Escapees March/April 2016

RV Power

Shore Power

Main Control

(+)

(-)

Cabinet Temperature Sensor

the NO COLD error and indicates that the cooling system is not operating. If your refrigerator has error code storage capabilities, it is a good idea to know how to access the error codes before you need them. Consult your user manual for more information. My wife, Mao, and I also discuss error codes in the troubleshooting section of our Website www.ARPrv.com . Recalls and Safety Around the mid-1980s, RVers wanted larger refrigerators. Due to a number of factors (some beyond the scope of this article), safety issues arose and the manufacturers initiated recalls. These recall campaigns were to minimize risk to life and property, but the recalls did not protect the refriger- ation process itself. One of the initial campaigns recalled around 300,000 refrigerators. The ¿ x was a thermal switch that sensed the temperature in the cooling unit compartment outside the boiler housing. Another method to improve safety was the introduction of the controller that produced the NO CO error code. The NO CO error code is initiated if the main controller calls for cooling by turning on a heat source and re- frigeration does not occur. If the Main Controller

Fuses in control box and RV

shuts off and then the controller dis- plays the NO CO error code. Both of the aforesaid methods were not found responsive enough to fully prevent failure of the refrigerator, which could lead to safety issues. There is one last recall we will mention. This recall turns on a red LED light and turns off the refriger- ator if the boiler has reached around 800 degrees Fahrenheit. This recall has had a number of complaints and issues that are not addressed in this ar- ticle because of its extensive coverage on the World Wide Web. The greatest issue with all of the recalls is that they really do not control the refrigerator in the sense that they are not protecting the cooling unit, nor can the recalls restart the refrigerator even if possible to do so. This is one of the reasons that the ARP controller unit was developed. As discussed in the previous install- ments to this series, the absorption refrigerator has a boiler that maintains a constant temperature during normal operation. Therefore, it is very easy to protect the refrigeration process and, in turn, the overall safety of the

refrigerator. As a point of interest, the typical RV refrigerator boiler should never get much over 400 degrees Fahrenheit. When the boiler over- heats, the cooling unit quits producing refrigerant, as described in the ¿ rst article in this series. If the boiler over- heats, irreversible damage occurs to the internal components of the refrig- erator cooling unit. The ARP control limits the boiler temperature; thus it is a proactive safety device that auto- matically responds to conditions that can cause cooling unit failure leading to safety issues. Better yet, the ARP automatically restarts your refrigerator when the boiler cools. In conclusion, the refrigerator controls are responsible for keeping the temperature in the refrigerator constant. This task is performed by using a temperature sensor that is generally of the thermistor type. The refrigeration control is also respon- sible for safety by monitoring the LP gas À ame. Recent advances in control technologies further improve absorp- tion refrigeration protection (ARP) and safety by monitoring the cooling unit boiler temperature.

Paul and Mao Unmack are mechanical engineers. Paul ran an automotive repair busi- ness in Red Lodge, Montana, for 20 years before receiving his engineering degree. He has practiced nuclear, fire suppression and industrial process control systems design. Mao designed pressure vessels for ammonia plants in China for 12 years, then came to the U.S. to get a master’s of welding engineering. She designed biodiesel plants and worked for a government-funded research and development organization. Paul and Mao run the entire ARP control business while taking on engineering consulting gigs. www.arprv.com

temperature sensor inside the refrigerator does not sense a drop in temperature in around two hours, it may be conclud- ed that there is some kind of problem. When the NO CO error is issued, the refrigerator

www.escapees.com | March/April 2016 | ESCAPEES . 67