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RVing message boards => Tech Talk => Topic started by: Gary RV_Wizard on November 03, 2013, 09:17:47 AM

Title: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 03, 2013, 09:17:47 AM
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 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 1.5" 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!

We've been telling folks that their fridge is OK if they can walk around comfortable, 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.  Without extensive laboratory testing I can't say how much 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 causes 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.

There is more information on the ARP controller and absorption fridge characteristics on Paul's web site, https://sites.google.com/site/arprvsafer/ (https://sites.google.com/site/arprvsafer/)

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.
Title: Re: Fridge: How Level is "enough"?
Post by: carson on November 03, 2013, 11:13:06 AM
Interesting, Gary.  Now is the time for an entrepreneur to come along and devise a hydraulic leveling system:  4 ram type cylinders and a pumping system controlled by an electronic controller. Piece of cake except for the wallet.  Patent not applied for yet. ::) 8) ;)

Title: Re: Fridge: How Level is "enough"?
Post by: kjansen on November 03, 2013, 01:31:41 PM
Gary,
Could you post a picture of the insulation you added to you unit.  My 5er came with 2 computer type fans that are on a thermstat, but I have only heard them kick in 1 time.  Couldn't figure out what was running so I pulled the vents and found them.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on November 03, 2013, 01:53:54 PM
After owning Dometics in 5 motorhomes it surprised me how hot the Nocold got if we were slightly off level and while traveling which was one of several reasonsxwe repkaced it with our Samsung. I don't know if it brand or unit specific but your monitoring system will probably open a lot of eyes.


Has your friend come up with a price target yet?
Title: Re: Fridge: How Level is "enough"?
Post by: Kim (skyking4ar2) Bertram on November 03, 2013, 03:20:52 PM
I think the fact that you and Paul now have some empirical evidence about the effects of leveling an absorption fridge is very important.

If your conclusions hold up in further testing, it would be something many consumers should consider monitoring.

The loss of a motorhome (or someone's life) over something so easily monitored and controlled as leveling the fridge should become a thing of the past. Kudos for your work and for sharing your results!

Title: Re: Fridge: How Level is "enough"?
Post by: Mavarick on November 03, 2013, 05:57:19 PM
Wow, very interesting. Wonder if this would be news to say a Dometic engineer or if this is just calculated into the lifespan. With all the trouble they have had in the past with these fridges I cant image they wouldnt have already figured most of this out right? With most items tested to failure I would guess the prevention methods were not cost effective until the safety factor is brought into play. Glad you shared all this testing though, I for one will pay a little closer attention to when I use the fridge and how level it is.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 03, 2013, 07:16:25 PM
Both Dometic and Norcold let their fridges pretty much run wild. The Norcold 1200 safety shut-off doesn't activate until something like 800 F (normal run temp is around 360 F.).  They just tell you not to run off-level for very long and say it's your fault if you do.

Of course the fridge doesn't self-destruct immediately if it runs hot, but why let it get ultra hot at all?  Once the boiler is hot enough to boil the ammonia solution, it can't get any more efficient at cooling, so there is no need to let it do so.  And it's pretty simple to hold the temperature down by cycling the heater off/on as needed, and it wouldn't cost much to include that on the controller circuit board. .  Well, Paul now holds a patent on the device that does that, so maybe they lost out!
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 03, 2013, 07:20:05 PM
Quote
Has your friend come up with a price target yet?

The talk has been of a $120 MSRP when sold through a dealer, but he has been selling to test-bed users for $70.  He just sold some at the Good Sam Rally in Atlanta - I'll ask him what he charged there.
Title: Re: Fridge: How Level is "enough"?
Post by: rebelsun on November 03, 2013, 08:03:47 PM
I hadn't given it much thought until I read this thread.
But on our return trip from Ma. to Fl. in Sept. of this year, we were at a standstill on I-95 in N.C. for at least 1/2 hr., on a fairly steep hill, because of a major crash, involving a TT unit, and a passenger car.  The fire dept. had to cut the car apart with the jaws, to get the occupants out, and a medical chopper landed on the interstate to transport a patient to the hospital.
I guess we were lucky to not have the refrig. either stop working, or ignite the MH on fire, which in that traffic, would have caused a domino effect, with the other vehicles around us, and the FD wouldn't have been able to get to the fire, because of the previous crash, and the medical helicopter on the highway.

YIKES!

I'm seriously considering replacing the refrigerator with a standard, electric only, house type model, when the time comes.  I know the disadvantage, of that decision, such as not being able to run it on propane while traveling, but safety is my primary concern.  I wonder how high the refrigerator temp. went during that delay, as well as the bumper to bumper crawl up onto the GWB (George Washington Bridge), and back down on the NJ side, and all the other rush hr. traffic crawls we encountered around Boston, DC, southern Ct./NYC/NJ metro areas?????
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on November 04, 2013, 09:42:23 AM
Gary,

Intuitively it would seem that gas heat would be a greater problem than using electric. Is that the case or did you gather any comparative data? I know that I almost never run the fridge on  gas since I need the generator for AC in any csse.

Also, data on specific conditions would be useful. A one and a half inch block under one side of the fridge would be about six degrees on an average unit for example. That compares to about 18 inches front to back on a 30 ft Mh. That information combined with a curve on the rate of temperature change could make a bunch of laywers rich :-\ :-\

Regards,

Ernie

PS How old was the test refrigerator? It would seem easy to redesign the boiler (actually the cooling coil) to eliminate the problem.

Note: A 6% grade is about 21 degrees!
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 04, 2013, 07:22:13 PM
Quote
   
Quote
Has your friend come up with a price target yet?


The talk has been of a $120 MSRP when sold through a dealer, but he has been selling to test-bed users for $70.  He just sold some at the Good Sam Rally in Atlanta - I'll ask him what he charged there.

Paul says he is maintaining the $70 "introductory price" for now. The data collection USB cable & associated software is $40 extra, if desired. It's not needed to install or get the advantages of the ARP, but it's interesting to see what the fridge is really doing. The software is compatible with a Windows PC only.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 04, 2013, 07:24:53 PM
I don't know the age of the test fridge - never occurred to me to ask. It was a 6 cubic ft Dometic. There was no visible rust or any other sign of a long or hard life, though.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 04, 2013, 07:47:50 PM
Quote
PS How old was the test refrigerator? It would seem easy to redesign the boiler (actually the cooling coil) to eliminate the problem.

Indeed, one has to ask why neither Dometic nor Norcold have done anything to improve the design of RV fridges in all these many years. One would think that Norcold especially would be anxious to develop something they could call "new and improved", but they keep on selling the "same old fridge". Atwood, a newcomer to RV fridges, has at least made an attempt with the safer helium+ammonia RV fridge (the others use hydrogen+ammonia), but their product hasn't caught on with RV manufacturers yet.

I don't see how it's "easy to redesign", though. Ammonia is inherently corrosive, and the high temperatures and pressures involved pretty much dictate a steel container. And neither of those is a problem if the fridge is level and not moved around all the time - they last for 25+ years when installed in off-grid houses. Heck, Servel absorption fridges haven't been made since 1956 and some are still running in remote cabins!
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on November 05, 2013, 07:30:35 AM
I'm thinking that the heating problem is likely due to restricted circulation, or possibly bad burner design. Circulation restriction would probably be due to condensate getting trapped in the condenser when the tubing gets off level and the fluid has to try to run up hill.  An increase in the slope of the tubing should help avoid that problem although it would require more tubing $$$. I do recognize there is a balance required here to ensure flow under all operating conditions, but I doubt that is an insurmountable problem.

The boiler is even simpler to solve if it should be the probkem, unlikely in my opinion.

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: weewun on November 05, 2013, 07:44:54 AM
I have installed the ARP Protection device on my NorCold 1210 and my BIL's Dometic 1292 (not sure the # is correct) as part of Paul's Beta Testing.

For the dollars involved it is the cheapest insurance you can buy.  It, in no way, alters the manufacturer's design and build, thus should have no effect on Warranty  claims or manufacturer' liability.

Installing the ARP and collecting Data for Paul taught me a lot about the Frig.  I was pleasantly surprised about how powerful NorCold's internal Diagnostics are.

I was not able to track the temperature data on my way from NC to Naples, FL but the ARP did trip once during the trip indicating an overheat condition, I was very please that it did which proved to me that it works.

Paul's current Controller is head-and-shoulders above the one I have installed and is much more User-Friendly than the original, I may swap mine out.

I know this sounds like an advertisement for ARP but it has saved me the time and expense of installing a Res Frig as the people beside me last year lost their 2006 Tradition to a NorCold Fire and my DW was not comfortable with the NorCold, she is feeling better now.

I should add that if the ARP controller should fail it will not affect the normal operation of the Frig.
Title: Re: Fridge: How Level is "enough"?
Post by: Phil Hyde on November 05, 2013, 08:21:18 AM
Sounds like a great way to monitor a running fridge and keep it running reliably.  However, the evidence you collected suggests that simply turning off the fridge while moving is a good idea.
Title: Re: Fridge: How Level is "enough"?
Post by: vmax1 on November 05, 2013, 10:22:07 AM
Now I really want a residential fridge in my RV
Title: Re: Fridge: How Level is "enough"?
Post by: Phil Hyde on November 05, 2013, 10:37:08 AM
Now I really want a residential fridge in my RV

My main concern with that, aside from the installation, is that a residential fridge probably isn't designed to be moved around constantly.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on November 05, 2013, 10:55:07 AM
My main concern with that, aside from the installation, is that a residential fridge probably isn't designed to be moved around constantly.




Phil


I have not heard of any issues with the motion of an RV on a resodential model and several OEMs have been installing them for years. Air conditioners basically use tge same tyoe compresser system


And it certainly is obvious that gas absorbation shoukdn't be moved!
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on November 05, 2013, 10:57:11 AM
Indeed, one has to ask why neither Dometic nor Norcold have done anything to improve the design of RV fridges in all these many years. One would think that Norcold especially would be anxious to develop something they could call "new and improved", but they keep on selling the "same old fridge". Atwood, a newcomer to RV fridges, has at least made an attempt with the safer helium+ammonia RV fridge (the others use hydrogen+ammonia), but their product hasn't caught on with RV manufacturers yet.

I don't see how it's "easy to redesign", though. Ammonia is inherently corrosive, and the high temperatures and pressures involved pretty much dictate a steel container. And neither of those is a problem if the fridge is level and not moved around all the time - they last for 25+ years when installed in off-grid houses. Heck, Servel absorption fridges haven't been made since 1956 and some are still running in remote cabins!


For seventy bucks I'll bet Norcold or Dometic should be negotiating with Paul for rights to use his patent right now!
Title: Re: Fridge: How Level is "enough"?
Post by: Phil Hyde on November 05, 2013, 11:12:59 AM
Thanks Jeff. My only personal experience with motion damaging a fridge is with the "apartment" or "dorm" style fridges.  In my experience, they don't hold up very well over time when being moved around.  Of course that could be attributed to many things, like cheapness of construction.  In general, though, I don't expect a residential appliance is designed to constantly be moved around.  As stated, it's just a concern I have.

Given the state of the RV industry, where so often corners are cut left and right in the name of profit, I can't imagine that manufacturers really caring if the residential models hold up or not.  It's what people want, so they install it.  Maybe I'm just pessimistic.  :o

Title: Re: Fridge: How Level is "enough"?
Post by: Tom on November 05, 2013, 01:11:26 PM
I'd have no issue putting a residential refrigerator in our coach.

We have separate residential fridge and freezer in the galley on our boat that haven't been bothered by movement. When we bought the boat, Chris had me remove a standalone ice maker from the bridge, and replace it with a $49 small Magic Chef fridge for soft drinks. The fridge hasn't been turned off in 13 years, except when the boat has been hauled, and still works just fine.
Title: Re: Fridge: How Level is "enough"?
Post by: carson on November 05, 2013, 01:21:27 PM
It is the luck of the draw in many cases. Hopefully everyone gets lucky.

In my old Rv, sold in 2009, had an LP Norcold fridge which was 14 years old..not one hiccup.
Title: Re: Fridge: How Level is "enough"?
Post by: Lowell on November 05, 2013, 01:53:51 PM
Well this thread has me thinking.  I've always started our fridge the day before a trip and left it on when traveling.  Since we often have 6% grades in the first 2 hours, one of which is a 5-6 minute climb, I am thinking I may turn it off until we reach more level country.  Hopefuly, our food will stay cool for that long.
Title: Re: Fridge: How Level is "enough"?
Post by: Larry N. on November 05, 2013, 02:35:08 PM
My main concern with that, aside from the installation, is that a residential fridge probably isn't designed to be moved around constantly.

My 2007 Beaver has a Jenn Air that is original equipment, and it runs fine. Of course I don't do washboard roads, but...
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 05, 2013, 06:28:52 PM
Quote
For seventy bucks I'll bet Norcold or Dometic should be negotiating with Paul for rights to use his patent right now!

You would think so, but Paul says neither one has shown any interest. Just the opposite, in fact... I suspect "Not Invented Here" applies.  Of course, they don't seem to think they need to do anything like that either.

It would not be expensive at all to include the logic on the fridge control board - just need a reliable temperature sensor mounted on the boiler tube.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on November 05, 2013, 08:28:36 PM
You would think so, but Paul says neither one has shown any interest. Just the opposite, in fact... I suspect "Not Invented Here" applies.  Of course, they don't seem to think they need to do anything like that either.

It would not be expensive at all to include the logic on the fridge control board - just need a reliable temperature sensor mounted on the boiler tube.


Tell him to talk to their lawyers, not the engineers. They are the ones whi will be defending all the lawsuits. ???
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 06, 2013, 09:55:33 AM
It's the lawyers that are fending off any fruitful discussion. I can understand that - Norcold has to be really gunshy these days, so doesn't want to admit that any design improvement is possible. It might be construed as an admission.

I don't want to say much here - it could prejudice future negotiations.  I have agreed with Paul to hold some things confidential.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 06, 2013, 10:03:44 AM
Quote
Could you post a picture of the insulation you added to you unit.

Sure, but there isn't much to see. Basically we re-wrapped the boiler & tube with some 800 degree fiberglass pipe insulation I got at Grainger Supply, and covered the whole area with foil tape.  When the Norcold 1200 recall sensor module is installed, they have to cut that area open and typically some of the insulation is lost, either then or as time goes on. Some install techs do a better job than others in re-sealing that area.

We also added a sheet of aluminum flashing along one side where the wood frame that supports the fridge is adjacent to the boiler tube. Figured that the wood was vulnerable to fire if a leak happened in that area, so may as well give it a bit more protection. Not a big thing, but easy enough to do while working on the insulation. I just slipped the flashing into place and it is held against the side by the insulation.

The dangling wires are the leads to the ARP temperature sensor.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on November 06, 2013, 10:16:08 AM
Gary just seeing all that rusted metal reminds me why we have a Samsung. ::)
Title: Re: Fridge: How Level is "enough"?
Post by: wb6kwt on November 07, 2013, 08:13:18 AM
How difficult is the ARP to install?

Bob
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 07, 2013, 08:57:53 AM
Not difficult at all, but requires a level of comfort with 12v wiring. You have to find a 12v power source behind the fridge and tap into it, and also splice into the 12v supply to the fridge (so the ARP relay can turn it off). Details vary by fridge model and RV brand/model, so install instructions are a bit generic, at least for now. Paul is trying to gather tips and photos for various fridge models, but the differences among RV brands make detailed instructions impossible.

Basically you snap a temperature sensor on the boiler tube and connect its wires to the ARP controller. You have to find a convenient place to mount the little ARP controller/display, either inside the RV or in the rear fridge access. Then mount a relay in the rear access area and wire that to the controller and the fridge power circuit.

There are some photos and tips on the ARP web site.
https://sites.google.com/site/arprvsafer/home
Title: Re: Fridge: How Level is "enough"?
Post by: Jim Godward on November 07, 2013, 12:00:14 PM
How difficult is the ARP to install?

Bob,

You should have no problem if you are comfortable with wiring etc.  From your call sign, I suspect you will consider the install rather trivial.    :)
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 18, 2013, 03:43:35 PM
Quote
Gary just seeing all that rusted metal reminds me why we have a Samsung.

Well, having had a 5.5 year old Samsung fridge go belly up in our stick house, I am not as sanguine as you are.

Besides, cooling units pit from the inside out due to internal corrosion. Surface rust doesn't much concern me. This fridge is 10 years old and the rust is superficial. I'm confident that it will see another 10 years if external rust is the only factor.
Title: Re: Fridge: How Level is "enough"?
Post by: yoda2405 on November 27, 2013, 09:19:08 AM
Gary,
I had been considering a fire suppressor add on and ran across this thread. Based on your recommendation and the information from their web site, I ordered a unit and expect delivery in a few days. This seems a better alternative than putting out a fire, but preventing a fire. Will post back my impression/results when I receive the unit and install it.
I plan on placing the controller/readout on the interior wall so I can see what is going on with the Norcols 1210.

Thanks for the information,
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on November 27, 2013, 10:21:08 AM
The ARP should extend the usable life of the fridge as well as preventing fires. There may be other causes of cooling unit failures than boiler over-temp, but managing the temperature better has got to help.
Title: Re: Fridge: How Level is "enough"?
Post by: Wagonmaster2 on November 30, 2013, 10:12:37 PM
On my Nocold 1200 it usually will keep the inside temperature in the 34-38 degree range if ambient temps aren't above 85 degrees or so.   I have one of the little flat 12V fans mounted in the outside frig compartment but even with that last July coming across I-70 in Kansas outside temps were approaching 105 degrees and the inside frig temps were above 45 degrees.

Has anyone ever tried removing the outside access frig door while traveling to get more air circulation or is there some reason this shouldn't be done?  I know it definitely helps in high temperatures to place a 6" 120V fan in the outside compartment also while in a campground, and that's even when I can hear the fans mounted in the vent tube running.

The ARP unit really sounds great but with so little room in that outside compartment I'm not sure I'd have the ability to hook it up there.   It was really tight in there re-wiring the Norcold recall box after the RV dealer's tech screwed it up so bad the box was making a clicking noise all the time and my fans in the vent tube weren't running.  (A fellow RVer e-mailed me his wiring instructions since I didn't think to ask for mine at installation time.)
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 01, 2013, 07:45:29 AM
Not to cast aspersions, but the device appears to be the same thing NoCold provides with a simple difference; it triggers at a lower temperature and resets after a delay. The difference is a couple of dollars worth of components!

I can readily understand why NoCold decided on their version. Imagine the liability if, after detecting a fault, you reset and the next fault causes a fire! :( :( :(

Hopefully, I'm missing something, but somehow I don't think so.

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 01, 2013, 08:56:24 AM
I suggest you go to the site that Gary referenced and read all of the information available there to see why the ARP is very different from the NorCold and Dometic one shot "fixes".  There really is no comparison.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 01, 2013, 09:54:21 AM
Ned,

Sorry but it appears to be a simple bang bang controller. I can't get his slide show to work correctly, but it basically says " if temperature exceeds nnn degrees, turn off the heat!". His extensive explanation is interesting,  but adds nothing to the facts. I'll conceed he may turn it back on at a lower temperature rather than use a timer, but the timer would accomplish the same thing!

I don't doubt it may extend the life of the unit and may well be worthwhile on that basis. Otherwise, it does the same thing as the existing device, but at lower temperature and without shutting off the heat source permantlyl

What do you think I'm missing?

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 01, 2013, 11:01:25 AM
The long explanation is much more than we can get into here as it involves a thorough understanding of how an absorption refrigerator works and some fairly heavy physics and thermodynamics, but if it were that simple don't you think NorCold would have done it that way?
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 01, 2013, 11:20:04 AM
I don't think you are missing much of anything, Ernie. The basics are as you say - turn off the heat if it ever begins to exceed what is necessary to boil the ammonia solution, and turn it back on again when it is safe to do so.  The algorithm to figure out when to shut off and when it is safe to turn it back on is more complicated than a simple thermostat, and each make and model of fridge has different temperature parameters, but the net effect is still just off and then on again.

The operational concept, however, is totally different. The Norcold recall device is a simple fail-safe, intended to catch catastrophic failures after the 12xx's standard management controls have failed. Norcold's standard control is to run the boiler flat-out as long as the fridge interior has not reached the desired temperature. The ARP acts like a governor, limiting the boiler operation to the heat range necessary to drive the absorption process. Once the boiler reaches the temperature to  make ammonia gas from liquid, there is no possible benefit from making it any hotter, and a couple major drawbacks from allowing it to get hotter. ARP adds the management needed to keep the boiler in that optimum range, whereas Norcold (and Dometic too) simply allow the boiler to run amok.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 02, 2013, 10:02:32 AM
Thank you Gary. I wasn't trying to cast aspersions, just make an observation.

I do understand how these refrigerators work. I've written software to permit use of a bang bang controller on large steam heated platens; a considerably more difficult task, but one that is quite analegeous. It occurs to me that he could have implemented a similar PID control to some advantage here in that different refrigerators will have different thermal inertia (although probably not much) and therefore require different delays in removing and reapplying heat. That would permit running closer to the optimum temperature. He could also have incorporated tilt sensors. Either or both of these, particularly PID control, could prove beneficial. But I didn't see any suggestion that he has done either one.

I'm sorry, but he simply doesn't have the data to do any more than I've described! All of the slides and diagrams have absolutely  nothing to do with with the "HOW" except to perhaps explain how he picked the temperature something I could determine from any physics book in a few minutes.

As to the appropriateness of this venue for the discussion, you guys get to determine that, but I do think it's the right place for it and that many here will benefit from the discussion.

My Last 2c Worth on the Subject,

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 02, 2013, 10:39:00 AM
Quote
different refrigerators will have different thermal inertia (although probably not much) and therefore require different delays in removing and reapplying heat.

The ARP is tailored to each refrigerator at installation time using a procedure called auto-tune.  That let the ARP determine the normal steady state operation of the refrigerator and program the ARP for that particular unit.  It's much more complicated than just a simple temperature sensed off switch, as we've stated before.

I'll have a review of the Amish cooling unit, along with the ARP, in a few days when we get done with the installation and testing.  Paul is doing considerable data collection on the cooling unit as this is the first one he's had an opportunity to work with.  So far, the performance of the cooling unit is exceptional.
Title: Re: Fridge: How Level is "enough"?
Post by: yoda2405 on December 02, 2013, 11:58:33 AM
To those that have installed the ARP on a norcold 1210 or similiar unit:
I received my ARP and am getting ready for the install. Looking through the small access that Winnebago provides, it appears the fiberglass wrap around the burner/heat assembly is solid, no obvious way to unwrap. Do I slit this with a razor knife then use the metal ac tape to tape the slit back together? Trying to determine the best way to gain acccess to the boiler tube. The insulation seems to be solid fibergalss with an aluminized exterior layer on the wrap. It seems pretty rigid not spun like the illustrations shown for the 1200.
My concern is sealing it back after slicing through it. I suppose I could add an additional layer across the slit to seal it.
Any thoughts or suggestions?

David
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 02, 2013, 07:18:24 PM
Yes, easiest method is to slit it with a razor knife. Then tape it back together with the foil-back duct tape (not the cloth type).  If you damage or lose some of the insulation, it can be replaced with high temperature insulation, available at places such as Grainger Supply.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 02, 2013, 07:41:03 PM
Dave,

Paul asked me to post this link for you to aid you in your RTD installation.

https://sites.google.com/site/arprvsafer/-10-norcold-1200-series-rtd-install
Title: Re: Fridge: How Level is "enough"?
Post by: yoda2405 on December 03, 2013, 08:15:51 PM
Thanks for the replys. I had looked at the directions, I just don't see a picture that looks exactly like mine and was concerned about cutting into the insulation, but I figured that was what was going to be required.
Probably will not tackle until I travel to Beaumont as the weather here is turning wet and cold, so not too conducive to working outside.

Safe Travels,
David
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 04, 2013, 09:33:56 AM
Ned asked "why don't the companies use this method?" or words to that effect. It caused me to rethink a statement that I made to the effect that "they both do the same thing,  just at different temperatures". After some reflection, I suspect that I was wrong and I decided to reenter the discussion because there may well be a SAFETY reason. My reasonig:

A. The manufacturer is atempting to identify an overtemp condition due to the boiler running away due to the loss of fluid. This would identify a leaking system and FIRE HAZARD.

B. The new device simply regulates the operating temperature. This may well extend the life of the refrigerator, but it may also defeat the SAFETY feature of the manufacturers device.

A system that may last longer, but will then fail catastrophically is not progress. I honestly hope I'm wrong here, but nothing I've seen addresses this question. Thoughts Gary?

Ernie

PS Ned, the only tuning possible is the PID function I described above, so perhaps he did incorporate it. This is standard throughout industry for control of characteristics that have inertia.

PPS I considered posting this as a seperate subject, but decided that would be inappropriate if he has actually addressed the above case and found a solution (I don't see one myself).
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 04, 2013, 09:43:26 AM
The failures usually occur because the boiler has been allowed to get extremely hot, and over time it fails.  The ARP prevents those overheating conditions and prolongs the life of the system.  The overheating typically is caused by out of level operating conditions, and from Gary's experience, it doesn't take much to allow the temperature to climb quite high.  Not high enough to trip the manufacturer's catastrophic shutoff, but enough to cause cumulative damage to the system.

The ARP doesn't use a snap switch sensor but an RTD (thermistor) that reads the actual temperature of the boiler.  I don't know what PID you're referring to but the ARP does not use any of the cooling unit circuitry for its operation.  I doubt that the cooling unit controller even puts out any PID codes.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 04, 2013, 10:19:57 AM
Actually, I have figured out how he could possibly have avoided catastrophic failure, but your response does not give me confidence that he has.

PID does not require anything other than data on how fast the system responds to an input. In this case, how fast the boiler raises the temperature of the unit. It then uses that data to shut off the heat early so that temperature does not overshoot.

It would be theoretically simple for an intelligent system to avoid catastrophe as follows:

A. On activation,  determine the slope and record. This value would never update after that time. Itis also a "sloppy" value since the slope will be different for electric than gas.
B. Watch for an extremely high slope indicating a dry boiler and shut off completely if it should happen. This will be much more difficult in practice than theory, but might be possible.

I have acknowledged that the new device may extend the life of the system and may alleviate ONE potential cause of failure. It does not address the other potential causes of failure and it is ASSURED that the unit will eventually fail. I am not at all certain that it will outlast the motor home.

We all make choices like this one often, but I strongly believe we are entitled to know we are! Incidentally, there are 10's of thousands of refrigerators in service and a few hundreds of the older ones fail each year. Six years experience on a few units is not sufficient to even demonstrate actual improvement in reliability!

Ernie

PS  My comments are not a personal attack on anyone, including the originator of the device, although they may reasonably be construed as being critical questioning.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 04, 2013, 10:27:23 AM
A PID (Parameter ID) is a string of data output from a device, usually a computer controller, that contains the value of a particular measurement.  I don't understand your use in this context, as no PIDs are involved in the operation of a cooling unit.

I suggest that if you want to pursue this further you contact Paul directly and discuss it with him.  He is more than willing to go into whatever level of detail you desire to explain exactly what the ARP controller does.  His email address is on the web site that we referred you to earlier.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 04, 2013, 10:33:35 AM
Quote
B. The new device simply regulates the operating temperature. This may well extend the life of the refrigerator, but it may also defeat the SAFETY feature of the manufacturers device.

A system that may last longer, but will then fail catastrophically is not progress. I honestly hope I'm wrong here, but nothing I've seen addresses this question. Thoughts Gary?

I can't imagine what you are alluding to, Ernie. Nothing in the ARP in any way interferes with the fridge's own safety mechanisms. Whatever the fridge's own controller does, it still does it.  And if it has a catastrophic temperature sensor, ala the Norcold recall box, that should be left in place and it still functions if the boiler ever got hot enough to trip it. The boiler shouldn't ever get that hot because the ARP will shut off the heat source long before the catastrophic temperature is reached, but the fail-safe is still there if needed. If, for example, the ARP failed to measure the heat properly, the safety sensor still works.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 04, 2013, 11:03:07 AM
I understand that Gary, but I fear the efect is that the temperature will never be permitted to exceed the regulated temperature and therefore the gas gets turned off and then back on when the temp drops. Remember this device is in series with the manufacturers device, the cycle might repeat until ignition. It is an avoidable problem as I described or by inhibiting operation if it heats too soon and probably other means, but nothing I've seen says it is.

That is to say the EMERGENCY cut off never gets to function.

Ned, PID is exactly what I described. If he incorporated it, the output of the device is effectively the output of a PID controller.
          This discussion is here and people are buying the device based on recommendations made here. I have no interest in disputes with the manufacturer, just in making sure all sides of the issue are discussed.

Ernie


Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 04, 2013, 11:16:04 AM
Quote
I have acknowledged that the new device may extend the life of the system and may alleviate ONE potential cause of failure. It does not address the other potential causes of failure and it is ASSURED that the unit will eventually fail. I am not at all certain that it will outlast the motor home.

 ;D    I'm chuckling, because Paul and I had a vigorous debate on this very issue just a couple weeks ago, with me as the devil's advocate. There simply isn't enough reliable evidence to know ALL the possible causes of fridge failures, but we do know that boiler temperatures can get excessive even though the RV is operated within normal parameters. We also know that elevated temperatures cause a loss of sodium chromate, and that reduction of the sodium chromate definitely leads to internal corrosion of the cooling unit and ultimate failure. What nobody seems to know is whether other potential causes may also exist, e.g. defective welds, impurities in the coolant cocktail, insufficient sodium chromate from the factory, too thin a metal in the tubing, poor installation practices at RV builders, etc. Many of these things could easily result from poor quality control at the fridge manufacturer (or after market cooling unit manufacturer), and some could result from poor design decisions.  What seems probable, though, is that many of these unknowns would still either result in a boiler overheat condition or be exacerbated by higher boiler temperatures. My conclusion is that an ARP would still be available addition to a fridge for most of those possible "other causes". Whether it catches most of them or just some of them is a matter of conjecture, but I see no downside to installing a device just because it may not solve 100% of the possible problems.

My bet is that an ARP will catch a substantial portion of the conditions, regardless of the root cause. At the very least it should extend operational life, even if flaws exists, and at the worst case it will prevent a catastrophic failure well before the built-in safety measures. That seems like a valuable tool to me.


By the way, Paul's wife (Mao Unmak) is also an engineer and her specialty is the design and control of pressure vessels, of which an absorption cooling unit is a prime example. She is an expert in high temperature and high pressure containment systems, so Paul has her expertise to draw on as well.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 04, 2013, 11:17:57 AM
Whatever your motives are, to dispute or just understand, I still say you should contact Paul directly rather than rely on our second hand knowledge of the ARP unit specifics if you truly want to know more.

As this discussion seems to be going nowhere, I'm done here.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 04, 2013, 11:36:51 AM
Quote
I understand that Gary, but I fear the efect is that the temperature will never be permitted to exceed the regulated temperature and therefore the gas gets turned off and then back on when the temp drops. Remember this device is in series with the manufacturers device, the cycle might repeat until ignition.

By "ignition" do you mean it catches fire? How is that going to happen if the heat source if always cut off (whether gas or electric) before temperatures get excessive?

In any case, the ARP has a progressive restart algorithm that extends the cool-down and restart period in each repeat cycle and will lock-out any further restarts after 5 repeats. It won't just keep restarting over and over again. The ARP is more than just a simple boiler thermostat that switches off and on again.
Title: Re: Fridge: How Level is "enough"?
Post by: weewun on December 04, 2013, 05:24:49 PM
For what it is worth I installed the ARP and elected not to control the Frig operation via NorCold's overheat circuitry.  I do not wish to argue with NorCold that my addition of the ARP Control affected their normal operation thus negating their culpability in case of a "fire".

I wired the ARP to control the input 12vdc to the NorCold and it is doing all I understood it would do.  If it fixes one deficiency of the NorCold that is a deficiency I don't have to worry about.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 04, 2013, 08:07:18 PM
Gary,

I meant the motor home catching fire from the repeated gas ignition.  As long as the new device is operative, the manufacturers device is prevented fron working! The progressive restart is the answer to my comments/concerns.  We can argue whether five restarts is the right number, but now everyone is on the same page.

As to pressure vessel experts, I've designed  three unique steam autoclaves, all of which are still in use after at least 20 years in service. The largest is 12 feet in diameter. My concerns were primarily vibration effects and I suspect that is one of the primary reasons for refrigerator failure.

PID =proportional-integrative-derivative,  usually applied in a controller.

Ernie

PS I'd like to believe he has introduced a leak and found that the five restarts is not sufficient time for a dangerous condition to develop (at least three times).

I'll leave it alone now.


Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 04, 2013, 10:18:07 PM
Maybe you should start engineering your own control, Ernie. Seems as though you have a handle on what needs to be done and the skills to do it. Opportunity is knocking at your door!
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 05, 2013, 07:13:27 AM
Gary,

Thanks! I guess! But I don't see a solution that seems practical to me, including the one under discussion. One of my issues is the liability that exists the first time a fire results when a device is in place that defeats the refrigerator manufacturers SAFETY feature. Regardless of merit, you'd lose in court every time. I hope he has lots of liability insurance in place. Incidentally, in your place I'd be thinking about liability as well.

The sole viable approach I see, given the above, is to use a tilt sensor. There are a number of problems with that, but at least it avoids the liability issue since it would be functionally in parallel rather than series.

Ernie

Incidentally, I lay awake several hours last night debating whether a stronger warning was in order and had decided to leave it alone.

Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 05, 2013, 07:58:29 AM
It's been a good discussion. Brought up points that are well worth consideration.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 05, 2013, 08:14:07 AM
For anyone following along, the ARP does NOT change the operation of the refrigerator, nor does it defeat any safety features put in by the manufacturer.  If the ARP unit fails, or you just disconnect its power, the refrigerator will perform exactly as it did without the ARP controller, including shutting down with the manufacturer's safety feature when it gets hot enough to catch on fire.  The ARP controller is designed to prevent that catastrophic condition from occurring.  It replaces nothing, it's an additional safety device.

For those that are truly interested in learning the hows and whys of the ARP controller, go to the ARP web site (http://whatis.arprv.com) and study the detailed information found there.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 05, 2013, 08:32:39 AM
As long as the device is performing its avowed purpose (preventing high temperature excursions) it does have to prevent  the safety device from operating! It is a temperature regulator and the safety device triggers on occurrence of a higher temperature than it regulates to.

Please feel free to suggest the designer review this thread and respond! At this point, it doesn't matter to me; I'm not installing one of his devices.

Ernie
,
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 05, 2013, 09:34:01 PM
Quote
As long as the device is performing its avowed purpose (preventing high temperature excursions) it does have to prevent  the safety device from operating! It is a temperature regulator and the safety device triggers on occurrence of a higher temperature than it regulates to.

I'm struggling with the notion that preventing an unsafe condition from occurring is somehow defeating a safety device. Just because the safety device never sees the condition that would trigger it, how is it not operational?  Using that logic, the thermostat in a water heater prevents the P-T safety valve from operating too. Is that a bad thing?   I don't see any merit in your argument, so I'm not about to help you carry it forward. If you want to debate the point with Paul Unmack, you will have to do it without assistance from me. Contact him at [email protected]
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 06, 2013, 08:40:35 AM
Gary,

Two last comments/clarifications:

When I said "I'm not installing one!", I was simply stating a fact. I certainly see your side and believe it's an individual call.

I'd like to say that I appreciate your civility and the rational nature of your responses; I hope I stayed within the lines as well. I was not seeking further discussion with anyone in my last post.

Regards,

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: moisheh on December 08, 2013, 09:31:38 AM
Unlike some of the posters I am just a layperson with one of the infamous fridges. I like the idea of that device but I see another problem. According to David Force(Amish Cooling Unit) and others one of the problems with the 1200 series is that the cooling unit is undersized. When it is warm outside the fridge runs full  time. If this is true wouldn't the ARP be shutting down the fridge and you would lose cooling ability? So the device might prevent a catastrophe but your food will be warm. Or am I misunderstanding and the device just prevents overheating and the boiler will still be hot enough to function? BTW: I am of the opinion that Norcold ( Thetford) will end up in bankruptcy. The pending lawsuits will likely cause them to lose the ability to obtain liability insurance. Even their toilets have become problematic. I cannot  understand why they have not redesigned that fridge. It is a cash cow  with a huge price. Why would anyone mfr. a fridge that not only does not cool well but the door gasket can only be bought by getting the whole door at about $500. Ridiculous. The recall device is also problematic. If it gets wet it shuts the fridge off!

Moisheh
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 08, 2013, 11:11:17 AM
Do a Google search on norcold door gasket and you'll find sources for replacements.  No need to replace the whole door.
Title: Re: Fridge: How Level is "enough"?
Post by: moisheh on December 08, 2013, 03:10:04 PM
Hi Ned:  A search brings up many posts with people complaining about having to buy most of the door to get the gasket. There is NO GASKET listed for the fridge. Here is a link to the part with the price[urlhttp://www.amazon.com/Norcold-627992-Lower-Right-Assembly/dp/B008KWOEH0][/url].  If both gaskets on the lower doors are gone it is getting close to $1000 !!! If that gasket is available on it's own please give us the part #. Many RV'rs would love to buy one! Thanks

Moisheh
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 08, 2013, 03:17:39 PM
Did you search using your refrigerator model number?  And use Google, don't just search on Amazon.
Title: Re: Fridge: How Level is "enough"?
Post by: moisheh on December 08, 2013, 06:44:54 PM
If you read my last post I stated that it turned up a bunch of complaints about not being able to buy just the door gasket. Yes I did do a Google with model# !! I downloaded the parts manual for my 1200 and it too showed only a door liner assembly. This has been discussed ad nauseum on many RV forums. No one has ever posted a positive reply nor a link or part # for the door gasket. Amazon was just one of many sites that sell the part. I did find it for a few dollars cheaper but it was plus freight. Still just south of $1000. I did not even bother to price the freezer gaskets. I do remember seeing a post somewhere you can you use a heat gun or hair dryer to try and rescue the gasket ( seal). I should also mention that Norcold's customer service is also horrible. It really does not exist. They will just refer you to a dealer. They now have that same philosophy for their Thetford division. When Thetford was independent they would send you parts. Once they even sent me a new toilet for a 5 year old MH as they did not have the parts! The manner in which the recall is performed is strange. The dealers have to submit all the data on your fridge and RV. Then they send a recall box to the dealer. Why not just send every dealer a bunch of recall boxes and ask for the data when the work is performed? If your recall box fails ( common occurrence) the dealer has to resend all the data and you have to wait for the box. Norcold is more interested in CYA than serving the customer. I hate to see a family business go down but they are doing nothing to prevent the inevitable. Did you do a Google with a refrigerator model # ( 1200 xxxx)? What were your results? Did you look online at the parts manual and the parts diagram? Did I miss something?

Moisheh
Title: Re: Fridge: How Level is "enough"?
Post by: Snowman9000 on December 09, 2013, 07:36:03 AM
One thing I take away from the discussion is that the answer to the post's title question is that you want to be very close to level.  I read the early posts and linked info a few weeks ago, and maybe this was covered:  If a fridge is fitted with the ARP, anyone care to guess what the answer to the title question is then?  ie How much out of level tolerance does the device give us?  Thanks!
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 09, 2013, 07:43:49 AM
That gasket will be a very expensive molding and you are unlikely to find it. I do expect that you can find a replacement with the same, or similar, cross section and just buy it by the foot. Try Granger.

Cooling performance woukd not be impacted by the modification.

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 09, 2013, 07:45:23 AM
The ARP doesn't measure level, it measures one thing, the boiler temperature.  How far out of level the refrigerator can be before the boiler temperature reaches the set point depends on the cooling unit construction and other variables that we have little or no control over.  The ARP does make it possible for you to test your own refrigerator to see what the limits are.
Title: Re: Fridge: How Level is "enough"?
Post by: Snowman9000 on December 09, 2013, 10:17:10 AM
The ARP doesn't measure level, it measures one thing, the boiler temperature.  How far out of level the refrigerator can be before the boiler temperature reaches the set point depends on the cooling unit construction and other variables that we have little or no control over.  The ARP does make it possible for you to test your own refrigerator to see what the limits are.

I am under the impression there are two problems with being off level.  One, which I was unaware of, is the heat.  Which the ARP regulates.  The other, the one I always had read, was improper chemical reactions due to inability of the fluids to flow downward properly.  But does the latter only become a problem due to the heat? 

In any event, the info linked from this thread suggests that without the ARP, being off level less than a degree causes heat to rise to undesirable levels.  So, does using the ARP get us back to the 3 & 6 degree out of level tolerances attributed to one of the manufacturers?  ie With an ARP, can I run 3 degrees off level without concern?  Because the ARP keeps the heat from building up in that situation?
Title: Re: Fridge: How Level is "enough"?
Post by: Lou Schneider on December 09, 2013, 10:23:17 AM
The problem with off level operation is not getting enough liquid back to the boiler, which then runs dry and overheats.   ARP may mitigate the overheating by turning off the boiler, but it does nothing to improve the flow of liquid when you're off level.

If you don't mind your refrigerator shutting down (i.e. not cooling) when you're off level, have at it.
Title: Re: Fridge: How Level is "enough"?
Post by: Snowman9000 on December 09, 2013, 12:42:30 PM
The problem with off level operation is not getting enough liquid back to the boiler, which then runs dry and overheats.   ARP may mitigate the overheating by turning off the boiler, but it does nothing to improve the flow of liquid when you're off level.

If you don't mind your refrigerator shutting down (i.e. not cooling) when you're off level, have at it.

I'm not proposing to run 20 out of level.   Let me try again.

I take from this thread that, in stock configuration, ANY measurable amount out of level -> excess heat -> over time, shorter lifespan and diminished cooling ability.

So, with the ARP -> up to X degrees out of level -> what?
Will 1, 2, 3 degrees off level yield perfectly acceptable cooling, with no long term detriment?
Does it increase the real life tolerance for off-level?   (It would seem so.)   If so, how much?

Title: Re: Fridge: How Level is "enough"?
Post by: codgerbill on December 09, 2013, 01:01:32 PM
Does it make a difference if you are running the refrigerator on electric?
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 09, 2013, 04:15:22 PM
Quote
I like the idea of that device but I see another problem. According to David Force(Amish Cooling Unit) and others one of the problems with the 1200 series is that the cooling unit is undersized. When it is warm outside the fridge runs full  time. If this is true wouldn't the ARP be shutting down the fridge and you would lose cooling ability? So the device might prevent a catastrophe but your food will be warm. Or am I misunderstanding and the device just prevents overheating and the boiler will still be hot enough to function?

There are two key points you are missing:

(1) Once the ammonia solution reaches its boiling point, the cooling process works as good as it is ever going to work. It doesn't work any better, i.e. colder, if the boiler runs even hotter. If the boiler starts to overheat, the algorithm in the ARP shuts off the heat source just long enough to let the boiler fall back to the normal operating range. The ammonia solution continues to boil because the heat is still sufficient even though the external heat is temporarily off. The boiler temp might drop enough so that boiling stops briefly, but it would be a very short time before heat was restored and the cycle resumed.  I suppose that could result in some very short term loss of cooling if the boiler overheated multiple times in a short period, but that would indicate a cooling unit problem anyway.

(2) Even though the boiler is running full time in hot weather (and yes, it does that), it typically does not overheat if the fridge is level and in good working order. My 1200 stays at a rock steady temperature for hours on end when the ambient is in the mod 80's or higher. ARP doesn't care how long the heater runs, just as long as the boiler temperature stays in the optimum zone.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 09, 2013, 04:31:27 PM
Quote
So, with the ARP -> up to X degrees out of level -> what?
Will 1, 2, 3 degrees off level yield perfectly acceptable cooling, with no long term detriment?

I don't think there is any general answer to that. Each individual fridge model and installation would,  at some degree of tilt, be off-level enough for  overheating to begin. ARP would manage that, so some cooling would continue on an intermittent basis, but the overheating would probably re-occur. ARP will not let repeated overheats go on indefinitely - it will shut off and not restart if the boiler continuously goes into overheat condition. This was explained previously in this discussion - there is currently a limit of 5 restarts. Repeated overheats indicates some sort of problem that needs to be addressed. The ARP has prevented internal damage to the cooling unit, but it doesn't enable you to run indefinitely off-level. CAVEAT: With the current version of ARP, it is possible for the owner to manually adjust the ARP parameters to make the restart tolerances greater.  That's risky in that it defeats the purpose of ARP by letting the burner run hotter and thus greater potential for long term damage. I would not be surprised to see that manual override tuning feature disappear from future versions, but it is currently there.

In the test runs I watched, overheating took off quickly once the tilt threshold was reached. It started somewhere around 3 degrees, but we made no attempt to determine if it was 1 or 2 or 4. The point was that it did not have to be very much of an angle, an angle well within what many people would consider comfortable, and an angle easily reached during travel or brief stops. And when the temperature began to rise, it shot up rather than rising slowly.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 09, 2013, 04:38:06 PM
Quote
Does it make a difference if you are running the refrigerator on electric?

No. The source of the heat is not a factor.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 09, 2013, 04:55:35 PM
The reason the boiler temp begins to skyrocket is that insufficient liquid is returning to the boiler from the condenser & evaporator tubing. That can result from a clog, or it can result from excessive heat in the system. If the ammonia solution doesn't cool enough, the gas doesn't condense, the cycle stops and no liquid runs back to the boiler.  Getting back to a tubing clog, the most likely reason for a clog is crystallization of the sodium chromate in the solution. Guess what causes that? TOO MUCH HEAT!

So, IF the cooling process still works at 1 degree of tilt, the fridge keeps working fine and temperatures stay stable. Ditto, perhaps, at 2 degrees. But at some point the liquid return flow stops and as soon as that happens the boiler temps will immediately soar, not just a few degrees but 100's.
Title: Re: Fridge: How Level is "enough"?
Post by: ArdraF on December 09, 2013, 05:32:31 PM
Gary, thanks for some good explanations in plain English!  ;)

ArdraF
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 09, 2013, 06:17:25 PM
This thermal physics stuff gets complex real quick if you try to get too deep into it. My head was spinning for days trying to wrap my mind around the theory and then the practical application in our fridges.  ???

This is a device that will prevent long term internal damage by limiting high temperatures that can occur (often briefly) in typical RV operation. In doing so it also prevents a catastrophic overheat that could result in a burst cooling unit and a fire. But it's not a miracle device - the fridge manufacturer's installation and usage instructions still have to be obeyed.

Think of it as a thermal surge protector for the fridge. Many of us have bought surge protector devices for our shore power cords to limit the range of transient voltages. We do that as insurance against the possible effects of a chance high voltage spike. The ARP is doing much the same for temperature spikes that can weaken or destroy the fridge cooling unit. In know that's not a perfect analogy, but I hope it gets the main point across.
Title: Re: Fridge: How Level is "enough"?
Post by: carson on December 09, 2013, 06:23:18 PM
Quote
So, IF the cooling process still works at 1 degree of tilt, the fridge keeps working fine and temperatures stay stable. Ditto, perhaps, at 2 degrees. But at some point the liquid return flow stops and as soon as that happens the boiler temps will immediately soar, not just a few degrees but 100's.

Gary, One curious thought...  Are we creating a bit of a mania here ?  I understand everything you are saying and I agree.

Now about the rapid high temperature rise.  Imaging the real possibility of going up and down a long mountain climb of 4-5-6 degrees. Many are present in the West, at reduced speed.

  Should we all start to worry immensely ? What say ?
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 10, 2013, 10:29:04 AM
Carson,

Mania? That's a bit extreme, but yes, an alarm is being sounded. The evidence shows that normal RV operation will result in periodic episodes of extreme high temperatures in the cooling unit boiler, and it happens everywhere, not just in the Rockies. The fridge manufacturers have told us that short periods of excess tilt are not a problem, but the underlying science tells us that there will be significant internal stress and some irreversible damage every time it occurs. Clearly Norcold and Dometic feel these shorter episodes are not harmful enough to worry about, but it is equally clear that at least some of their products fail prematurely and for unexplained reasons. To my way of thinking, that makes their engineering judgment suspect. They may well be estimating that 95 or 98% of cooling units will last 5 or 8 or 10 years despite the high temperature episodes and that is "good enough". Those who own the remaining 2% or 5% that fail earlier probably don't agree. [These numbers are just conjecture and are used only to illustrate a point].

I don't know if every RVer needs to worry about failures due to excessive boiler heat, so I don't know if everybody needs an ARP.  However, I am confident that ARP eliminates a significant source of fridge cooling unit problems because the science and engineering behind it seem incontrovertible.  We do many other things to avoid potential problems in our RVs, things that may not be strictly required but serve to avoid situations that are difficult to know about specifically. For example, we change engine oil on a regular and conservative basis because it avoids long term damage from oil contamination or degradation. We probably change it earlier than strictly necessary, but that's a smarter alternative than risking long term damage to an expensive component. We put surge protectors on our power cords and TPMS on our tires for the same reason: to prevent a more serious problem that MIGHT occur if we had no protection. An ARP is in that same category, a device that provides us with insurance against a problem that we know occurs, but cannot be sure if it is going to happen to us personally. Buying and adding an ARP to gain this protection is a strictly personal decision, but it is neither expensive nor difficult to install.
Title: Re: Fridge: How Level is "enough"?
Post by: carson on December 10, 2013, 11:12:02 AM
Great explanation, Gary.  Thank you.

(If I hadn't said Mania, I doubt that your post would have occurred).

Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 10, 2013, 12:01:15 PM
Quote
Those who own the remaining 2% or 5% that fail earlier probably don't agree.

Especially if the failure mode is a fire.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on December 10, 2013, 02:23:03 PM
As the RV population has aged it seems just about everyone we know has had gas absorption refrigerator problems of some kind.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 10, 2013, 02:51:40 PM
You don't hear about as many problems in the smaller sizes, e.g. those typically found in travel trailers. It's not clear whether there are less problems, or just less talk about it. We know absorption fridges fail, regardless of size, but it is less sure if all makes and models have the same failure rate, or whether certain types of RVs or certain modes of use suffer more failures. It may be that using an absorption fridge 5-10 weekends a year simply doesn't stress it often enough to generate the kinds of problems seen in larger RVs and longer duration usage.   There is blessed little data available, and neither Norcold or Dometic is telling what they know about it.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on December 10, 2013, 03:46:38 PM
Gary you are absolutely right. We had three smaller sized refrigerators going back to 1972 and absolutely had no problems with any of them. I shudder to think some of the places we parked with them out of level back before anyone worried about it


Our issues have been with the 4 door models in the past ten years, one Dometic and the other a NoCold 1210.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 10, 2013, 04:04:51 PM
Our Dometic RM3862 lasted nearly 17 years in full time operation under all types of conditions and 147,000+ miles.
Title: Re: Fridge: How Level is "enough"?
Post by: moisheh on December 10, 2013, 05:15:35 PM
We have been rving for 45 years. Had some small trailers and a few 5th wheels with no problems. They were all Dometic. In the 80's I had a Dometic in a MH. Replaced the cooling unit twice. Once was my fault. I left the fridge on for 5 days and it was way off level. In the last 20 years we have replaced ignitors and main boards. Again they were all Dometic. We had a Norcold 1200 9 years ago and it was fine. Our Norcold in the Bounder is a 1200 and so far so good. But I do worry about it failing.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 10, 2013, 05:19:50 PM
My Norcold 1200 works great too, and has since January 2004. Doesn't mean it couldn't explode tomorrow, but its been a good fridge. And now it has an ARP on it, so it's even better!

Watching my own fridge's temperature log has been enlightening. Looking at the temperature track, I can tell when I made a stop for lunch,  when I drove through a town and encountered traffic, and when I pulled into the RV park to register, and again when we moved to a site. The temperature reactions are nearly instant and very evident. But mine hasn't reacted enough to cause the ARP to trigger. Yet.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 11, 2013, 09:51:37 AM
I asked Paul Unmack about ARP and off-level operation, to make sure I understand it correctly and gave a correct reply here. He made a couple of further points:

1. The cooling unit is sensitive to the direction of the tilt, i.e. a tilt to one side quickly disrupts the flow of liquid ammonia back to the boiler (because it has to flow uphill), while the same degree of tilt in the opposite direction lets the liquid flow downhill to the boiler and has less impact. It might even help a bit at a very small tilt angle. Tilts to the front or back have relatively little impact on boiler operation until the 6 degree mark. The bottom line is that we can't make broad statements about tilting a fridge or what ARP does or does not do for it. We have to consider the direction of tilt as well as the degree.

2. There are three possible tilt scenarios:

  2a. If the fridge is only slightly off-level, or off-level in a less-critical direction, it may not over heat at all, so no worries.

  2b. If the fridge is close to the critical point, the return of coolant may slow or become intermittent. This will cause a boiler temperature rise and ARP will catch it, preventing further overheating, and then restart normal operation after a brief cool-down. Another overheat event may occur, but perhaps not for a several minutes or a few hours. Cooling continues in between, as long as the 5 restart threshold is not reached. In this scenario, ARP has made continued operation possible without damage to the cooling unit.

  2c. If the fridge is sufficiently off level, coolant return ceases and an event will quickly be triggered. ARP will shut down for a cool-off, and then re-start. But if the fridge remains off-level, another event will SOON re-occur. And another and another. After 5 events, it shuts down with no restart, and the fridge interior begins to warm up because all cooling has stopped. It would have stopped anyway in this scenario, but the ARP has prevented cooling unit damage.

In 2B and 2C, ARP has in essence made it safe to operate the fridge off-level, where safe means no internal, long term, damage to the fridge.  So in that sense, ARP gets us back to the manufacturers 3/6 degree level specification.
Title: Re: Fridge: How Level is "enough"?
Post by: hes4all on December 11, 2013, 10:50:55 AM
Thank you Gary for all your work and reporting on the ARP. I am in a quandary now. My Norcold 1200 has the Amish unit on it but now it needs a new board. The igniter doesn't work anymore.

So do I buy a new board and the ARP. Or change it out for a Samsung?

Regardless, I would have to put a new board on the Norcold to sell it and I would not be caught without any thing that offers protection to my family and me (ARP) for the cost of the ARP (cheap) in my book.

And here in Idaho, i can sell the Norcold pretty easy.

Sorry for the ramblelings, thanks again Gary!
Title: Re: Fridge: How Level is "enough"?
Post by: Snowman9000 on December 11, 2013, 11:59:26 AM
Thanks, Gary.
:)
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 11, 2013, 08:52:28 PM
Quote
So do I buy a new board and the ARP. Or change it out for a Samsung?

Well, it's much cheaper to buy the board and an ARP, but with the Samsung (or similar) you get a much larger fridge, self-defrosting, and probably better cooling in hot weather too.

If your 1200 works well enough to keep ice cream in the freezer and beer ice-cold in the fridge, I might be reluctant to spend the extra $2200 or so to changeover to residential. Gotta weigh the $$ versus the extra benefits, and of course the family budget too. But if performance was only so-so anyway, I'd replace it.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on December 11, 2013, 10:00:42 PM
Our Samsung was $1050 plus $400 for installation.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 12, 2013, 09:15:40 AM
Sounds like you got off light, Jeff. Most coaches need more than a few cabinet mods, plus the expense of removing a window to get it in, getting rid of the old fridge, etc. Maybe you found some cheaper labor than typical RV shops?  Or did some of it yourself?  From what I have read elsewhere, typical professional installation cost is around $1000, plus $1000-$1400 for the fridge itself. The fridge price seems to be stabilizing in the $1100 arena lately, so I guess I should amend by previous estimate to be around $2100, and potentially as low as $1500.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 12, 2013, 09:47:01 AM
Those prices make an Amish cooling unit plus ARP control look cheap.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on December 12, 2013, 12:14:23 PM
The appeal of the 18 cu ft Samsung is that it is a counter depth model that is 4" higher than NoCold 1200 but fits the cutout for a 1200 for width and depth. With the doors removed the 1200 and the Samsung are 23" deep and both went out and in through our coach's door so installation including removing the 1200 took about 3 hours. The only mod to get them through the door was moving the copilot seat and a rubber seal on the door.


After the Samsung was installed I pulled it out of the wall and altered the base to satisfy myself by lowering the refrigerator about 3". Materials to do that were $35.00.


Ned unless you travel to Indiana most quotes I saw to have an Amish unit shipped and installed were in the $1600-2000 range.
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 12, 2013, 01:56:52 PM
Dometic Amish cooling units are $635 from rvcoolingunit.com, plus $160 shipping.  Installation by an experienced installer shouldn't be more than about 4 hours, I would estimate.  Remanufactured are $525.  Add about $100 for an ARP.
Title: Re: Fridge: How Level is "enough"?
Post by: Jeff on December 12, 2013, 03:48:54 PM
Sorry Ned, I forgot you had the smaller Dometic. The new Norcold 1200LR is $1165 plus freight.
Title: Re: Fridge: How Level is "enough"?
Post by: toastergirl on December 12, 2013, 06:45:03 PM
Okay, so for those of us who are RV newbies, most of this technical stuff is pretty confusing, but I am trying to learn. If I understood the post correctly, a lot of RV fridges need to be kept level, and if you leave them on and drive up or down hills or park somewhere where you are not level, it can cause problems up to and including catching your RV on fire. Is that right?

And your friend invented something to stop that from happening?

Sorry for my lack of knowledge, but I am still trying to figure all this stuff out. If I got the jist of the post, that sounds like a pretty awesome invention!
Title: Re: Fridge: How Level is "enough"?
Post by: Molaker on December 12, 2013, 07:13:06 PM
Okay, so for those of us who are RV newbies, most of this technical stuff is pretty confusing, but I am trying to learn. If I understood the post correctly, a lot of RV fridges need to be kept level, and if you leave them on and drive up or down hills or park somewhere where you are not level, it can cause problems up to and including catching your RV on fire. Is that right?

And your friend invented something to stop that from happening?

Sorry for my lack of knowledge, but I am still trying to figure all this stuff out. If I got the jist of the post, that sounds like a pretty awesome invention!
Mostly, you've got it, but leaving them on while driving is not a problem even when going up or down hills.  When moving there is enough motion and vibration to keep the coolant circulation going and not cause blockage and possible dangerous heat build-up.
Title: Re: Fridge: How Level is "enough"?
Post by: hes4all on December 12, 2013, 11:57:06 PM
The appeal of the 18 cu ft Samsung is that it is a counter depth model that is 4" higher than NoCold 1200 but fits the cutout for a 1200 for width and depth.

Jeff, you say that the Samsung in only 4" taller? I always thought it was 7"? Boy, this is really got me thinking now.

The repair for my 1200 is about $150 for the board and $80 for the ARP. I do the work because I work cheap.

Not to bad changing the cooling unit out , just to let you guys know. My son and I changed out the cooling unit to the Amish one and it took about 6 hours including a few calm down breaks!

And Gary, our 1200 works great now. The only time I have ever gone above 5 was in Leadville this year @ 10,000 ft elevation. Had to set it on 6.

But I do like the idea of extra room of the Samsung too. What do I do?

Fix the Norcold then go from there. Can't sell it the way it is and I don't do that to people.

Thanks guys!
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 13, 2013, 11:29:17 AM
Quote
Okay, so for those of us who are RV newbies, most of this technical stuff is pretty confusing, but I am trying to learn. If I understood the post correctly, a lot of RV fridges need to be kept level, and if you leave them on and drive up or down hills or park somewhere where you are not level, it can cause problems up to and including catching your RV on fire. Is that right?

And your friend invented something to stop that from happening?

You got it pretty well.  ALL absorption RV fridges need to be very close to level to operate correctly. RV fridge manufacturers say that being a little off-level, or intermittent off-level while driving, is no problem. My friend Paul's research indicates this is not entirely true and that internal damage happens in those situations, albeit slowly in most cases.  Paul believes the ultimate result of that internal damage is failure and possibly a fire when it fails.  His invention prevents that damage.

The subjective part of the debate is how much damage and how long does it take to accumulate to the danger point.  And that, of course, varies with the the individual fridge and how it gets used.
Title: Re: Fridge: How Level is "enough"?
Post by: carson on December 13, 2013, 11:40:22 AM
In other words, for people without the ARP, it would be advisable to turn the fridge OFF when anticipating a lengthy climb and descent until they are back on level ground. Not a big deal to do.

Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 13, 2013, 07:11:33 PM
And when you stop for lunch or pull into a fuel station or...
Title: Re: Fridge: How Level is "enough"?
Post by: Molaker on December 13, 2013, 08:20:03 PM
Maybe I'll just get a block of ice. :)
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 14, 2013, 08:26:47 AM
Like most everyone else, I never worried about the effects of uphill/downhill on the fridge, nor was I very concerned about brief stops where I was off-level. Watching the ARP demo, the thing that astounded me most was how quickly the boiler temperature shoots up once the tilt exceeds the critical value. What I had envisioned as a slow process that could be tolerated for short periods turned out to be more like a rocket launch, where it transitions from nothing to major effect in under a minute. Couple that with the scientific fact that the sodium chromate corrosion inhibitor is heat sensitive and you have, I think, adequate cause to be concerned.  Clearly the owner can manage this by turning off the fridge when at risk, but it sure is nice to have a device watching for the symptoms and automatically handling it for us. That way I get to enjoy RVing more.
Title: Re: Fridge: How Level is "enough"?
Post by: Molaker on December 14, 2013, 09:10:07 AM
Perhaps what is needed is a "level" detector that senses the attitude and shuts the fridge off when too far off.  In fact, with all the hoopla and bad history, I don't know why it's not built in.
Title: Re: Fridge: How Level is "enough"?
Post by: jje1960 on December 14, 2013, 01:18:21 PM
While not having anything to do with leveling.... This picture is from a fridge fire that was very scary ( I was there and put the fire out) not something I wish to deal with again!  Our neighbor last summer was awaken by a big 'boom' and toxic fumes that quickly consumed the Endeavor MH.  End of the ordeal, they got out alright, we got the fire out before the fire trucks arrived.  Flames were already 4' when we started, not a nice situation.  RV fridges are wonderful comforts, however sometimes things go wrong.
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 15, 2013, 10:00:47 AM
I think the reason that fridges don't have a built-in level sensor is that it is not a simple task to get it right.  If they put in a simple sensor, basically one that shut down at 2 or 3 degrees of tilt, they would be shutting the fridge off unnecessarily. The spec for "level" is 3 degrees in one direction, but 6 degrees in another. Plus, they would probably want to include a time parameter as well as angle (though the ARP demo suggests the time is very short). If they just put in a tilt sensor that shut down at, say, 6 degrees, then some people would have failures at less than that value and would rightly complain that the tilt sensor didn't do its job.  But probably more to the point, the fridge makers appear to believe that most fridges survive off-level operation in normal use, so no extra-cost sensor is necessary.

Atwood's new helium based RV fridge does have a level sensor as one of its features. However, in an independent test the fridge was tilted far to the side and the sensor did not activate, so its not clear how it works. For more on the Atwood fridge, see the series of videos from FRVTS. Here is their video that shows the Atwood tilt test: http://www.youtube.com/watch?v=3YysfHocCQI
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 15, 2013, 10:22:17 AM
For one data point, our motorhome is off by about 1/2 a bubble both side to side and fore and aft.  I collected the boiler temperatures over a 24 hour period using the ARP and the graph shows normal cycling with no tendency to overheat.  The ARP set point was 174C and the maximum boiler temperature was 158C during that time.

Edit: Fixed temp units
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on December 15, 2013, 08:57:32 PM
Cycling nicely!  While the data collection cabvle isn't a standard part of the ARP package, it is kind of fun to watch how the fridge cooling unit operates.
Title: Re: Fridge: How Level is "enough"?
Post by: Just Lou on December 15, 2013, 10:16:23 PM
For one data point, our motorhome is off by about 1/2 a bubble both side to side and fore and aft.  I collected the boiler temperatures over a 24 hour period using the ARP and the graph shows normal cycling with no tendency to overheat.  The ARP set point was 174F and the maximum boiler temperature was 158F during that time.
Ned, why does the chart say the temperatures are in Centigrade Celsius?
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 16, 2013, 07:17:08 AM
Ned, why does the chart say the temperatures are in Centigrade Celsius?

Because they are.  I fixed the message units.
Title: Re: Fridge: How Level is "enough"?
Post by: Ernie n Tara on December 16, 2013, 07:56:20 AM
Level sensors are relatively expensive components. With the associated controller, it could add as much as $70-80 to the manufacturing cost. A flow sensor based system would probably be less expensive and more effective.

Ernie
Title: Re: Fridge: How Level is "enough"?
Post by: Just Lou on December 16, 2013, 10:30:48 AM
Because they are.  I fixed the message units.
LOL... I knew that, I just didn't want to point out that my hero made a typo. ;) :D
Title: Re: Fridge: How Level is "enough"?
Post by: Ned on December 16, 2013, 12:01:13 PM
It was the computer that did it, honest :)
Title: Re: Fridge: How Level is "enough"?
Post by: Just Lou on December 16, 2013, 01:32:08 PM
It was the computer that did it, honest :)
I understand completely. :)   My keyboard develops an attitude from time to time also ;) .
Title: Re: Fridge: How Level is "enough"?
Post by: dirko on January 31, 2014, 06:36:39 PM
Hi Ho:  I'm impressed with the work and thought in this thread.  Over the years I've found that enough additional data can often lead to an improved understanding of what is happening, and perhaps to a solution to a problem that was not apparent (or even thought about) when the experiment began.   So here's an additional question:  If enough historical temperature data is available can one infer anything about the current condition of a cooling unit?  Or put another way:  As the cooling unit degrades over time can a history of boiler data determine anything about the degree of deterioration?  Also, if enough data is available from similar units in similar coaches can one determine if a particular installation is at risk?
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on January 31, 2014, 08:07:58 PM
It seems likely, but nobody has enough data to know.  Well, maybe the fridge makers know, but they aren't telling.
Title: Re: Fridge: How Level is "enough"?
Post by: Back2PA on August 24, 2015, 08:01:41 AM
So... I did a search on the subject topic, read through all of the thread that appeared on this two year old topic, and now I still have to ask, "how level is enough?"

Working through the bugs on delivery of an '05 coach w 4 door Norcold (1200LR). Fridge seemed like it was doing very well, especially given the 105 degree temps here in AZ. Then I took it home and temporarily parked in driveway a couple days while provisioning. Driveway has what I would call moderste slope, nose probably down about 12-15". I was used to fridge problems in the RVs I had years ago (very sensitive to out of level, no cooling fan, poor cooling in high heat, etc) but thought the newer fridges were much less sensitive. I was surprised to have cooling issues.

And without a rehash of all the technicals, is this ARP thing generally considered a good thing?
Title: Re: Fridge: How Level is "enough"?
Post by: Gary RV_Wizard on August 24, 2015, 09:00:22 AM
Probably depends on what "general" you talk to!  I happen to be a fan of ARP. It does a better job of protecting the fridge from overheat conditions, and that also results in safer operation (reduced fire risk). It can't fix an out-of-level condition, but it can and does prevent the damage caused by it.

If your 1200LR fridge is on the driver side of the coach, a nose-down attitude is the worst possible off-level condition. That's because the boiler is mounted on the right (as you face the backside) and thus on the uphill (high) side. The ammonia solution is largely, or maybe even completely, prevented from flowing back to the boiler. Cooling performance drops rapidly and boiler temperature climbs dramatically in just a few minutes. Norcold says that 3 degrees of tilt is the max side-to-side, and that's about 6" over the length of a 40 ft RV. Visually, not a lot of tilt.

The odd thing is that a moderate nose-up attitude would actually help the cooling unit a little because the refrigerant runs back to the boiler nicely.

All Norcolds and most Dometics have the boiler on the right side (looking from the rear). If the fridge in on the driver side, that makes nose-down the worst. If on the passenger side, nose-up is the worst.