This post is of interest to all fridge-interested listees.

Marshall Ruskin
----- Original Message -----
From: "Davidson" <wdavidson@THEGRID.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, April 27, 1999 10:42 AM
Subject: Adding Dometic Fans by Bill Davidson

> Regarding Adding Fans to the Dometic fridge:
>
> But first, it's hard to stress strongly enough how important the inside
fan
> and
> packing of food for airflow are! (More important the extra fans behind the
> fridge!) You can have a fridge that is working perfectly and still not
have
> cold food if there is not adequate air circulation inside the fridge! I
> pack the bottom pretty tight and make it a point to leave the middle of
the
> center shelf clear except for the fridge fan. Pay particular attention to
> the use of plastic bags which tend to spread out and form natural blocks
to
> airflow! The fridges are small, but remember: The only things that
> absolutely have to be refrigerated are meat and milk (though some claim
> that cold beer is a necessity too!). If you need more space than a loosly
> packed Dometic can provide, it is better to take along an ice chest than
to
> pack the food into the Dometic so tight that nothing gets cold.
>
> Regarding adding 12v fans to the back of the fridge:
> First I have to acknowledge Derek Drew because I got some of my ideas and
> much of my inspiration for working on the fans from his article
> "Refrigerator Madness." Thanks Derek! Derek includes lots of other good
> stuff besides adding fans to the Dometic. You can find his article at:
> ftp://gerry.vanagon.com/pub/technical/Refrigerator-Manual.txt
>
>
> And now for "Refrigerator Fan Insanity":
> I spent A LOT of time figuring this out so I am happy to help others save
> time by sharing my experience. However, I will assume that you will figure
> out some of the details since it would take so long to remember and write
> out. But, if you get stuck on something or just need more information,
> please feel free to email me.
> I checked out the current usage ( with amp meter), the force of airflow
(by
> wiring up with alligator clips & blowing each on my face), and the noise
> factor on four fans that were readily available (I did not search far and
> wide for fans). The four fans were: the stock Dometic fan, the Radio Shack
> dc brushless computer fan no. 273-243B, the Fridgemate model A10-2710 Coil
> Fan, and a solar powered fan that Camping World sells (the name of which I
> forgot). I found the Fridgemate to provide the most air movement for the
> amps and it was the quietest of all four fans. It was rather subjective,
> but I felt that each of the Fridgemate fans blew between 1/3 and 1/2 the
> air volume of the stock Dometic fan and used less than 1/3 the amps. I am
> not familiar with the "muffin fans" that you mentioned. If I remember
> correctly the Fridgemate uses about 65mA, the stock Dometic about 220mA,
> and the Radio Shack computer fan about 120mA. I did not make my choice on
> price. I really wanted a quiet, efficient fan system.
> I visualized the airflow path (under the fridge, up the back of the fridge
> through 2 sets of cooling fins, and then out from behind the fridge two
> ways: out the grill behind the top of the fridge and out the grill that
> adjoins the table). Feeling the heat and slow air movement at the grills,
I
> felt that the two air exit grills were restrictive and inadequate. So
first
> I enlarged the rectangular side grill hole by about two inches toward the
> front of the fridge until it was flush with a horizontal board that is
> beneath the stove burners. I made a new, larger grill, that was more
> permeable to airflow out of flat expanded metal (1/2 inch I think). I
> painted the new grill the light auto flat gray. I bought some 1/8 inch
> black rubber tubing at an auto parts store, slit one wall of it lengthwise
> and fitted it around the edge of the new expanded metal grill. (this keeps
> grill from rattling and looks neat.) Buy taking care with where I cut the
> metal I was able to use the two screws and screw covers from the stock
> grill to mount the new expanded metal grill. Even without extra fans I
> believe that this larger air exhaust vent would improve the cooling of the
> fridge in hot weather.
> The fans were placed as follows:
> One fan about where the original fan was mounted (beneath the lower set of
> cooling fins), but positioned better (in center, from left to right, of
> fins and pointed directly through the lower fins to maximize air flow).
The
> second fan was mounted between the lower and upper set of cooling fins
> (careful not to drill through the cooling pipe that travels from right to
> left inside the fridge walls!!). Again positioned more or less in center
> (from left to right) of the lower of the upper set of fins and angled to
> blow air directly through fins (careful not to blow directly on thermo
> switch). The third fan was mounted on the top of the fridge, immediately
in
> front of and blowing directly through the enlarged air exhaust vent at the
> side of the fridge. (I put this one on about a 1 inch block of wood to get
> it into the center of the vent hole and wired it with conveniently located
> wire connectors (out of the way of the fan blades) so that it can be
easily
> removed when you need to take the fridge out to service it.) This
> arrangement of fans spaces them out along the air flow path and each fan
> adds momentum to the air at crutial points where the fins both need the
> airflow and where the fins slow the air down. The third fan, on top of the
> fridge, also helps to move the hot air that is generated by the propane
> exhaust pipe!
> Some tricks:
> Because the mounts of these Fridgemate fans hold the blades out further
> from the back of the fridge, I was concerned about clearance between them
> and the wall of the van after installation. (It was hard to measure.) Not
> to take chances, I altered the Fridgemate fans by drilling new fan motor
> mount holes in the L shaped mounts such that the result would be the
> Fridgemate blades would be the same distance from the back of the fridge
as
> the stock Dometic fan blades. I also eliminated the thermo switches on the
> Fridgemate fans by cutting the white plastic tubes on which they mount to
> about 1/8 inch and using shorter screws. I think I had to reverse the
lower
> fan on the mount to get it to position correctly in relation to the
cooling
> fins. The fan on top of the fridge also had to be reversed so that the fan
> mount would fit between existing wire strap and the vent hole. Be careful
> when reversing fans on their mounts that you wire them to blow in the
right
> direction!! (I wired and tested before reinstalling fridge.)
> All three fans were wired to the original thermo switch after I removed
and
> reinstalled it with heat sink compound (from Radio Shack). I also found
> that the original thermo switch mounting bracket bends easily and needed
to
> straighten it and take care while remounting that it fit snuggly against
> the cooling fin.
> I also put a very small toggle switch in the circuit for the fan at the
> exhaust grill. I mounted this switch on the expanded metal grill so that I
> could switch this fan off since it is closest to my ears when sitting on
> the back seat. Sometimes it is nice to switch this fan off when I don't
> want to hear it (the other two fans continue to work with this one
switched
> off).
> I think that about covers the fans! Good Luck: Bill Davidson
>

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