Fridge fan installation ... DIY info please

Lenny HB said:
Not seen the Brunner one all the ones I've seen had fixed thermostats and a ugly control panel you need to mount somewhere.
I just like doing things the hard way, no fun in buying something and just bolting it in.:ROFLMAO:
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I am beginning to warm to your way. How did you fix the fans onto the grill? Am I also right in thinking that I could mount your controller on a wood panel?
 
I bought 2 120mm computer fans, attached them to the cover with small cable ties and attached them to a cigarette lighter plug after drilling a small hole through a partition into a cupboard next to the fridge with a 12v socket for a TV.

No thermostat, plug it in when it gets hot, unplug it when not, low tech, simple......I like simple:)
 
It does make me wonder. If people have to fit fans inside and out to control temps on these fridge freezers, are they fit for purpose?
Its not as if they are cheap! they are not.
The whole sector needs more manufacturers, because it seems its wrapped up by a few, who seem to have a monopoly.:(
 
peterc10 said:
I am beginning to warm to your way. How did you fix the fans onto the grill? Am I also right in thinking that I could mount your controller on a wood panel?
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Mounted the fans on the grill with cable ties.
Yes you can mount the controller though a wood panel it has panel mounting clips that are adjustable for panel thickness.
The hardest part of the job is getting the cables through that applies to what ever you fit.
In the last van I used one of the cheap 3 quid controllers it worked very well. I put it in a plastic box and left it behind the fridge.
PM me if you want any info or help, I'm travelling around France at the moment back at the end of next week.
 
Since turning my fridge up to max the fins at the top have ice on them but centre of fridge hovering around 5-6 deg with the bottom at 8-10.
Only Dometic could design a fridge that is warmer at the bottom, just not on that's where the beer goes.

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Sorry just re read your last post Lenny. I read the figures as being in the minus.
Still applies to a larder fridge though I am told.
 
bjandlin said:
Larder fridges without an ice box tend to be colder at the bottom. Heat rises etc.
BJ
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It is a larder fridge a 8505 fridge freezer, only Dometic could design a product that defies the laws of science.:D
 
should have bought a kit here @Minxy Girl :D

http://www.accesorioscaravaningvima...esa_details.tpl&product_id=214&category_id=52

peterc10 said:
When I last looked at this a couple of years ago you could buy a kit complete with everything including fans, controller etc. A couple of companies seemed to make them, one was Brunner I think. Has anybody seen them on sale in the UK? Tried a google search but found nothing.
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As above. The other site I have used Eurocaravanas.net ship to the UK .
jessthedog said:
It does make me wonder. If people have to fit fans inside and out to control temps on these fridge freezers, are they fit for purpose?
Its not as if they are cheap! they are not.
The whole sector needs more manufacturers, because it seems its wrapped up by a few, who seem to have a monopoly.:(
Click to expand...

If you turn the central heating up to 30º+ in your kitchen your fridge temperatures inside will rise. All require a difference in temperature to ambient to actually dissipate the heat absorbed from the product inside to the air outside.
Once they get to 30º ambient there are problems.
 
gus-lopez said:
should have bought a kit here @Minxy Girl :D

http://www.accesorioscaravaningvima...esa_details.tpl&product_id=214&category_id=52


As above. The other site I have used Eurocaravanas.net ship to the UK .


If you turn the central heating up to 30º+ in your kitchen your fridge temperatures inside will rise. All require a difference in temperature to ambient to actually dissipate the heat absorbed from the product inside to the air outside.
Once they get to 30º ambient there are problems.
Click to expand...
But it seems Dometic, dont know that, or they would fit fans inside and out(y)

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bjandlin said:
Larder fridges without an ice box tend to be colder at the bottom. Heat rises etc.
BJ
Click to expand...
Lenny HB said:
It is a larder fridge a 8505 fridge freezer, only Dometic could design a product that defies the laws of science.:D
Click to expand...

Science has to make way to practicality sometimes. That is why us Engineers are different to those scientists.

Every "larder fridge" and "freezer fridge" I have ever seen had the cooling element at the top. The idea was that the cold air at the top would then drop to the bottom, replacing the hot air, which would rise and then be cooled. The problem comes about when we start insisting on filling our fridge to the gunnels with stuff. That prevents, or at least hinders, the movement of the air. Hence warm air remains at the bottom.

Solution? Leave some bloody room for the air to move about, or suffer the consequences.

Another solution is to fit mechanical means of moving the air around. Until recently this was not done even for home fridges, although larger, American style, fridges like we have, have had these fans for many years. Its just the smaller ones did not have them - and all fridges in European motorhomes are "small" in this respect. Our new Samsung American style fridge has a very good air circulation system that keeps all parts of the fridge at the correct temperature.

The manufacturers could put these as standard on motorhome fridges but, firstly it will cost more and secondly it will use more electricity. So if you want to fill the fridge right up, do what @Robert Clark has done and fit an internal circulating fan.
 
Even when my fridge was empty the top was -2 but the bottom +4, once you put anything in it it can not get to recommended temperatures to keep food safe and that was at 15deg ambient.
Not fit for purpose.

As well as an internal fan may put some fans on the bottom vent to pull air in as well, rediculous that we have fit all these fans just to make the product work as it should.
 
Our 3 way fridge doesn't cope well when putting warm things in, the temperature stays high (7c ish) for a while. But I've got a digital Max/min thermometer in it and over night it easily pulls down to 1c. It's like what we used to say about freezers, they aren't made for freezing things, they are made to keep things frozen that you buy ready frozen.

Fridges that are made to cool things down are called 'Blast chillers' (-10c)
Freezers that are made to freeze things are called 'Blast freezers' (-50c)
And they probably cost as much as a Motorhome too :)
 
I think that possibly the way the fridges are fitted by the converters has a major impact on their efficiency.

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tonyidle said:
Latest Dometic absorption fridge performance:


DOMETIC RMV 5305

Absorption refrigerator - single-door model

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As I said not fit for purpose. +7 is not considered cold enough to keep raw meat safely .
Also they quote the +7 at an ambient of 32 deg, pretty useless for a fridge in a motorhome that is used all over Europe in countries where temperatures are often in the 40's.
 
Our Dometic Tower is working really well in Spain. I have three 100mm 12v fans running at 1/2 speed so they are nice and quiet. If it's really warm I can switch them to full speed. Temp behind the fridge can get up to 40 Degrees with the fans on full it can be reduced to 30 Degrees but it can be a bit noisy. You certainly need fans that can move air effectively. 12v ones can have speed adjusted with a simple resistor in the circuit.

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Hi Q4
I thought I was doing well having installed what appears to be the same fan as you have use behind our Dometic Tower fridge. Your installation of 3 appears to be controlled by a thermostat . or at least that what I think is standing up in the middle of your picture.
The reduced speed sounds a great idea and the additional fans obviously move more air. Any chance of a simple wiring diagram and what resistor did you use?.

Wolf

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Rather than reduce the speed of a noisy fan it is much better to buy decent quality fans, a good fan will be quiet and still shift a good quantity of air has they have more efficient blades.
 
The resistors will get hot too as a wattage will be dissipated in them. Better to wire 2 fans in series if you want to quieten them down. Better still wire in a series/parallel switch, Google for diagram.
 
Richard and Ann said:
The resistors will get hot too as a wattage will be dissipated in them. Better to wire 2 fans in series if you want to quieten them down. Better still wire in a series/parallel switch, Google for diagram.
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Will two fans in series shift as much as two in parallel? I'm just about to wire mine up and could do either. Are they quieter in series because they are running at lower speeds?
 
Voltage will probably be to low for the fans to run even if they do run at ½ voltage they will probably pass less than a ¼ of the volume of air than if running at 12v.
Why mess about a couple of decent quiet fans is only about 12 quid.
 
Lenny HB said:
Voltage will probably be to low for the fans to run even if they do run at ½ voltage they will probably pass less than a ¼ of the volume of air than if running at 12v.
Why mess about a couple of decent quiet fans is only about 12 quid.
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I have two decent? (Arctic) fans. I've read a few suggestions that they are wired in series rather than parallel but cannot work out why.

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Mattyjwr said:
Will two fans in series shift as much as two in parallel? I'm just about to wire mine up and could do either. Are they quieter in series because they are running at lower speeds?
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No they won't shift as much in series, but they are loads quieter. Mind you my fans are a bit more high powered than the normal computer fans. Try them in parallel first to see how noisy they are.
 
All set up and ready for use :) Two arctic fans in parallel with the thermostatic switch set at 28oC to start with.

Thanks for your advice and help.
 
Update on my loaded up fridge.

The freezer had 48 ¼lb burgers and 32 sausages in it but that won't make much odds as the freezer is a slave to the fridge.
The fridge had 18 bottles of wine and food crammed into the top and bottom.

Outside temp was 16 deg, and while juggling to get it all in fridge temp rose to 15.
The internal fan was running but external fan controller was turned off as it was only 16 deg outside.
After a couple of hours the internal temp was about 11, switched the controller on and temp above the coolant fins was 40deg so fridge was working hard considering it was only 16 outside.
After a couple of hours with the external fans running fridge down to 6, and overnight dropped to 3 deg. I was measuring temp ⅔ of the way down the fridge in the centre of the shelf.
Monitored it for a couple of hours in the morning, min 2.9, max 3.3.
Well pleased considering how loaded it was. Obviously won't get that sort of performance in 30deg plus, but pretty good result.
 

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OK, tempting fate here. Why is there a need for an expensive fan controller for fans mounted behind the top fridge vent? I bought 2 Arctic computer fans - which are indeed almost silent - and connected them to an existing permanently live feed to the fridge. They are connected with a 0.5amp inline fuse, the feed then going through a cheap temperature switch, a 35 degree normally open type, mounted up high behind the fridge.



You have no control to manually turn it off and on, but why does that matter? If the fridge is running you want the fans to be ready to come on anyway, they'll come on when it gets to 35 degrees above the back of the fridge, inside the vent.

If the fridge isn't running and the side of the van gets hot enough in the sun to turn the fans on, who cares? They use next to no power and my solar panel will easily cover the consumption in that heat. Living in the UK the chances of my van reaching 35 degrees are remote anyway! I've had it like this for a year now and it seems to work well.

Am I missing a downside? Just seems a simple, easy and cheap way to add fans and wire them in. You could use a different switch if you wanted a different temperature, they are after all only a couple of quid.

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