Atwood Helium Refrigerators

[markopolo]

Not exactly new tech having been introduced in 2011 but I first learned of them today in an email from Mike.

http://www.atwoodmobile.com/refrigerators/

and the owner manual:
http://www.atwoodmobile.com/manuals/ref ... nual_8.pdf

With larger fridges showing up in B vans maybe these will be used.

Features and benefits:
http://www.atwoodmobile.com/images/Refr ... rpoint.pdf
- Non-flammable Helium
- Tilt sensor
- Door ajar alarm
- LED interior light
- “Airing Position Cards” for the storage latches

[booster]

Interesting stuff. I had always assumed the absorption frigs still used ammonia, but they say hydrogen. Live and learn. They don't say they will run OK off level, just that they will not be damaged as easily. A clarification on that would be interesting. They do have a level sensor, which makes a whole lot of sense, and all absorption frigs could sure use one. The how level question comes up constantly. The fact that they have the level sensor would indicate they need to be pretty good, but is it more or less than others? I hope they get it to work. Anybody know how efficient helium is as a refrigerant? It could use more or less propane based on it.

It is good that manufacturers are getting with innovative frig designs, as it is still one of the things folks have the hardest time getting the way they want it.

[Mike]

I'll let you know when I do next week sometime.
Reading the doc, it implies they adapted the absorption system to use helium by modding the plumbing somehow. Maybe as simple as larger diameter tubing/venturi configuration?
"i The Atwood refrigerator uses a gas
absorption system, but has replaced
commonly used Hydrogen with nonflammable
Helium.
i This was achieved by modifying
portions of the cooling system and
varying the charging pressure to
compensate for the larger helium
molecules."
I would think the performance will be as good as previous incarnations of the refrigerators.
We used ours so sparingly it will be hard to compare. I'll be happy if it works. I'm concerned about the Sprinter/DEF system similarity. The system will only run off level (no idea what the "severe angles off level" means) for so many iterations, before popping a "get service" warning and shutting down. I suppose it's a good way to prevent damage that would require an expensive replacement.

[booster]

I am not totally up on absorption technologies, but I think the gas properties are very critical in achieving efficiency and setting of the operating parameters. Ammonia was the original gas everyone used, even though it is horrible to work with as it is very corrosive and toxic. I didn't know they had switched to hydrogen. Perhaps there is a refrigeration person on here who can explain better, but I am sure lots changes with different gas, that would have a different heat capacity, boiling point, etc.

[markopolo]

I don't know either but maybe the Hydrogen relates to Hydroxide as in the liquid ammonia hydroxide in the absorber.

[markopolo]

It used to be that you smelled ammonia when the fridge cooling system in an absorption fridge leaked ..........
Now you'll know it is leaking if your voice get higher pitched and squeaky from the helium

[Mike]

or if kids ask you if you can fill their balloons from your fridge.

If the hydrogen was the component in the ammonia version of the absorption fridges, it's being replaced by an element that's twice the size at the atomic level, if my periodic table memory is correct, so maybe the physical hardware changes required are by a factor of 2 to get it to work? Just guessing. Helium is inert and won't combine (easily) to make a larger molecule, so is the ammonia portion completely gone from the system now? I would guess so, but I'm not a chem engineer, nor a fridge expert. Maybe they've combined the best features of both worlds, by adding some compressor function to the absorption model?

There must be a diagram that explains it out there somewhere.

[mlts22]

Call me a cynic, but what I would love to see would be Atwood, Dometic, or Norcold make a fuel cell that uses propane that generates enough electricity to keep a set of batteries charged. Then pair that up with a conventional compressor refrigerator. That way, the worry about ammonia, hydrogen, as well as having to be within a couple degrees of level would be in the past.

[Mike]

I think booster has a Norcold compressor model that is very light on power consumption. If I had had a choice for our trailer, I would have opted for one, too. On a positive note, I have read that the helium charged absorption fridge we have is more efficient than the hydrogen charged ones. For what it's worth, it may not be that much better, but every bit helps.

[markopolo]

Originally Posted by mlts22

.......... what I would love to see would be Atwood, Dometic, or Norcold make a fuel cell that uses propane that generates enough electricity to keep a set of batteries charged.................

These quiet propane generators might be the next best thing to propane fuel cell: http://www.classbforum.com/phpBB2/vi...php?f=9&t=2493

[booster]

I just did a quick read about the helium vs hydrogen. It appears both gasses are used in addition to the ammonia and water in the frig. They are the third leg of the the "3 gas" units. The helium is just used in place of the hydrogen. I couldn't find anything that really said either was a whole lot better than the other, and it is the ammonia that is corrosive. I think the anti-corrosive is what plugs the tubes when they overheat from out of level, so I don't see how that would change.

It will be interesting to see more information from experts on the Atwood.

[mlts22]

Call me dumb, but what keeps Norcold, et. al, from having a level switch. Off level by enough to damage refer, the board turns off the element or cuts off the gas. Perhaps add an override switch, but this would at least end the problem of "am I level enough?"

[Mike]

They figure a written warning will suffice? They want to sell more refrigerators and replacement parts?
I think Atwood is trying to create a refrigerator nanny state, by shutting you down, if you don't comply.
Hoping not to find out.

Does Norcold make absorption fridges, as well as compressor types that aren't "level challenged"? Dometic makes absorption for sure, I have one.

[teachergal]

I think an "out of level" light on the fridge would be a GREAT addition!!!!

I know my fridge alerts me if it's power source cuts off (assuming it's not on "auto" but I never put it on "auto" because of the potential to drain the battery) and turns itself off if I leave the door open too long...so it's certainly smart enough to tell me when it's not level enough.

[Mike]

I have one.
heh heh heh.......

[markopolo]

That is nice feature. Hopefully Dometic and Norcold will add it (if new models don't already have it).