# Fridge vent temperature



## bjandlin (Sep 15, 2009)

Good evening, A little advice please.
In readiness for a hot summer I'm fitting cooling fans to the fridge vents.
I have an adjustable thermo switch but am not sure what vent temperature I should be trying to maintain. Any ideas please.
I've looked back at a lot of previous threads on the the forum but can't find anything that give any figures.
Thanks 
Barrie.


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## inkey-2008 (May 24, 2008)

Any air flow is better than none you can not cool it enough on a hot day. I would just set it to maximum and let it run.

But only on hot days. best if you can park with the fridge vents away from the sun.

Andy


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## provencal (Nov 5, 2008)

Have a look at http://www.outdoorbits.com/fridge-flow-fan-p-81.html where it says 30°C.

With our fitted in the outlet flow, the fan runs nearly all the time.

Brian


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## Razzo (May 1, 2005)

*Fridge Vent Temperature*

I have fitted computer fans to a couple of motorhomes. I have never had one that had temperature control. My rule of thumb is to switch on the fan at an ambient temperature of around 30°c. With ammonia systems I am unfamiliar with their optimum operating temperature range. A 5°c temperature increase would not be unreasonable. I suggest you set it to 35°c if the thermostat is near the top of the space at the rear of the fridge. See how that relates to my 30°c. Then adjust your setting to fine tune it to what you feel comfortable with.

I like the idea of the thermostat as then you can set and almost forget and it will come on and go off when you are away from the van

For those who do not know the principles are the amount of heat removed from the fridge equates to the air flow over the coil by the increase in temperature of that air. The closer the temperature of the incoming ambient air is to the temperature of the ammonia in the coil, the less is the rate of heat transfer. An increase in airflow assists this.


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## bjandlin (Sep 15, 2009)

Thanks everyone.
I'd more or less come to the conclusion that 28/30 degrees was about right, so thanks for the conformation.
All I need do now is work out the stat settings,
Thanks again.
Barrie.


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## stevegos (Jun 23, 2013)

> For those who do not know the principles are the amount of heat removed from the fridge equates to the air flow over the coil by the increase in temperature of that air. The closer the temperature of the incoming ambient air is to the temperature of the ammonia in the coil, the less is the rate of heat transfer. An increase in airflow assists this.


So, the hotter it is outside the fridge, the less efficient the fridge cooling is and cannot take as much heat out of the interior?

When you say "air flow over the coil" is the coil the black radiator thing on the rear?


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## vicdicdoc (May 14, 2005)

stevegos said:


> > For those who do not know the principles are the amount of heat removed from the fridge equates to the air flow over the coil by the increase in temperature of that air. The closer the temperature of the incoming ambient air is to the temperature of the ammonia in the coil, the less is the rate of heat transfer. An increase in airflow assists this.
> 
> 
> So, the hotter it is outside the fridge, the less efficient the fridge cooling is and cannot take as much heat out of the interior?
> ...


Yes the black 'snakey' tubes - best to direct fan air towards upwards over the tubes (hot air rises)


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## bjandlin (Sep 15, 2009)

*fridge fans*

Thanks for previous replies everyone.
Another small question please.
I remember some where a comment about the proximity
of the gas exhaust vent in the top grill area.
Is it necessary to extend the pipe towards the grill ?
I think Techno 100 mentioned it somewhere.
Any comments as always appreciated.
Thanks.
Barrie.


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## listerdiesel (Aug 3, 2012)

It depends where the exhaust vent is now. There are also restrictions on where it can be located in respect of opening windows etc.

We've got a small 40mm fan from a Hewlett Packard computer power supply, it is 12V but run with a resistor in series to cut down the noise and airflow.

While in France in June we had no issues with the fridge at all, but our layout is slightly different to most motorhomes as the air vents open up into the rear compartment and we left the tailgate open on the safety straps so there was a volume of air flowing through.

We did think about a larger fan, but it seems to have done the trick as fitted.

Fridge is the Electrolux RM2267.

Peter


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## teensvan (May 9, 2005)

Hi.

I fitted 2 100mm computer fans directly under the fridge fins with tie wraps. Works very well. Just switch it on and leave it running all the time we are up when it is hot & sunny. Both fans use under 1 amp. Solar panel is 130 watt so no need to worry about power use. I have used this system in our last 2 vans over 9 years now. 

steve & ann. ------------ teensvan


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## Mrplodd (Mar 4, 2008)

I am a great believer in KISS

Keep
It
Simple
Stupid

It's better to draw the cooling air up rather than trying to force it up through the cooling coils, the important thing is that the hot air is drawn away from the fridge coils so that (relatively) cooler air flows over the heat exchanger coils to remove as much heat from it as possible. 

So I have a single fan fitted to the top vent controlled by a switch inside with a warning LED.

It's a dead simple modification that really does work surprisingly well.

It uses negligible power and there is little if anything to go wrong. Why complicate matters with a thermostat?? If it baking hot turn the fan on, when it cools down (night time?) switch it off, who needs a thermostat to that? Not rocket science.


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## Snunkie (Mar 21, 2011)

I've come across these threads a lot about extra fridge fans and we've travelled to Europe for the past 3 years and will probably continue to do so and wondering if it's something we should fit?
Is it easy enough to do? Do you take a feed from the fridge somewhere? Does the fridge need to be removed? 

Sounds like a job a bit beyond me. Although I recently fitted a solar panel so could I fit a fridge fan? :?:


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## listerdiesel (Aug 3, 2012)

It is easy enough to fit but does require some thought.

We put our tiddly fan at the top of the rear kitchen wall where the heat collects before going out of the top vent.

We have six through-floor air inlets running across the floor, three under the fridge coils and two under the cooker, the last is under the central divider/cupboard.

You also need to remember that heated air expands up to three times its volume, so the outlet(s) have to be bigger than the inlets.

The fan is there to help shift heated air out and allow cooler air in.

The fan needs to be quiet enough to leave on all the time and at night, ours has run continously for 18 months without stopping, and it was a used fan to start with.

If I do fit another, it will be the same type and size but on the far side of the top vent.



















Finishing it off with a standard bit of trim makes a neat job of it.

Peter


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## bigcats30 (Aug 13, 2012)

Snunkie said:


> I've come across these threads a lot about extra fridge fans and we've travelled to Europe for the past 3 years and will probably continue to do so and wondering if it's something we should fit?
> Is it easy enough to do? Do you take a feed from the fridge somewhere? Does the fridge need to be removed?
> 
> Sounds like a job a bit beyond me. Although I recently fitted a solar panel so could I fit a fridge fan? :?:


As MrPlodd says...KISS

at the back of the fridge will be a live 12v feed (live when power is switched on in hab area)

buy a cheap 12v 120cm computer fan (I used two)

cut off the ends of the cable....connect to the 12v source

You don't even have to worry about +/- as all that happens is the fan turns in the other direction.

fit to back of fridge cooling fins (I used a couple of cable ties)

I fitted an small inline switch that I can access with a pen etc through the fridge vent to turn on off

and all done.....

Simple


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## Easyriders (May 16, 2011)

Rather than fitting a fan to the outside grid to extract, the best method is to fit a fan to blow upward through the fins.

That is what Dometic themselves recommend (and also what they fit to their fridges in tropical areas).

Also a good idea to always have the fridge side facing north, if you can. But you will still have problems over 40ºC, which is why we bought a Waeco compressor fridge/freezer. We got sick of having to throw food away.

You do need mains or 12v to operate it. But if you use it as a freezer, as we do, you can then freeze those blue freezer blocks every day, and put them in the fridge to help it along.


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## Pudsey_Bear (Sep 25, 2008)

See pics 115 on from my link below, 3 100mm fans drawing air upwards and out, pointless putting them at the bottom, you're just blowing air about, so mine suck it out the top to assist the natural flow, not inhibit it.

I also have a 100mm fan inside the fridge compartment to help keep the cold air circulating and not just cold by the fins, the fan blows downwards, as this is the natural way, cold sinks, heat rises.

The fans do inhibit the passage of air when not on of course, but they draw less than 2amps when on so the solar panel is more than enough to keep them going, and they are on a manual switch as I didn't have time to source a decent stat switch when I was fitting them, so looking for a suggestion for one.


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## pippin (Nov 15, 2007)

Goooooooooooooooooooooooooooooooooooooooogle search for

Velleman Thermostat Kit

Cheap as chips and easy to assemble if you can solder.

If you can't then I can do it for you.


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## Pudsey_Bear (Sep 25, 2008)

Thanks, I was looking for something more like this really, so I can see what's going on rather than a PCB which is hidden behind a panel.


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## Baron1 (Mar 9, 2011)

I put a couple of PC fans from Maplins (I think) behind the top vents of my 'fridge, this sucks the hot air out from where it accumulates in the top of the void behind the fridge.
Fitting was easy peasy, I just mounted them both on a piece of angled ally which I then fixed in place behind the top grill, picked up a 12volt feed which I connected to the positive wires of the fans and interrupted with a switch, then earthed both the negative wires. 
I mounted the switch just inside the m/home door and as soon as it gets a bit warmish I flick the switch on (it's illuminated so you can't miss it when you enter the van)
This set up works perfectly for us and it is quite amazing how much hot air comes out of the vents when the fans are running!! 

Mel.


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## Pudsey_Bear (Sep 25, 2008)

Great minds think alike, almost identical to my set up, I went for three fans as my vents are undersized by about 10%


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## pippin (Nov 15, 2007)

Handy Hint Nr 397 from pippin.

If you wire two fans in series the noise diminishes hugely.

OK, not so much air is sucked/pushed but with two fans at half-cock there is still plenty of movement of air.

If you have one fan and find it a bit noisy especially at night then simply fit a second one in series.
Ditto if you already use two.

I noticed (I think in Listerdiesel's picture) that someone was using a series resistor to drop the voltage. 
Wasted energy as extra (unwanted) heat!

For the computer fans I have installed in the roof windows I have two in each.

The ones over the bed bring fresh air in, the others in the hab/kitchen area blow hot air out.

By simple wiring of a switch it is easy to have them either at full (noisy) tilt when required or in series at half speed (at night) when they are really quiet.


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## Zebedee (Oct 3, 2007)

> Baron1 said:- I put a couple of PC fans from Maplins (I think) behind the top vents of my 'fridge, this sucks the hot air out from where it accumulates in the top of the void behind the fridge.
> Fitting was easy peasy, I just mounted them both on a piece of angled ally which I then fixed in place behind the top grill, picked up a 12volt feed which I connected to the positive wires of the fans and interrupted with a switch, then earthed both the negative wires.
> I mounted the switch just inside the m/home door and as soon as it gets a bit warmish I flick the switch on (it's illuminated so you can't miss it when you enter the van)
> This set up works perfectly for us and it is quite amazing how much hot air comes out of the vents when the fans are running!!
> Mel.


I did exactly the same as Mel, even to using the same little green illuminated switch from Maplins, and I agree that it works a treat.

I would disagree with most people in one small detail however. If you wait until it's so hot the fridge is struggling, you then have to cool it down far more than if you prevent it from getting so hot in the first place.

Since the fans consume almost negligible power, why not switch them on first thing in the morning when it's likely to be a hot day? Then the fridge is *kept *cool, which is far more efficient.

Three of us have now done tests by switching on first thing, and by waiting until it's very hot before switching on, and the early switch-on wins hands down!

Hope this helps

Dave


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