Dometic Vent Fan Install
I have a dometic (3 way) absorption fridge in my camper. Absorption fridges are rugged, dependable units because they don't have a compressor and only need a heat source to function - a 3 way means it can be powered by AC, DC, or propane.
Because they relay on convection to operate effectively, they have a vent at the bottom and a vent at the top. Cool air is drawn in at the bottom and expelled at the top. This is what the top vent looks like on the roof.
In a perfect world - not too hot, parked in shade, and the wind is not causing negative pressure on the side of the camper where the fridge is (and trying to make the flue work 'backwards') everything is great. On days when the world isn't perfect, the fridge can use a little help to get the convection going as designed. There are plenty of kits out there, but I wanted to roll my own. I ordered 4 Antec TriCool 120mm Case Fans for $20. These are very common, very inexpensive fans with a good reputation. If I run them all on high speed they pull about 10 watts.
I fabricated mounts out of HDPE for the fans. I like HDPE - easy to work with, doesn't rot, doesn't rust, inexpensive.
Since computer fans use so little power, I was able to wire everything up with 3M Scotchlok connectors. I really like using those when I can - There's a reason the phone company uses them, they are quick install and just don't fail.
Since I only wanted the fans to run when necessary, I installed a normally open mechanical thermostat.
I made it so that I can adjust the thermostat through the fan blades with a suitably long screwdriver.
Next the question was how to power the fans. Since they were on the roof, why not throw on another solar panel - there's room, and the fans probably only end up wanting to run when the sun is shining anyways. I got a good deal on a nice little 15W panel with a controller. I built some standoffs using some aluminum square tube, and used 3M double sided outdoor adhesive tape to secure the panel to the roof.
Here's the controller and the control switch. I like covered switches like this - when the cover is closed you know that the switch is in it's normal operating position. Still a little cable cleanup to do.
Down = Normal (Thermostat), Middle = Off, Up = On (Bypass mode)
Oh, I also put in a small AGM battery in the bottom of the fridge vent flue to balance the power demand and generation, and also installed a baffle in the bottom of the flue to direct air over the coils. Out of uploads though.