How To Keep Your RV Fridge Cool In Hot Weather
You can keep your RV fridge cool in the summer; however, as any RVer will tell you, the hotter the weather, the cooler your RV fridge needs to be, and the harder it is to do that. Maintaining a comfortable interior temperature together will ensure your summer camping doesn’t result in a serious food spoiling from a warm refrigerator.
This article addresses warm weather operation for both absorption and residential RV refrigerators. Major players in the RV fridge business are Dometic and Norcold. Each brand offers what is known as an absorption refrigerator. Simply put, both types of fridges move the heat from the refrigerated compartment to the outside of the compartment. Of course, each type of fridge does this in a different way. In any event, let’s call it the transfer of heat.
The residential fridge in your RV
Just like the beast sitting in your house, the RV residential fridge gets hot. That warmth is coming from the condenser on the back of the fridge. That heat broadcasts to your cat or dog who has snug up to the fridge to get that warmth. At the same time, in an RV, this means the heat from inside the fridge is nothing short of a warm front crashing into the RV living space.
Warm fronts often bring stormy weather. In this case, it is an awful trip, frustrated by food spoiling in a warm fridge. The first line of defense to keep your RV fridge cool is to remember the following: the cooler the RV, the cooler the inside the fridge will be. This is the first statement of the second law of thermodynamics: heat flows spontaneously from a hot to a cold object.
A closer look in and out
Let’s start with the residential and 12VDC fridge. On the back of the fridge, there is a condenser that gets hot for most 120VAC residential-type refrigerators. On some 12VDC refrigerators, it is simply the refrigerator steel housing that gets hot. This is how the heat is taken out of the fridge and put into the local environment.
Generally speaking, keeping the inside of the fridge cold depends on moving heat from one place to another. Think of it like this: if you are using a residential or 12VDC fridge, any heat from inside the fridge has to go somewhere. Because these don’t vent outside, the inside of the RV gets heated up. Again, the formula to keep your RV fridge cool is to also keep it cool inside your RV.
In practical terms, this is a cooling system, dependent on each part to do its thing. The fridge is spewing hot air out. The air conditioner (AC) runs to keep the RV cool. Lots of work going on to move heat! On a larger scale, how many times have you experienced campground power outages during the summer?
Many have and this is the reason. A lot of energy is required to move heat from object to object. Anyone who has boondocked (limited electricity/solar) with a residential refrigerator has found out just how uncomfortable it is in hot weather because the fridge has to work, and this work heats the inside of the RV. As the RV heats, the fridge warms inside.
Dometic or Norcold absorption refrigerators in your RV
Even though the same principles of thermodynamics apply to both an absorption refrigerator and a residential-type fridge, is there any benefit for one over the other? Starting with what we know so far, keep in mind, the cooler the back side of the fridge is, the easier it is to keep the inside cold.
The absorption fridge is run by heat. On the back side of the absorption fridge is a heat source that drives the entire process; the heat source can be either an electric heater or a propane flame. Though the absorption fridge vents outside the RV, making for a better living space, the heat source on an absorption fridge adds to the difficulty of transferring heat away from the fridge and into the environment:
- There is more heat that needs to be transferred for an absorption fridge to cool
- When the boiler stops working, the refrigeration process stops
If you have been deep diving into the RV life, wanting to know how to keep your RV fridge cool, you will definitely want to know the importance of keeping these absorption fridges level. If not, bad things could happen. Not only is leveling important, but also keeping the air moving inside the fridge and moving air over the coils outside in the compartment.
What is heat stagnation?
Heat stagnation is just what it sounds like: heat that just sits and makes it difficult to keep your RV fridge cool. The transfer of heat from the absorption fridge to the environment is not happening efficiently; this is generally not a problem with the residential fridge because the heat transfer is inside the RV. However, with the absorption fridge being outside the RV, two factors can result in heat stagnation. One is the wind around the RV; the second is the actual heat inside the cooling unit compartment.
Heat stagnation is due to the buildup of heat within the cooling unit compartment. As heat accumulates, this aggravates the transfer of heat. Now add the fact that the temperature is 98ºF outside, where the cooling unit compartment is getting hit by the sun. Based on the 2nd law of thermodynamics, your fridge will stop cooling and damage to the fridge may occur.
As the wind blows
While sitting outside and a cool breeze moves through, it is easy to think wind will help keep your RV fridge cool as it passes over the venting. Well, yes, to a point, and as long as all conditions are right. First, the wind has to be blowing in the right direction. So even if you are driving, the wind factor can be a nonfactor in cooling down the fridge.
Here is a great illustration of the physics behind this. Recently when flying, we were approaching the airport and went through rain clouds. Raindrops started collecting on the 737; for an engineer, this was just too cool! I was able to study fluid dynamics by seeing the streams of raindrops moving across the boundary layer of the aircraft moving at around 150 mph.
The window is recessed on the 737; on the indent where the window is, water was not moving! There was an eddy where the wind stagnated. This same stagnation occurs around your RV when either the wind is blowing at your campsite, or like the 737, when you are moving through the air and driving your RV down the road.
The perfect storm
Here you are driving along to your destination. The fridge is packed full and turned on, doing its thing. Unbeknownst to you, the perfect storm is brewing as a result of the effect of wind combined with heat stagnation.
Think about it. You pull up to your site, expecting you did everything to keep your RV fridge cool so you can enjoy a cool drink. But then you open the door to realize everything is still warm. After four hours, how can that be? Is it broken? Did I pack too much in at one time?
That is when the troubleshooting begins and you search online why the fridge will not cool. The common solution to heat stagnation is to use fans. But, wait a minute, I was driving down the road at 55 mph! Shouldn’t the fan fix work?
The imperfect solution
Back to the 737—the answer is no, fans cannot outpower mother nature. A prop-type airplane or helicopter may not be able to take off when it gets really hot, or at high altitude, or worse—both. Hot air is less dense than cool air; the prop on an airplane becomes less efficient as the air gets thinner. The same holds true for a small fan that you spent hours researching and installing.
You have the fan in there to get ahead of the potential problem, but as the heat increases, heat stagnation causes the fan to become either less efficient or not work at all. When the fan stops working, the absorption fridge boiler overheats. The result is either reduced cooling or no cooling at all. The fridge simply is useless at this point and should be turned off until the boiler overheating condition can be resolved.
The perfect solution that covers all the bases
Keeping your Dometic or Norcold absorption fridge cool in hot weather requires a two-pronged approach:
- Keep the boiler from overheating
- Run an efficient fan controller that only runs the fans when needed
The Fridge Defend will keep your RV fridge cool because it provides the perfect coverage and best solution. The Fridge Defend works with mother nature by turning off the heat when the heat is damaging your cooling unit and warming the inside of your fridge.
We are all happy to have a fridge in the RV. We expect it to work and mostly there are no issues. Yeah, it takes awhile to cool down. Yes, you need to pack it just right. Did I mention it takes awhile to cool down?
Now we know the true science behind these well-designed but limited appliances. Keeping any RV fridge cool in hot weather is a challenge, but simply remember, the cooler the environment that the fridge is used in, the cooler the inside the fridge will be.
For all refrigerators, the less one opens the door of the fridge, the better, so plan ahead and keep the fridge door shut as much as possible. Keep your AC thermostat at the sweet spot of around 78ºF. This is where energy efficiency and the temperature your fridge likes to operate at come together. If you are a fulltime RVer, remove your fridge every one to two years and clean the back side of the fridge. Lint buildup insulates the heat exchanger, which in turn results in low efficiency in hot weather.
Make sure your fridge ventilation is not obstructed. Look for anything blocking the ventilation. Use a protective and proactive automatic controller combined with a fan controller that is designed for RV use. The Fridge Defend is the only product that meets this long-felt need due to patented protection.