Fridge: How Level is "enough"?

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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.
 
Gary, thanks for some good explanations in plain English!  ;)

ArdraF
 
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.
 
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 ?
 
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.
 
Great explanation, Gary.  Thank you.

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

 
Those who own the remaining 2% or 5% that fail earlier probably don't agree.

Especially if the failure mode is a fire.
 
As the RV population has aged it seems just about everyone we know has had gas absorption refrigerator problems of some kind.
 
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.
 
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.
 
Our Dometic RM3862 lasted nearly 17 years in full time operation under all types of conditions and 147,000+ miles.
 
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.
 
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.
 
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.
 
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!
 
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.
 
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.
 
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