Res fridge blowing warm air

[Almot]

After I bought a 2-zone fridge thermometer I noticed how strange res fridge works.

When it starts cycling - sometimes, not always - it blows warm air in both fridge and freezer compartment, for a minute or two. Temperature in the freezer goes up from, say, 0F to 7F. Then it starts blowing cold air. I put a small bottle with water and planted a wired thermometer sensor in there, frozen solid. Frozen bottle gets warm to say, 6F before it starts cooling again.

[Gdetrailer]

Almot wrote:

Gdetrailer wrote:

It is possible that some fridges may simply run the heater with compressor off but have the fan on for a short defrost cycle.

Seems to be the case. I'm still not happy with freezer temp swings. If it were swinging while staying below 0F all the time, this is one thing, but it swings from -3 to +6. This is block of ice, not just the air. A separate designated freezer would've solved the problem I guess.

I don't think having the probe inside the ice in a freezer works as well as probe in water in the fridge. Using water in the fridge is about slowing down the the temperature swing of your digital thermometer.

You will still get temperature swings recorded even if the probe is in a solid block of ice.. So basically you are still reading the air temp and the ice may be just changing the speed of the reading a bit.

As long as the freezer is delivering an average of 0F or a bit below it is plenty cold for any food you put in there to stay properly frozen for proper long term freezer storage. At 0F your frozen foods will stay frozen.. If you were seeing 20F-30F in the freezer then I would be concerned.

The place to be concerned about is your fridge temps, 34F-40F is ideal and recommended for safe food storage.. I try to keep fridge temps as close to 32F as possible without freezing things.

[Dutch_12078]

Almot wrote:

Gdetrailer wrote:

It is possible that some fridges may simply run the heater with compressor off but have the fan on for a short defrost cycle.

Seems to be the case. I'm still not happy with freezer temp swings. If it were swinging while staying below 0F all the time, this is one thing, but it swings from -3 to +6. This is block of ice, not just the air. A separate designated freezer would've solved the problem I guess.

Are you measuring the internal temperatures of your frozen food? The warm up is such a short duration that you'll find they don't vary much at all. Your thermometer is much faster acting than the food packages. I've taken ice cream out of our freezer right after the defrost cycle, and found it to be just as solid as when the thermometer shows -5 deg.F.

[Almot]

Gdetrailer wrote:

It is possible that some fridges may simply run the heater with compressor off but have the fan on for a short defrost cycle.

Seems to be the case. I'm still not happy with freezer temp swings. If it were swinging while staying below 0F all the time, this is one thing, but it swings from -3 to +6. This is block of ice, not just the air. A separate designated freezer would've solved the problem I guess.

[wa8yxm]

Almot wrote:
So it does this on purpose? I don't get much frost, all it does is warming up my food. And it blows warm air in the fridge compartment as well, where it doesn't make any sense. Probably embedded in the firmware, can't be deleted.

Modern "Frost Free" refrigerators actually have heaters in them to melt the frost from the fins.. You are seeing the hot air because the fins are well above freezing to insure they dry off before the next cooling cycle. Takes a bit for the fins to cool down..

Same is true when you start your car in the summer.. Air coming out those vents at first can be well over 100 degrees. then drops like a rock as the compressor and other parts do their thing.

[Gdetrailer]

Almot wrote:
So it does this on purpose? I don't get much frost, all it does is warming up my food. And it blows warm air in the fridge compartment as well, where it doesn't make any sense. Probably embedded in the firmware, can't be deleted.

You should not see any frost with a "frost free" residential fridge, if you do, it has a problem.

How FF fridge works is the cooling coils are in the back of the freezer behind a false wall. There is a fan which pulls the air across the coils, some of the air is directed into the freezer section and some of the air is directed to the fridge section.

Over time frost builds up on the coils in the freezer section so the idea is clear the frost off the coils quickly enough so you don't end up with a block of ice at 32F instead of the sub zero F you would get from the bare coils..

How the clearing works is there is a small 120W-250W 120V heater attached to the coils in the freezer. The heater is cycled on with typically the compressor and fan turned off for a preset time only when the T stat calls for cooling and the proper amount of compressor run time has elapsed.

In the case of my home fridge conversion in my TT, the manufacturer used a mechanical timer which runs the defrost cycle once for ten minutes for every ten hrs the compressor has been running.

It is possible that some fridges may simply run the heater with compressor off but have the fan on for a short defrost cycle.

I would not take much concern about it blowing some warmer air for a minute or two as long as it cools down fast. Basically the air in the freezer may be warmer than the coils and until the compressor kicks on and starts cooling the coils the fan is just circulating the warmer air..

[Almot]

So it does this on purpose? I don't get much frost, all it does is warming up my food. And it blows warm air in the fridge compartment as well, where it doesn't make any sense. Probably embedded in the firmware, can't be deleted.

[Lwiddis]

The no frost fridges come with an energy price.

[prichardson]

Defrost cycle.

[afidel]

Defrost cycle probably.