Atwood Helium Fridge problem

TXiceman wrote:

The manufacturers have caused the fire problem due to changes in the design. They have thinned the tube material, reduced coil area and raised boiler temperature to increase the capacity (due to the smaller coil areas).

I have had my last RV with a gas absorption unit. I love the 22.5 cu.ft. unit with ice and water in the door, inverter, battery bank and solar charger.

There's the irony- the manufacturers got beat up by the OEMs to reduce weight and cost- to the point of ounces and pennies. Now you have replaced it with several *hundred* pounds of equipment, due to savings of a couple of pounds.

Ammonia will only burn in the presence of a flame. Remove the flame and NH3 will not burn. The amount of hydrogen in the u nit is pretty small...a few ounces. The helium replaces the hydrogen and farther reduces the potential for a fire.

I do not see much difference in the operation or safety for that matter with hydrogen or helium.

The manufacturers have caused the fire problem due to changes in the design. They have thinned the tube material, reduced coil area and raised boiler temperature to increase the capacity (due to the smaller coil areas).

I have had my last RV with a gas absorption unit. I love the 22.5 cu.ft. unit with ice and water in the door, inverter, battery bank and solar charger.

Life is good...the icecream is frozen and the wobbly pop is cold all of the time.

Ken

A couple of points- I really do not think that the hydrogen plays a huge part in refrigerator fires- the ammonia is flammable as well, the hydrogen is at the top of the unit, not at the burner, and there just isn't all that much. While it certainly adds fuel to the fire, it isn't the main danger.
The other point is that many, if not most of the fires are from simple overheating. The refrigerant leaks out and the thing gets hot enough to ignite surrounding materials.

I'm kind of ambivalent about the Atwood refrigerator (and air conditioner). Probably not many here remember the Atwood refrigerators from the 1980's- I worry about orphaned appliances, like the Carrier air conditioners.

pnichols wrote:
Soo ... I repeat why hasn't "everyone" been using helium instead of hydrogen all along??

On the surface,it seems like a no brainer for absorption refrigerator manufacturers from day-one to have been using helium. Unless, as Chris mentioned, it's helium's higher partial pressure that kindof made it, or makes it ... a show-stopper ... and that Atwood is really taking a chance on adequate product performance by using helium this far along in the history of absorption refrigerators.

I still think absorption refrigerators are an absolute genius invention and perfect for drycamping RV use - especially if RV manufacturers would mount them on a gimbal mechanism (which I would pay the extra $$ for) so that they were always level no matter what angle the RV was at. ;)

Dometic and Norcold believe that Hydrogen will get colder than helium, and be more efficient. Atwood had to do something different than Dometic and Norcold, to be able to tout why their unit would be better. Doug

Soo ... I repeat why hasn't "everyone" been using helium instead of hydrogen all along??

On the surface,it seems like a no brainer for absorption refrigerator manufacturers from day-one to have been using helium. Unless, as Chris mentioned, it's helium's higher partial pressure that kindof made it, or makes it ... a show-stopper ... and that Atwood is really taking a chance on adequate product performance by using helium this far along in the history of absorption refrigerators.

I still think absorption refrigerators are an absolute genius invention and perfect for drycamping RV use - especially if RV manufacturers would mount them on a gimbal mechanism (which I would pay the extra $$ for) so that they were always level no matter what angle the RV was at. ;)

Thanks Chris, NICE!

Great post Chris.

Here's a page I wrote a looong time ago explaining how an absorption unit works.
The helium has, from what I can find, a somewhat higher partial pressure than hydrogen, so the absolute lowest temp that can be achieved would be somewhat higher than with a hydrogen system. The temp for a properly charged hydrogen system is around 44 below zero, F, which is, after all, plenty cold. Not sure what the temp with helium would be.
Remember that the whole thing is due to Dalton's Law, which states basically that the pressure of gasses in a vessel is equal to the sum of all of the pressures, but that each gas is at its own pressure, so the upper part of a cooling unit will only have hydrogen (or helium) gas present, and the pressure will be much lower than at the bottom of the unit, where the ammonia has evaporated to a gas.

Bill.Satellite wrote:

Clay L wrote:

Bill.Satellite wrote:

Old-Biscuit wrote:

pnichols wrote:
I'm curious ... what is "helium" refrigerator technology?

Helium replaces the Hydrogen in the absorption fridge.

Hydrogen? BOOM! I think you meant ammonia.

Nope, there is hydrogen in most of the RV refrigerators out there. It is used as part of the phase liquid/gas change process of the ammonia.
that is what catches fire from leaks. The helium is now being used instead of hydrogen because it won't burn.

I love this stuff......now, prove it!

Helium does NOT burn. It just REDUCES the chance of a chemical fire if it leaks. Hydrogen is more combustible. Until Atwood gets at least 30% of the OEM market, I will not use or recommend them. Doug

Clay L wrote:

Bill.Satellite wrote:

Old-Biscuit wrote:

pnichols wrote:
I'm curious ... what is "helium" refrigerator technology?

Helium replaces the Hydrogen in the absorption fridge.

Hydrogen? BOOM! I think you meant ammonia.

Nope, there is hydrogen in most of the RV refrigerators out there. It is used as part of the phase liquid/gas change process of the ammonia.
that is what catches fire from leaks. The helium is now being used instead of hydrogen because it won't burn.

I love this stuff......now, prove it!