Dometic 3n1 absorbtion- what's realistic ?

[mkguitar]

Ours is in a 2006 Pleasure Way, we bought last year.

On our recent trip we were generally on AC at night, DC while driving and propane while parked during the day.
We rotated blue ice packs from freezer to fridge through the day ( freezer always stayed below 28º
the fridge would go as high as 44º some days...then cool at night

This has a single 100CFM fan mounted under the fins.


Now that we have returned, I bought a bunch of 3" fans, each is good for about 50 cfm.
I have mounted 4 of them pushing out the top vent- party obstructed but moving good air out the top, which draws in pretty good from the bottom.

running on AC

ambient temps are maybe 88º at 6 am, 100 by 10 am and peaking at 110 at 3 pm, staying above 100 to about 9 pm
( the van windows are open as we work on our homemade screens and vent fan is on- the van is close to ambient temps)

charting through the day with van parked beside the house ( level) and a harbor freight "carport" kit providing pretty good shade, I am charting generally 55º to 60º cooling below ambient.
the fridge is empty- I know that with goods in it the temps should be more stable

Compared to other dometic 3n1's- how am I doing- fair, good, great?

thanks, Mike

[mkguitar]

with the 2 fans exhausting ( side by each) mounted to the left side of the top vent I have managed to keep temps below 37º the past 24 hours.

Our ambient temps have dipped with a storm system moving through- but close to 100º most of the day- and no lower than 84º.

so I am getting cooling about 65º below ambient on AC- this is a slight improvement.

I have to look at the propane- It doesn;t seem to cool markedly better than the AC.

I have cleaned the vent and hanging baffle- there was not much in the way of carbon.
Next step will be to examine the jet and make sure it is correct size for our model and check the thermocouple.

...which I have just done- everything I looked at was clean, but i cleaned anyhow- the gas controls work as expected and the thermocouple put out 34mVDC...right within spec.
Fun little project.

We plan on heading out mid-week after everyone is back from their long week end





easy to do this while we are home, rather than scratching head in a campground.

mike

[GaryKH]

My wife is good at keeping the temps at around 40 in 100+ weather. She uses 2, 2liter (quart) plastic milk jugs & rotates them every day from the freezer to the fridge. This makes the whole system work like a regular cooler in addition the fridge. I do my part by either having the van in the shade, or providing temporary shade for the fridge vents (with air flow).

[Vulcan_Rider]

mkguitar wrote:

It may well be that 4 fans are better for AC operation,

4 fans is just gross overkill, regardless of the mode of operation or the environmental conditions.

IF you have them blowing in series, any more than one is a total waste.

[bsinmich]

One thing I have used is to get a couple pieces of dry ice to help the initial cooldown.

[mkguitar]

Sorry if that wasn't clear, In the 1st post I described 4 x 3" fans pushing out the top vent.

What I am up against are our high ambient temps from May to Mid September over 100º with about 20 days over 110º. Our low temp is typically still above 85º

I'm trying to get the best I can out of this for our climate- get predictable results under various conditions.

It may well be that 4 fans are better for AC operation, and 1, 2 or none fans are better for propane operation- I'll find out.
DC doesn't really figure into this as air flow from driving will be the largest variable

and add to that the method of rotating frozen stuff to the fridge area to help stabilize temps

Mike

[Vulcan_Rider]

mkguitar wrote:

I am wondering if the 4 fans are too much and the airflow is interfering with the propane heating the fluid.

I think I said that already.
And asked where the fans were located.....but you never responded to that.
I have no real problem with mine.....with ZERO fans. I can't see ever thinking that more than 2 (one inside and one outside) would be of any advantage but sometimes things just get stuck in our brain it seems. 😉

[mkguitar]

As of now- on AC mode consistrntly 55 to 60º below ambient is possible with the 4 fans I added.

However the propane is not cooling well- or as well as I think it should.
I am wondering if the 4 fans are too much and the airflow is interfering with the propane heating the fluid.


so the MKII version is now just 2 fans, and placed at the end farther from the propane.

Running AC mode today and cooling seems to be about as good- but hard to tell we had a couple of storms come through today and the ambient temps were not stable.

I'll see how the AC does, then switch to propane mode and see how that is.

Mike

[cbigham]

I leave mine on gas, occasionally rotate frozen soup or drinks from the freezer to the top shelf in the fridge. Things that must be kept cold I put on the bottom.

[mkguitar]

Yes, I saw your post on that somewhere...

Luckily we are in the habit of putting the same things in the same places in the fridge so a quick grab and shut.
And that does help with the fridge temps

Mike

[stan909]

My fridge works pretty good but my wife does not. Where I try to grab stuff quick and close it , she leaves open far too long and the poor thing is no match for her.

[goreds2]

PSW wrote:


I always tried to park the RT so that the sun hit the side with the refrig the least amount of the time....sunnyside on the other side than the refrig.

This is the only way my fridge will seem to cool properly. I was going to post this. A very important step. Shade is key.

[mkguitar]

Yes the seal is pretty good- did the dollar bill test all around the edges.

and do have a remote thermometer sender inside the fridge so we can see how it's doing.

thanks, Mike

[PSW]

When we had our 2007 Roadtrek with the dometic, we ran it like you do: dc going down the road and AC if we had hookups (seldom)and propane the rest of the time, most of the time since we boondock for days at a time. We had no problems when the temps were 100+ and the temps stayed at mid 40s in the heat of the day, cooling down with the day.

I always tried to park the RT so that the sun hit the side with the refrig the least amount of the time....sunnyside on the other side than the refrig.

Also, I think a ten buck wireless indoor outdoor thermometer is a necessity. Put the outdoor sender in the center of the fridge and monitor the temps from somewhere else in the coach. My wife is a fanatic about keeping the proper temps. We had that rig seven years and had no problems keeping it cool in hot weather. She kept the indoor/receiver unit velcrowed to the dash in front of the passenger seat so she could monitor going down the road as well as when parked.

No doubt about it: DC is really good only to keep what is cold cold and you better be running the engine or your coach batteries will drain pronto.

Is the seal around your door in good shape? Is the material still flexible and "alive"?

Paul

[mkguitar]

I have a small camco 2xD cell fan inside- it is a gentle waft..and does help

I have no 12 volt inside the fridge, one of the things I will look at is running 12 VDC inside for a fan and light

the gap between the coils and outer wall is about 3/4"- even with no fans there is good convection in the bottom, out the top.


Propane; one of the things I will look at is jetting we live at 1400' but much of our camping is 5000'~8000'
I'll save that until I have charted some baselines

mike