Absorption fridge tests and new safety device

[Gdetrailer]

I have been stating for YEARS that operating an absorption fridge off level of ANY AMOUNT affects the fridge in a bad way...

Well, I noticed on a different RV forum that there has been some testing of this theory.. AND it PROVES my assumption..

It detects unsafe temps of the boiler and can shut down the fridge BEFORE the Norcold safety device detects overheating.

I would highly recommend folks to READ the link below..

FRIDGE PROTECTION DEVICE

For those too lazy to look at the link here is some of the text from the opening post..

"I'll apologize in advance if this sounds like a sales pitch: it is not. It's a report of what I learned while participating in a field test of a new device designed to protect RV absorption refrigerators. In doing so, I became a lot smarter about how these fridges work, and came to respect the engineering that went into designing the ARP device. So onto the report...

RV fridges made in the last 20 years claim to be fairly tolerant of being off-level and generally are spec'ed to allow up to 3 degrees side-to-side and 6 degrees front to back. That's from the perspective of the fridge, which is normally sideways in the RV, so it's 3 degrees tilt fore & aft in the RV.

Recently, though, I've been helping Paul Unmac test his invention, a patented device called the ARP that will control the heater (boiler) in an RV absorption fridge in a much narrower range than the factory control board. Paul believes this will extend the life of an RV fridge as well as preventing fires in failed cooling units. One of the test beds is a skeleton Dometic 6 cubic foot fridge set in a portable frame that can be carried around (for demos) and tilted in any direction at will. With an ARP installed and its optional data collection package connected, we can watch how the boiler reacts when the cooling unit is tilted.

The results amazed me! Merely tipping the fridge a few degrees to one side (by sliding a board under one edge), the boiler temperature immediately soared! And I do mean soared - it climbed over 100 degrees F, in less than two minutes and showed no signs at all of stopping. We quickly re-leveled the cooling unit to avoid damage - Paul didn't want to risk the unit he is using for demonstrations at RV shows this fall and winter - and the temperature began to fall again nearly as quickly. I'm sorry I failed to get a picture of the display graph as the temperature climbed, but I was literally too amazed to click the shutter!

Why does the temperature climb? Basically because the ammonia refrigerent solution stops condensing back to a liquid and flowing back into the boiler at the end of the cycle. Without liquid in the boiler, the temperature shoots up quickly, guaranteeing that the cycle won't restart on its own becasue it is now too hot to ever cool sufficiently. It's a vicious cycle that quickly gets out of control after even a brief hiccup.

RV gurus have been telling folks that their fridge is OK if they can walk around comfortably, but now I'm not so sure. According to Paul's research, high boiler temperatures cause the internal rust inhibitor (sodium chromate) to crystallize and lose it rust preventive qualities. Loss of the sodium chromate increases allows the extremely corrosive ammonia to attack the steel tubing and eventually cause a leak. And a leak is both a failed cooling unit and a fire risk. The sodium chromate crystals (they yellow stuff you see in a failed cooling unit) is also the main ingredient in a clog that can block flow through the condensor and evaporator tubing. Without laboratory testing I can't guess how much sodium chromate is lost, how quickly, and how much temperature rise is needed to cause it, but I think there is sufficient cause for concern.

Another thing I have learned by having the ARP data collection package installed on my own coach is that the boiler temperature can swing widely while driving. Mine actually was getting about 25 degrees (F.) cooler while underway at interstate speeds, and that is enough to cause the temperature in the fridge to rise (which I have observed). I can also see the boiler temperature move quickly when I pull into a rest area, slow down in traffic, or stop at the campground office to check in. The changes are immediate and dramatic. Paul says that climbing a highway grade also causes wide swings, sometimes hundreds of degrees. I surmise that wind is blowing down from the roof vent while driving ay highway speeds and that cools the whole process off. I have since added insulation around my boiler area but haven't been out on the road to see if it helps stabilize the temperature.

Paul has also measured temperatures on fridges installed in slide-outs and found then running substantially hotter than non-slide fridges. Slide-mounted fridges have the upper vent in the side and do not provide as much air flow over the coils as roof-mounted vents. He recommends adding a good sized fan at the bottom of those fridges to improve cooling unit performance as well as extending its life.

As part of the testing I arranged for about 20 others RVers to install an ARP and give feedback. All are working fine and there have been no complaints of any kind, either problems with the ARP or impact on normal fridge operation. Since then Paul has been selling the ARP at RV shows and online via his website. I don't know sales numbers, but it's into the hundreds.

There is more information on the ARP controller and absorption fridge characteristics on Paul's web site, ARPrvSafe

I have no financial interest in this product but I did receive a free controller and data collection package in exchange for my help in testing it. "

[gkainz]

Ok, say one wanted to get the fridge as close to absolute level as possible. What part of the fridge are you going to trust?
The freezer shelf?
The fridge floor?
Somewhere on the back of the unit?

[Chris_Bryant]

Francesca Knowles wrote:

Chris Bryant wrote:
Pay me now or pay me later 🙂 If a 10 year lifespan is fine on a machine with no moving parts, fine. If you want it to last much longer (and not burn down in the mean time), it's an inexpensive device.
Cheap insurance, as it were.

The O.E. fridge in my much-used 1978 trailer has lasted thirty-five years. So far.

Yep- and there is no way in the world a new model will last that long. If you can convince Dometic and Norcold to go back to the heavier tubing and separate perc tube a new one might last like an old one.

Of course the cost would be way more than the ARP control.

[Francesca_Knowl]

Chris Bryant wrote:
Pay me now or pay me later 🙂 If a 10 year lifespan is fine on a machine with no moving parts, fine. If you want it to last much longer (and not burn down in the mean time), it's an inexpensive device.
Cheap insurance, as it were.

The O.E. fridge in my much-used 1978 trailer has lasted thirty-five years. So far.

[Chris_Bryant]

Pay me now or pay me later 🙂 If a 10 year lifespan is fine on a machine with no moving parts, fine. If you want it to last much longer (and not burn down in the mean time), it's an inexpensive device.
Cheap insurance, as it were.

[dougrainer]

You ALWAYS level the refer, NOT the RV.
The normal operating temp is in the 300 to 350 degree area. The TRIP for the 1200 Norcold Safety recall Thermocoupler is 700 degrees. I do NOT know the trip for the Dometic disc on the burner flue cover. Leveling has to do with FLOW and condensation of the Ammonia mixture. Out of level will cause a disruption of the flow of the Ammonia mixture. NOT because of increased heat from off level. I have no opinion of if the device is good or bad, if you want one, get one. Doug

[Francesca_Knowl]

Road Runners wrote:
I think this is an invention that is searching for a need. I am not convinced that this device is necessary. I am on my second fifth wheel. Our present unit has rolled over 100,000 miles on all sorts of roads. I level it the best I can where ever we are. It is not always exactly level. In all that time, I have never had a problem with the refrigerator.

:E

Never mind your actual proven experience, and that of thousands of other RVers who've used these fridges slightly off-level since The Dawn of Time!!!!

You need this latest-and-greatest.
If you don't buy it this very minute, don't blame us when your groceries spoil, your rig burns up, and your wife leaves you.
Taking the dog with her! 😉

[BobsYourUncle]

I don't level my TT, ever.

I level my fridge! LOL The rest of it doesn't matter much! :B

[Road_Runners]

I think this is an invention that is searching for a need. I am not convinced that this device is necessary. I am on my second fifth wheel. Our present unit has rolled over 100,000 miles on all sorts of roads. I level it the best I can where ever we are. It is not always exactly level. In all that time, I have never had a problem with the refrigerator.

[Old-Biscuit]

Francesca Knowles wrote:

Gdetrailer wrote:


Well, I noticed on a different RV forum that there has been some testing of this theory.. AND it PROVES my assumption..

"Testing of this theory"???? One guy does his own backyard testing, identifies a "problem", invents something to solve that "problem", and puts up a website to sell it.

I wouldn't call that "tested proof" of anything except that there'll always be a market for new gizmos. We'll see how it sells...

6 years of testing and patented (applied for in 2007......issued in 2011).

Works based on pressure/temp relationship.
As an old industrial boiler operator......he is right on.
Stop operation when in the 'safety' zone of 'out of bounds' pressure/temp BEFORE entering the 'damage' zone.
Simple design---------proven concept (since man started boiling water under pressure)

Good for him!
Sad comment on absorption fridge manufacturers

[pianotuna]

Hi,

I used two small carpenter's levels in the freezer set at 90 degrees from each other.

I'm pretty certain that I'll get one of these devices in the near future. If it is good enough for Chris Bryant, it is good enough for me.

popeyemth wrote:
How did you level the fridge-from the inside or the framework or...
PM me if you wish. I intend to level mine.
Thanks,Mike

[Francesca_Knowl]

Gdetrailer wrote:


Well, I noticed on a different RV forum that there has been some testing of this theory.. AND it PROVES my assumption..

"Testing of this theory"???? One guy does his own backyard testing, identifies a "problem", invents something to solve that "problem", and puts up a website to sell it.

I wouldn't call that "tested proof" of anything except that there'll always be a market for new gizmos. We'll see how it sells...

[popeyemth]

SWD wrote:

pianotuna wrote:
Hi SWD,

That is why I leveled my fridge--and then installed the bubble levels. But I agree, quality control and RV rarely belong in the same sentence.

I'm interested in acquiring one of the units. But I wonder if a simple "snap disk" thermostat would not work?

Did the same thing....leveled the fridge then put on the bubbles.

How did you level the fridge-from the inside or the framework or...
PM me if you wish. I intend to level mine.
Thanks,Mike

[Old-Biscuit]

Post from 12/8/2013 discussing off level operation (one on numerous posts).......LINK

Notable post by Chris Bryant on 1st page.

[SWD]

pianotuna wrote:
Hi SWD,

That is why I leveled my fridge--and then installed the bubble levels. But I agree, quality control and RV rarely belong in the same sentence.

I'm interested in acquiring one of the units. But I wonder if a simple "snap disk" thermostat would not work?

Did the same thing....leveled the fridge then put on the bubbles.

[Gdetrailer]

pianotuna wrote:
Hi SWD,

That is why I leveled my fridge--and then installed the bubble levels. But I agree, quality control and RV rarely belong in the same sentence.

I'm interested in acquiring one of the units. But I wonder if a simple "snap disk" thermostat would not work?

Snap disks placed in the correct place might in a pinch "work" but it would be trial and error not to mention snap discs come in a variety of on/off temps and may have too wide or even narrow hysteresis.

I suspect that their ARP is a bit more involved than a simple snap disc especially when it can be teamed up with some sort of optional data collection module..