018 08:11pm
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I have a 4.4 cu ft Danby all fridge.
Inverter shows 50 watts while running.
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Wilbour
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# Posted: 21 May 2018 09:55pm - Edited by: Wilbour
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Quoting: Bancroft bound Inverter shows 50 watts while running
That's a good number. Shows you how the efficiency of a fridge is not directly related to it's size. Mine is a third the size but the same wattage while running.
Perhaps my 1.7cf mini runs at 50w for a third of the time a larger unit would? Would need some serious experimenting to answer that. That's where the energy rating comes into play. It measures the total use over one year.
I wanted the smaller unit knowing it wouldn't overstuffed. A medium bar fridge, in my case would be half empty most of the time. An empty fridge takes more energy to run than a full one.
But as I found out, the startup draw can be a killer.
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darz5150
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# Posted: 21 May 2018 10:06pm
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So are you saying the kill a watt meters are that far off. I can believe that they are not sensitive enough for micro surges etc.? There's a pretty big difference between 124 and 50 running watts. Also the start up surge.
Mainly use the kill a watt to figure actual cost of running appliances. Our local power company loans them out to figure out how to cut power costs.
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paulz
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# Posted: 3 Aug 2019 12:38pm - Edited by: paulz
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Another revisit. Bought this at the local rummage sale yesterday for, as you can see, $19. Testing at home with Killawatt. 350 or so at startup, 60 after that. 40 degrees inside, frozen cup of water in the freezer section. Cooled very quickly. 70-80 in the house.
Not sure what the plan is but I could sure use a cold drink at the cabin. I was thinking I might keep it in the truck bed, plugged in a home, then for the two or three days at the cabin try to keep it cold with a generator. Or just keep it at the cabin and run the generator a few time a day. I have small solar for DC but no inverter.
It doesn't seem very insulated, anyone had one apart? Could I spray foam inside the walls or something? Or rigid foam on outside?
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Brettny
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# Posted: 3 Aug 2019 02:32pm
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60w at 120v..you could run that on such a small inverter it would plug into a cigarette lighter.
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ICC
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# Posted: 3 Aug 2019 03:19pm
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A Kill-A-Watt does not react fast enough to accurately measure the actual peak. IIRC the killawatt samples about once a second. A start up surge can be measured by specialized meters. Fluke makes several. They have an "inrush" button. Expect to pay $350 and more. The inrush duration is measured about 400 times over 100 ms or so, then averaged, IIRC.
I glued 2 inches of foil faced physio insulation to all the sides, top and bottom and door of my Truckfridge 130 litre 12 vdc fridge That cut power use by almost a half. I also installed a latch that squeezes the door seal shut better. The door was finished with some aluminum angle around the edges and a new door panel front glued on the polyiso.
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paulz
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# Posted: 3 Aug 2019 04:25pm - Edited by: paulz
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Sounds good, I have a sheet of that foil insulation sitting around. Did you do the whole back side? The bottom half of the back on mine is open exposing the working parts. Guessing that's where the heat escapes.
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ICC
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# Posted: 3 Aug 2019 05:46pm
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I did mine all over except for the cutout where the compressor is located. Wherever yours dumps the heat should be left clear. Mine uses a small fan for moving air over the coils.
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groingo
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# Posted: 4 Aug 2019 10:38am - Edited by: groingo
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Mine is a Haier 2.7 Cu ft, It starts at 175 watts then quickly drops to 45 watts, Using a Reliable 1000 watt Pure Sine Inverter with soft start but whenever the fridge kicks on the lights dim which has cooked some LED lights.
My other Inverter which is 750 watts but not Pure Sine Wave would not run the fridge as it kept kicking the overload on the inverter which made zero sense, fridge seems very fussy about power type.
For those wanting to use less power on your fridge over time, taking a simple 1/2 styrofoam sheet to partition your fridge inside so your not cooling an unused area, cuts run time significantly.
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Wilbour
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# Posted: 4 Aug 2019 03:28pm
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My answer was staring me in the face long before I posted my first findings. The information tag on the back of the fridge indicated a 6.x amp pull at startup. 6.x times 120 is over 720 watts.
My 500w inverter has never failed to start the fridge but it does get the fan going for a second or so.
paulz good score on that fridge. It's just like mine.
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paulz
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# Posted: 4 Aug 2019 05:08pm - Edited by: paulz
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Back of mine. Says .8A at 115V
That black pot is too hot to hold a hand on. Don't see any fan.
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Wilbour
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# Posted: 4 Aug 2019 05:47pm - Edited by: Wilbour
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Fan is on my inverter
My fridge started on the chart on the back of the fridge thr startup amp draw of 6.x amps. (Cannot remember the exact figure)
https://homeguides.sfgate.com/check-amperage-refrigerator-44156.html
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groingo
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# Posted: 5 Aug 2019 06:57pm
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Wilbour,
Good catch, checked mine also says 6.3 amps, explains a lot, even with soft start that's a good punch.
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