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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 08-07-2008
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Inverter question

i'm debating getting a norcold ac/dc fridge for my boat. it draws .71 amps at 120v and 3.5 at 12v. if i installed a small 12v to 120v inverter, plugged the fridge into the inverter, would it run at .71 amps since it's running at 120v?
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Old 08-07-2008
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No.
Ohms law: Electrical & Electronics, Ohm's Law, Formulas & Equations

It's obviously using a different heater element @ 120v and 12v therefore the power consumption (wattage) is different - but the 12v heater element is still needing 42 watts of power (3.5ah x 12v). The draw would be the same, plus the power draw the inverter inherently needs (and the built in inefficiency of conversion). The 120v uses 85 watts by the way, the give away to it being two separate heaters is the resistance/ohms.
No such thing as a free lunch, or a free watt when you need it.

You are better off using the 3.5ah at 12v
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chuckes,
thanks for dashing my hopes of stumbling on some sort of electrical breakthrough.
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Old 08-07-2008
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chuckes,
thanks for dashing my hopes of stumbling on some sort of electrical breakthrough.
HEHEHEHE!!

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Ahem. I dashed nothing, Ohm did.
I merely pointed out that perpetual motion devices were about as unrealistic as solar stiks that get 100% efficiency, or solar powered cruising vessels that need no diesel engines.
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Ahem. I dashed nothing, Ohm did.
I merely pointed out that perpetual motion devices were about as unrealistic as solar stiks that get 100% efficiency, or solar powered cruising vessels that need no diesel engines.
You beat me to it chuckles, I was getting ready to post a solar stik joke.
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Old 08-08-2008
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Assuming 80% efficiency with an inverter you would be drawing about 8 amps DC.

Not sure of the exact model, but the compressor is likely a DC motor powered by an AC power supply in AC mode. Wouldn't make a lot of sense to turn DC into AC, and then AC back into DC. Thats how I power my laptop... sucks the juice like no other.
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