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Fridge Update - What sized inverter?


Doodlebug

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Hi all,

 

you may remember I was having issues with my fridge. It was suggested I needed to find some shoreline to test whether it works and I have finally found one and tested it. It works fine!

 

So the next question is what to do. It doesn't run of our 850w pure sine inverter generator. But obviously I don't want it on a generator anyway. So the question is what inverter do we need to run the fridge.

 

What is confusing is that the fridge is rated at 50w and it doesn't work on 850w. When plugged in there is an initial surge from the generator and then it sits at half revs and then overheats. Do you think if it doesn't get going in the first moment its plugged in that it acts as just a coil of wire hence the overheating. Does that make sense?

 

Its an argos A+ rated fridge if that helps.

 

Do I get a bigger inverter (our current one is 300w) which is just big enough for the fridge or do I go with one big enough to run our dishwasher (which would be about 1600w). If its on all the time it could be wasting quite a bit of power so i'm thinking I should go with a smaller inverter for each purpose. But what is the smallest I can get away with. For instance:

 

Our generator does 850w regardless. I could get a 600w inverter which has a peak of 1200w. So in theory it might work. But how can I know for sure.

 

Next question is do I get pure sine or modified.

 

Sorry for all the questions!

 

Thanks

 

Doodlebug

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A fridge will have a motor and the start (10 seconds) power drawn can be 10 to 20 times the running power.

 

Beware the "surge rating" it's sometimes (all my inverters) 50milli seconds that's nothing to start a motor.

 

Realistically you need the biggest inverter that you can afford. You need to supply the fridge with 500w for 10 or so seconds then it will fall back to a much more friendly running current.

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A fridge will have a motor and the start (10 seconds) power drawn can be 10 to 20 times the running power.

 

Beware the "surge rating" it's sometimes (all my inverters) 50milli seconds that's nothing to start a motor.

 

Realistically you need the biggest inverter that you can afford. You need to supply the fridge with 500w for 10 or so seconds then it will fall back to a much more friendly running current.

 

Yeap that makes sense but surely 500w isn't enough it it wont run off 850w. And also if I got a 2000w inverter rather than 1000w I could be using far more standby power? Which is not ideal.

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Bigger / more expensive inverters don't necessarily have a higher quiescent current..

 

I think our Victron 3000W has a 0.8A quiescent drain in "saver" mode - even if it was 1 amp, thats likely only 12- 15 amp hours assuming you don't turn off at night, when the engine is stopped ( assuming you cruise at least 9 - 12 hours a day like the rest of us !!! )

laugh.png

Nick

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Simple fridge might run on MSW but I wouldn't risk it for a dishwasher with electronics inside.

 

For a standard fridge I'd say at least 1kW continuous inverter with 1.5kW+ surge capability will probably do, but 1.5kW to 2kW continuous is better to be on the safe side.

 

Maybe get a small inverter for things like chargers?

 

cheers, Pete.

~smpt~

Edited by smileypete
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What you need to look at is not the average rated power of the inverter but the surge capability. This is the overload capability / extra grunt that's needed to get the motor in the fridge spinning. For a typical fridge this can be in the 1500W region, but only for a fraction of a second - something a cheap inverter can't supply. We run our fridge on an 800W Sterling MSW inverter.

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