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Inverter for Fridge Compressor?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Inverter for Fridge Compressor?

Unread postAuthor: PeteS » Sat Oct 05, 2013 6:34 am

I am thinking about trying to use my fridge compressor where there is no AC power. Does anyone have an idea of how many watts a fridge compressor draws? I know they will vary, but a ballpark number would at least give me an idea how feasible this is and how much the inverter might cost.

Mine immediately trips the overload on a 60 watt inverter. Just a WAG, but the amount of heat it produces would seem to indicate it is probably well under 1000 watts.

Inverters in the 400-500 watt range range seem to be pretty affordable, but above that the prices go up quickly. So if it requires 1000 watts or more I will likely use other options like co2 or air tanks, 12v pumps, or a stirrup pump.
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Unread postAuthor: Technician1002 » Sat Oct 05, 2013 1:46 pm

Most fridge compressors will run on a 1KW inverter. My Prius inverter setup ran a full size fridge for a weekend during a power outage. The issue with inverters is two fold. The compressor uses a higher start current than the run current, so the inverter must be big enough to handle the start watts or it won't start. Some fridges run at under 300 Watts, but may draw over 600 starting. The second issue is the AC motor is an inductive load with a relatively high power factor. Some inverters don't like inductive loads even when the inverter is big enough. Check the application list in the inverter specifications as to whether it will run a freezer or fridge. I've had good luck with the Zantrex brand and use it to power a small air compressor. The inverter was bought at Costco for about $60 on sale a few years ago. They are about $100 US now.

Image

Do not try to use a computer UPS inverter with a compressor. They are not designed to handle the inductive load. I tried it and got smoke.
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Unread postAuthor: jsefcik » Sat Oct 05, 2013 10:32 pm

Just get a portable generator
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Unread postAuthor: PeteS » Sun Oct 06, 2013 8:35 am

Another option I have looked at is cheap 12V compressors. They were kind of wimpy though. One claims 250 psi, but was lucky to do 70. The gauge was so far off that it read 120 when it was at 70 psi. At least it was really cheap at about $8 (on sale at Harbor Freight).

The other was similar in maximum psi but at least it had a decent gauge.

Has anyone found any of these 12v pumps to actually reach decent pressures? I'd be happy to find one that did 200 psi, but more would be better.

Another option I have looked at is cheap 12V compressors. They were kind of wimpy though. One claims 250 psi, but was lucky to do 70. The gauge was so far off that it read 120 when it was at 70 psi. At least it was really cheap at about $8 (on sale at Harbor Freight).

The other was similar in maximum psi but at least it had a decent gauge.

Has anyone found any of these 12v pumps to actually reach decent pressures? I'd be happy to find one that did 200 psi, but more would be better.

I just pulled the trigger on an inverter. It is a BESTEK "Rated power:1000w , Max power: 1200w, Peak power:2400w". They specifically say it is ideal for household appliances and mention refrigerators so I think it should be OK. It was $64.99 via Amazon. I'll report back when I have tested it.

Edited by jrrdw.
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Re: Inverter for Fridge Compressor?

Unread postAuthor: Technician1002 » Wed Oct 09, 2013 5:19 am

The wire size and length is very important for high power applications. A long run or a small wire gauge will cause enough voltage drop to alarm the inverter on low voltage. I visited a welding shop and bought welding wire instead of using the light gauge wire that came with mine. I sized it for a 2KW inverter. A good battery is also a requirement for good performance.
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Re: Inverter for Fridge Compressor?

Unread postAuthor: BigDeutcher » Wed Oct 09, 2013 10:19 am

Watts = voltage times your current

w = v x I

Get the current draw off the back of your plate on the fridge will be measured in amps times the voltage in your area 110 or 120 (north america), multiply them togther and get your wattage.

all motors have a surge current draw unless they are a soft start compressor or motor
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Re: Inverter for Fridge Compressor?

Unread postAuthor: Technician1002 » Fri Oct 11, 2013 10:33 am

Frost free fridges include the wattage of the defrost heater. This may overstate the compressor requirements.
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Re: Inverter for Fridge Compressor?

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