Author Topic: Converting 120v fridge for use on 220v solar power system  (Read 828 times)

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Offline solarnewbee

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Converting 120v fridge for use on 220v solar power system
« on: October 22, 2019, 11:55:00 am »
Howdy everybody!

I was kind of thinking this might be thought of as automation as in automating it to be as efficient as possible to enjoy some luxury on our renewable energy system.

I am hauling my fridge from the states to the Philippines because you just can’t buy this kind of fridge over there. You get used to having water and ice in the door kinda like breathing. I have a water treatment system with ceramic filters and UV so I’m good there. 99% of the folks there don’t have safe municipal water so there’s not a market for water/ice in the door fridges.

The necessity of this design is to avoid having a high wattage xfmr sucking up battery 24/7.

The compressor is variable speed with an inverter board attached to it. As you can see on the diagram, 120v is supplied constant and control voltage from the control board +12vdc and pwm signal possibly. I notice that the compressor only ramps up and down but nothing in between like a pure inverter fridge or HVAC.

My original idea was to use 2 step down xfmr’s , 1 low wattage to power the control board (on 24/7) and the other of sufficient wattage (on when called) to power the compressor powered on by a relay from from the compressor output on the control board. Output from step down  xfmr tied to compressor.

Since the output from the control board is different, how do I approach this dilemma. When I have more time I want to see if the 12vdc is there constantly or only when called by thermostat. In that case I could make a circuit to energize the xfmr to supply ac for the inverter. If not, is there a way to tap into/sense the signal line without interfering and do the same task needed.

SN

Any day above ground is a day for potential mishaps

Offline Pete

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Re: Converting 120v fridge for use on 220v solar power system
« Reply #1 on: October 22, 2019, 04:27:05 pm »
Hi Solar, there is always the old simple way.
A step down transformer, simple reliable and no mucking around.
Or a Step Down switch mode power supply if you want more complicated.
I don't know enough about fridge controls to suggest any chopping and changing on the boards.
Pete

Offline Warpspeed

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Re: Converting 120v fridge for use on 220v solar power system
« Reply #2 on: October 30, 2019, 11:22:01 pm »

My original idea was to use 2 step down xfmr’s , 1 low wattage to power the control board (on 24/7) and the other of sufficient wattage (on when called) to power the compressor powered on by a relay from from the compressor output on the control board. Output from step down  xfmr tied to compressor.

Yes, very sound thinking.

I did something very similar with my garage door opener.  There was this huge hot running transformer running 24/7 just to power the radio receiver.
So I used a modern switching type 12v wall pack to power just the radio receiver.

When I hit my remote, that closes a relay that cuts in the monster transformer and starts the motor action.
Works great, and the power saving is enormous.

Offline solarnewbee

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Re: Converting 120v fridge for use on 220v solar power system
« Reply #3 on: November 07, 2019, 08:37:42 am »
Hey Pete and Warp,

Never heard of a step down switch mode transformer before but may be worth looking into. Still haven’t had time to look at the control board or as one appliance techy online calls them “muthaboards”. I sort of detected his distaste for these boards necessary for today’s efficiency requirements. Old school doesn’t always like change. I have have a few step up/down transformers here to test with since some of my test equipment runs on 220v.

I will do some testing and get back.
SN

Any day above ground is a day for potential mishaps

Offline noneyabussiness

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Re: Converting 120v fridge for use on 220v solar power system
« Reply #4 on: November 07, 2019, 03:19:57 pm »
Something like this, direct from your 220v...

AU $38.80  15%OFF | 1000W Pure Sine Wave Inverter Power Board Modified Sine Wave Post Amplifier DIY free shipping
https://s.click.aliexpress.com/e/df0eRnRS


After suitable bridge diodes, Adjust the voltage down to 110v.

Win win, low idle current, small parts count..