Extra fridge fans WHY!!!

Lanerboy

Lanerboy

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Carthago 4.9 superior
I have a new MH with a Dometic fridge freezer that I think is pretty standard in a lot of MH's not sure of the fridge model but the MH is a carthago 2018, I have not had any issues with it but I have only used it in temps max 26 deg outside so why do people fit fridge fans and is my model the type that needs an extra fan or not.

I am asking as we are thinking of heading to the south of France again in the summer and need to be prepared as we are going for about 4 weeks.

Also in plain English please how does the extra fan help keep the fridge cooler than it is now

Also are there any funsters that use this type of fridge regularly in hotter climates and have no issues and all works fine

Thanks
 
I have always fitted fridge fans, they work well at keeping inside fridge and freezer temperatures lower than without them on hot days.
We have a new van with Dometic fridge. From new, they don’t get that cold. I think the ideal temperatures inside should be around 4 degrees C for the fridge and -18 c for the freezer.
Mine goes down to about 7 in the fridge and -12 in the freezer.
Anyway, I just fitted the fridge fans and after a couple of hours running, the freezer dropped to -14 and the fridge to 6. That was with outside temps at 26c.
I don’t know the technicals of exactly how they work but they clear the warm air out of the fridge vents quicker so allowing more heat to be dissipated from the cooling fins
Whatever, they do make a difference.

Here’s the new fans fitted in the top vent.

6CFDCDBA-177F-4076-95E9-28FFC0A5E374.jpeg
 
Hi, I fitted external and internal fridge fans and they work brilliantly, I followed Lenny HB’s post on how to fit them and found it relatively easy. His post is called “modding my new gin palace”
 
This is the first hot trip with our fans. They have been working overtime on automatic setting for over a week here in Bavaria. I’ve noticed a definite improvement in frozen things staying frozen and I’ve only had the setting on one above the lowest.
I’m sure that it’s used a lot less gas too, we’ve not been on EHU at all and normally would have used up a lot more. Free solar to run the fans seems like a good deal !
Got the same or similar to those above that come with a frame and a controller.
 
I got a toilet extractor fan from the bricolage, used a sucker to hang it on the top vent outside and connected it to 240 volts. Very simple and does work.

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Nirvanauk said:
I got a toilet extractor fan from the bricolage, used a sucker to hang it on the top vent outside and connected it to 240 volts. Very simple and does work.
Click to expand...
Would be better if 12v ?

As an edit to my post above, we went out one day and left van in full sun on over 30 deg day. I forgot to turn fridge to gas from battery when we stopped. The fans obviously kept running and I was pleasantly surprised to find all contents of fridge still nicely frozen and chilled upon our return over 4 hours later. So even with the fridge “off” the vent fans produce a change of temperature over the cooling fins.
 
Just read Lenny HB thread on fridge fans and i'm embarrassed to say it may as well be in Chinese as I don't understand a word of it. I can just about put a 3 pin plug on if I follow a diagram but that's my limit. Who could I get to install some fans like Lenny has in the Midlands area

Thanks
 
Sorry can’t help you there as I live in the Deep South but dometic do their own version and I think the instructions on those are relatively straightforward. Isn’t Dave Newell in the midlands
 
Lanerboy said:
Just read Lenny HB thread on fridge fans and i'm embarrassed to say it may as well be in Chinese as I don't understand a word of it. I can just about put a 3 pin plug on if I follow a diagram but that's my limit. Who could I get to install some fans like Lenny has in the Midlands area

Thanks
Click to expand...
Hi try Alan DMS he can sort it for you he is a Dometic supplier as well
 
Lanerboy said:
Just read Lenny HB thread on fridge fans and i'm embarrassed to say it may as well be in Chinese as I don't understand a word of it. I can just about put a 3 pin plug on if I follow a diagram but that's my limit. Who could I get to install some fans like Lenny has in the Midlands area

Thanks
Click to expand...
If you can't follow my simple instructions :D

Here are a couple of easy ways of doing it.

CBE Fridge fan kit.

Vento Fridge fan kit.

Did you read about the internal fas as well as that makes a bit different at recovering temperature after the door has been opened.
 
This site contains affiliate links for which MHF may be compensated.
This is my (simple) understanding of the process:
The fridge relies on circulation of the refrigerant by means of natural circulation.
This is achieved by the fact that a warm fluid will naturally rise to the highest point in a system (where it will cool and fall back down to the heat source to be heated again and the cycle continues).
In a fridge circuit, the refrigerant is cooled by the cooling fins at the top of the fridge. This provides a differential temperature between the top of the circuit and the bottom of the circuit (where the heat source is applied). The greater the differential temperature, the higher the natural circulation flow rate and hence the more effective is the cooling effect in the fridge/freezer.

Thus providing a means (fridge fans) to increase the differential temperature will increase the effectiveness of the cooling medium.

The above makes no attempt to explain how the refrigerant medium works and seeks only to explain the means of circulating the cooling medium.

Ian
 
Riverbankannie said:
Would be better if 12v ?

As an edit to my post above, we went out one day and left van in full sun on over 30 deg day. I forgot to turn fridge to gas from battery when we stopped. The fans obviously kept running and I was pleasantly surprised to find all contents of fridge still nicely frozen and chilled upon our return over 4 hours later. So even with the fridge “off” the vent fans produce a change of temperature over the cooling fins.
Click to expand...
No, I specifically wanted 240v. 2 fans running on 12v for a long time have the potential to flatten the battery.
 
Lenny HB thanks for the links I have read the bit on your thread about the fans arriving and you fitting them over and over but its just mumble jumble to me sorry but I just can't take it in, I can't find any post on there about internal fans though. I understand that the ones on the outside behind the vent push more air over the unit (I think) but that's about it I will have to get someone to do it for me.
 
Nirvanauk said:
No, I specifically wanted 240v. 2 fans running on 12v for a long time have the potential to flatten the battery.
Click to expand...
They take so little current and if operated by a temperature controller the current over a 24hr period is negligible. Also when off grid the power taken by an inverter to run 240v ones would take far more power.

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Lanerboy said:
Lenny HB thanks for the links I have read the bit on your thread about the fans arriving and you fitting them over and over but its just mumble jumble to me sorry but I just can't take it in, I can't find any post on there about internal fans though. I understand that the ones on the outside behind the vent push more air over the unit (I think) but that's about it I will have to get someone to do it for me.
Click to expand...
Just to make your day a link to my internal fan.
 
Lanerboy said:
Lenny HB thanks for the links I have read the bit on your thread about the fans arriving and you fitting them over and over but its just mumble jumble to me sorry but I just can't take it in, I can't find any post on there about internal fans though. I understand that the ones on the outside behind the vent push more air over the unit (I think) but that's about it I will have to get someone to do it for me.
Click to expand...
I don't know if this is any easier, I installed a kit and it only needs a couple of wires, ignore the bit about the diode as it was only me messing about with solar and AES,

www.motorhomefun.co.uk

Fitting CBE fridge fans

When this was discussed recently there seemed to be some interest in a thread on fitting this kit so here goes. I bought the CBE kit from the Netherlands for Euro 54.50 inc delivery, it was a lot more from UK sites and the Dometic kit is around £80. So in the kit you get two fans in a frame...
www.motorhomefun.co.uk www.motorhomefun.co.uk

Martin
 
Lanerboy said:
Also in plain English please how does the extra fan help keep the fridge cooler than it is now

Also are there any funsters that use this type of fridge regularly in hotter climates and have no issues and all works fine

Thanks
Click to expand...

A fan is not essential which is probably why the manufacturers don't fit them. All that happens is the fridge doesn't get as cold as it does when ambient temperatures are lower.

Absorption fridges work with a touch of magic as they achieve what intuitively shouldn't happen - the creation of cold out of heat.

The cold is generated when a gas evaporates, which it can only do by drawing heat from somewhere, say your beer or cheese inside the fridge.

The evaporated gas is then absorbed into a liquid, typically a brine.

Heat (gas or electric) is then used to boil the gas out of the brine. The hot gas rises until it reaches the finned tube at the back of your fridge. The fins cool the gas and this cooling can be aided by fans drawing air over them. The finned tube isn't horizontal but slopes downwards slightly. As the gas cools it condenses back into a liquid which runs down the slope. This is why absorption fridges don't work if they are tilted and the liquid can't run downhill.

The now cooled liquid runs back into the fridge where the magic happens because it will now boil at a much lower temperature. This happens because it shares this space with hydrogen and the low partial pressure means it can boil at -18C or even lower.

There are variations and different gases etc can be used.

A few vans now have a top fridge vent on the roof. This acts like a chimney and these don't need fans from what I've read.

But as suggested at the start, they are not essential and probably 99% of vans don't have them and their owners are still alive*. :)

Try without, see how you get on. I didn't fit fans for the first few years.

*Warm beer is not harmful but cold beer is nicer.
 
If you get the CBE kit ( other kits are available) or a kit with an automatic controller, the fans don’t always run at full speed unless you use the manual setting or the internal temperature is very high, so power usage will be very little.
 
There is a dometic kit, saw it at Chester on I think BossHog van. It is more expensive that DIY and they fit the fan just above the bottom grill.

Dometic AR-VKIT - Ventilation set for absorption refrigerators

Dometic AR-VKIT - Optional ventilation extra for optimal performance of 4-series and 8-series refrigerators. Thermostat-controlled, extremely easy to install.
www.dometic.com www.dometic.com

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We were in France for a month last year with the temperature over 38 and we noticed no drop in temperature inside the Dometic fridge/freezer.
The beer was still cold and no obvious problem with frozen food.
We have thermometers in both sections of the Dometic to check for any drop in temp.
Adding extra fans may do some good but from my experience they are rarely necessary.

?
 
Dometic AR-VKIT
I have this fan, (£60) very easy to fit the fan screws into pre drilled holes left hand side of back of fridge, just below pipework. the thermostat clips onto the pipe as directed and the supply wires just literary clip into the rear of the fridge 12 volt supply... it really is a plug and play system...
does it work...... umm did not help our fridge to cool below 9c last week in France.:(
so thats being ripped out and two vent fans will be fitted
 
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Put simply a fridge works by extracting heat from the inside and dissipating it on the outside. The faster the heat is able to dissipate the more effective the fridge will be. Hence the fans
 
Lenny HB said:
One tiny fan with a bimetal temp switch for £55 they are taking the pee.
Click to expand...
One good thing about the thermostat is that it doesn't continually use 150ma like the OTT (imo?) controllers.

My 555 circuit uses virtually nothing too ????

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The temperature across the cooling fins on the back of the fridge has a sweet spot which gives the optimum performance of the fridge.

This is our fridge fan setup.

3 x 140mm whisper quite fans.
311978




An internal fan to push the air around in the fridge to even the temperature top to bottom.
311979



And temperature controllers for the fans. The fridge was not on when the photo's were taken hence the temperature readouts on the controllers.
311981
 

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Thankfully it’s been so sunny our 100w solar has been keeping up as I have also been running a Thule omnivent in the roof and a John Lewis 12v desk fan by my bed
 
Nirvanauk said:
No, I specifically wanted 240v. 2 fans running on 12v for a long time have the potential to flatten the battery.
Click to expand...
This doesn't really sound sensible. A 12v fan won't run down your battery if you've got ehu as the battery will be on charge and will still work if you haven't. A mains fan won't work if you don't have ehu unless you run it off an inverter which will flatten your battery more. A 12v fan uses negligible current and is much cheaper.
 
Not bothered and never had a problem.
 
Nirvanauk said:
No, I specifically wanted 240v. 2 fans running on 12v for a long time have the potential to flatten the battery.
Click to expand...

Our fans are thermostatically controlled and normally only run for maybe 30 to 40 seconds dependent on the outside temperature in a 10 to 15 minute period to maintain the fridge cooling.

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