how long does the fridge stay cool?

[pianotuna]

Hi,

I was forced to park in a manner where I thought it prudent to turn the fridge off.

I've often seen folks claim the fridge is cool after many hours. This appears to be apocryphal.

The fridge:

Dometic Royale Tri-Fuel Fridge (6 cu. ft.)

The conditions:

I parked with the fridge on the north side so it was not in direct sunlight. Ambient temperature was 22 C (71.6 f). There was mixed cloud, and it was 1 p.m.

Interior of the RV was 22 c (71.6 f)

Interior of the fridge was 2.7 c (37 f), measured on the top shelf of the door.

After 2 hours the interior of the fridge had risen to 6.4 c (43.5 f)

The drain tube is properly set up with a dip in it to prevent air infiltration.

As I knew I would have power later, when I restarted the fridge I did it on 120 volts via the inverter. Input from alternator and solar to the fridge were about 25 amps. I drove for about 2 hours and the batteries were quite happy to start recharging at 24 amps once I had shore power. While the fridge was playing catch up duty cycle appear to be 100%.

The fridge was not opened and the interior was still at 4.5 c (40.1 f) after the two hours of run time. It is equipped with a dual interior fan, and dual "chimney" fans that sucks air over the exterior coils. The unit has the ARP control installed. (I love having that btw--no more driving in endless circles in parking lots to get perfectly level!)

My conclusion is that the fridge can be shut down for only one hour from a safe food storage point of view.

[ksg5000]

pianotuna wrote:
Hi ksg,

Where do you keep the sensor (inside the fridge)? What make and model of fridge do you have?

I keep the sensor on top shelf of fridge. Not sure of model - std Dometic that is about 8 yrs old. I suspect the variance is do to thermal mass because when I travel my fridge tends to be full of "pre cooled" stuff - might make a difference.

[pianotuna]

Hi CJ,

Here is a list of what was inside:

1 liter of milk, 1.5 liters of water, 8 eggs, 1 lb of carrots, 1/2 loaf of bread, 1 liter of vinegar, 1 pound of butter, 1 pound of margarine, .3 liters of mustard, 1 pound of cheddar cheese, 1 liter of jam/jelly/honey/peanut butter (the little packages from restaurants), 1 box of baking soda, 1 liter of oil, 1 liter of pomegranate juice, one jar of green relish, l liter of maple syrup, 1 tin of ginger ale and one bottle of Worcestershire sauce.

The freezer, on the other hand, was pretty much fully packed.

[CJW8]

You left out one important piece of date. How much stuff was in the fridge?
If it is jammed full and everything is cooled down it will stay cold longer than if it is only half full. The more cold thermal mass pecked inside, the longer it will retain the cold.

[2_many_2]

turbojimmy wrote:
Am I the only one that had to google "apocryphal"?

I didn't even try :h :B

[time2roll]

I have left the milk out on the table for an hour. Still good for the week.
One 8 hour drive is not going to spoil all the food. Every day would be a different story.

[turbojimmy]

Am I the only one that had to google "apocryphal"?

[Almot]

Old-Biscuit wrote:
Measurement of 'contents' is correct method to test cooling temp (probe/thermometer in container of water)

Yes. This is what I did to establish the optimal position of the switch warm-cooler-cold. Thermometer in glass of water. Doesn't even have to be wireless - inertia of water will let you take measurements while opening the door.

But... Don asked "how long".

40F at the door means that it is few degrees cooler inside - where it matters more. And, while it is cooler inside, it also warms up faster there, because the rate of warming up is proportional to temperature differential btw cold items and warm ambient.

So... repeat the experiment with probe deeper inside.

[mike-uswest]

In the summer we are looking at 90-105 degrees outside temp, often higher in the trailer, and we are happy to keep it below 45 degrees in the fridge.

Mike

[Old-Biscuit]

pianotuna wrote:
Hi Old,

I'm measuring air temperature on the top door rack.

Seals appear to be in good shape, and will hold a sheet of paper in place.

Air temp is NOT the correct measurement of 'cooling' in absorption fridge.

Food section fin temp is what is measured for thermostat controls.
Fin temp runs 10*F lower than actual compartment temps
Measurement of 'contents' is correct method to test cooling temp (probe/thermometer in container of water)

[Almot]

I wonder who needs Yugo mini in a country with average 2-3 children per family :)... Sorry for distraction.

[MEXICOWANDERER]

With my monster Vestfrost refrigerator, with temps of 85F, I can shut it off at 39F and four hours later interior temp has gained three degrees. It costs weight and bulk to do this.

Vacuum panel insulation is really the only intelligent answer but gas cooling units are as long lived as a Yugo in Mexico.

[pianotuna]

It may be my choice of sensor location in the Fridge.

Almot wrote:
Don, I think what you see is not uncommon, though yours seems to be worse than average.

[pianotuna]

Hi Old,

I'm measuring air temperature on the top door rack.

Seals appear to be in good shape, and will hold a sheet of paper in place.

[Old-Biscuit]

How are you 'measuring' food compartment temp?


Is remote temp probe in a bottle of water so it is measuring 'contents'
OR'
is it measuring 'air temp'

Either way.........your fridge is NOT holding temp
Door seals leaking?

My Dometic 8 cu.ft. will hold temp (measured in a bottle of water) below 40*F for 6 hrs.

BUT I still run with it ON........