Dometic 3- Way Fridge

[ChicagoTom]

DoneWorking Mine takes up very little space, and the airflow on low is more than enough to keep things cool. I'm glad you get the idea. I keep telling others about it, but many want to put in a complex variety of fans and remote temp checker gizmos. Like the old saying, "Keep it Simple Stupid" The ones I have do not have the same shape as what I posted. It's the same fan, but with a handle. Mine takes up less space than a small can of soup. LOL I'm sure even the one I linked can sit in there without taking up much room

[mkguitar]

I bought the valterra fan- it ran through batteries and was bulky ( its sitting in a box somewhere, come and get it!)


-BUT was proof of concept


I wired a fan internal to the fridge, at first a .200mA whch I bought as a "3 pack"- the other 2 on the exterior fins IN addition to an earlier installed fan w/ temp sensor.


I now use a smaller fan which I removed from an old dead vcr ( I work with electronics and often salvage parts from failed devices) it draws closer to .08 mA and works as well I think
( run wires out through hole for drain hose)



we are in AZ- keeping stuff cold above 90º is tough- I know I can get about 60~65º below ambient with my fans on propane...easier/quicker if the van AC is on ( my overnight pre-departure strategy)


I also rotate "freezer packs" between freezer and fridge sections


and monitor with a cheap indoor/outdoor wireless thermometer


Long days rolling on DC are toughest to hold temps



Mike

[Rlum]

Was just in Arizona. Buckskin mountain was 109 during the day. Refrigerator stayed in the 60s. Even bought 10 lb ice to place into the refrigerator. Only would go down to 44 at night or early morning. Frig running on shore power. Yes it is a 3 way Dometic. I have have two exhaust fans outside running. Four fans running inside the box. Removed the freezer door because wanted more refrigeration space. We do not use the freezer space.

My question is. Does the three way run better on propane? Also will look at replacing the fan with this clip on model.

Thanks!

[Rlum]

Thanks. Would you consider the larger fan? Maybe takes up too much space?

[mkguitar]

Originally Posted by Rlum

Does the three way run better on propane? Also will look at replacing the fan with this clip on model.

Thanks!

MUCH better on propane than AC or DC


as above, I can get 60~65 degrees below ambient on propane with fans



Mike

[Rlum]

Thanks. Thats what I thought. I should have switched over to propane but was on shore power.

[Bud]

Originally Posted by Doneworking

I have used this fan for years. You can find it at Walmart, on Amazon, etc. It takes up little room and right underneath the fins works and will run for over a month continuously on two A batteries. I bought a different model of a rv refrig fan and it didn't work as well as this old reliable. The fact that it only takes a few cubic inches of space makes it an attractive possibility. It will not, of course, stir up air as well as what ChicagoTom posted above, but space is a real priority for us in our Roadtrek refrig.

I live in hot weather country and this little fan and a small fan I installed on the outside for the coils have never given us any problems and we keep the refrig at the proper temps.

https://www.walmart.com/ip/Valterra-...l-Fan/55355999

Seems you meant 2 D cells.

[Doneworking]

Bud, thanks for catching the error. You are correct: two D cells.

I get at least four weeks use out of the two batteries. I must also say I recently examined a new one in a store and came to the conclusion it was not as well built as my very old model.

I think we all agree on the fact that a fan inside the refrig is a good method to assist in cooling. The model, power source, etc. is an individual preference but the important fact is ChicagoTom's that moving air is the secret.

[GallenH]

I'm probably going to head out to dispersion camp near the end of the month in AZ higher elevation. Waiting to see how bad Covid gets; we're at an upswing right now. Anyways I have an old Dometic 3-way. No circuit board; just a snap lighter. If I do go, I'll try to document in/out temps at various stages and on various fuel sources.

My only "upgrades" have been to recently add more side insulation and carefully tape so that no air infiltrates to the sides; top or bottom. I also took out some small computer fans that were blowing on the back of the fridge near the bottom and put in 2 larger fans that push air out of the upper body vent. We'll see how that works in comparison with the old setup.

I also have a small fan in the fridge.

[peteco]

Another factor that affects performance is the geometry of the air flue between the lower and upper vent. My Roadtrek 210p had too much gap between the coils and the wall, which does not allow sufficient airflow over the coils. This sounds backwards, but the air velocity decreases if the gap is too large, thus reducing the airflow over the coils. I installed a false wall to decrease the gap to meet Dometic specs. Check your installation manual for the fridge manufacturer flue specs.

Here is a discussion of this and other mods to improve my fridge performance. I am borderline OK after all these mods. I suspect I had some damage done by the previous owner running the fridge off-level. Or it could be my fridge has always been marginal. I think that is the case with some Dometics.

https://www.classbforum.com/forums/f...ance-8484.html

[engnrsrule]

I have appreciated all the commentary. After some recent marginal performance (as the weather is warming up) I decided to relook. I also added an internal fan It is a D-cell model as I did not want to have to remove and recharge the lithium ion kind every other day. The one I got was a bit larger than I expected but what a difference. No longer need to set to max setting (if I do fridge part drops below 32 degrees). I also decided to add 2 more fans to the rear cooling. I originally had 2, which did produce some draft, but figured 2 more would improve the movement across the fins. I have attached some pics -the larger inside fan that I hang on the door, the baffle I made to direct the airflow behind the fridge, and the 2 and 4 fan array.

Just because I needed a REAL test...travelled to Louisiana. Temp in the 90's. So what happens? I get a 12v circuit breaker snafu that left the system shut down for a few hours of driving. When I got breaker fixed fridge had gotten up to 56. Dropped into the 40's fairly quick. Went out this morning, came back this afternoon and fridge was at 36. So I would call this success...

[Bud]

Originally Posted by engnrsrule

I have appreciated all the commentary. After some recent marginal performance (as the weather is warming up) I decided to relook. I also added an internal fan It is a D-cell model as I did not want to have to remove and recharge the lithium ion kind every other day. The one I got was a bit larger than I expected but what a difference. No longer need to set to max setting (if I do fridge part drops below 32 degrees). I also decided to add 2 more fans to the rear cooling. I originally had 2, which did produce some draft, but figured 2 more would improve the movement across the fins. I have attached some pics -the larger inside fan that I hang on the door, the baffle I made to direct the airflow behind the fridge, and the 2 and 4 fan array.

Just because I needed a REAL test...travelled to Louisiana. Temp in the 90's. So what happens? I get a 12v circuit breaker snafu that left the system shut down for a few hours of driving. When I got breaker fixed fridge had gotten up to 56. Dropped into the 40's fairly quick. Went out this morning, came back this afternoon and fridge was at 36. So I would call this success...

4 fans is over kill, imo. If you did not seal up completely the area not covered by the 2 fans, the fans Will Seek Air from the Path of Least Resistance, least energy. It will loop air in and out of the exhaust area, too much so and not from the intake below. But I'll bet those 4 fans will get the job done covering the rest of the space or not.

What I found interesting were the fans not running. There was plenty of air (not driving) between the fan blades. Cold refer with fans not running.

Bud

[booster]

Originally Posted by Bud

4 fans is over kill, imo. If you did not seal up completely the area not covered by the 2 fans, the fans Will Seek Air from the Path of Least Resistance, least energy. It will loop air in and out of the exhaust area, too much so and not from the intake below. But I'll bet those 4 fans will get the job done covering the rest of the space or not.

What I found interesting were the fans not running. There was plenty of air (not driving) between the fan blades. Cold refer with fans not running.

Bud

Interesting about the fans not running, but working anyway. Best guess would be wind conditions that put slightly higher pressure on the upper opening than the lower and, if you have it like we do, bottom vents. The angle of the fan blades may have been just right to work as a mini anti reversion flow device.

[engnrsrule]

Bud and Booster,

The pic of the 4 fans was on the hot day and they are all spinning. The pic of 2 fans was from the bench, not running. With 4 about 90% of the upper grill space is now dedicated to forced exhaust. given the tendency of heat to rise, the baffle means replacement air essentially has to be drawn up from the lower grill and across the fins. The fans are on the top grill exhausting, which draws air in the bottom. I agree that when it was only 2 fans I figured air might possibly recycle in the space above the baffle. The size of the grill drove me to 9cm fans. 12cm might just fit vertically but would be tight, and 4 9's moves a bit more air and at less amp draw than 3 12 cm fans (not enough room for 4 12's across). They are super quiet. They are also set to thermostatic control based on the temp at the top of the fins. I tested my airflow assumptions by holding a sheet of newspaper across the lower vent, where the draw is sufficient to suck the paper against the grill.

[InterBlog]

I've put this info on other fridge threads but apparently not this one, so here goes.

If you travel in hot weather, specifically if you travel long hours in the summer in the contiguous United States, I don't think you will get a Dometic 3-way fridge to remain below about 45 degrees during the day. Someone please post hard data if you think I'm wrong - I would invite a rebuttal.

The only reason why this is not more widely known is that, historically, the smaller Dometics have not had integrated thermometers. So owners ASSUME that they are staying cold, but I doubt that they really are.

Road jostling upsets the normal pattern of ammonia circulation in the fridge, and this something that is rarely if ever talked about on forums. And without proper circulation, efficient cooling won't happen. You can re-jigger the things with fans and whatnot, but the core issue will remain.

There's also the issue of fridge-flipping restoring some lost efficiency.

I summarized these points and more in this blog post in which I talked about our TWO Dometic 3-way fridges, and our eventual replacement with a Vitrifrigo.

It's a huge expense and hassle to get to the point of being able to run a unit like the Vitrifrigo and not have to worry about the power draw. In almost 6 years of Class B ownership and frequent forum participation, the number of people who I've heard say that they regret making that investment? Absolutely zero.

FWIW.

[SteveJ]

Originally Posted by InterBlog

I've put this info on other fridge threads but apparently not this one, so here goes.

If you travel in hot weather, specifically if you travel long hours in the summer in the contiguous United States, I don't think you will get a Dometic 3-way fridge to remain below about 45 degrees during the day. Someone please post hard data if you think I'm wrong - I would invite a rebuttal.

The only reason why this is not more widely known is that, historically, the smaller Dometics have not had integrated thermometers. So owners ASSUME that they are staying cold, but I doubt that they really are.

Road jostling upsets the normal pattern of ammonia circulation in the fridge, and this something that is rarely if ever talked about on forums. And without proper circulation, efficient cooling won't happen. You can re-jigger the things with fans and whatnot, but the core issue will remain.

There's also the issue of fridge-flipping restoring some lost efficiency.

I summarized these points and more in this blog post in which I talked about our TWO Dometic 3-way fridges, and our eventual replacement with a Vitrifrigo.

It's a huge expense and hassle to get to the point of being able to run a unit like the Vitrifrigo and not have to worry about the power draw. In almost 6 years of Class B ownership and frequent forum participation, the number of people who I've heard say that they regret making that investment? Absolutely zero.

FWIW.

Not exactly sure what you mean by hard data but my Dometic stays in the 30's when traveling with temps around 100 as well as when parked, if I mostly stay out of it. BTW, when parked I'm often gone for the day and come back to the Roadtrek having an interior temp of plus or minus 100.

[Bud]

Originally Posted by booster

Interesting about the fans not running, but working anyway. Best guess would be wind conditions that put slightly higher pressure on the upper opening than the lower and, if you have it like we do, bottom vents. The angle of the fan blades may have been just right to work as a mini anti reversion flow device.

Sorry, must have misspoke. I was just saying with the fans off, there is not much space for the hotter air to escape. Yet, it works well for an absorption refer in say 85 degrees not driving.

[GallenH]

I think that we have to recognize different functions and habits in our uses of a RV in this discussion. Interblog makes some interesting observations and her dealings with the Dometic are a good read. I understand the desire for a compressor fridge if you are traveling long distances. Operating a 3-way off of 12v for several days of driving is not an easy task. Personally I wouldn't want to continually do it, but it is doable. It took us 4 days to get up to Glacier from Phoenix and we managed fine on 12v driving/LP camping. But there IS anxiety in the process that probably wouldn't exist with a compressor fridge. Short camping trips are, for us, another matter. We get out of Phoenix into the high country where it is cooler in several hours. It's generally not a problem getting there and once we're there, the LP does a good job.

My dometic is 24 years old. Original with no significant repairs. I did have the line at the fridge blown out once and did the flip once at the same time. It WILL go on me. When it does I'll probably upgrade electrical and get a compressor. But until it does I have no regrets working with what's there.

This, of course, just my experience/opinion.

[mkguitar]

Originally Posted by InterBlog

I don't think you will get a Dometic 3-way fridge to remain below about 45 degrees during the day. Someone please post hard data if you think I'm wrong - I would invite a rebuttal

based in PHX, lots of hot weather running & on 12 volt
spent time doing all the manual stuff, went through and cleaned all the electrical connections I could find, and the fuse block



what works:


start fridge at least a day before sailing, if hot ( it's 105~110 here these days) use propane rather than ac power for fridge.
put aircon on overnight ( on shore power) to cool van



2 added fans on the fins ( original owner had 1 with thermostatic switch...so 2 sometimes 3 fans running)


checked seals with dollar bill


internal fan to circulate air in fridge around the food


full fridge ( even water bottles to fill space)




RF thermometer- can read temp without opening- I aim for 37º



plan door openings


"blue freezer packs", I rotate these from freezer to fridge when it's hot..the freezer always freezes easily


ac on in the van, temps in the van about 75º back there


this works for us haven't lost any food



It could be better, but my electrical system would have to be completely revamped


Mike

[InterBlog]

I should clarify that we installed our own digital thermometers in both of our Dometics, so that we would not have to open the door to read the temp, so we could monitor the temperature patterns over time, and so that we could ensure that the thermocouples were being held in representative positions. Because obviously a poorly-functioning 3-way is going to look better than it actually is in terms of performance if a thermometer is reading a cold pocket.

We also used redundant thermometers because half the time, I was looking at the digitals in disbelief (image below).

As RVs go, Class Bs are fleet of foot - they are optimized for long-haul travel. They are not the types of rigs that lumber slowly a few hours a day from one scenic campground to the next. They might also be disproportionately subject to more severe road jostling by virtue of their smaller sizes (said someone who used to travel routinely by regional bus service). For these reasons, the issues with 3-ways may not have the same potential to impact the rest of the RV market as much as they do Class Bs.

Our ammonia circulation impairment did not manifest solely in elevated on-the-road temperatures within the fridge itself. It was also apparent from the way that the fridge gobbled up propane while on the road. We would fill our tank (Manchester #6813, 5.5 gallon capacity) before leaving Houston, and by the time we got to Bangor three days later, we'd have just 1 gallon of propane remaining! All that propane burned in just 3 days! And this happened with both Dometics! The circulation was disrupted by road jostling and both fridges attempted to compensate for that and keep their temps low by running wide open almost all of the time. A valiant if vain attempt on their parts.

But of course, we drive up to 13 hours per day. A Dometic owner who putters down the road for much less time per day might not find this circulation impairment to be as noticeable.

All that being said, there remains a gremlin factor with 3-way fridges that, to this day, I don't think I understand. Some really do seem to work better than others. YMMV quite a bit.