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Dometic fridge/freezer cooling?


Deffheads

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Hi we have recently arrived in Spain, 10 days ago, to retrieve our Dethleffs from storage. I am experiencing problems keeping the fridge/freezer working in nearly 40C temperatures. I put the awning out and have a cooling fan in the upper vent. What else can I do? Warm lager is not an option, running on gas, as mains electric is rubbish.
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You need the fan to run all the time with those temperatures. Try to reduce the area in the fridge if you can. Roll a blanket or a couple of towels in a plastic bag and put in the bottom of the fridge. The less space it has to cool the better it will work.
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It may seem silly but actually many people put in 2 fans in 40 c, it is high I know, we have done that temperature.

 

It is essential that the rear of the fridge is sealed from the inside, all the air needs to be dragged across the back and out the top quickly, if the top vent feels like hot air is coming out ( a lot hotter than 40 c), there is not enough through draft ( a bit warm yes but not hot). Lots of fridges do work better on gas but all have problems with 40 c continuous. Do check the internal temperature for food safety, its amazing how warm the stuff gets before you work out thats why its gone off. Chill the beer a bit more one at a time in the freezer part .

Basically the designers have had it wrong for years and have learnt nothing.

They do have Chest freezer types that cope better as cold air stays in when the door is opened and the cooling systems are designed for it, they even run on solar 12v okay. In Australia these are more popular with their regular 40 c temperatures.

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Deffheads - 2020-07-18 8:44 AM

Fridge is full [beer and food] no room for blankets, I can't take off the top vent as the fan is attached to it. It's seems this forum contributors know more about 'Garage lighting] than the workings of a motorhome fridge!

 

It seems your van was in storage locally, probably in full sun, so the whole structure will have become very hot, including the fridge. Even for "normal" use the advice is to put the fridge on for 24 hours before storing food in it. I assume that may not have been possible. Liquids are dense, so take much longer to cool than most other produce. It sounds a bit as though you've started with a very hot fridge, possibly not given it time to come properly down to temperature before filling it - possibly very full - and also put a substantial quantity of liquid into it. Under present operation conditions, it didn't stand a chance.

 

The fridge should recover somewhat overnight, and the liquid should provide some "ride-through" cooling for the first part of the day. But, try taking all but one beer from the fridge, and only cool these as required, over night, for consumption next day. Ditto wine/water. That should relieve some of the stress on the fridge, and also allow greater internal free air movement.

 

Simple, but obvious, general advice is to open the fridge door/s as little as possible, and to make sure they are fully closed and not obstructed by the contents.

 

There also needs to be space within the fridge to allow air to move around, or you will get quite wide temperature variation within the fridge from the area near the condenser cooling plates to those at the lowest shelves.

 

Shade as far as possible from direct sun whichever side of the van has the fridge vents, to reduce heat gains from the outside wall in the vicinity of the fridge.

 

If the fan thermostat is adjustable, reduce its "on" temperature by about 5C. Failing that, disconnect the fan and remove both top and bottom vents.

 

But, simply put, 40C shade temperature is probably outside the working temperature range of the fridge. Have a look at your fridge manual. You will probably fine a statement similar to: "Dometic refrigerators work according to the absorption principle. Due to physical reasons, an absorption system responds slowly to changes made on the thermostat controller, or a loss in cooling through opening the door, or storing food. The devices fulfill the cooling performance requirements of the Climatic Class SN acc. to EN/ISO 7371 in the temperature range of +10°C to 32°C ambient temperature." (I would expect Thetford fridges to state similar.)

 

But also, with the external vents removed, see if you can look into the void behind the fridge, to see if it has become obstructed while in storage. Even cobwebs will reduce air flow over the rear condenser coil/sand these and dust may be partially obstructing airflow over them. Clean these as far as access permits - but be careful, as they can become extremely hot when the fridge is working hard.

 

You may find that the fridge installation is not as recommended by the manufacturer (many aren't), particularly regarding the provision of an angled baffle at the upper air vent to help guide the rising air column at the rear of the fridge through the vent.

 

Last thought: have a look at, and clean off, the insect meshes on the back of both vent grilles - at 40C, every little helps!

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Brian, I understand all principles of keeping in shade etc, and I would not be in Southern Spain normally it's just we are retrieving moho after lockdown and experiencing 40 degree plus inside and outside , now in the Algarve things are better but not great, would not put any meat in freezer as it barely copes, except over night when ambient temp is mid to high 20's. On the plus side I still have cool beer but no ice for the wife!!

 

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As has been mentioned do not over fill the fridge and turn the temp setting down a notch ..I found this works in those temps. Have you checked the flue is not sooted up that will reduce the fridges efficiency and you have a nice blue flame. And all the other suggestion as well......
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When you ask for advice on a problem you might have the courtesy to realise people are trying to help. Over forty years in the caravan motorhome trade. If your fridge is full as Brian says especially liquid it will take longer to cool. If in extreme temperatures if you run the fans constant as the temp reduces overnight it gives the fridge a chance to catch up. By reducing the cubic volume of it means there is less to cool again reducing the load. Allowing the air to circulate around the rest of the fridge by reducing what’s in there will help. Beer wont go off if it’s not in the fridge food will. Covering a couple of bottles with a wet cloth and placing them under the van will lower the Bottle temp a bit, then hopefully as you fridge cools down you can slowly put more in it. As to knowing more about garage lighting it would appear that some of us know slightly more about the workings of a fridge than others. Certain attitudes to replies discourages people from posting, hope you stay safe as the infection rate would appear to be on the rise in some parts of Spain.
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Many thanks for all suggestions, I gas flue is clear and as always it runs better on gas than mains electric,as for taking the beer out, that's not an option [warm lager is disgusting]

For a while I have contemplated renewing the door seals as I have found a company that make them,as Dometic pricing is ridiculous, as the fridge is now 15 years old and might be at end of life. But on the good side we are now on the Algarve and it's pleasantly warm in the low 30's and fridge is coping just! No ice for the wife though!

I read a post on one FB forums of a guy who had converted his fridge using a marine Isotherm GE80 Fridge Kit. Any thoughts on this?

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Deffheads - 2020-07-19 8:56 AM

 

Many thanks for all suggestions, I gas flue is clear and as always it runs better on gas than mains electric,as for taking the beer out, that's not an option [warm lager is disgusting]

For a while I have contemplated renewing the door seals as I have found a company that make them,as Dometic pricing is ridiculous, as the fridge is now 15 years old and might be at end of life. But on the good side we are now on the Algarve and it's pleasantly warm in the low 30's and fridge is coping just! No ice for the wife though!

I read a post on one FB forums of a guy who had converted his fridge using a marine Isotherm GE80 Fridge Kit. Any thoughts on this?

Lots of the new PVC motorhome have compressor fridge options which work far better than normal motorhome fridges but there are a few postings on different forums saying they are noisey at night as they kick in and out ..there is a night settings which reduce the noise ...some light sleepers say they have to turn it off and put a bag of ice cubes in for the night ...dahhh.. you need to investigate,, marine application is ok as boats are much noisier than a parked up motorhome ...

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I think if you are running at 40oC and you go by the excellent suggestions given here , you won't go to far wrong for good advice, Maybe on your return a new fridge may be in order, if you have exhausted all those avenues,(replacing seals etc') Ensure as Brian pointed out that your 3 way can actually cool over 40oC . not many will ,without using more fans or some ice blocks along with your beer and that is still pushing it.
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My experience with the two Dometic fridges we had previously is they are next to useless in anything above about 25c. In contrast the Thetford fridge we have now is still chilling beers to icy cold even at 30 degrees outside. Of course 40c is another level but I would imagine the Thetford would do better based on how it is coping so far. Both were absorption fridges so not sure why the Thetford seems so much more capable.
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webpax - 2020-07-19 9:46 PM

My experience with the two Dometic fridges we had previously is they are next to useless in anything above about 25c. In contrast the Thetford fridge we have now is still chilling beers to icy cold even at 30 degrees outside. Of course 40c is another level but I would imagine the Thetford would do better based on how it is coping so far. Both were absorption fridges so not sure why the Thetford seems so much more capable.

One possible reason might be, based on my own experience, that Hymer tend to do a better fridge installation than a number of other m/h manufacturers. Another possible reason might be that the fridge you have now is taller than others, which creates a longer "flue" at the rear of the fridge, in which a stronger "stack effect" can develop. The stack will be notably weaker behind the "shorter" fridges.

 

But there seems to be an acceptance by Dometic that absorption technology is inherently limited in its cooling ability, with the maximum reliable temperature reduction being about 22C below ambient. So, to keep the fridge at around 5C, 30C ambient is about the limit. Above 30C only compressor fridges can cope, but even then should be designed for hotter regions than our "northern temperate" zone. But, compressor fridges bring their own problems, most notably off-grid battery drain, and noise.

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Brian Kirby - 2020-07-20 11:08 AM

But there seems to be an acceptance by Dometic that absorption technology is inherently limited in its cooling ability, with the maximum reliable temperature reduction being about 22C below ambient. So, to keep the fridge at around 5C, 30C ambient is about the limit. Above 30C only compressor fridges can cope, but even then should be designed for hotter regions than our "northern temperate" zone. But, compressor fridges bring their own problems, most notably off-grid battery drain, and noise.

 

I've just found a Dometic website which compares Absorption vs Compressor fridges and it clearly states...

 

"ABSORPTION REFRIGERATORS... Not suitable for use in extreme ambient temperatures above 95°F" which is 35 °C.

 

https://www.dometic.com/en/se/lp/rv-refrigeration-technology

 

Keith.

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I think Brian has hit the nail on the head,Anything over the 30oC mark for a prolonged period is pushing it. Especially in direct sunlight, poor fridge intstallation or bad flue draught .Campsites with ice come in handy or one with an inside freezer in those very hot climates. Hope we were of some assistance to you , Safe home.
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We have a 2019 Burstner with a Dometic absorption fridge freezer, we are near Chalus Haute Vienne currently 33c have fridge set on 2, fridge side facing the morning sun this side has the awning. Set right out to shade the van. Running on electric fridge is doing ok but we are careful not to overload it so allowing the air to circulate.. no fans fitted as yet.
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Brian Kirby - 2020-07-20 11:08 AM

 

webpax - 2020-07-19 9:46 PM

My experience with the two Dometic fridges we had previously is they are next to useless in anything above about 25c. In contrast the Thetford fridge we have now is still chilling beers to icy cold even at 30 degrees outside. Of course 40c is another level but I would imagine the Thetford would do better based on how it is coping so far. Both were absorption fridges so not sure why the Thetford seems so much more capable.

One possible reason might be, based on my own experience, that Hymer tend to do a better fridge installation than a number of other m/h manufacturers. Another possible reason might be that the fridge you have now is taller than others, which creates a longer "flue" at the rear of the fridge, in which a stronger "stack effect" can develop. The stack will be notably weaker behind the "shorter" fridges.

 

But there seems to be an acceptance by Dometic that absorption technology is inherently limited in its cooling ability, with the maximum reliable temperature reduction being about 22C below ambient. So, to keep the fridge at around 5C, 30C ambient is about the limit. Above 30C only compressor fridges can cope, but even then should be designed for hotter regions than our "northern temperate" zone. But, compressor fridges bring their own problems, most notably off-grid battery drain, and noise.

 

You may be on to something there Brian the 'good' Thetford fridge we have is at least twice as tall as the 'bad' Dometic fridge.

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