New Fridge Topic: A Different Approach

[rbryan4]

Originally Posted by cpaharley2008

Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?

Jim, I' don't encounter the zero degree scenario like you do, so I can't speak to that. But I am basing my opinion on experience. This July it got up to 105 degrees in my garage, and yet my little compressor based fridge almost froze the beer.

I suppose it isn't that the technology of compressor based fridges is better at heat exchange than absorption is, but that the design of the currently available absorption based fridges is not as robust as their older counterparts. Jon mentioned a 1953 absorption fridge that's still going strong, and I've heard other reports along the same lines.

We may just be dealing with an inferior product, not an inferior concept.

[hotfishtacos]

Originally Posted by cpaharley2008

Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?

I think it is simply that compressor driven heat pumps are much more efficient than absorption type; they apply much more energy to the process and run the process much faster transferring heat at a much higher rate.

[Parker]

So, remember what this thread was about? I kicked it off, suggesting that people call Dometic with their concerns. Has anyone else done so? I've called three times, and to my surprise I got an email from them a couple of days ago asking about my initial warranty claim (which I also suggest current owners to consider). I'll keep you posted.

[tractors1]

Originally Posted by cpaharley2008

Something does not add up here, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box. As anyone knows, heat pumps are ideal in temperate zones, but poor performers in cold and extreme heat. So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?

Different refrigerants. Compressor versions can exchange more heat due to pressurization/differential than ammonia versions.

[Ron in BC]

Originally Posted by cpaharley2008

, a compressor refrigerator is like a heat pump, it cools by pumping the hot air out of the box.

No, it removes heat from the air. The air stays in the fridge

Ron

[Brian B-P]

Originally Posted by cpaharley2008

So explain why a compressor refrigerator will work more efficiently/effectively in -0- weather as well as 100 degree weather than the absorption unit?
The heat exchange does suffer in both scenarios in both units does it not? Basic physics here. So why would one out perform the other?

The temperatures at which each cycle can work are limited by the characteristics of the refrigerants, and by the physical process occurring the cycle (absorption versus a phase change of a Freon-like refrigerant), which are different.

In addition, while both systems are challenged by high ambient temperatures, the refrigerant in a compressor-equipped refrigerator is pumped around by the compressor, while the refrigerant in an absorption-based RV refrigerator is moved by another heat-based cycle involving hydrogen (or helium) gas. The absorption unit's pumping action is limited by the temperatures at various points in the cycle, but the compressor works regardless of temperature.

Originally Posted by grc

Mr Escape Artist pointed to residential usage ammonia refrigerators by the Amish. They brand they used to use was Servel, but Lehman Brothers has several other brands. Ammonia refrigeration is not just used in small scale, rv's and residential, it is used in large scale commercial food storage and processing, along with massive concrete construction.

I don't know about the domestic units used by the Amish, but commercial-scale ammonia refrigeration is not quite the same as the system used in an RV appliance. We have an extra circulating gas (that hydrogen or helium) which drives the cycle without needing a motor (done to avoid any need for electrical power), but commercial units normally use an electrically-driven pump.

Also, I don't think that many Amish communities are located in areas where very hot weather is common.

[tractors1]

When I explained the thermodynamics of cooling/heating to my dad, once I explained the heat was removed from his beer in the fridge and expelled out the coils in the back, his initial comment was "So I really need to keep the back clean!"

[Cypherian]

Originally Posted by Brian B-P

The temperatures at which each cycle can work are limited by the characteristics of the refrigerants, and by the physical process occurring the cycle (absorption versus a phase change of a Freon-like refrigerant), which are different.

In addition, while both systems are challenged by high ambient temperatures, the refrigerant in a compressor-equipped refrigerator is pumped around by the compressor, while the refrigerant in an absorption-based RV refrigerator is moved by another heat-based cycle involving hydrogen (or helium) gas. The absorption unit's pumping action is limited by the temperatures at various points in the cycle, but the compressor works regardless of temperature.


I don't know about the domestic units used by the Amish, but commercial-scale ammonia refrigeration is not quite the same as the system used in an RV appliance. We have an extra circulating gas (that hydrogen or helium) which drives the cycle without needing a motor (done to avoid any need for electrical power), but commercial units normally use an electrically-driven pump.

Also, I don't think that many Amish communities are located in areas where very hot weather is common.

Hmm Amish Tourism in Texas | USA Today

Delaware Amish » Amish America

Who Are the Amish? - Mission to Amish People

[Kountrykamper]

Lets get back to the OP's original suggestion that we call Dometic to voice our concerns over the performance of their 8XXX series fridges. I did, have you?

[Cypherian]

Originally Posted by Kountrykamper

Lets get back to the OP's ogional suggestion that we call Dometic to voice our concerns over the performance of their 8XXX series fridges. I did, have you?

You are correct KountryK mea culpa to the OP for adding to thread derailment.

Cypher

[Jim Bennett]

Originally Posted by tractors1

When I explained the thermodynamics of cooling/heating to my dad, once I explained the heat was removed from his beer in the fridge and expelled out the coils in the back, his initial comment was "So I really need to keep the back clean!"

Great explanation, and a good observation by your dad.

I know I have mentioned it before here, but I like the way a thermodynamics instructor put it to us, and a great way to look at, and understand, heat transfer. There is no such thing as cold, only an absence of heat.

Understanding that helps a lot with understanding how heating, and cooling, works. It is either heat applied, or removed. That is until you reach absolute zero (-273°C)

[Dave Walter]

I think that it has been too many beers since my university thermodynamics courses. It is all just a fuzzy memory.

[davescape]

Originally Posted by Jim Bennett

Understanding that helps a lot with understanding how heating, and cooling, works. It is either heat applied, or removed. That is until you reach absolute zero (-273°C)

...and I thought -55C in Edmonton was cold. BRRRR. The way I see it, absolute zero is when the temperature drops enough to form ice on my wind shield, and that's cold enough

[jamman]

Inadequate cooling registered with Dometic customer service.

[Parker]

Excellent. I'm now getting some interaction going with Dometic on ours. I'll post the outcome when I know more. I think it helped that I took it in originally as a warranty claim for this problem, but I have no way of knowing that.

[escape artist]

Originally Posted by Jim Bennett

Great explanation, and a good observation by your dad.

I know I have mentioned it before here, but I like the way a thermodynamics instructor put it to us, and a great way to look at, and understand, heat transfer. There is no such thing as cold, only an absence of heat.

Understanding that helps a lot with understanding how heating, and cooling, works. It is either heat applied, or removed. That is until you reach absolute zero (-273°C)

Hi: Jim Bennett... During my last year of work at transit... my degree of cooperation dropped to near absolute zero!!! Alf
escape artist N.S. of Lake Erie

[Jim Bennett]

Originally Posted by escape artist

Hi: Jim Bennett... During my last year of work at transit... my degree of cooperation dropped to near absolute zero!!! Alf
escape artist N.S. of Lake Erie

I'm starting to feel the same way Alf, yet not certain of when I will be retiring yet.

[Parker]

Actually, this thread was supposed to be about getting disappointed Dometic owners to contact the factory to register their complaints. That's why I called it "a different approach."

[gbaglo]

Tried to sift through posts and moved home heat pump posts to their own thread.

[Parker]

I just talked with Nicki at Dometic. She is new to the office and has been exploring the various complaints that at least a few of us have registered with Dometic. As requested, I'll be taking our Escape in for another warranty visit to have a bypass test conducted, which may help uncover a problem. The fact that it's now getting cooler here may complicate that, but we'll see what happens. She said Dometic is coming more and more to recognize the problem and she believes they are working on a solution, but whatever is happening is close-hold for now. She did say it's important for me to go ahead with the bypass test at the RV shop, so I'll do it. They can apparently contact the Dometic techs and conjure up some way to simulate hot day conditions. It's not scheduled in until Nov 3, so I'll come back to report on what happens.

I again suggest that people call Dometic to express your concerns. She said they are becoming more aware of the problem, and that can only be because a growing number of people are voicing their concerns, rather than trying to solve the problems themselves. Once again, the number is (574) 294-2511.

Please, let's try to keep this thread about working with Dometic on this issue. There are lots of really interesting discussions elsewhere in the forum about how things work and innovative solutions when they don't.

Thanks,
Parker