For some time I have had some issues with my dometic fridge not coping with changes to of temputure from day to day. I followed some posts to instal a couple of computer fans to the outpot grill with a obvious improvement in the fridges ability to cope with temputure changes. While things had improved there were still issues that needed to be sorted.

After reading JC's mods to the fridge in the form of insulation on the sides and top of the fridge has brought about a marked improvement in the operation of the fridge with a more stable operation.

After chating with Jim about the topic of air flow up behind the fridge came up and in our discussions the matter of the possible disruption to the air flow from the fans by air being drawn in via the remaining top grill on each side of the fans. Before carrying out the modifications I tested the amout of air flowing through the bottom grills to check if there was any improvement  to that air flow after the modification was carried out.

Using a tissue to check the airflow effect,  the tissue that was about 30 mm way was drawn towards to grill but would not reach the grill. The modification was then carried out, that was with two output grills that did not have a fan mounted on them were blocked off so no air from the outside could be drawn into the cavity behind the fans and the airflow test with the tissue was carried out again.

this time the tissue was drawn to the grill from 50 mm away and onto the face of the input grill where it stayed. The modification showed that by blocking off the air from outside the exit grill and allowing the fans to draw air from only the input grills is getting more air flowing past the rear of the fridge and hence remove more heat from the fridge.

With the two modifications carried out, insulation and fans with the two side vents blocked have given rise to a better operation of the fridge. The final testing of the fridge will come when the hotter days arrive but after seeing the improvements so far I am convinced that the fridge will cope better during those hot days.

i know that a bit of a long post but I know that there are many people who have done the fans modifications but they will operate so much better after the vent blocking mod is carried out.

Tryi it and see for yourself

Brian

Hi  Doug, no I don't run the fans all the time but if there is going to be any hot weather around then I switch the fans on before the hit days arrives so that the fridge is not having to try and get rid of built up heat and in that way the fridge is not trying to get rid of that heat and operate normally as well.

looks like the way forward with this matter.

Brian

-- Edited by briche on Tuesday 7th of January 2014 08:39:47 PM

-- Edited by briche on Tuesday 7th of January 2014 08:42:27 PM

Well done Brain, so my crazy theroy wasn't wasn't so crazey after all.

If we keep battling this issue we might happen to make a good fridge some day. LOL

Beats me asto why these socalled manufactures can't do as the fridge people recomended with the insulation.

It would cost bugger all for material & easy to do under assy.

I look at it this way, walk through a c/park in hot weather, fridge vents are off, shade protection fitted, fans running etc.

All with the same prob, so there has to be a common denominating factor.

What keeps heat out in summer, what keeps cold in???????????????????????????????????/

INSULATION!

JC.

hako wrote:

---

Brian, I'm no engineer (it shows!), but by blocking off the grill in the manner you describe, you would be reducing the nett airflow over the condenser when the fans are not in operation thereby reducing the efficiency of the fridge. You may then have to use the fans all the time otherwise efficiency will suffer. Just a thought.
Regards
Denis

---

HI Hako

Yes ,

100% correct ,

. NOT a good idea .

All one needs to do is apply a bit of physics ,to understand what is requirec & what may be detrimental at times

That includes using natural draft effects as well as fans

PeterQ

brian wrote:

---

I don't use any special ducting, vent alterations or fans either inside or outside, and my fridge maintains cold temperatures right up into high ambients and on any angle, and I can open the door as often as I like....Ohhhh hang on, it's a compressor fridge..lol

---

 HaHaHaHaHa

and

Ditto..lol..

Hi,

A friend recently made these modicifations and is more than happy with the result.....

 www.dreampod.net/boroma/fridgefan.html

Hope this is of some help.
 

Cheers
George

Briche I had the same problem but took a different tack. The problem I had was the gap between the fridge and the wall of of the van As the air from the bottom vent was taking the path of least resistance and flowing between the wall and the cooling fins then bottling up at the boxed area at the top of the fridge.

Mod 1. Installed a false MDF wall to reduce the gap between the wall and the fridge down to 10mm.

Mod 2. Installed a curved alum sheet from the to of the fridge to the top of the vent. The air now can flow out the vent without the bottle neck. Remember that the easier the air flows out the more (draft) cooler air flows in.

Mod 3. Insulated the rear sides of the fridge so that the air is drawn from the bottom vent only.

Mod 4 Installed a fan through the floorat the base of the fridge to draw the cooler air in from under the van. (installed a dust sheild in front of the fan).

Mod 5. Installed a tube fan above the cooling vents.

The fans are on a 3 way switch so I can have bottom/top/all on. It is important to remember that the air flow can not be to fast as it needs time to absorb the heat from the fins. I can now maintain around 3 degrees in Nth Qld summers and only use the fans if the sun is on that side of the van. As long as SWMBO does not hold the door open while she makes up her mind what we are going to have for tea.

Wassa

Thanks oldtrack123 for your comments and duly noted. after commenting to Dougwe I gave it some thought about turning the fans off but have now Decieded  to leave the fans running for most of the time. If at any time I turn the fans off I will remove the blanking plates to as you say, to allow enough normal air to to happen. For everyone's posts I thank you for all the comments are what this forum is all about. 

briche

HI Wazza

Yes,If the fridge is roof vented, then  a fan in the top orks great provided as you say any side vents above the condenser line are blocked off again 

That is actually the way I have done my motor home  

One fan under the condensor   ,baffled to the side wall so very little cooling air can bypass the fins, so no cooling air is wasted.

Then made a tube to fit under the roof vent with a fan inside the tube

I actually used small car fans in both situations ,as I did this a long time ago [.about 20YEARS ago ]They are thermostat contrlled by an old stem type thermostat that I had at the time , tied to the top of the condensor fins 

Reason I put it there is because it is the coolling of the refrigerent that counts & is required

They very successfully reduce t,he refrigerent to near , ambient temp [before it enters the evaporator ' & the fridge has operated almost as normal in 40C temps

AS in my earlier post ,I also used a vertical baffle behind the fridge to keep the boiler heat away from the rest AND to not cool the boiler

I also packed foam insulation ln the side gaps & the one above the fridge BODY

one little comment on your post ,if you do not mind ,

The faster the air flow the better the cooling of the fins

I  wired  the fans  via a switch that allowed  series or parallel operation [slow or full speed ]

while slow was ok in the lower high temps  when temps went real up full speed wswas needed

In the end I just left them on full speed [paralled]

Each run time was ,usualy,only a few miutes

PeterQ