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.

[BadgerMcAdams]

jimh425 wrote:
I don't usually camp when it is that hot unless I've got AC running. I'm a bit surprised that those of you using propane at 100. Why not use AC mode?

Where we camp, they don't have the new Tree to AC adapters yet...but when they do, I will be first in line!!!
😄 😉

My old Six-Pac had a Pla-Cool evap cooler on the roof when I bought it, but as it was deteriorated to the point of being un-repairable, I removed it and put a powered fan in. But an A/C would be nice sometimes.

[jimh406]

I don't usually camp when it is that hot unless I've got AC running. I'm a bit surprised that those of you using propane at 100. Why not use AC mode?

[BadgerMcAdams]

rexlion wrote:
I am bumfuzzled. :h Everything I've read up until this thread had led me to understand that ammonia rv fridges can't achieve more than about 35 degrees difference from ambient temp. Everyone said so; it seemed to be "common knowledge." This alleged "fact" would translate to a fridge temp of about 65 degrees if the outside temp was 100. But a couple of you folks seem to be indicating that your fridge temps hold steady below 40* even when it's 100* outside. Unless I've misread, I need to completely re-adjust my understanding of these fridges! Or am I missing something? :?

I should add that my last two trailers had small (2.5-3.0 cu ft) units with side venting only. Their performance was abysmal. I did manage to get right around that 35* differential when I hung an O2Cool fan just outside the upper vent to suck air out through the vent system at a high rate. I can't imagine how that fridge could have been capable of a 50 or 60 degree temp drop, though!

While I haven't yet added the extra insulation and such, I too was under the same impression that the temp difference between outside and inside was approx. 35 degrees. I wondered why the Amish thought that these things were so wonderful if the temp would swing that much.

My Dometic 2310 will get cold, but as the outside temp rises...so does the inside. I live in Phoenix and will take the camper to Prescott or Pinetop and depending on the outside temp, the inside temp will fluctuate (Sometimes enough to worry about food temp safety so I always carry a cooler for backup)

SideCar, I will have to look at the insulation around mine and see what I can do. There probably isn't a lot as it hasn't probably been touched since leaving the factory. I do agree that the more insulation around an item, the harder it is for outside influences to cause a temperature change to the inside of that item. Also, moving hot air away from the device will cause cooler (relatively) to move in.

As mine is 26 years old, I'm not sure how much longer it will last...but until it goes the way of the Dodo Bird, I want it to work as best as it can.

[rexlion]

I am bumfuzzled. :h Everything I've read up until this thread had led me to understand that ammonia rv fridges can't achieve more than about 35 degrees difference from ambient temp. Everyone said so; it seemed to be "common knowledge." This alleged "fact" would translate to a fridge temp of about 65 degrees if the outside temp was 100. But a couple of you folks seem to be indicating that your fridge temps hold steady below 40* even when it's 100* outside. Unless I've misread, I need to completely re-adjust my understanding of these fridges! Or am I missing something? :?

I should add that my last two trailers had small (2.5-3.0 cu ft) units with side venting only. Their performance was abysmal. I did manage to get right around that 35* differential when I hung an O2Cool fan just outside the upper vent to suck air out through the vent system at a high rate. I can't imagine how that fridge could have been capable of a 50 or 60 degree temp drop, though!

[dave17352]

JimK-NY wrote:
I superinsulated the area surrounding the refrigerator. I also opened up some large spaces for ventilation and added two computer fans.

Well I checked you previous posts and see you have a NOVA KOOL.

I have only had mine running in a little over 90 degree temps but it had no problem what so ever keeping up. It is a 7.3 cubic foot and may even have the same size compressor as yours. Have you called there support line. I am curious. They were very helpful when I called during install. I am really curious what the problem is you are having. Mine is not opened to the outside. It is vented from underneath with its own fan. But I no problem keeping the temps stable and I did not run the ac in the TC. It was 90 inside the TC and little over 90 outside. I did wrap all sides and ceiling except one with a double layer of polyiso foam board which gives me about a extra r14 insulation.

[JimK-NY]

I superinsulated the area surrounding the refrigerator. I also opened up some large spaces for ventilation and added two computer fans.

[SidecarFlip]

JimK-NY wrote:
My compressor refrigerator does not do well in the heat. By the time the ambient temps reach the mid 80s, the refrigerator runs constantly or close to it. Because the energy consumption is so large in the heat, I need to keep the camper in the sun so the solar keeps up. It is a vicious cycle.

Have you checked / added cavity insulation? The more insulation, the better.

I was amazed at how ittle insulation there was with my ammonia unit and adding almsost 1/2 roll of R13 unfaced in the cavity, made a BIG difference. I bet it would do the same with your compressor unit too. Insualtion is insulation, don't matter what the mechanics of the cooling unit is....

Think I'd look at additional fans on the condenser too. Again, no matter what the mechanics are, the unit has to get rid of the heat.

I don't do solar at all so it's of no consequence to me. The only 'solar' I do is on my body, it turns me brown,,,

[SidecarFlip]

rexlion wrote:
Take a vacation to the SW US in July. 100+ degree daytime temps. You will see the need.

Why I bought the Dometic / Danfoss for the back seat, for those items that may perish above 40 degrees... Gotta keep my popsicles froze. Looked at Engle and ARB, Dometic is the best value.

[SCVJeff]

rexlion wrote:
Take a vacation to the SW US in July. 100+ degree daytime temps. You will see the need.

well I LIVE in the SW, and if we have 100degree temps in July, it's a cold spell. I replaced the ammonia cooling unit with He last year (so now my fire hazard is gone too). When we came back from the beach it was 102+ at the house... a perfect test.. the RV sat in front of the house for two days with the afternoon sun on the fridge side for several hours, and night time temps in the low 80's iirc. After two days, watching both the fridge and the freezer with tracking thermometers, the fridge maintained temps approx 34 and the freezer in single digits. There was a 2 degree swing total from Sunday afternoon to Wed night.

So... I fail to see the need

[JimK-NY]

My compressor refrigerator does not do well in the heat. By the time the ambient temps reach the mid 80s, the refrigerator runs constantly or close to it. Because the energy consumption is so large in the heat, I need to keep the camper in the sun so the solar keeps up. It is a vicious cycle.

[Kayteg1]

We've been camping in 110F with ammonia fridge and it worked just fine.
Just try to put the fridge side north, so the wall will not get 180F with sun exposure.
When compressor fridge is superior, I am not dumping good working fridge that just sips propane.
For us 5 gallons of propane last for almost 100 days of camping. Usually using heater at the end of the season will use it up as the fridge and water heating barely make a draw.

[rexlion]

Take a vacation to the SW US in July. 100+ degree daytime temps. You will see the need.

[SidecarFlip]

I ran my Dometic 3 way on propane from a full tank to empty and it lasted a solid month so propane use in minimal IMO. I got a Dometic / Waeco, Danfoss for the back seat of the truck but as far as replacing mine in the camper, I don't see any need. Besides, it's only 2 years old.

[NightSailor]

I keep hoping my two way fridge will die. I will be going Danfoss as I have plenty of Solar 825 watts. I want to reduce my dependency on propane. I am also putting in a solar hot water heater an eventual a electric heat boost.

[SidecarFlip]

Mine runs fine (after mods). Today was 86 and sunny and I was using it. Never got over 40. I went and bought a Danfoss Dometic portable unit for the backseat of the truck to keep stuff in while I'm driving...like vanilla ice cream...