Converting our 3 way fridge to compressor.

[MisterB]

Great thread, if only I was that clever and industrious!

Great work everyone !

 

[Swifter]

Whoops wrong thread

 

[Richard n Ann]

There's no freezer now, just one plate evaporator at the back.

The standard controllers I'm looking at one uses 4va, the other is specified at 3w which is around 250ma the red display needs to be able to be switched off too I'll have to give them a coat of looking at in my soldering room first

 

[Richard n Ann]

These new elitech controllers only run at 65ma and that's with the relay energised

i think I can cope with that, so I'll be fitting this tomorrow the display isn't very bright so I'm leaving that alone.
I've also ordered a VT9 auto defrost domestic thermostat to replace the useless thing that came with the compressor kit, I'm going to switch it in parallel with cooling relay output ready for when the controller blows up in Benidorm

Technical bit: These elitech controllers are 230v only so I've removed the step down 12v transformer and bridged it out on the pcb with a piece of wire and a diode (to give a voltage drop along with the bridge rectifier drop for when the supply is 14.4v). The controller and relays still work OK on 9vdc

I know you can buy 12v STC1000 controllers but they are crappy copies of Elitech.

 

[Richard n Ann]

Working great, looks like a little commercial fridge now

Switching off at 0°c with a diff of 4°c. The sensor is on the side under the evap so it has to be set quite low, the front of the shelves are warmer...(for butter )
It stays off for an hour when it's reached set temperature.

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[BOWHOUSE52]

This is really doing my head now you are so clever love to be able to do this Got to go and have another lie down

 

[BOWHOUSE52]

Hi Richard&Ann if you don't mind can you tell me roughly what this would cost to do

 

[Richard n Ann]

Hi Richard&Ann if you don't mind can you tell me roughly what this would cost to do

About £430 with the new controller, polystyrene, expanding foam, VT9 stat and switches.
The compressor kit is now £380

 

[Richard n Ann]

It's 6am. The moment we've all been waiting for and the data is in

8ah used over the last 12hours
Compressor runs for about 18 minutes and then off for 1 hour.

Temperature at the front of the top shelf.


Plenty cold enough, could easily set it 2° warmer

 

[BOWHOUSE52]

Hi Richard&Ann can this be done to a Domestic fridge with freezer on top

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[Richard n Ann]

Hi Richard&Ann can this be done to a Domestic fridge with freezer on top

Yes, theoretically easier. You just need to change the compressor to a 12v one.
Would need to be bigger than one just running a fridge. Next size up is the Danfoss BD50f (it's the BD35f on mine).
Would it be the right size though? Probably would be my answer but it's a lot of money to spend if it isn't. You'd need a fridge engineer to do the job too, most wouldn't be interested.

Ideally the refrigerant in the fridge freezer should be R134a.

 

[Lenny HB]

Hi Richard&Ann can this be done to a Domestic fridge with freezer on top

Did you mean Dometic?

 

[BOWHOUSE52]

Did you mean Dometic?

Thanks Lenny HB this is the trouble with getting old

 

[Richard n Ann]

For a 3 way... Easiest way is use 2 systems so twice the cost.

It could be done with 1 bigger compressor and condenser but it would involve a pressure switch on the compressor, 2 solenoids and 2 thermostats. More complicated but that's how many commercial systems work

 

[Hoovie]

This video may be of interest to show the kind of process Richard did.

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[Richard n Ann]

The VT9 thermostat came yesterday so fitted it as a backup and tested over night. By 5am 5ah used (6pm to 5am)
Just screwed it to the back, had to butcher the case as it's different to the original stat, don't take any notice of the numbers, think it's set to about 3.

Wired it in series with a rocker switch on the front panel so it can be disabled.
The electronic controller can be switched off or just set out of range to use the stat.
Temperatures are good, electronic controller Vs stat

These auto defrost stats have a fixed cut in temperature of 3.5°c so the evaporator is always defrosted by the time the compressor restarts.

 

[martin2603]

Met à Guy yesterday who had a 21plate Globecar PVC. It had a largish compressor fridge, he had solar, 2 100 amp leisure batteries plus a lithium portapack and it was still draining the batteries.
My daughter has a small one in her leisure drive VW and that seems ok. Looks like size is very relevant in these matters.
Hope yours goes ok

 

[Shrimp]

Sounds good.

 

[buttons]

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... View attachment 625691
View attachment 625692

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

View attachment 625695

Your work bench could do with a sweep off

 

[Pusscat]

Fantastic thread!!

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[Pusscat]

…may have missed it but what solar / battery set up do you have?

 

[Richard n Ann]

…may have missed it but what solar / battery set up do you have?

80ah gel battery and 150w solar panel tiltable for use in autum in Benidorm. Wouldn't keep up in winter without engine running every other day.

 

[wfdTamar]

I’ve found the 30amp Votronic B2B charger works great if I start driving before the solar had recharged the battery.

I reckon I could have gone for a smaller lithium battery (or a cheaper gel), maybe 60Ah and 200 watts of solar would’ve been enough (I gave the fridge battery 300 watts of solar). Fridge is a 240 volt 105 litre.

 

[wfdTamar]

This thread is very interesting. Only thing is not a lot of people would be brave enough to do what Richard has. It about the knowledge/time/money equation. Richard has the knowledge to put in the time to do it this way. I had a bit of time (though it did come out of holiday time) and gathered a bit of knowledge to do it the next less involved way. Someone else might just pay for someone to install a 12 volt compressor fridge and extra solar & batteries to power it (the most expensive way to get a fridge).

If you wanted to try what I've done (240 volt fridge run by inverter) get an 800VA inverter (for a 100 litre fridge). This converts the 12 volts to 240. I used a 500VA one which did it, but complained of being overloaded for 20 seconds when the compressor starts (just means it hums for a second or two when overloaded). It would probably do an 80 litre or less fridge ok. About £225 for a good 800VA one (there's a Victron Phoenix one on ebay currently for £175).

Then a fridge - they seem to start at about £130 (I went a bit more expensive for an efficient and particularly quiet one). You need to be very sure about measurements and any clearances it requires for cooling. I think you want one that has the cooling wire grid on the back (the alternative is no wire grid and a fan that cools the compressor) so you can use the vents in the side of the vehicle made for the 3way fridge.

So it might cost as little as £300 for a 100 litre. I also put a fan in the back on the top vent. Let's say £350, but remember you most likely will need extra power capacity for it. Unlikely it will run off your existing leisure system unless you've already beefed that up (with solar and maybe a B2B charger). Even so, it's still likely to cost less than a new 3way fridge (£1200 installed when I priced one in 2019). Also you end up with a far better fridge than a 3way. Proper cold ice creams, beer or even storing frozen food at the correct temperature (below -18).

This is about my installation:

Additional solar system & B2B for compressor fridge

Hi. I've had a 2002 Hymer Classic B584 for a season and fitted solar to it. I'm fairly competent mechanically and technically, but the finer points of electrics are not something I do often enough to warrant learning it. I use my Hymer in the warmer months for long periods. My current leisure...

www.motorhomefun.co.uk

 

[Richard n Ann]

No more problems with the controller, been working great all summer. I upped the setpoint by 1° to 2°c

Not even had to deploy the portable solar panel on the cloudy days in Scotland

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[Shrimp]

Bet you’re pleased with how it is working.

 

[Richard n Ann]

Bet you’re pleased with how it is working.

Delighted can't remember the last time I filled the LPG bottles must have been in Benidorm in 2021... And I'm still on the 1st bottle