ARP versus Norcold Recall

This page uses Norcolds words to compare the Fridge Defend by ARP versus Norcold Recall and why Norcold leaks result in RV fridge fires that may have been prevented.

Hammer Head On this page the brown fonts are quoted from Norcold letter to us & Norcold NHTSA letter. The red fonts are quotes from Norcold patent application 13/279,361 menu item Norcold ARP Endorsement.

Table of Contents

The ARP Control is an Ounce of Prevention

What does the ARP Control do? When installed and maintained properly, the Fridge Defend by ARP Control helps prevent "catastrophic conditions" by not allowing the cooling unit boiler to experience "high temperatures" that permit the fluids in the system to overheat. These temperatures generally do not exceed 400F. If the fluids in the system are maintained at proper temperatures the result is limiting "stress, which in turn prevents personal and property damage" caused by a leak and the possibility of losses " due to fire and explosion when a system ruptures ".


"ARP Control solves problems with the refrigerator whereas the Norcold control solves a legal issue.

If these fridges were in airplanes, the FAA would prohibit them to fly without the ARP Control because the FAA mission is to continually strive to improve the safety and efficiency".

Quoted from Retired Rolls Royce Avionics Engineer - Indio, CA 2013


Norcold took the first step to try and solve the issues that resulted in cooling unit failures. The 2 steps that Norcold took attempted to address the issues that result in fire. We at Fridge Defend took the last step; we found the control parameter that protects the fluids within the cooling unit. Please click for ARPC LLC policies.

Read on to understand why you may need a ton of cure if the Fridge Defend by ARP is not on your fridge!
Please click here to see the science behind boiler temperature regulation.


Letter from Norcold

This image is of a letter from Norcold which describes the Norcold 1200 series recall kit function. Some potential customers and a few RV repair technicians have stated that there is not a difference between the Fridge Defend ARP and the Norcold Recall, even worse, it is the party line to state that boiler protection such as the Fridge Defend is not necessary! This is just not true; the proof is in the correspondence.

Following we will use the right use of reason backed by science to help RV owners understand the difference between the ARP Control and factory recalls and repairs. We will include Norcold's correspondence so that the facts are gleaned clearly.

Hot Norcold

What does Norcold say about their own control?

The Norcold letter above states this about the function of their recall kit:

"Norcolds Recall Kit 634737 does not and cannot address off-level tilting conditions. Norcold's Recall Kit 634737 functions only to address extremely limited, catastrophic conditions in which liquid is drained from the system (e.g. as a result of a leak). Heat input to the cooling unit is not adjusted until a sensed temperature of over 800°F. Such temperatures are only experienced at the location of the Norcold sensor if the cooling system experiences a leak."

Cause and Effect

Clearly one cause of an RV fridge failure is a leak. The effect of this type of failure is either the complete failure of your fridge, or possibly in the worst case fire and explosion when a system ruptures . Why go there? Would it not make more sense to address one of the known root causes of failure, such as the Fridge Defend by ARP already does? This will all be explained in the next sections.


Norcold NHTSA Letter

ARP Control -- A Proactive Controller & Norcold Problem Statement

Following is the relevant contents of a letter from Norcold sent to the NHTSA in the year of 2002, seen above. A discussion of the ARP Control with regard to the text will follow. References are used (R1, R2, R3,...) to relate the context of the NHTSA letter to the ARP Control function and solutions.

Norcold Recall Box

Norcold Letter: We have determined that a defect relating to motor vehicle safety exists in some specific gas absorption cooling units used on refrigerators supplied by Norcold to manufactures of RVs.

R1) As presently understood, nature of the defect (and subsequent recall) is low cycle fatigue failure in the section of the cooling unit which generated the refrigerant (commonly called the boiler).

R2) The potential safety problem is induced by elevated heat during operation in the AC electric mode. Also, click here to read Norcold has voluntarily recalled N841, N821, N641, N621 and 1082 gas/electric refrigerators .

R3) The consequences of this fatigue failure can lead to the liquid solution slowly leaking from the sealed pressurized cooling unit through a small crack which could occur from the thermal expansion created from the AC heater design. If a leak occurs the cooling performance of the refrigerator will deteriorate requiring a replacement of the cooling unit.

R4) If the refrigerator continues to be operated after the majority of solution has leaked and solution circulation has ceased, the heat source can generate very high temperatures.

R5) At that time, the steel material can soften and rupture. NOTE: See stress strain figure, failure starts to occur between points 2 & 3 on the curve.

R6) If the pressurizing gas is still in place when the rupture occurs, hydrogen gas may be expelled and can under extreme conditions, be ignited by the high temperatures thereby possibly causing a fire.

Norcold 1200 Failed
Fridge Boiler Soften Rupture
Stress-Strain

R7) Tests indicate that refrigerators will exhibit signs of unacceptable cooling performance prior to the unsafe condition arising. Field experience reflects that consumers have replaced the affected cooling unit under our standard warranty program before a safety problem actually arose.


The Fridge Defend by ARP Solves Problems & Keeps Your Fridge Running!

NHappy RV Fridge

R1) Clearly, at the time of the writing of this letter, an assumption was made, and in the course of time a program was implemented to resolve this described structural issue. But, 12 years later it is clear that the initial assumptions were only a small part of the big picture.

R2) Norcold does acknowledge the need for the Fridge Defend by ARP in this statement. "Elevated heat" is a major contributing factor that leads to excessive stress on the cooling unit boiler assembly. The ARP control limits the temperatures in the boiler when installed and maintained correctly.

R3) Clearly, the Norcold engineers understand that "thermal expansion" results in leaks in the cooling unit. "Thermal expansion" is limited by limiting the temperature of the boiler assembly.

R4) And here we see the proof that the Fridge Defend by ARP is needed. Anytime the "solution circulation has ceased", the boiler (generator) can and will produce very high temperatures. This is the crux of the matter, the Fridge Defend by ARP is designed to limit boiler temperatures and in turn the "soften and rupture" that leads to failure.

R5) At "800 degrees" combined with a typical pressure in a cooling unit being 350psi, this is dangerously close to the yield point of steel (See Stress-Strain figure above). What is the yield point? For a cooling unit the yield point is when the pressure inside the cooling unit is high enough to result in a failure of the steel vessel, this will occur sometime after point 2 on the above stress-strain curve.

R6) This is a well known fact now. It must be added that ammonia is flammable gas , so the hydrogen gas is not fully responsible.

R7) Clearly, operation of the cooling unit while the "solution circulation has ceased, the heat" does result in "very high temperatures" The Fridge Defend by ARP is proactive in prevention of operation of the cooling unit if the "solution circulation has ceased". The Fridge Defend is the best method to prevent unsafe conditions from arising in the first place. As a matter of fact, the essence of the Fridge Defend is to monitor the fluid flow at the boiler and turn off the heat source if the fluids stop flowing. Please click here to see video showing how this happens. Regarding the last sentence, "before a safety problem actually arose", hindsight brings this statement into question.

Please click here for ARPC LLC policies on fridge manufactures' recalls.