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Pure sine wave for frig


bigjim

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Have pity and keep me from having to research. What is a reasonable size pure sine wave to run a small household Refer/freezer and a little leaway for the future? Currently I am using a small dorm size refer/w separate freezer and if I remember my kilawatt meter says it is pulling less than 2 amps running. I might like to upgrade later to a small apartment size refer/freezer so that is why I am looking for the leaway. It would be nice to get it right the 1st. time. I think my current one is about 4.1 cu/ft. but I am going off memory here at the library at that is asking for trouble. (going off memory I mean) If I can remember I will write pertinent infor when I get home for next time I can get on line.

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The necessary inverter size depends on the fridge's maximum starting current. For example, our Samsung RF197 requires up to ~11A max starting current (according to Samsung). A 1kW inverter would probably be sufficient but to be more careful one might want something more like ~1.25-1.5 kW. Your choice of inverter will depend on your choice of refrigerator.

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Heres the deal, sure if you know the full load running current plus the max starting current (may be 3 to 6 time run current) and the Inverters rating and short term surge rating you can size what Inverter is needed. HOWEVER its been my engineering experience if you're anywhere near the minimum borderline the Inverter may be insufficient to start and properly operate the fridge.

 

If it pulls say 2 amps full load one may think hmmmmmmm 2 A x 120 Volts = 240 watts and then figure 3 to 6 times initial surge start up current IF I WERE BUYING AN INVERTER FOR THAT FRIDGE ALONE I WOULDNT GO LESS THEN A 1000 WATT. NOTE Im NOT saying a 400 may not work (depends on and would need a high surge current rating which I doubt it would have!!!!!) , Im ONLY saying I would buy a 1000 as the absolute MINIMUM.

 

HOWEVER if you're buying an Inverter anyway and you want to allow for a bigger, say a 4 amp fridge and/or to allow room for expansion I WOULD BUY AT LEAST A 2000 WATT PSW INVERTER AND BE DONE WITH IT. AGAIN for that 2 amp draw fridge a 1000 watt will most likely (subject to Inverter design) WORK to start and run it if you're on a tight budget and cant afford more.

 

My auxiliary dorm size 120 VAC fridge draws around 1 amp but I went ahead and bought a 2000 Watt Inverter. Some dudes on here may have 3000 or 4000 or even 5000 watts but based on what you said Id buy a 2000 but NO LESS unless money is a limiting factor, but then still a 1000.

 

John T Long retired EE and rusty on this stuff so no warranty, this may be wrong as rain

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I have a full size Frigidaire in our 5th wheel. It takes around 84 watts to run (120v X .7A). Our first inverter was a 1000 watt, but couldn't handle the compressor surge of 900 watts (120v X 7.5A). Although the inverter specs stated it should handle a 2k surge, it would reset and shut off 4 out of 5 times. We currently use a Magnum 1000 watt pure sign wave. Works great, Runs cool. I've had the frig run off batteries for over 60 hours with no problems. One thing to remember is the size of the cable from battery to inverter. If you plan to step up, check you cable amperage chart and make sure the cable is sized for the compressor kick.

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  • 2 weeks later...

I just installed a Haier 10.1 cubic ft fridge in my TT. (I had repaired the Norcold for the last time) The Haier is not energy star certified and it shows on the starting surge. While my Prowatt 2000 ran it just fine at home, I noticed it alarmed as the compressor surged once we got to the campground. I didn't notice any overheating at the compressor and was willing to give it a try.
The first night I decided it was time to upgrade the inverter. Not only was the beeping annoying, it had a way of shutting my CPAP off every now and then when the compressor cycled. (we went to running the generator at night)

Running on the batteries all day, I was only at 12.8V when it was time to turn the generator on and go to sleep.

Whatever inverter you buy, as soon as you open the box, connect it to the fridge and see how it does. If you need to go a step larger, best to find that out before you're boondocking in Martinsville. ;-)

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I just installed a Haier 10.1 cubic ft fridge in my TT. (I had repaired the Norcold for the last time) The Haier is not energy star certified and it shows on the starting surge. While my Prowatt 2000 ran it just fine at home, I noticed it alarmed as the compressor surged once we got to the campground. I didn't notice any overheating at the compressor and was willing to give it a try.

The first night I decided it was time to upgrade the inverter. Not only was the beeping annoying, it had a way of shutting my CPAP off every now and then when the compressor cycled. (we went to running the generator at night)

 

Running on the batteries all day, I was only at 12.8V when it was time to turn the generator on and go to sleep.

 

Whatever inverter you buy, as soon as you open the box, connect it to the fridge and see how it does. If you need to go a step larger, best to find that out before you're boondocking in Martinsville. ;-)

How much battery do you have? Your problem sounds more like too little battery than too small an inverter.

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The newer Kisae have been improved considerably. They are actually pretty good for the price. Even the old ones were a lot better than the "no name" brands you find in places like Costco/Sams and truck stops.

 

I would put a Kisae in my truck without a second thought. For long term heavy use in my RV I prefer the Magnum.

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For long term heavy use in my RV I prefer the Magnum.

 

X2. My personal preference as well, but I realize not everyone will dump that kind of cash for a single purpose inverter.

 

For this particular application, my number 2 choice would be based solely on reliability to cost. Even if you decide to upgrade your reefer in the future, 1000-1500 watt inverter might be a little overkill. IMO

 

Kisae's aren't bad, but there are some bells and whistles you probably won't need in a dedicated inverter. I would go with the Samlex PST-600-12. Or from Don Rowe. They're both the same price, but I would opt to purchase from Amazon simply for their excellent return policy (and 2-day prime shipping if you have prime).

 

The PST600 will surge to 1000w, but the main selling point for me would be that it is a long term proven workhorse that will deliver continuous 600w without breaking a sweat. Especially when you're talking about a reefer.. reliability is key.

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Do you know for sure KISAE is bad? I know a couple reputable installers that install KISAE and I also have found that if DonRowe.com sells it, it is good equipment.

I don't know for sure if they're all bad. What I do know is that rated power is often highly optimistic on cheaper inverters. Just a heads up. In my world there are always downside surprises in cheaper products, and upside surprises in more expensive units.

 

And when they're described as 'pretty good for the price', that's a red flag to ME. YMMV

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And when they're described as 'pretty good for the price', that's a red flag to ME. YMMV

I don't mean that as a red flag. All products have price/performance tradeoffs. Including inverters. I find that the Kisae is a very good inverter for the money spent. Can you get a better inverter? Probably. Especially if you want to spend in the thousands of dollar range.

 

If I was putting in a dedicated inverter for a fridge probably my first choice would be the small Magnum. My second would be the Kisae or the Samplex. When I worked up the product offerings in this area for New Horizons I specified the Magnum for the dedicated refrigerator inverter.

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I'm going to give Cotek brand a try...have a Samlex running @24v now. When the basement gets hot the unit will crash much above 28vdc. Not supposed to do that.

 

Cotek is one of the few mfrs who make a 48v model, which is what I'm going to do. I could go Outback, but that's way overkill for my app.

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I'm going to give Cotek brand a try...have a Samlex running @24v now. When the basement gets hot the unit will crash much above 28vdc. Not supposed to do that.

 

Cotek is one of the few mfrs who make a 48v model, which is what I'm going to do. I could go Outback, but that's way overkill for my app.

Or, you could use a Victron. But if you think Outback is overkill a Victron would be like a nuclear bomb ;)

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