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Misleading information in fridge article

Submitted: Saturday, Feb 03, 2007 at 12:46

pixiemops

These fridges use a source of heat - 12 or 240 volts or gas.

* Electric power: 12v, 240v

* Can run on gas: Yes

* Can warm food: No

* Can freeze food: In cool weather

* Cooling at 20 degrees: -10

* Cooling at 40 degrees: +3 to +15

* Maximum amps on 12v: 10

* Average amps on 12v: 10

* Amp hours per day: 240

* Noise level: Low

* Heat output: High

* Fast cooling: No

* Capacity range (litres): 39 to 50

* Price range: $350 to $1200

This is information about absorption fridges in an article on this website. I have been conducting temperature measurements on a dometic rc1180 chescold . In 40 degree heat it comfortably kept the freezer section between -10 to -15 degrees . At the moment it is running without the divider and it is reading outside 32 degrees and inside -10 degrees . This is very good considering the divider is out.
I feel the authors of this article need to review it . Doesnt surprise me but when you have a look at the advertisements below each post on this forum .

regards
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AnswerID: 219446   Submitted: Saturday, Feb 03, 2007 at 12:53

pixiemops replied:

Whoops in 40 degree heat that meant to read -15 to -17 degrees not -10 to -15. sorry
Reply 1 of 10
AnswerID: 219451   Submitted: Saturday, Feb 03, 2007 at 13:30

Member - Jon W (QLD) replied:

Pixiemops,
We have the same fridge bought new in 2000. Had the condenser (I think) replaced last year prior to heading off for 10 weeks. Other than that, it has not missed a beat and has performed well in +40 and below zero temps. We only run it on 12 V on the move and avoid opening it whilst on 12 V unless we have to.
Even my wife now agrees it is the best Xmas present she has ever received.
Jon W

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This is Central QLD.
Reply 2 of 10
AnswerID: 219504   Submitted: Saturday, Feb 03, 2007 at 18:35

wazzaaaa replied:

Sorry Pixiemops I have to say on gas I definitely do not get the results you are getting. Fired up my electrolux caravan fridge in the garage and also my fathers chestcold and on 240v I got it down to -09 but on gas struggled to to get it down to -2 in 32 deg outside temp. Fathers chestcold an esky would of done better.
In a camping situation I have found it even worse as you tend to put more hot things in and open the lid a lot more. Just my experience with them but I do love the idea of lighting them and forgetting them until the gas runs out.
Wazzaaaa
Reply 3 of 10
AnswerID: 219567   Submitted: Saturday, Feb 03, 2007 at 23:34

brett replied:

Yep I agree, I've never seen a gas fridge have a temp differential of 50 degree's. I've got an old chescold and at mid 20 deg outside it will be close to zero inside, can freeze stuff in lower overnight temps. Used it a few times at 40 deg and inside temp was closer to +10. I find very little difference in performance on gas or 240V.
Reply 4 of 10
FollowupID: 480129   Submitted: Saturday, Feb 03, 2007 at 23:45

pixiemops posted:

Guys the chescold I have is a modern one . I cannot make any assessment of the older ones as I do not have one . The article obviously lumps all into one basket. Therefore it needs updating. All Im telling you is that at 40 degree ambient my modern rc1180 achieves a temperature in the freezer of around -15 degrees.

Regards

FollowUp 1 of 1
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AnswerID: 219603   Submitted: Sunday, Feb 04, 2007 at 09:17

Robin replied:

Hi Pixie

I would have left the last line out of your question , if you really want to get to bottom of why yours seems to perform above average.

Drawing a connection between misleading information article and a ad requires a reasonable level of proof and tends to get people's backs up.

Robin Miller
Reply 5 of 10
FollowupID: 480194   Submitted: Sunday, Feb 04, 2007 at 10:52

pixiemops posted:

Robin I am not making any suggestion that my unit performs at below or above average. Im stating what performance I get out of a modern rc1180 Chescold model.

The article makes no mention of models or vintage so in my opinion is misleading full stop regardless of adequate testing proof etc. . How can you place them in one basket so to speak. So please don't imply I am responsible for getting peoples backs up . The authors of the article in my opinion are the ones who need to ensure that they are providing correct information and not misleading people (this is what gets people backs up).

regards

FollowUp 1 of 10
FollowupID: 480197   Submitted: Sunday, Feb 04, 2007 at 11:06

Mike Harding posted:

Robin, I think if you take a close look at responses on the forum you will find a number of people who report good performance, in line with the above, from 3 way fridges (we all agree they are not great on 12V). These two posts for example: 41187 and 30140.

I would agree with Pixiemops (just have to love that nick :) that the description of the 3 way is appropriate for my 20? year old Finch 3 way fridge but not for the two top Chescolds fridge/freezers sold today.

Mike Harding
FollowUp 2 of 10
FollowupID: 480201   Submitted: Sunday, Feb 04, 2007 at 11:25

brett posted:

Has something changed in the way these fridges are made? I was under the impression that aborbtion fridges had a max temperature differential that couldn't be improved on due to the chemicals or gasses used in them. Just like a compressor fridge on R134a gas has a limit, it reaches a point where the gas just cannot get any colder regardless of the compressor or condensor etc. The old R12 could go slightly colder and was considered a more efficient gas
FollowUp 3 of 10
FollowupID: 480220   Submitted: Sunday, Feb 04, 2007 at 12:19

Mike Harding posted:

Hi Brett

It's not my field so I can only go on what I read but many on this forum have reported excellent performance and this manufacturer:

http://www.gasrefrigerators.com/faq.htm#hotweather

quotes a fridge temp of 0F (-18C) at 100F (+38C) ambient.

Can't seem to find specs. on the Chescold?

Mike Harding
FollowUp 4 of 10
FollowupID: 480232   Submitted: Sunday, Feb 04, 2007 at 13:33

pixiemops posted:

Thanks alot Mike good link. Seems similar to the performance I have been getting .In 40 degree ambient -15 degrees in the freezer with the rc1180.

FollowUp 5 of 10
FollowupID: 480282   Submitted: Sunday, Feb 04, 2007 at 17:48

Robin posted:

Hi Pixie

I thought your post was quite good while you were laying down the performance of your unit. But as soon as you say that the those fridges read badly , and that this could be related to an advertizer then the credibility and your good work goes down the drain.

You may well be correct , but there is no reason why the next poster could not say in a similar vein that your post is biased as well but in the opposite direction.

If judgements were on a single good report then we would all be installing finches in our cars, and taking them out the following week as a followup bad report came in.

On the actual fridge question , I would progress that arguement by quoting the manufacturers claims from your handbook to show that they support what you say.

Robin Miller

FollowUp 6 of 10
FollowupID: 480286   Submitted: Sunday, Feb 04, 2007 at 18:07

Mike Harding posted:

>If judgements were on a single good report

But they are not Robin, are they?
FollowUp 7 of 10
FollowupID: 480302   Submitted: Sunday, Feb 04, 2007 at 19:09

Robin posted:

Now be fair Mike , you have cut a piece out of my text line which referred to both single good and bad reports.

There have been many good reports and many less favourable reports as to their performance so its reasonable to call in square on that level.

As I suggest , a reference to the manufacturers claims may be a good place to start and I suspect these may be a surprise !

Robin Miller
FollowUp 8 of 10
FollowupID: 480326   Submitted: Sunday, Feb 04, 2007 at 20:34

Mike Harding posted:

I am being Robin - your whole post is just a couple of inches up the screen for all to read.

Logically: we have a lot of people who report good results from these fridges - particularly the more recent models - we all (hopefully?) understand they have limitations and must be operated within those but the fact that many people give good reports and the manufacturer I mentioned gives specs. (-18C at +38C) would suggest they do what is said? Unless you are suggesting there is some sort of curious anomaly in the production process which leads some to perform and other not to...?

I suspect the issue is more that people are comparing my old Finch to the modern day units and/or are not operating them properly or understanding their limitations.

Mike Harding
FollowUp 9 of 10
FollowupID: 480392   Submitted: Monday, Feb 05, 2007 at 07:06

Robin posted:

Hi Mike

Then in reading my replies above it would be obvious that I have been concerned within a post titled

"Misleading fridge info " and has the ast sentence
" Doesnt surprise me but when you have a look at the advertisements below each post on this forum "

And not the performance of the fridge.

Robin Miller

FollowUp 10 of 10
AnswerID: 219675   Submitted: Sunday, Feb 04, 2007 at 14:00

Flash replied:

You'll find the Rc1180 is one of the best 3-ways around.
Very few others will perform as well.
Cheers
Reply 6 of 10
FollowupID: 480285   Submitted: Sunday, Feb 04, 2007 at 18:05

Mike Harding posted:

As far as I am aware there are only two 3 way camping fridge/freezers available in Oz, both Chescolds; the blue RC1180 and the green F400. I'm interested in why you make the above comment (and do you have any support info?) and also how people think the F400 compares to the RC1180?

Mike Harding
FollowUp 1 of 2
FollowupID: 480295   Submitted: Sunday, Feb 04, 2007 at 18:42

Big Woody posted:

Hi Mike,
I previously had the green F400 for camping trips to Fraser Island etc. and it performed faultlessly and had no problems maintaining a temp of -10c in an ambient temp of 35c.
I now have a 70 litre Evakool only because I have a trailer sailer yacht and wanted a fridge freezer I could use for sailing as well as camping. Maintaining the fridge in a level position in a yacht is not an option hence my change to a compressor fridge.
I must say I do miss the cheap running costs of the 3way on gas and have not yet completely resolved the problem of having enough battery power/solar panels to keep my current set up running for extended periods of cloudy days.

Cheers,
Brett
FollowUp 2 of 2
AnswerID: 219737   Submitted: Sunday, Feb 04, 2007 at 19:05

wazzaaaa replied:

Just on 3 way fridges, while I think they arn't anywhere near as good as compressor fridges when I did use them a couple of tips I got was with 3-way fridges it is common for the refrigerant gas to get airlocks. Before you have to use them tip the fridge upside down untill you don't hear the refrigerant gas running down (about a minute) then right it then use it as normal. It helped my fridges but that was when I struggled with them now I am over the moon with my waecos and my engle that the past is the past and I don't want to revisit the 3 way fridge hastle again.
Wazzaaaa
Reply 7 of 10
FollowupID: 480414   Submitted: Monday, Feb 05, 2007 at 08:55

pixiemops posted:

As Mike pointed out above we need to compare like with like . The older style three ways compared with the modern f400 and the rc1180 isnt a good comparison . Likewise we are not talking on the same playing field comparing compressor fridges and absorption ones. Just like talking Holden v/s ford in my opinion. Im not saying one is necessarily better than the other depends on how you are going to use it etc. Im very happy with around a -15 degree freezer at 40deg ambient on the rc1180. I don't like the idea of having to buy solar panels etc for camping so the rc1180 is great for me .

There is another fridge model b533 I think a grey fridge one that has a metal cabinet. Cheaper than the f400 and rc1180 but is only a fridge and green one or blue one is the one to go for. I have both but when I was a student all I could afford at the time was the grey one. Buy the f400 or blue one .

cheers
FollowUp 1 of 1
AnswerID: 219771   Submitted: Sunday, Feb 04, 2007 at 21:23

Member - Richard S (SA) replied:

The absorption refrigerator is a refrigerator that utilizes a heat source to provide the energy needed to drive the cooling system rather than being dependent on electricity to run a compressor. These refrigerators are popular where electricity is unreliable, costly, or unavailable, or where surplus heat is available, e.g., from turbine exhausts or industrial processes.

An absorption refrigerator is similar to a regular compressor refrigerator in that the refrigeration takes place by evaporating a liquid with a very low (sub-zero) boiling point. In both cases, when a liquid evaporates or boils, it takes some heat away with it, and can continue to do so either until the liquid is all boiled, or until everything has become so cold that the sub-zero boiling point has been reached. The difference between the two is how the gas is changed back into a liquid so that it may be used again. A regular refrigerator uses a compressor to pump the gas to the condensser, forcing it to become a liquid again once the heat has been removed. An absorption refrigerator uses a different method that requires no moving parts and is powered only by heat.

In these types of refrigerators the either use a ammonia base or lithium bromide that is disolved in water, the main reason you may have to turn the fridge before using it is that the ammonia or lithium bromide that is disolved in water has seperated.......hope this is helpful, if I went into the full refrigeration theory and thermodynamics i would be here for years.

In 3 way fridges you have very little control over the temp. in side the fridge because there is no way of controlling the heater side (unlike compressors in normal fridges taht cycle or change capacity AKA inverteror variable displacement types ).

Regards Richard
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Reply 8 of 10
FollowupID: 480798   Submitted: Tuesday, Feb 06, 2007 at 19:43

pixiemops posted:

Thanks Richard have been doing some reading on how these units work . Have read that there are two parts to the evaporator . A low temperature evaporator (the freezer part ) and a high temperature evaporator the fridge part.

In the low temperature evaporator the boiling point of ammonia is about -28 degrees celsius. As you say the liquid ammonia coming form the condenser will continue to boil until there is no more ammonia or until the temperature reaches -28 degrees. Of course you wont reach that in your freezer. So with good insulation a big condenser and a good heating unit -15 degrees seems obtainable. (note 13 degrees from -28)

In the high temperature evaporator( fridge section) the pressure of the ammonia has increased and so has the boiling point to about -9.5. So the ammonia will continue to boil until -9.5 is reached. Lets say a fridge is running around 4 degrees that is 13 degrees from -9.5. Interesting .

I am no expert on the physics /chemistry of an absorption fridge .

cheers
FollowUp 1 of 1
AnswerID: 219906   Submitted: Monday, Feb 05, 2007 at 14:06

Ron173 replied:

Interesting post, personally I have trouble faulting my Angel!, sorry Engel LOL

Joking aside, I'm always very interested in fridges, and have often thought of buying an additional gas fridge for long term camps in one place, but been put off by the absorption type not being able to pull high neg temps in 40 deg, which we get often.

I have a van with an absorption dometic in it, which is fine in 40deg if the annexe is up to allow it to expel heat, if no annexe its trying to fight against the heat soakage from sun and struggles, so I now run my Engel as a freezer with a solar panel and can go a week easy.

I do lots of different levels of camping from ute n swag to full van/boat/family/ 2 4bys, and I'd still be interested in a good gas unit.

Which brings me to ask the question of pixiemops here, and anyone else who can answer.......

OK pixiemops and others are saying the rc1180 is the dux nuts and can pull high neg temps in 40 deg, now I'm prepared to accept that, but my question is:-

As an absorption fridge which is a basic principle, which apparently hasnt changed over the years, how can it achieve this where others struggle to get 10deg?

What has changed in the technology? as I'm sure its not just better insulated?

If this is true and its using a better chemical or something, then it'd be a worthwhile investment if it can run for 3 weeks at -15deg in 40deg ambient from a 9kg cyl?

comments?

Rgds

Ron
Reply 9 of 10
FollowupID: 480488   Submitted: Monday, Feb 05, 2007 at 15:03

Robin posted:

Hi Ron

Some of the seeming misinformation may have come from
the RC1180 manual. (which I read today)

For example it says that it consumes 240AH per day
(same as quoted at start of this post).
This statement is not qualified by words to the effect that this is a maximum etc.

Worth thinking about for a moment !
This implies 10amps, its normal current, 24 hrs per day.

As well as this the manual, does not quote a temperature
differential for this performance and implies typical use.
Whereas Waecos latest, similar type quotes 30c typical differential.

The bottom line is that these fridges pull a lot less heat
out of the food than compressor types for same energy consumption
and rely on heavy power use and good insulation to maintain acceptable results.

The reason they work well on gas is because the effective gas power input
is over 200w based on their stated daily gas consumption.

A gas bottle holds a lot more energy than a battery and hence
they can be quite practical if used this way, and if nett heat loss is low
can achieve high temp differentials.

Robin Miller
FollowUp 1 of 2
FollowupID: 480515   Submitted: Monday, Feb 05, 2007 at 16:10

pixiemops posted:

I cannot answer that Ron. All I can report is the results I am getting . Have a look at the link provided by Mike further up . A search around this forum also has others posting -15 degree performance in high amient temperature with one person quoting -23 with the rc1180 (not sure of the ambient temperature).

I have sent an e-mail to the manager of dometic to see if they can provide me with some of their laboratory test data.

cheers



FollowUp 2 of 2
AnswerID: 219920   Submitted: Monday, Feb 05, 2007 at 15:15

Ron173 replied:

Thanks Robin,

10amps.... thats a lot! if on elec, which is not a way i'd choose to run a fridge of this type.

So it would prob use a fair bit of gas too, that wouldnt worry me, as long as it keeps well into the neg in stinking heat,

I like to see my Engel below - 10, figure it gives me a bit of a time buffer to act if something goes wrong with battery or panel etc.

I figure you can never go wrong with an extra freezer, especially as often we have 2 vehicles on trip.

Might look into this one a bit more come tax cheque time.

Ron
Reply 10 of 10
FollowupID: 480503   Submitted: Monday, Feb 05, 2007 at 15:42

Member - Brian H (QLD) posted:

Ron,

I have a Chestcold M2 I think and its over 20 years old I beleive as it was my mums. Now i had it serviced before a trip and as a matter of course I asked how long the fridge would last on a 9kg cylinder. He indicated it would last approximately 29 days. As for on the battery I beleive mine _Affordable_Storage_Drawers.aspx 12 AH and I only use that driving from location to location and it is hooked up to a 130 AH deep cycle which is charged from the vehicle.

I did the Cape (approx 30 days) with this unit and I just put it on gas at night and it worked fine. I figure if it was only used as a freezer it would have worked a lot better. Instead of being opened all the time.

At least it kept the food cold and beer really chilled :)

Brian
Does me
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FollowUp 1 of 1