Running dorm fridge with inverter - Fiberglass RV


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Old 01-11-2013, 08:37 AM   #1
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Running dorm fridge with inverter

I have a Lil Snoozy with the standard Magic Chef 3.6 cu ft 110vac dorm style fridge. The manual doesn't say but IIRC the "running" power draw is around 70 watts, maybe less. Who knows what the starting current really is. I figured 6X when I sized the inverter.

I have a Samlex 600 watt (900 surge) true sine wave inverter, 12v 220 ah battery bank and short 4 gage cables connecting the inverter to the battery.

Everything was new last summer. Used the fridge for a three night trip in Sept and it started fine with the inverter. Tried it in December and it won't start, inverter displays current overload error every time. Thought maybe it would work better after it had been run on shore power and here in warm Florida. No dice. Fridge works fine on shore power.

Inverter is working fine recharging running computer chargers, even a soldering gun.

Any thoughts? Anyone used a 'hard start kit' (essentially a big capacitor) wired to the motor windings?
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Old 01-11-2013, 09:03 AM   #2
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We had a magic chef and it started marginally with an 800 watt inverter, non-sine wave in our case. It worked fine with a 1200 watt non-sine. It's the starting current with compressors, starting is much greater
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Old 01-11-2013, 09:26 AM   #3
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Maybe try getting it chilled on ac and then hooking up to dc and see if it works, then you know it is the start up pull.
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Old 01-11-2013, 10:29 AM   #4
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Starting current

Quote:
Originally Posted by honda03842 View Post
We had a magic chef and it started marginally with an 800 watt inverter, non-sine wave in our case. It worked fine with a 1200 watt non-sine. It's the starting current with compressors, starting is much greater
The starting current of a motor NOT under load is 400% to 600% of the motors FLA . A motor starting under load has a starting current of 700% to 1200% of the motors FLA . A fan motor is an example of a motor not started under load , the load picks up as the fan speed increases .An air conditioner ,air compressor and refrigeration equipment are examples of motors started under load . (Against head pressure) and have high inrush currents at times reaching the point of LRA. The NFPA allows 1400% of the FLA in Art 430 of the code for hard starting motors. Your inverter may have internal protection that sees the starting current of the refrigerator as a short circuit.
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Old 01-11-2013, 10:53 AM   #5
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Contact lil snoozy and ask them what size inverter you need, they should know for a fact since they offer the fridges to be run off of your batteries.

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Old 01-11-2013, 11:13 AM   #6
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You could go buy a 12VDC compressor fridge. Use your inverter to run toys.
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Old 01-11-2013, 11:19 AM   #7
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I think Lil snoozy, like the EggCamper uses 12v refers which run directly off battery without an inverter. I maybe wrong with LilSnoozy but I know EggCamper is that way. Using an inverter to convert 12v to operate a 120v appliance is not as efficient as using a direct 12v appliance.
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Old 01-11-2013, 11:25 AM   #8
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Since the Norcold 12VDC fridges run on 3A, (36W @ 12 VDC) They are already about half the power. Since the inverter can't be 100% efficient the power draw will only go up.
Your battery can easily supply the 1400% of full load starting current.
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Old 01-11-2013, 11:26 AM   #9
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Thanks for the quick replies.

Snoozy doesn't offer the inverter, they expect the fridge to run only on shore power.

My puzzlement is that the inverter would start the fridge last fall but not now.

I realize I should have gotten a bigger inverter but here I am with a $200 600 watt unit.

I tried running it for a while n shore power then switching to inverter - didn't work.

A 12v / 110v fridge is about ten times the cost of the $150 fridge I already have.

Hoping against hope there is a solution using my existing fridge and inverter
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Old 01-11-2013, 11:26 AM   #10
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I spoke with lil snoozy and he said they use a real efficient ac powered unit... I agree an efficient 12 volt unit would be wiser.

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Old 01-11-2013, 11:36 AM   #11
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I precool a 2.7cu.ft. Dorm fridge on AC and then power it on the road thru 1500watt true sine wave on a 6' 1/0awg leash. I have roughly half your amp hour capacity and extended runs of greater than 16 hours aren't possible without solar battery charging and are sketchy with it so its use is usually confined to hookup situations. I have not tried a "hot" start and cool down of the fridge from battery/inverter. This method of cool down is, I suspect, a big battery drawdown due to sustained compressor runtime. Too bad Snoozy doesn't see fit to spec and/or provide a system operational "portal to portal."

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Old 01-11-2013, 12:01 PM   #12
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Quote:
Originally Posted by MCDenny View Post
Thanks for the quick replies.
A 12v / 110v fridge is about ten times the cost of the $150 fridge I already have.
My local wrecker sells RV fridges for $25. I have purchased an RM36E propane fridge from them, and it works. The last fridge I found was an older 12VDC compressor unit. If I had a use for it, I would have purchased it.
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Old 01-11-2013, 12:01 PM   #13
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I bought a $59 non-sine wave 1200 watt inverter at a black and decker outlet store. It powered everything from TV to fridge.

We've used it in our Sunline trailer and have since moved it to our SCAMP
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Old 01-11-2013, 12:09 PM   #14
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Jack,
If one is off the grid, propane is really required and some of the best spots are off the grid.

One way we extended the run time was to charge the batterys from the tow vehicle while driving, keeping the fridge really cold while driving and the battery charged

During our cross Labrador trip with a dorm fridge we carried a 1000 watt generator $120.00. The gen was only 1 foot on a side and weighef 40lbs
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