Dometic Fridge Food Safety

[peesalot]

I assume the fridge will run on either 12v OR 110V. i WAS CURIOUS IF THE TOP LEVEL COOLED BETTER ON 110v ? FINCAPLOC

 

[e9999]

well, it's not because you see the air temperature at 43 up top that a solid object would be at that temperature if it's of significant size and/or touching other objects or the walls

 

[MCtree]

well, it's not because you see the air temperature at 43 up top that a solid object would be at that temperature if it's of significant size and/or touching other objects or the walls

Yes. Agreed. This is a flaw in my test that I realized after I started it.

Unfortunately, the little thermometers I used are not water proof. So if I run the test again, I can’t put one directly into one of the Tupperware containers.

It did occur to me to put the thermometer into a zip-lock and then put it into the Tupperware.

At least I don’t think the zip-lock will affect the readings.
And sure, I know it won’t match the temp of the water in the Tupperware precisely, but it might be informative all the same.

 

[MCtree]

Because I'm obsessive, I re-ran this test again yesterday.

I found I have one more of the little, Bluetooth thermometers so I put it in a zip-lock and put it inside the top Tupperware container that was filled with ice water - to address what @e9999 said above.

Same basic results. The top of the smaller compartment in the cooler does not get down to what the FDA calls safe-food temps when I have it set to 33F. Though it’s very close (probably within the margin of error for my thermometers).

I also put a blanket on top of the fridge – this didn’t seem to make any difference.

Also, the inside of the top container was slowly rising throughout the test. I expect that if I had run the test for longer, it would have left the “safe-zone.”

I’m wondering if the flaw in my test is that the smaller side is designed as the freezer section and the larger the fridge. So perhaps I will re-run the test while testing the larger compartment as the fridge and the smaller set to below freezing.

Also, I should note that my first test was run on a day that saw max temps of 68 while yesterday saw 80F. Interesting that this didn't seem to make much difference.

 

[e9999]

I'm more likely to pursue excruciating measurements than most, sadly, but that said, I think you may be making too much out of this, TBH. There will always be some difference in temperature throughout the inner space. It happens in your kitchen fridge too. I have some thermometers in there and I frequently see the air temperature spike to well above 40 when the door has been opened. It doesn't matter much. The food inside will not jump easily in temperature from that.

As to your ziploc test, note that water will also -like air- readily show significant temperature differential between top and bottom due to natural convection. It will be different if you have a solid item in there, for which conduction will be dominant.

Just put the critical items at the bottom. I often put some frozen items at the bottom of the fridge section to thaw if I expect to eat them in the next few days. I'll put easy to spoil things on top of those if I'm worried. But it's not like you will instantly die if your mayo is at 40 for a day or 2 anyway, I would think.

 

[FrazzledHunter]

Clarity, I own a Dometic CFX3 75L dual zone and this subject interests me.
Kudos for doing the heavy lifting for measurements - this is EXACTLY the kind of thing I'd do LOL!

Anyone know where the Dometic's temperature sensors are?
I'm imagining myself a 'fridge/freezer designer and having to decide where to place the sensors for the compressor to kick on and off. Placed at the bottom, I'd guess anything at the top of the freezer and refrigeration sections would be very warm. Placed at the top and the freezer might do ok but things in the bottom of the 'fridge would likely freeze.

This is why large walk-in refrigerators & freezers have fans to move air around.
Obviously you can't do that in the Dometic.
So I'm guessing an engineering decision was made to do the best one could by having a "unhappy medium".
The only thing I can think of is to keep the 'fridge partially full to afford more air circulation.

I've noticed some obvious signs of this issue in our RV's fridge. Cans of coda freezing in the back with soft almost melted butter on the door.

We're obviously not alone:
Beech Lane RV Fridge Fan
https://www.amazon.com/Beech-Lane-Multiple-Increase-Construction/dp/B09GCH9ZZZ?tag=ihco-20

RV Refrigerator Fan
https://www.amazon.com/Makevivi-Refrigerator-Fan-Fridge-Preservation/dp/B0C6KLY2M9?tag=ihco-20

Camco Camper/RV Fridge Deodorizer & Airator
https://www.amazon.com/Camco-Fridge-Airator-Off-Switch/dp/B01E5SNB5I?tag=ihco-20

Not sure how well one of these will work in a Dometic. But I'll probably get one or two for the RV before we head out in the hot weather.

 

[bicycleagent003]

In my experience, the top of the frig being in the sun is a killer. The frig then works really hard and can't keep up with cooling. I have that foil insulation from Lowe's that I've cut for my windows at night. During the day, on the trail or during breaks, I make sure that stuff is on top of the lid of my Dometic. Now that I think of it, I'm going to use some adhesive velcro to help make sure it stays better next time. It slides off rather easily.

 

[MCtree]

I'm more likely to pursue excruciating measurements than most, sadly, but that said, I think you may be making too much out of this, TBH. There will always be some difference in temperature throughout the inner space. It happens in your kitchen fridge too. I have some thermometers in there and I frequently see the air temperature spike to well above 40 when the door has been opened. It doesn't matter much. The food inside will not jump easily in temperature from that.

As to your ziploc test, note that water will also -like air- readily show significant temperature differential between top and bottom due to natural convection. It will be different if you have a solid item in there, for which conduction will be dominant.

Just put the critical items at the bottom. I often put some frozen items at the bottom of the fridge section to thaw if I expect to eat them in the next few days. I'll put easy to spoil things on top of those if I'm worried. But it's not like you will instantly die if your mayo is at 40 for a day or 2 anyway, I would think.

Yeah. I know I’m overthinking all this.
But I kind of enjoy it.

Really I’m just trying to find the optimal way of dealing with this situation. (Obviously it’s not insurmountable.)
Like putting the beer at the bottom of the compartment. And setting the temp to 29 since beer has a lower freezing temp.

 

[MCtree]

Clarity, I own a Dometic CFX3 75L dual zone and this subject interests me.
Kudos for doing the heavy lifting for measurements - this is EXACTLY the kind of thing I'd do LOL!

Anyone know where the Dometic's temperature sensors are?
I'm imagining myself a 'fridge/freezer designer and having to decide where to place the sensors for the compressor to kick on and off. Placed at the bottom, I'd guess anything at the top of the freezer and refrigeration sections would be very warm. Placed at the top and the freezer might do ok but things in the bottom of the 'fridge would likely freeze.

This is why large walk-in refrigerators & freezers have fans to move air around.
Obviously you can't do that in the Dometic.
So I'm guessing an engineering decision was made to do the best one could by having a "unhappy medium".
The only thing I can think of is to keep the 'fridge partially full to afford more air circulation.

I've noticed some obvious signs of this issue in our RV's fridge. Cans of coda freezing in the back with soft almost melted butter on the door.

We're obviously not alone:
Beech Lane RV Fridge Fan
https://www.amazon.com/Beech-Lane-Multiple-Increase-Construction/dp/B09GCH9ZZZ?tag=ihco-20

RV Refrigerator Fan
https://www.amazon.com/Makevivi-Refrigerator-Fan-Fridge-Preservation/dp/B0C6KLY2M9?tag=ihco-20

Camco Camper/RV Fridge Deodorizer & Airator
https://www.amazon.com/Camco-Fridge-Airator-Off-Switch/dp/B01E5SNB5I?tag=ihco-20

Not sure how well one of these will work in a Dometic. But I'll probably get one or two for the RV before we head out in the hot weather.

Thanks!

I can’t say where the dometic’s thermometers are. Like you, I would guess at the halfway point.
Though I guess we should also wonder if they are up against the other compartment or not. Like if one compartment affects the other.

As for air movement, yeah, I think a fan would help. Though those ones you linked are pretty large for a dometic. I’m going to look for a smaller one.
Also, in this second test, I made sure I had plenty of air gaps to allow for circulation - it didn’t seem to matter much.

 

[MCtree]

This is a smaller dometic than mine, but watching this guy replace the thermistor surprised me. It looks like it’s at the bottom of the compartment.

 

[peesalot]

I dont suppose you ran a test on 12V & 110 V ? I think you will be surprised. Is your lid plastic or metal ? FWIW before I got solar when my batt voltage would get low the top of fridge chamber warmed first, what are you cycle times ? how long does comp run vs how long it stays off ?

 

[DrRock]

@MCtree Are you running the test with a cover on your fridge or just as is? We have an older CFD 35 in our 60 and even in 90deg F ambient conditions it remains at 35deg F towards the bottom of the fridge while in 12VDC. Thanks for putting in all this test work, great stuff.

Cheers, James

 

[MCtree]

@MCtree Are you running the test with a cover on your fridge or just as is? We have an older CFD 35 in our 60 and even in 90deg F ambient conditions it remains at 35deg F towards the bottom of the fridge while in 12VDC. Thanks for putting in all this test work, great stuff.

Cheers, James

Mostly, it’s just as is.
I did put a blanket on it halfway through this most recent test, but it was a fairly thin blanket.

But note that the fridge maintains the target temp very well near the bottom of the fridge.

I do think some improved insulation would help to make the temps more homogenous; I’ll have to look if they make anything specific for my fridge.

 

[FrazzledHunter]

Mostly, it’s just as is.
I did put a blanket on it halfway through this most recent test, but it was a fairly thin blanket.

But note that the fridge maintains the target temp very well near the bottom of the fridge.

I do think some improved insulation would help to make the temps more homogenous; I’ll have to look if they make anything specific for my fridge.

I bought Dometic's insulator cover. It helps. I think.

 

[MCtree]

I bought Dometic's insulator cover. It helps. I think.

This one?

Dometic CFX5 Protective Cover 95

Durable, Precision-Fit Cover for 95L CFX5 Electric Cooler

www.dometic.com

I have previously thought about purchasing it, but it no where in the description does it mention it insulates. It just mentions protecting the cooler from scuffs.

But if you think it’s also somewhat insulated, I’m game to try it. Does it feel like it’s insulated?
In the name of pseudo-science, I’ll buy one and run my test with it on.

Or is there another one than I’m missing that is insulated?

 

[FrazzledHunter]

This one?

Dometic CFX5 Protective Cover 95

Durable, Precision-Fit Cover for 95L CFX5 Electric Cooler

www.dometic.com

I have previously thought about purchasing it, but it no where in the description does it mention it insulates. It just mentions protecting the cooler from scuffs.

But if you think it’s also somewhat insulated, I’m game to try it. Does it feel like it’s insulated?
In the name of pseudo-science, I’ll buy one and run my test with it on.

Or is there another one than I’m missing that is insulated?

Yes that's the one I bought but for my CFX3. Insulation is minimal as the top is 1/4 in foam on top. Better than nothing I guess. Notice I said with regards to insulation I said it helps "I think" LOL. It definitely helps with scuffs and bumping it around.

The top covers fray with use. See photo.

Going down the rabbit hole...
I've given this some thought after staying at Arches with 100+F temperatures and dust carried by high winds making it so I couldn't open the LC's windows. What would be required would be either making a shell out of 1" or thicker styrofoam or putting the Dometic unit inside a BIGGER insulated cooler. The 2nd approach would obviously require a cutout for the fan.

But, at elevated temperatures such as these insulating it won't matter even if you did all that because the ambient temps wold be too high (I assume) for the Dometic to draw heat out of the cooler. You would then need a vent outside the car.

 

[peesalot]

I made a styrafoam lid, 4" thick, used heat shield on the metal sides, used the transit bags, take all that crap off and keep fridge shaded. If the top 3 " or so is warmer than the bottom its not good. Can you feel the diff with your hand or just with thermometers ? Again I would run it on 110V and see if same condition exists. FWIW I have heard reports that fridges freeze everything on bottom and top stuff is moderate, not sure what brand or conditions but have heard this and thought it to be a cheap fridge.

 

[MCtree]

Before I spend the cash on the dometic brand cover, I may try some more testing with homemade insulation to see if that moves the needle.
Obviously, this would be less elegant but perhaps I could test if that’s the issue before purchasing.
I worry that the covers would cause things to snag. When I travel I put duffle bags on top on the cooler and I would worry about ripping the cover when sliding the bags in and out. But I would certainly put up with snagging if it increased insulation led to more uniformity of temps.

 

[MCtree]

I made a styrafoam lid, 4" thick, used heat shield on the metal sides, used the transit bags, take all that crap off and keep fridge shaded. If the top 3 " or so is warmer than the bottom its not good. Can you feel the diff with your hand or just with thermometers ? Again I would run it on 110V and see if same condition exists. FWIW I have heard reports that fridges freeze everything on bottom and top stuff is moderate, not sure what brand or conditions but have heard this and thought it to be a cheap fridge.

No. I haven’t tried the 110V yet. I will eventually but am hoping I can solve it with other means since I don’t have a great way to use 110v while traveling.

I did just come across this thread:


What an interesting theory! That it’s the compressor itself that’s warming the smaller compartment.
This furthers my interest in running the same test I have been running but on the larger compartment - since it’s further away from the compressor.

 

[FrazzledHunter]

Before I spend the cash on the dometic brand cover, I may try some more testing with homemade insulation to see if that moves the needle.
Obviously, this would be less elegant but perhaps I could test if that’s the issue before purchasing.
I worry that the covers would cause things to snag. When I travel I put duffle bags on top on the cooler and I would worry about ripping the cover when sliding the bags in and out. But I would certainly put up with snagging if it increased insulation led to more uniformity of temps.

I'd think your duffel bags would provide insulation; likely better than the cover that's 1/4 in foam.