Fridge/Freezer Temperature

[stephanfeb]

Hello

I have separate fridge and freezers installed onboard. My freezer is not keeping anything frozen, and because of it's location aboard (behind nav station), it's compressor is located in a poorly ventilated locker.
I purchased remote/wireless thermometers and monitored the fridge (not freezer). The lowest recorded temp on the fridge was 8 degrees celcius (45 Fahrenheit).

Before I embark on trying to "fix" things, I would like to know what typical achievable temperatures are for fridges and freezers aboard without massive reengineering effort. All help is much appreciated.

Both my fridge and freezer uses a coldplate (frigoboat).

Regards
Stephan
SV Andiamo II

[MBWhite]

Greetings Stephan,

I am not familiar with your fridge, but I am certified in HVAC so take that for what it is worth.

To start, has your system been working and now it has just started getting warmer? If so, has anything changed when this happened (sailed 600 miles south, built a new bookcase, get a spider infestation over last weekend, etc)

How old is the system?

Your freezer should be able to make ice at the very minimum, and I would expect it to keep ice cream hard (0F) if it is running properly.

To begin to fix the problem, the first thing is to make it as easy as possible for the heat to get removed from the compressor and condenser areas. Start by cleaning all of the dust and dirt from these areas. If you can see and reach everything by hand then just use water and rags. If it is hard to get to use a vacuum cleaner with a thin extension wand. If there are coils you cannot reach but can tell they are dirty, the ultimate weapon to clean them is an electric leaf blower but first cover the inside of the boat with sheets and blankets as it will put the dust and dirt -everywhere- !!

The cabinet temperature where the condenser is mounted cannot be over 90F or you are guaranteed to have issues such as yours, so after everything is clean take the temperature several times to make certain yours does not get that high.

Also, the cold plate in the fridge needs to have unrestricted air too so make sure there are no bags of food stacked around it as you can get frozen peas that are 0F on one side and 35F on the other side. Check it also for any ice build up.

I have found the absolute best tool for measuring temps to be the "non-contact IR thermometers" that are sold online for $5-$25. They are great for so many things in addition to measuring fridge temps- oven baking temperature, where you need additional insulation on your boat hull, misfiring cylinders on engines, hot bearings on electric motors, etc. Lots more than just helping you out to fix your fridge.

Anyway, to recap for your fridge first clean out all the dust and cobwebs and make sure the plate is uncovered (if it is a hollow design make sure something has not fallen inside it and is blocking airflow). If the air around the compressor and evaporator feels too warm put a small fan on it to see if that makes a difference to the fridge temp.

Hope that helps!

Mark

[onestepcsy37]

Fridge temp is supposed to be 38 F, freezer temp 0 to 10 F, if I recall correctly.

[stephanfeb]

Thanks for the advice. I'll do a proper cleanout, check ambient temp and see how I can ventilate a little better.

Cheers
Stephan

[MBWhite]

Good luck and keep everyone here informed on how it is going!

[skipmac]

Hi Stephan,

A very big help to diagnose the problem is the question Mark asked which is, have things changed in the fridge/freezer? Did it used to be colder or has it always been this way? If the boat is new to you then I guess you don't have experience with the system to judge.

Additional information to help with the diagnosis.

- What brand/model is the fridge and freezer?
- What is the design: holding plate, evaporator, air cooled, keel cooled, engine drive compressor, etc.
- How old is the system?

Good luck.

[gordwedman]

I have a Danfoss BD 50 running a large holding plate on the freezer side. There is a 2 inch blue foam board separating this from the fridge side which is just cooled by spill over. I try to keep the freezer at -6C. That is cold enough to make ice and it keeps the fridge section around 4C. One problem with all these temperature measurements is the location of your measurement. Things are going to be a fair bit colder at the bottom than near the top where you might have a basket holding food. If you wanted 4C at the top you might have frozen stuff at the very bottom. I tried one of those battery operated circulation fans once but the batteries did not last long enough to make it useful. I should wire in some small fans...

[MarkJ]

Hi Stephen,

I did quite a bit of research into these apparently simple questions of what temps the fridge and freezer needs to be.
I found out they can be quite arbitory! The freezer temp is "set" as -18C because zero degrees in fahrenheit is a simple number!!

The actual temps set are assesed with food spoilage rates, so frozen at -18C something will virtually never go off. But if a fluid filled food, like meat, is frozen hard at -4C it will still be unspoiled for over 3 months. Meat at -10C is 6 months, aprox, if I remember correctly.
So it realy comes down to how long and what you wish to keep. The longest passage is 30 days, so -4 for meat is fine. But at -10C ice cream is mush because of all the sugar.

Fridges are the same. +4C will keep meat for 7 days, butter indefinitly etc. but if you have your meat frozen before use you can have your refridge at +8 and the butter will still be fine for 6 months... But you've eaten it by then!

But can you drink 8C beer?

It might sound like I am being over finikky but in the tropics when ambient temp is 30 to 32 dropping it down to 8C take a hell of a lot of electricity, but its miniscule compared to 4C or -4, -8, -10.... And my freezer is on 24 hours a day at -10 and will not go lower and takes 2 days to get there.

My thiughts are to run at the highest temp that suits your food/consumption equation and if you have a special icecream treat be prepared to run the power bill up

[tomfl]

Originally Posted by MarkJ

SNIP

It might sound like I am being over finikky but in the tropics when ambient temp is 30 to 32 dropping it down to 8C take a hell of a lot of electricity, but its miniscule compared to 4C or -4, -8, -10.... And my freezer is on 24 hours a day at -10 and will not go lower and takes 2 days to get there.

My thiughts are to run at the highest temp that suits your food/consumption equation and if you have a special icecream treat be prepared to run the power bill up

Agree with this. I would add you can make ice at a much higher temperature than is needed for ice cream to not be mush. One tip I got from a refrigeration guru was that you should let your fridge settle down for two days before changing the thermostat.

I set my digital thermostat at 37.2 degrees, YMMV.

[MBWhite]

I agree about fridge/freezer temperatures not being set in stone. There is a difference between keeping foods cold and preserving them for extended periods.

As mentioned, if you do not have ice cream or something else that needs to be kept solid, most of the time you do not need to keep a freezer at 0F. Even things like frozen orange juice will still stay fresh in the can at 15F or 20F and you can still make ice, it just takes longer. Depending on where your thermostat is located in the freezer, you can also put down a layer of food or other things that need to be kept frozen, then put cardboard or a blanket on the layer and other less perishable food on top.

Also, the recommended way to bring a freezer down to temp the quickest is to turn it on empty and let it cool down that way, then put your food in it when cooled down, a bit at a time if possible.

[MBWhite]

Oh, one last thing to mention-

If you have a refrigerator or freezer that has a separate compressor/condenser unit, it can also be vary beneficial to put a blanket or two over the whole shebang (freezer or fridge) if you are concerned about saving every little tiny bit of energy you can.

[Dauntlessny]

I have vitrifrigo fridge and freezer with external danfoss bd35 compressors.
I love them.

Freezer at max was -23, I now have it set one tick up and it's -18.

Fridge at near warmest setting is now +6.

No matter what setting, neither vary by more than 1° if not opened.

Sent from my SCH-I605 using Cruisers Sailing Forum mobile app

[stephanfeb]

Thanks for all the advice everyone.

My typical need for this is not so much ice cream, but frozen food storage. One of my children has acute food sensitivities and requires a special diet. Things would be massively simplified if I could prep packets of frozen veggies, fish and meats before we head off, and keep them frozen for the duration of the trip. We only go into the remote asian islands off Malaysia/Thailand for one to two-week trips at a time, so I guess I don't really need a "deep freeze".
I *did* notice on our last trip that frozen meat kept in the bottom of our fridge will slowly defrost over a few days' time and still be perfectly fresh one week after purchase.

I just want to give you a quick update. I did a cleanout or radiator, fans and components as suggested, but this did not work.

The next thing I noticed was that thick blocks of ice was forming around the exposed copper tubing for the refrigerant. I bought a length of fridge tube insulation and wrapped that around the copper tubing and "sparingly" secured my wrapping with duct tape . In spite of these efforts the temperature would still not go down.
I have now decided that I will replace the cold plate next. My frige has a large L-shaped cold plate which seems very effective. The problematic freezer has a smaller (about half size of fridge) "frigoboat" cold plate which is either past it's life or just too small to be effective in the freezer.

I will next replace the cold plate with a larger one and keep you posted on my results.

Thanks
Stephan

[Mycroft]

Are you sure it's not just low on refrigerant?

[stephanfeb]

@MyCroft - Yes, that's a possibility. I intend to have a specialist do the job so hopefully any issues related to leaks/refrigerant or insulation can be professionally addressed this time. I've reached the limits of my DIY refrigeration skills

Cheers
Stephan