Converting our 3 way fridge to compressor.

[Richard n Ann]

Been trying to keep busy over the last 2 days so I started my compressor project. Mainly to save gas and the inconvenience of filling up, the compressor fridge will run off solar easily but even if the battery gets a bit low you can fit a resistor to the controller so it will switch off at 11v (default is 9.6v).

First job was remove all the absorption gubbins and just keep the insulated box...

I see the heat transfer paste is still good from I think 2017

 

[Richard n Ann]

Oh forgot to say, I bought this the other week, I did some measuring up and all is good. Our fridge is the Dometic RMS8400

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[Richard n Ann]

Next phase got a bit destructive.. No going back now. I removed the freezer divider and bonded in a new acrilic back panel

 

[Richard n Ann]

Then I fitted the evaporator and thermostat phial.

 

[Richard n Ann]

Then to the back and started building it back up with 1" polystyrene sheets and expanding foam for the gaps. Got 3 in to bring the back flush again.

I've lagged the suction, as is usual procedure, stops condensation running down it and the cool gas back helps to cool the compressor. (some compressors actually overheat without it)

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[Richard n Ann]

I fitted a tube for the stat phial so it can be replaced. The condenser unit is on angle aloominum as the back is just that silver cardboard stuff..

 

[Richard n Ann]

On/off switch no more faffing with selector knob. (or for those of you with auto, wondering why it's selecting the wrong thing )

I fitted the optional fault code diode too.

 

[Richard n Ann]

Ran it over night with the logger in and the temperature is held much more constantly than the absorption plant ever did.

Compressor:

Absorption:

 

[Richard n Ann]

PS you don't need to be a fridge engineer, the quick couplings are super easy to connect and the system comes pre charged with R134a you can't go wrong.

Runs at about 2.5amps

 

[Raul]

I’m impressed, well done for a super efficient conversion.

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[Just smiffy]

Wow…. That kept you busy for a while, but wouldn’t it of been cheaper to sell the old fridge and buy a compressor fridge..?

 

[Raul]

Compressor fridge is 550 squids for a 48L.

 

[CamperJack]

Very interesting and you seem to know what you're doing. How much does the conversation cost? How many amps a day do you reckon it will use?

Well done for keeping busy.

 

[Sasbo]

Your one clever fella. Good on you for keeping busy and occupied

 

[Richard n Ann]

Very interesting and you seem to know what you're doing. How much does the conversation cost? How many amps a day do you reckon it will use?

Well done for keeping busy.

I posted a link to the kit, was about £364 but it's gone up 15 quid now, after that all you need is the acrilic sheet, 9 pound something, polystyrene available on ebay and expanding foam.

Power consumption wise I think I read somewhere it averages at 1ah so 24ah per day

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[RedFrame]

Drexxer This is the way I think we'll go when needed.

Cheers
Red.

 

[Swifter]

Brilliant thread . Fantastic advice and photos .
It’s also the time of year we normally get hot weather in the U.K. so we can expect to see the pictures of that awesome fan unit you made for the skylight and the modified fan speed for night time . Just hope the weather comes soon .
Keep posting this kind of stuff buddy . I love it

 

[Steve and Denise]

Brilliant Richard your a clever guy I am sorry to hear of your loss.
But please keep posting your mods we do all enjoy the content
Brendan

 

[Richard n Ann]

Not impressed with the thermostat it's switching the compressor on every 6.5 minutes (no wonder it maintains a steady temperature). The diff must only be 2°c. On a domestic fridge auto defrost stat the diff is more like 18 so the compressor runs longer but then stays off longer to defrost the evaporator.
I can always fit a digital thermostat later I suppose, I just begrudge the 50ma quiescent current

Run time 1m 37s
Off time 6m 36s
Internal temp 3.5°c

Also the first 30 seconds running is at 3.8amp but then it drops to 2.8amps for the remaining run time. So the less start ups it does the less the power used.
Maybe the compressor runs slightly faster at first but can't hear any change in speed.

I've reset the battery monitor AH counter and switched off the charger so we'll see how many AH it uses over the next 12hours. The night usage is the important bit of course, the solar's there in the day so who cares about that

 

[RedFrame]

I've been running a 12v Dellonda compressor fridge freezer constantly for the last 10 months or so. As a ball park comparison ...

At 5 deg/-18 deg I get 6 min run time and 12 min quiet.

Overnight Jan/Feb, I find approx 20a is drawn.

Is there a reason you run at 3.5 deg ? Food standards only require 5 deg, raising it may improve performance without any harm...

Cheers
Red

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[Richard n Ann]

Is there a reason you run at 3.5 deg ? Food standards only require 5 deg, raising it may improve performance without any harm.

It's about 4c at the top and the lower sensor is on 3.3c so I could higher it slightly

 

[Richard n Ann]

This is one run cycle, you can see the voltage drop more for the first 30 seconds when it's drawing nearly 4 amps.

 

[Tombola]

Very informative.
thanks

 

[pampam]

You clever clever thing it scrambles my brains

 

[Richard n Ann]

It's just coming up 12 hours then, think I reset the AH counter about 6.15pm. Only 7AH used since and the single 80AH battery is still above 80%, I'm under no illusion though, it would probably use double in spain. Internal temperature has dropped slightly but been pretty steady.

Starting up about 5.3 times every hour so better.

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[Clive Mott]

Impressed, very. Not your usual DIY job. Hats off.

 

[Bolti]

Most impressed and if you ever need an apprentice would you consider me please.

I have a compressor fridge Vitrifigo 90L and even on half setting things often freeze on the top shelf below the freezer box.

 

[Richard n Ann]

Most impressed and if you ever need an apprentice would you consider me please.

I have a compressor fridge Vitrifigo 90L and even on half setting things often freeze on the top shelf below the freezer box.

What's the freezer temperature? If that's plenty cold enough you can replace the thermostat, if it's not it's just how the fridge is.

 

[Richard n Ann]

I'm keeping the fridge fans, they probably won't run much mind.
I've blocked off the surround so they'll extract properly if they come on.
I'm cable tieing the sensor on the compressor discharge pipe, it will bring the fans on if it gets to about 45°c

The external covers will need to be on most of the time too, otherwise a gale will be blowing in round the fridge as the aluminium cowling has now gone.

 

[Steve and Denise]

It's just coming up 12 hours then, think I reset the AH counter about 6.15pm. Only 7AH used since and the single 80AH battery is still above 80%, I'm under no illusion though, it would probably use double in spain. Internal temperature has dropped slightly but been pretty steady.

View attachment 626054

View attachment 626053


Starting up about 5.3 times every hour so better.

View attachment 626056

Even if it uses double you will have twice the sunshine on your solar so should not be a problem

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