Turning Freezer into Fridge

[Zanshin]

(hopefully Mr. Kollmann could explain this issue)

I have a fridge and freezer unit from Vitrifrigo aboard the boat. Being in tropical waters, the freezer eats up a lot of energy and now I have eaten all the frozen steaks I'd purchased and have turned the unit off to conserver energy.
On my previous boat I had a switch in the freezer to allow it to function as a fridge. I sent an e-mail to Vitrifrigo asking about getting a different thermostat or if they had a suggestion as to what I should do. I got a response from customer service asking for the unit serial number and details and when I'd supplied that they stated that this conversion couldn't be done.
When I asked about details they wrote that it would cause too much condensation and that the cooling plate is overdimensioned and wouldn't correctly distribute the coolant and that the end result would be excessive energy use and lots of condensation.

While I believe the response I got, I have to admit that I don't understand it; I would have thought that running at a higher temperature in a unit designed for colder ones would save energy and be a simple matter of changing the thermostat temperature range.

I'd still like to optionally use my freezer for cooling beverages and would welcome suggestions.



p.s. I've appended the text from the last Vitrifrigo mail:

If you try to install a different thermostat, such as with a different setting for the fridge temperature , you head for some problem .
I try to explain the reason :

First of all probably , the system can’t cool the entire plate , because the compressor turn off to soon respect the timing of freezer thermostat .
That will result a lot of condensation, and the fridge will consume more, in order to switching on and off more frequently .

These are our advice because we want that the fridge works well
Differently from that point, you can try that, but I would like to inform you that ,with this ,the fridge will be out of warranty for the modification that we don’t authorize

The technical data of your thermostat now are :

At the maximum cut in at - 23 cut out - 28

At the minimum cut In at -12 cut out - 16.5


I remain at your disposal

[byo]

Hi Zanshin, Frigoboat do two thermostats, one for a freezer P/N E250700 $45-00 AUD and a fridge thermostat P/N E250500 $43-15 AUD. Either can be used on their system with no problem, on our yacht I replaced the fridge one with a freezer one which allows the large fridge area to be used as a freezer, I installed a small fan between the big fridge and the small one to circulate the cold air, the freezer area will go to -12 degrees and the smaller fridge will be around 2 degrees. Before that we had two fridge spaces so its dependant on which thermostat you use. Hope this helps,
Cheers, Bruce.

[sailbleu]

Zanshin please check on of my topics on the hints and tips section , more specific the one about the frigoboat fridge problems.
Near the end you will some find pictures of the digital temperature controller.
Just read what I posted about that and you'll have your answer to your worries.
Those little things are small in size but big in possibilities.

Edit:
If you dont want any hassle with regards to the warranty , use this controllor.
Leave the standard installation as it is , and lead the main supply via this unit . Of course you will need to place the sensor somewhere in the fridge because this sensor will eventually tell the tempcontroller what to do.
Also leave the original thermostat setting as it is , no matter that it's set to min 20 or whatever.
Remember you will also be able to set a delay on the digital controller , maybe it's easier you start by reading my essay.
jeanneau.proboards.com/index.cgi?board=general&action=display&thread=1623&page=6



Regards

[Zanshin]

Thanks for the replies. My problem is not in adding another thermostat for the new temperature range - that is easy and quick to do and I would prefer a digital controller as in Sailbleu's post. The electrical parts are easy, as the compressors are simple standard Danfoss units. I don't know if it makes a difference, but the freezer compressor is keel-cooled while the standard fridge is air-cooled.

My worry is the problems regarding excessive switching of the compressors and condensation on the plates, which hasn't been addressed (apart from the manufacturer telling me that doing this is contraindicated)

When I had the 49DS with a Frigoboat fridge there was a switch in the freezer to allow the 2 temperature ranges; this Vitrifrigo fridge has no such switch, but they offer 2 different thermostats, one for the fridge temperature range and the other for the freezer temperature range.

[sailbleu]

Zanshin , why would it make a difference if the freezer is keel-cooled , it's only to condensate the gas.
With regards to condensation on the plates , first of all that will depend how many time you open the freezer , second : I suppose you have a drain inside no ?
I have eliminated , or lets say bypassed , my original thermostat also , and there is indeed some condensation . But the benifits of this transformation surely outway the negatives.
I also had the controller command a heavy duty relais , installed a (fused) direct line from the batteries to the relais and by doing so I solved the problem of voltage loss caused by the long and thin supply leads Jeanneau designed.
You know , with this controller you can even switch back to a freezer with just a few settings if you should wish to do so.

Regards

[Zanshin]

Sailbleu - if you look at the original post, I pasted the manufacturer's response. If the manufacturer, who knows their devices, says that it will not work by merely replacing the thermostat, then I believe them. I'm posting this thread here in the hopes that there might be some other modification in addition to the thermostat which will avoid the problems that Vitrifrigo thinks will occur. I can live with condensation, as this extra fridge will be used exclusively for drinks and fluids so I can drain it frequently, but from the Vitrifrigo description the duty cycles of the compressor will also be affected (adversely).

That's why I hoped that Kollmann was still active in this forum and might add a second professional opinion to that of Vitrifrigo.

I did check my wiring and things on the Jeanneau 57 are a lot better because the boat is 24V rather than 12V for all of the bigger devices and the current losses are less because they have a minimum size for the cables and that is, I guess, calculated for 12V.

Can the thermostat that you specified be programmed to have a minimum duty cycle? That might solve some problems, once it kicks in it run until the specified temperature is reached but must run at least nn minutes. With a little 12V fan as you installed and mainly dense liquids in the unit that might work - not freezing the bottles closest to the plate but distributing the cold into the big heat sink of liquids, then it might take longer before the temperature sensor reaches the cut-in value.

Of course, I could just buy all sorts of frozen foods and run the thing as a freezer

[sailbleu]

Not sure what you mean by minimum duty cycle , but I suppose you want the compressor to run for a minimum of time.
If that would be the case , you are out of the woods my friend.
There is such a thing as delta temp setting.
You can have this small digital computer display cut the power at a certain temp. and have it restart the compressor a few degrees higher than the cutoff.
If I remember correctly , there is a 10° Celcius delta possible.
Also , to avoid compressor torque you have an adjustable time delay to make sure the compressor doesn't start immediatly after it switched off.
I really didn't exaggerate when I praised these cheap Chinese wonders into heaven .
Of course they're around much longer than the Chinese decided to manufacter them , like most things they're copies of European or American stuff , but it must be said , at a ridiculous price.
You know , I'm a bit addicted here , I have installed one to power up/down my home sauna that was manually switched before.
And I also have such a device controlling the heating up of my new bigger homemade waterboiler.
So the pics in the hint and tips section are a bit obsolete , there are now 3 lovely displays showing off.

As you can see , when it comes to controlling temperatures I instantly think about these magical objects.
I even have some spares lying around here , just in case :-) It's Chinese right , but so far so good.

Regards