Air Circulation & Venting for Absorption Refrigeration

All propane refrigerators, whether they are the type in a recreational vehicle (RV) or the type made specifically for in home use, operate from the same process known as Absorption Refrigeration.

The theory of this process is simple, absorb the warm air from interior of the refrigeration box and replace it to the exterior thus making the interior cold. While the theory is simple, the process is a little more complex. To understand the process in simple terms we can explain it as follows; The heat of the flame boils the ammonia and water solution to turn it into a pure ammonia liquid state at the point of the condenser. During this process, the absorption system pumps the solution to the top of the unit. At this point the pure ammonia liquid flows via gravity downward through the freezer compartment and then the refrigerator compartment all the while absorbing the warmer air of the interior. Once it reaches the point of full saturation, the pure ammonia liquid now exits the insulated interior to the non-insulated exterior where it begins the mixing process with the water. At this point it dissipates the heat that it has absorbed through the absorber coils to the exterior air. See more information on the Absorption Refrigeration System.

At the point of the condenser and the area of the absorber coils, air circulation is critical for maximum performance and efficiency of the unit. If air circulation is limited in these areas, not only will short term performance suffer, but long term permanent damage may occur.

In order to allow for proper air circulation and allow the absorption unit to breathe, there are only a few rules to follow when designing the gas refrigerator space. In most cases, fans or special ducting is not needed. Allowing for ample clearance around the unit is usually enough to allow proper air circulation.

One of the most common questions we get asked is “What are the clearance minimums for a propane refrigerator?”  Although there is not one answer for this question due to the variety of environments and usage cycles for any given family, we can give best practice estimations of 8” above,  1” on the sides, and 1” on the back.

We realize that all kitchens spaces are not created equal. Below we will try to describe the most common kitchen arrangements and the best venting applications for each.

Absorption Refrigeration Venting Examples

Figure 1 – Best case
We describe this as best case since there are no structures (cabinets, shelves, sofits, etc…)  above  to obstruct the heat from rising out from the rear of the unit and also with at least one side being completely open, there is no need for further ventilation. Note – For hotter and more humid climates, an air intake at or near the floor level combined with an vent from the burner exhaust of the fridge to the outside may be added to aid in this climate type.

Figure 2 – Limited top vent
A limited air escape at the top rear of the unit must be addressed with a vent to allow the hot air to rise up and escape. Trapping the hot air behind the unit will cause poor performance and long term damage. There are a number of different ways to allow the air escape. Depending on construction of your space will determine which method is best for you.

One method is to place a vent through the wall at the rear of the unit to the outside or another well ventilated room (not a bedroom). This vent must be placed at least to the level of the top of the refrigerator or higher. A vent with the area equal to 8” x 24” is adequate.

Another method is to allow the hot air to pass behind the upper cabinet or through the upper cabinet and escape to the ceiling area above or attic space above. This can be accomplished by relocating the cabinet forward 6 inches from the rear wall to create a passage way. Cutting holes in the cabinet floor and cabinet ceiling will also accomplish a passage way. Installing a false back inside the cabinet in order to keep objects from covering the holes is a good idea.

Since most of the heat that the fridge produces, comes from the burner exhaust, direct venting the burner exhaust will further aid promoting air circulation.

Figure 3 – Boxed in. Worst case
The built-in type of construction is worst case scenario and is not recommended without proper ventilation. Some manufactures will void warranty for this type of install and no or limited venting. Rear floor vents and top exit vents as described above are both required in this case. A direct burner exhaust is also recommended.

We highly recommend “testing” the ventilation prior to using it long term. The testing process is simple. Operate the fridge in an open space near the final destination. Record the fridge and freezer interior temperatures as well as exterior ambient room temperatures for a period of a week at normal operating usage. Then install the fridge into the final space and proceed to measure the temperatures for the next week. Compare these temperatures to determine if the final destination space has adequate ventilation and air circulation. If interior temperatures stay the same and no thermostat adjustment is needed, then the final space is good. If not, then more air movement is needed.

Some owners have elected to use a small fan to circulate the air behind the gas refrigerator or freezer. These fans are available with DC/solar power sources.

More ventilation suggestions can be found on the EZ Freeze Refrigerator Manufacturer site.

Keep the absorption coils and fins clean from dirt and debris to allow for better heat transfer. Never set anything on top of the refrigerator the covers or partially covers the cooling fins, thereby restricting airflow through the fin area.

Venting the burner exhaust (flue pipe) directly outside or into the attic with similar plumbing as a water heater requires will rid the area of most of the heat the refrigerator produces. Metal type vent pipe from 1 ½” to 3” diameter works well. Hot water heater type venting is available at most hardware stores. Do not make a sealed connection between the fridge burner exhaust (flue pipe) and Vent Pipe connection. Simply hover the vent pipe over the flue pipe thus allowing for some cool air to draft in at this point in order to create a good flow and cool the exhausting air. Be sure to cap the vent at the exterior with a shield to prohibit air to back draft into the vent and blow out the burner flame.

The above are simply suggestions for proper air circulation. Other techniques may be used. Just remember that air circulation and venting are best practice for peak gas refrigerator performance as well as proper safety practices.