Ammonia versus Compressor Fridge...

[SidecarFlip]

After all the talk about Danfoss compressor fridges and how much better they were than the old school Ammonia Units, I decided to 'fiddle with mine and do a long term test using a remote digital recording thermometer.

First thng I did was open up the rear cavity. My fridge is a side vent, that is, not through the roof, intake low (with plumbing and control board) and the upper vent vertical on the side of the camper at the height of the top of the fridge.

I opened it up and removed the one small 12 volt muffin fan Suburban had installed. It was a cheapo sleeve bearing fan, very noisy. I replaced it with 2 Fluid Dynamic Bearing 120 MMM high flow computer fans (23 bucks, E-bay. Had to make up a set of brackets as I wanted the fans as close to the upper condenser as possible. Suburban has already installed a snap action thermostat (on at 90 off at 70) so I wired both into the existing thermostat.

I also added a lot of R13 unfaced insulation between the fridge and the cabinet. I actually stuffed almost 1/2 roll in. Plenty now.

I also fabricated an upper baffle that fits tight against the back of the upper condenser and screws into the camper side,inside, effectively channeling the air flow with no turbulence as it passes through the condenser.

I took a full 20 pound bottle of propane (valved off my second bottle) and set the fridge on gas only (it is shore powered sitting in the yard.)

So far, it's been running for 3 weeks straight on that bottle, I'm expecting over a month. Amp draw with the fans running is 1.8 amps, with the fans off. .2 amps..Temperature swings (day and night) (and the camper gets the afternoon sun on the fridge side) is 4 degrees.

Last year I had to run the fridge on setting 5 to maintain 40 in the compartment. It't drifting between 33 and 36 inside now..... on setting 2...

I measured the cool down time from ambient as well. It took exactly 3 hours from ambient to 33 degrees.

Still chugging along out there as I post this. When it runs out of propane, I'll post it.

If it ever dies, I'll install a Danfoss unit but for now the old school fridge appears to be doing well.

[Kayteg1]

rexlion wrote:
... But I see in another thread that you got a new TC and your new fridge (although same model as before) won't cool well. Did you ever figure out why?

I did not see the question over a year ago, so this is late reply.
When the tests I posted on page 8 were done on my Fleetwood, the camper did have some dryrot damages, so when I discover that right before going for "trip of my retirement" I bought Lance, who is the same year, having the same refrigerator.
I post some questions at the time since Lance fridge did not perform at first, but later it did and here is my conclusion about absorption refrigerators.
-they need 24 before they will cool down
-the sliding thermistor in fridge compartment is tricky at first, but it does the job
-fridge part will always cool less than freezer part.
Usually the last issue is not a biggie since food in fridge goes fast, when we want the ice-cream frozen, so we did not do anything to improve that, but I read some members add fans for better air circulation, some freeze a water bottle and than put it at bottom of refrigerator.
We did the frozen bottle trick in extreme situation, like 120F outside, or loading lot of fresh food.
I still own both campers, where Lance is my guesthouse in California and I use Fleetwood for trips and fridges work just fine.
Fact is that since 2017 we did not get 124F for several days again.

[rexlion]

Kayteg1 wrote:
TEST RESULTS
This is for my Dometic 6cu-ft 3-way refrigerator with separate freezer door. About 14 years old.
Rated 1500 BTU/hr
2.7 amp @120v=324W
18 amp @12v = 216W
Actual consumption @120v was 400W at start, 350W later
Loaded with 2 gallons of juice in refrigerator and 2l of water in freezer. All started at 80F
I open the door for few seconds for readouts, what I think makes it real life test.
1st row is time, amb=ambient temp come from my roof-mounted weather station, inside measured on countertop.
fd/rf is temp next to juice in refrigerator, measured with stick thermometer.
flr/fr is freezer floor measured with stick thermometer.
fd/fr is temp of water in the clear bottle measured with infra-red, what is not very accurate, so take it with 😉
tm-amb-ins-fd/rf-flr/fr-fd/fr
12--80--80--80----80----80
1---87--84--78----64----80
2---90--86--78----35----71
3---91--88--74----23----55
4---94--90--69----17----46
5---94--90--68----13----36
6---92--90--64-----8----32
7---93--90--63-----9----32
8---89--89--57----12----36
10--79--85--55-----8----32 (water froze)
6---64--74--47----10----32 ......day 2
9---76--75--45-----9----26 (thermostat cycled off)
10--87--78--40-----0----15
12--94--87--42-----5----18
1---99--90--40-----2----13
4--103--96--39-----0-----6
5--104--94--40-----0-----3
6--100--96--40-----0-----1
8---93--95--40---(-5)----1
10--88--92--34---(-3)----4
turned off for the night/switched to propane
6---77--82--50----40----40..... day 3
7---77--82--50----30----36
9---86--85--48-----5----24
11--88--89--50-----2----11
12--92--92--55-----0----11
1---95--94--55-----0-----7
3--102--97--50---(-2)----2
4--103--98--50---(-2)----2
5--103--99--52---(-6)----1
7---99--99--50---(-5)----0

These were some impressive results. Certainly not the norm from all I've read from other RVers who complain about their absorption refrigerators. But I see in another thread that you got a new TC and your new fridge (although same model as before) won't cool well. Did you ever figure out why?

[dave17352]

Kayteg1 wrote:
12v compressor is superior cooling wise- but when you have no solar, no 4-batteries and boondocks in quiet area, where generators are not welcome, you will have superiority issue.
Don't know if any manufacturer offers 12v fridge with solars option, but I would estimate that would be $2000 option.
Would I pay for it? I don't think so. I like to camp in shade with no noise and go for 1/2 day hiking or boating without worry if my solar is having enough power to keep my beer cold.

OK Kayteg1 I will give you that. Cooler areas of the country where camping in the forest a propane fridge is and would be more than adequate. If a camper spent his time boondocked there it would be a superior choice. Still have leveling though and it still needs the time to cool down.

To go 12 volt, you do not need 4 batteries but you do need 2. I thought about trying to get by with 1 but could see right away as others had told me that would not cut it. I will also agree you will spend more money getting set up for a 12 volt fridge so there is that also. It cost me roughly 2200 dollars for my solar extra battery and refrigerator. $1700.00 of that for the fridge shipped to my location.

These are the reason's a 12 volt fridge is ideal for my use.

1. Pulling my boat fishing and parking at very un level boat ramps for the day.

2. Living in a area with plenty of heat and generally plenty of sun and not a over abundance of shade.

3. Solar is fun. For some reason I get a real charge 🙂 out of installing and getting energy for free (kinda after you spend several hundred dollars on getting it set up!)

4. Having 7 grand kids keeping the fridge door closed is a real PITA.

5. The (superior for my uses) cooling and ease of use.

6. Also replacing 6 cubic foot fridge with a 7.3 in the same footprint.
Could have gotten a 9 cubic foot in if I was willing to remove the door.

JMHO

[Kayteg1]

My experience with ammonia refrigerator is that they need to be level only for starting the cycle. Camping in California my refrigerators never fail to work, even when our ClassC had no way for leveling.
Till at the end of the summer colder night made thermostat to cycle off and in the morning the fridge would not start cooling till we got it level.

[rhagfo]

pianotuna wrote:
You still have to worry about being level.

Well I prefer to sleep in a level bed to heck with the fridge!

[Kayteg1]

12v compressor is superior cooling wise- but when you have no solar, no 4-batteries and boondocks in quiet area, where generators are not welcome, you will have superiority issue.
Don't know if any manufacturer offers 12v fridge with solars option, but I would estimate that would be $2000 option.
Would I pay for it? I don't think so. I like to camp in shade with no noise and go for 1/2 day hiking or boating without worry if my solar is having enough power to keep my beer cold.

[dave17352]

Well I am a propane fridge basher:) I find results very close to what I would expect with your experiment. The fridge temp as you stated could use some help. I had a dometic 6 cubic foot in my truck camper. The freezer always out performed the fridge big time. I always froze bottles of water at home and then put them in the fridge when temps were going to be hot. Then I would transfer back forth between the fridge and freezer. This technique actually worked pretty good. I am not sure measuring the temps is equal to regular use by a camping crowd in terms of opening the door. The time to cool down is so very long with these fridges and they simply won't recover when really hot and the door is opened frequently. All in all I used the propane fridge's for decades and they did work. Just not as good as a compressor fridge.

Just for fun I did a little experiment today. I had to take a 120 mile trip there and back. So I took my truck camper rig and turned on the compressor fidge. A hour and half later when I arrived the fridge was at 44 degrees and the freezer compartment was 22 and the inner freezer section was 10 degrees. A couple hours later fridge was at 39 freezer 15 and inner freezer -1. This was set a 4 on a 1 to 7 scale. The temperature was only 80 degrees but driving down the highway was always when my propane fridge would have the very worst performance. In this case driving down the highway had zero effect.
By inner freezer I mean where they wrap the cold plate where you would put ice trays ice cream and items you want really really cold.

Power consumption is a non issue as I have 200 watts solar. A genny also if needed. Not having to level is great. Many say well whats the big deal not having to level. Well it is a big deal when you don't even have to think about it, ever. It is a big, big plus.

Ok I hope I filled the need for a response:) Like I say propane has its place but 12 volt compressor is clearly superior. With solar getting cheaper and cheaper if a refrigerator die's I just can't see replacing with propane. JMHO

[SidecarFlip]

Any ammonia fridge manual will tell you to first pre-cool the interior by running the unit for 'x' number of hours and then to load the unit with pre-cooled food and the freezer with pre-frozen food because the fridge won't react (cool down) nearly as fast as a compressor fridge will, However, I still believe it takes less power to do the job and power consumption is everything when camping off grid with no hookups.

Though I have never owned one (and never seen one in operation) I see you can get an ammonia fridge with an ice maker installed. Not sure how that would work (with the recovery time) but they are offered.

[Kayteg1]

I think my test when starting fridge at noon heat with 2 gallons of juice @80 F was pretty extreme. Doubt anybody will do so in real life.
Also note that the fridge wall was getting shade 1PM-5PM what I can read in results as well.
Still without fan refrigerator side seem too warm for me, even freezer performed so well.
I think on long run freezing ice and moving it to bottom of refrigerator will be in order.

[pianotuna]

Kaytag1,

Thanks for doing the test. I wish doing columns was easier on the board.

I did not see the test results until May 25 in the afternoon.

It is interesting to note that sometimes the freezer temperature rises when the ambient temperature is going down.

9 hours to first turn off of the thermostat is a useful number to know. It appears that safe temperature for food storage in the fridge was about 25 hours into the run time?

My own testing was done at much lower ambient temperatures. I did track the total wattage used. I did not test on propane because the thrust of my testing was electrical consumption. First cycle for me was after 6 hours but the ambient temperature was only about 68 f. I started my testing in the afternoon, which may have made some difference to the speed of cooling. My fridge and freezer were empty.

[SidecarFlip]

Our friends went to Alaska with their TC and ammonia fridge and got a message last night about how everything was freezing in the fridge compartment. It's a Dometic but the one with no external temp control so I advised him to check the position of the Thermister on the outboard fin on the condenser in the fridge and see where it was positioned and move it up or down if it was centered. I presume he did (one way or another). I also suggested getting an adjustable Thermister (snip the tip) and install that instead of the fixed probe.

His interior temp was 27 (f). The Thernister should be cycling the unit (on and off) at 32-34 degrees, independent of the freezer compartment.

I see no one replied / disputed your fridge findings, which, were about the same as mine.

Someone will come along and cry 'foul' I'm sure.....

[Kayteg1]

3 days since I posted test results and all those ammonia nan-sayers are still speechless?
It is not like this forum 😉

[Kayteg1]

I think my Fleetwood was top of the line model, before the plant shut down.
I am finding lot of cut corners on it, but it is attic + basement model with full winterizing heating.
I assume camper insulation is better than average, whatever average is.
Camper is easy to level.
When I had 16 tons conversion with no jacks, that was another story.

[SidecarFlip]

How is your insulation around the unit? Mine was sparse until I stuffed it.

I never checked the freezer, only the refrigerator compartment and of course I left the door closed the whole time...used a remote digital thermometer.

No complaints with mine either and amp draw (with 2 fans on the backside) is 1.4 amps on propane.

Personally, I think people run into issues when the aren't level (or close to) They have to be level )at least the coils have to be level for the solution to flow properly.

Now. if the fridge was mounted on gimbals, that would never be an issue....