Hot weather refrigerator performance

[Steve Sanders]

Circulating hot air isn't going to help. You have to get rid of the heat.

Since heat energy can't be created or destroyed, the system is moving heat from inside the refrigerator to outside. The outside coils must be able to get rid of the heat by heating the air in that location. If it is not able to get rid of the heat, because the outside coils are already in hot air, cooling performance suffers. You're fighting the laws of physics.

All refrigeration systems have a maximum temperature differential between the two sides of the system. As I recall, the electronic coolers can provide a 30 degree change in temperature. Absorption systems are more efficient, but may not be able to get more than 40 to 45 degrees of temperature differential. (I couldn't find any specs.) Regardless of the system, the hotter the "outside" temperature is, where the outside coils are, the warmer the refrigerator interior will be.

This situation is typically qhidden from us because our home refrigerators are in air conditioned space. We're used to consistent refrigerator temperature because it is in a room with constant temperature. In the camper, this is not the case. If you put your home refrigerator outside in the heat, you would see the same problem. The more you can cool the back side of the RV fridge, the cooler it will be inside the fridge.

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[MitchB]

So essentially we have to refrigerate the cooling coils to improve the refrigerator performance.  In the world of IT this closely resembles nested IF statements, makes perfect sense.

I'm thinking maybe I'll put a tent up over the entire RV and then refrigerate that tent

[Steve Sanders]

LOL

As a computer programmer, I get it and agree!

There's only so much that a refrigeration system can do. Whatever chemical process is used, it can only drop the temperature a certain amount. As the ambient temperature goes up, the ability to obtain 35 degrees on the cold side is lost.

I suspect the biggest problem is the installation. Consumers demand larger capacity in a limited space, so insulation suffers. It gets cool enough at night to get the inside cold, but the back and sides of the refrigerator are subjected to a lot of heat in during the day.

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[Steve Sanders]

For what it's worth, we have a small portable Dometic absorption refrigerator that we use in our 6.0 and now 8.1. Since it is not installed in the camper, the "outside" coils are inside the (somewhat cooler) air conditioned camper / tent. I've been quite pleased with the performance. Unless it's 95+ outside, it often freezes diet soft drinks and water bottles.

The ammonia cycle absorption system is capable of doing a very good job.

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[mojospeople]

Right around zero. Frozen!

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[mojospeople]

Circulating hot air isn't going to help. You have to get rid of the heat.

Since heat energy can't be created or destroyed, the system is moving heat from inside the refrigerator to outside. The outside coils must be able to get rid of the heat by heating the air in that location. If it is not able to get rid of the heat, because the outside coils are already in hot air, cooling performance suffers. You're fighting the laws of physics.

All refrigeration systems have a maximum temperature differential between the two sides of the system. As I recall, the electronic coolers can provide a 30 degree change in temperature. Absorption systems are more efficient, but may not be able to get more than 40 to 45 degrees of temperature differential. (I couldn't find any specs.) Regardless of the system, the hotter the "outside" temperature is, where the outside coils are, the warmer the refrigerator interior will be.

This situation is typically qhidden from us because our home refrigerators are in air conditioned space. We're used to consistent refrigerator temperature because it is in a room with constant temperature. In the camper, this is not the case. If you put your home refrigerator outside in the heat, you would see the same problem. The more you can cool the back side of the RV fridge, the cooler it will be inside the fridge.

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I've heard the same in regards to the a/c. That it can only lower the temp 15 degrees or so below the outside temps. All makes sense to me. I may set up a fan outside the lower vent to push more air this weekend however with temps predicted to be in the low 90s I'm not very hopeful. I think our site is in full shade though so we'll see.

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[mojospeople]

Wait, are we all IT here? I'm a software developer. Totally get the nested ifs.

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[Steve Sanders]

Wait, are we all IT here? I'm a software developer. Totally get the nested ifs.

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SAS database programmer.

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[Steve Sanders]

They should do better than 15 degrees, but that's the idea. They don't make "cold", they relocate the heat. If it can't heat the air outside, then it can't move the heat to make it cooler inside. If the outside coil is in hot air, 15 degrees could happen and explain this thread. With cooler outside air, 40 to 50 degrees or more is possible.

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[Paul]

Wait, are we all IT here? I'm a software developer. Totally get the nested ifs.

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I am a software developer too!

[mojospeople]

They should do better than 15 degrees, but that's the idea. They don't make "cold", they relocate the heat. If it can't heat the air outside, then it can't move the heat to make it cooler inside. If the outside coil is in hot air, 15 degrees could happen and explain this thread. With cooler outside air, 40 to 50 degrees or more is possible.

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The 15 degree cooling was in regard to the air conditioning problem my dad was having in high heat and humidity. Sorry to confuse.

Tonight armed with a screwdriver, wire brush and a can of compressed air I opened up the unit. Everything looked shiny and new. Did I mention we almost always run on electric so the gas hasn't been run much at all? No soot and minimal dirt and dust. So I guess I've done all I can do. It's turned on and cooling in prep for the holiday outing. I need to hope for cooler camping temperatures and pay close attention to the fridge temps in hot weather.

[mojospeople]

Yea! Current outdoor temp, 74. Current fridge temp, 36. Today is going to be low 90's with a heat index of low 100's. Will see what the fridge temp is tonight.

[Steve Sanders]

Yea! Current outdoor temp, 74. Current fridge temp, 36. Today is going to be low 90's with a heat index of low 100's. Will see what the fridge temp is tonight.

Keep the door closed as much as possible.

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[FastEddieB]

As data points, 21BHS with Dometic fridge...

In 94º to 96º daytime temps near Knoxville, TN, fridge temps can creep up to the high 40's during the day, but the freezer seems to stay below freezing. Overnight, temps drop down to mid-to-low 30's to start the day. This is all parked in partial shade, and running on 120v.

[djsamuel]

As data points, 21BHS with Dometic fridge...

In 94º to 96º daytime temps near Knoxville, TN, fridge temps can creep up to the high 40's during the day, but the freezer seems to stay below freezing. Overnight, temps drop down to mid-to-low 30's to start the day. This is all parked in partial shade, and running on 120v.

That about matches the performance of the Dometic in my 2013 21BHS.