BUTTE, Mont. — RV refrigerator fires have been a perennial problem for RV owners for many years and an expensive issue for RV manufacturers, refrigerator makers and insurance companies.
One class action lawsuit against Norcold was settled via a payout of $36 million. Another active class action suit against Dometic is still winding its way through the courts. But, that complaint suggests that RV refrigerator fires have caused more than $100 million in property damage since 1997.
Paul Unmack, an engineer by trade, has developed a device that he says will end RV refrigerator fires, given that the cooling units are made properly. This is done by shutting off the devices when the cooling unit boiler temperatures exceed approximately 400 degrees Fahrenheit.
“RV absorption refrigerators are exceedingly reliable instruments when operated and manufactured correctly,” he told RV Daily Report.
He has produced a series of videos that describes how absorption refrigerators work. They can be seen found at the ARPRV website.
His solution is a simple device that monitors temperatures on the refrigerator’s boiler assembly and the flow of fluids through the device. Fluids are essential to making the refrigerator work. In a nutshell, here’s how the system works.
Ammonia is absorbed into water, which makes it the perfect refrigerant, he explained.
“Ammonia boils at -36 degrees Fahrenheit and is an environmentally safe refrigerant. Ammonia is natural in the environment, a byproduct of decomposition of organic materials that releases no greenhouse gases,” said Unmack.
The ammonia-water solution is extracted from a reservoir and pumped to a boiler. As the mixture boils, the endothermic process allows the ammonia gas to separate from the water. The gas travels up the tubes to a condenser while the water falls back to a reservoir.
Then, in an exothermic process, the condenser liquefies the pure ammonia. The pure ammonia enters the evaporator where the ammonia absorbs heat from within the refrigerator compartments, which in turn cools the compartments.
The refrigeration process is completed when the ammonia gas is once again absorbed back into the water in the absorber coils. The solution travels back to the reservoir where the refrigeration cycle continues until the desired cooling level is attained.
However, the system must remain level in order to function properly. Something as simple as a 6 percent grade can allow all fluids in the boiler to overheat in six minutes and begin damaging the refrigerator components, said Unmack.
That’s less time than it often takes to go up or down a mountain. In fact, Unmack has spoken to several RVers who have destroyed their refrigerators by keeping them on while traveling through the mountains.
Another common way to destroy an RV fridge is to get a flat tire or have the RV towed, the owner is not thinking of turning off the fridge while the RV is off-level, they are thinking of solving their immediate problems.
“It is also critically important that RV owners ensure their RVs are level at campsites,” he explained. “It is reported that refrigerators are the No. 2 fire claim to insurance companies each year. One RV repair center told me that only drive train and engine problems rank higher for repairs than refrigerators.”
Because refrigerator cooling units are self-contained, no water or gas can be added to the system after it has been built without specialized equipment. The refrigerators are designed to work continuously unless something interferes with the process.
The Unmack’s have absorption type refrigerators made in 1937 that work to this day without repairs or failures “This proves how reliable absorption refrigerators are if made correctly and the boiler is not allowed to overheat,” he explained.
The big problem develops when pipes burst under pressure. So, how does that happen?
Included in the ammonia and water mixture is a chemical called sodium chromate, which is used as a corrosion inhibitor. Without it, the ammonia constantly running through the system would attack the steel pipes in a refrigerator.
So, as long as the RV is level and the gas and water mixture can circulate as the system is designed, there won’t be a problem. But, if the RV is not level and the refrigerator is being used, it can cause the ammonia to pool in one area.
“It is critical that the ammonia return to the boiler as described, this is because the ammonia boiling is the only thing that regulates the boiler temperature,” he explained. “If the boiler temperature is not regulated, the rust inhibitor in the system is destroyed resulting in the break down of the steel causing pock marks of corrosion to develop in the pipes.”
Overtime, those pockets can develop into cracks and once a crack makes its way through the pipe, the gas can escape and explode, causing the refrigerator to catch fire. The system basically corrodes from the inside out and the area of greatest weakness is always at the point the steel is welded, said Unmack.
He compared the process to something that Boy Scouts often learn to do, which is boil eggs in paper cups. As long as there is water in the cup, fire will not consume it. But, when the water boils out and there is no fluid left to cool the paper, it disintegrates.
“When the system is level, the refrigerator holds a constant temperature while it is running,” he explained. “However, when it goes off level, the ammonia pools in the system to the point it can’t make its way back to the boiler. The exterior temperature begins to rise as does pressure in the pipes.”
Water expands 1,600 times as it changes from liquid to vapor – dramatically increasing pressure inside the system, he added. Unmack’s patented controller will prevent the water in the system from boiling which in turn preserves the sodium chromate rust inhibitor.
Unmack developed a device called the Absorption Refrigeration Protective (ARP) Controller that not only monitors the temperature of the boiler, but also monitors the flow of material through the system. When it detects the temperature exceeding levels required for the system to operate, it shuts down the refrigerator and allows the mixture to cool before automatically restarting in a set amount of time.
After five successive shutdowns, it turns the refrigerator off and warns the owner, who has to manually reset the controller.
“It is very rare for a fridge to overheat five times in a row,” he said. “The RV would have to park off-level for three to five hours for this to happen.”
Unmack demonstrated his solution at the Family Motor Coach Association convention last year in Madison, Wisconsin. He sold hundreds of units to RV owners who could appreciate the value of his solution once they understand how the problems can occur.
“The RV industry has not embraced our product because everyone knows that refrigerator issues are the No. 2 reason for having RVs repaired,” he explained. “Which option would RV dealers prefer? Installing a $135 part or replacing a $1,500 to $5,000 refrigerator?
“Dometic and Norcold should be knocking down our door to install these devices, rather than knocking us down by telling people our system is not necessary,” said Unmack.
After reading information about the Norcold recall, he discovered that the refrigerators are programmed to shut off at 800 degrees – well beyond the point any fluid is left in the system, he explained. Not only that, but once the system is shut off, it is permanent. The RV owner either has to reset the recall box or take the fridge to an RV tech and have the recall replaced.
“Our system will shut down at the first sign of a problem, then automatically restart five times. If the problem still exists, it will shut down and alert the owner who needs to manually reset the controller,” said Unmack. “By telling the owner there is a problem with the system, it also gives the owner an opportunity to better level the RV to ensure that the system works as designed.”
For more information on the Absorption Refrigeration Protective (ARP) Controller, visit www.arprv.com.