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. "

[brincker]

I doubt it too, especially in their current legal situation. Any changes now would be tantamount to an admission that their designs were deficient to begin with.

I was merely lamenting that neither of the major RV fridge makers bothered to make an inexpensive and simple improvement that could have eliminated leveling concerns for RV owners. A lack of innovation that is sadly typical of RV appliance makers. RV builders buy their appliances for every RV made, regardless of quality, so they have no incentive to ever make improvements or spend money on R&D.

[moisheh]

Gary: You are using logic and I am afraid that Norcold is a company with no common sense and certainly no business sense. I doubt they will ever ad anything to the 1200.

Moisheh

[brincker]

I should clarify what I learned during the ARP field testing and the "long term damage" claim.

It became evident that the cooling unit functions perfectly fine until the tilt reaches a point where there is insufficient return flow to the boiler, and then the boiler temperature skyrockets past the point where temperature damage (crystallization of the sodium chromate) begins to occur. That degree of tilt is not something the RV owner can readily determine and it differs by fridge make/model and the direction of the tilt, so there is no useful "rule of thumb" except to keep it as level as possible. Most of us encounter some brief periods of off-level operation during travel, during rest or fuel stops, checking in at a campground office, etc. and each of these may trigger a high temperature episode. It's a classic "death of 1000 cuts", so some RV owners will never accumulate enough "cuts" to cause a total failure while others might reach the critical point fairly quickly.

So, those who say they don't have problem with off-level operation or high boiler temperatures may indeed be right. The concern is that none of us really know where we currently stand with respect to the damage threshold or how often we will add more high temperature events in the future. With an ARP doing both the monitoring and preventing an over-temperature condition, this source of potential future failure is eliminated. The value of that level of protection is something only you can decide.

The thing that bothers me the most is that the fridge makers could have easily and cheaply built in this level of boiler management and off-level protection. All the RV fridges made in the last 20+ years have circuit boards that could easily include the monitoring function and the temperature sensor for the boiler is only a few dollars in mass production quantities. The increment to the fridge selling price would be tiny, if any. If Norcold had built in ARP-like monitoring, they would not now be pouring millions of dollars into the 1200-series fire recall and compensation for victims of the failures. Dometic has had similar fridge issues, though not on the same scale that Norcold has had. It seems to me this was all preventable.

[Salvo]

I'm not convinced of long term damage with even modest off-level operation.

I see it as insurance and no concerns when MH is off-level. There have been a number of people that said their 30 year old fridge is still working fine. Is that the same argument as saying "I don't need seat belts, haven't gone through the windshield yet"? We all agree **** happens.

I'm presently boondocking in an arroyo on the beach in Baja. I got here late in the afternoon and didn't feel like leveling the MH at that time. With ARP I can stay off-level without worry.

Sal

brincker wrote:

There is solid science, backed with years of experimentation & testing, that shows that long term damage will accumulate with even modest off-level operation.

[brincker]

I'm the guy who wrote that piece on irv2.com and have been involved in testing of the device in real world use.

I don't know if everybody needs an ARP or not - I discussed that very point in a follow-up to the original message. Nobody says your fridge is going to roll over and die if you don't get one of these devices, just like your wiring isn't automatically going to burn up if you don't have a surge protector, or your engine isn't going to immediately blow up if you don't change the oil at 3000 miles. But we do know that a percentage of RV fridges fail prematurely, and that a percentage of those actually catch fire when failure occurs. Managing the boiler temperature to stay within the optimal range in all operating scenarios is intended to make sure your fridge has a long and happy life. And in doing so, it should also provide a safety shutdown in the event something goes seriously wrong.It's a better way of doing things.

There is solid science, backed with years of experimentation & testing, that shows that long term damage will accumulate with even modest off-level operation. You can learn more about that by reviewing the videos on Absorption Refrigeration on the healthyrvrefrigerator.com site.

I know Paul Unmack and his wife. Both are fully-qualified mechanical engineers, licensed and experienced in the design and building of industrial process control equipment and applications. This is definitely not a gadget invented by a backyard mechanic.

[Gjac]

Chris Bryant wrote:

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.

Does anyone know what year Norcold went to the thinner tubing? I camped with a guy with a 1973 class C Winnebago with no levelers, and looked at his tubing and it looked like a spiral wrap going over his tubing that was slightly thicker than mine. Mine is a 1996.

[gkainz]

My "what part of the fridge are you going to trust as 'level'" question was somewhat facetious, as I'm a "close enough" kind of guy. My class C fridge was 27 years old and still going strong when I sold it and bought the 5er. It was always leveled " close enough" with a bullseye on the floor of the fridge.

[Dutch_12078]

pnichols wrote:
What's really needed is the mounting of RV refrigerators on gimbal mechanisms just like the drink holders on boats. The refrig would always be level when camped, going down the road, and when parked along curbs in cities/towns.

It's a "no-brainer" to mount RV refrigerators this way accept for two gotchas ... it would take a tiny bit of genuine design work by RV manufacturers and a little more money on the buyers part.

Don't forget the third gotcha... More space would be needed for the fridge.

[Salvo]

Sounds good to me. I'll give it a try.

Sal

[Gdetrailer]

pianotuna wrote:
Hi Gdetrailer,

For a self propelled it makes more sense to have the levels visible from the driver's seat.

Yep.

Thats why I mentioned that mounting the levels outside on a Motor Home would NOT work too well.

The point being though is there is no excuse at all to not be able to level the fridge barring you are not parked on a mountain cliff (think Long, Long trailer movie).

But the main take away of my opening post is the mere fact that there HAS been a lot of research and development on just what does happen when the fridge is not level. The data they have collected really is important to anyone who owns a absorbtion fridge.

The ARP device has potential in reducing overheating of the boiler which should allow folks to GET 20 or more years of operation like the OLDER units USED to get.

The price of the device is PEANUTS compared to the cost to replace the CU or even the entire fridge.

An additional bonus feature... The ARP device turns off the fridge well before the 700 degree Norcold "safety" black box. The black box is for CATASTROPHIC FAILURE detection and too me at 700 degrees that IS well above the point of ignition of any combustible product like paneling.

I have no vested interest in the ARP, but I am reporting to folks on this forum that you might want to at least consider this device to help manage the life of your fridge and as a bonus perhaps reduce the chances of catastrophic failure which would lead to a fire...

[pnichols]

What's really needed is the mounting of RV refrigerators on gimbal mechanisms just like the drink holders on boats. The refrig would always be level when camped, going down the road, and when parked along curbs in cities/towns.

It's a "no-brainer" to mount RV refrigerators this way accept for two gotchas ... it would take a tiny bit of genuine design work by RV manufacturers and a little more money on the buyers part.

[pianotuna]

Hi Gdetrailer,

For a self propelled it makes more sense to have the levels visible from the driver's seat.

[Gdetrailer]

gkainz wrote:
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?

READ THE MANUAL.

Over the years some stated the fridge floor and some stated the shelving. It is BEST to find out from the SOURCE instead of depending on forum opinions.

It is easy to do, buy a simply ROUND BULLS EYE level.

Place bulls eye level where the fridge manufacturer states in the fridge.

Level your RV to that.

Then you place stick on levels on the OUTSIDE of the RV (although motor homes might not work well for this). Place on on the front and one on the side (this can be up near the front of the RV but on the side).

Make sure when placing the levels on the outside that you get them level.

Then you simply look at those outside levels when you are parking and setting up your RV.

To make it even easier there are some levels which also have markings in inches. This tells you how much you are out of level in inches., you simply then can add the amount of blocking in inches under the wheels.

I really don't understand why folks feel it is so hard to level..

Only takes a couple of minutes to do it right, its the first thing I do once the chocks are in place and the truck is disconnected from the trailer.

While my current TT has a home fridge conversion I can tell you this, the ARP would be a top mod in my book if I get another TT with a absorbtion fridge.

Even though I have a home fridge, leveling the TT is top priority. I do not like the tippy feel of a floor which is not level and to me worse yet is trying to sleep with my head down hill of the rest of my body...

[Chris_Bryant]

Generally, the condensor fins at the top on back- but on Norcold models, they are not level, rather have a specific pitch. On Dometic models they can either be level (the fins are level, the tubing in the fins is pitched) or pitched. Older Dometic models were sensitive to front to back (of refrigerator) because the evaporator was horizontal in the freezer. Modern units are not.

That's why the ARP is so neat- you really don't care about level, you care about the circulation of the ammonia refrigerant, which is what it monitors.