Adding Fans to Rear of RV Absorption Refer - How to Wire?

Thanks John-
I appreciate the detailed response and detailed charts and pics. I'll post back here what I do and the results.

UPDATE:

1. Found that my thermistor adjustment slide clip (inside refer) was in the UP (colder) position. However, the actual temp prob was in the middle of the plastic slide. I had moved it up, but the probe stayed put. It appears that there was no clack in the wire to allow it to slide up with the plastic slide clip.

I checked the wire inside access vent and sure enough the excess wire had been zip tied together to keep things nice and tidy. I removed zip ties and pulled a few inches of slack inside refer. I also tape the wire nd of the probe so it would not slide on plastic slider and the used a clip to hold slide in place. I moved the probe to the top of the fins.

2. I removed roof top refer vent. I wanted to inspect what was inside above refer. I did find that there is a cavity at the very top of refer between refer and roof. This cavity is approx. 24" wide by 8" tall x 8" deep. I will leave cavity alone for now and test my refer with new probe position. If needed, I can fabricate a piece of sheet metal flashing to remove cavity from upward flow of air. Not sure if I can make it fit by just cutting back wire mesh.

3. Fans....How well with they sucking air up and out of vent if mounted above wire mesh? I don't want to cut into the wire mesh to mount them just underneath wire mesh if fans will work as well above mesh. I wonder if these fans will work well enough to make up for the cavity above refer? I guess only testing will tell.

Thoughts?

I decided to add two fans at the top refer vent. They are thermostatically controlled as well as manual override. 3 amp inline fuse.

It is currently 89F in the shade. The two added fans have turned on to level 3/6 (auto mode). This means fans are turning at half speed. The hotter it gets, the faster the fans will spin. I can feel the warm air exiting the refer vent cover....good sign!

The single OEM fan has yet to turn on. If trailer/refer were in the direct sun, it would have turned on by now (last testing I did).

I'll do some testing over the next several days and see what I find. It's supposed to cool off into the low 70s by Saturday, so testing in the heat may not happen until next summer.

Hi Baha Man,

First off, you are welcome, glad to share to help the cause.

It looks like 2 fans at the top with your control system is working. Some fine tuning will come as you use it. Looks good.

The only thing I will add to think about, not sure if the cover is on the roof vent during your tests, I suspect the the cover being off or on changes the air flow dynamics. The cover is a restriction.

If you have not had the cover on, see how it fits with the fans. If you are not getting enough air flow, part of it "might" be that the cover is too close to the fan and is choking the fans output. The fan blowing out with no cover, has zero restriction on the exhaust end.

You may be able to adjust for the lost volume with speed, waste some speed to get the wanted end result. Or if you run out of speed, then moving the fans below the screen and deeper into the opening may shift the lost efficiencies of being choked being so close to the cover. Mine are about 3" below the screen.

I'm using a Camco vent cover in place of the Dometic. The insides of those two covers are very different, at least by looks. I have no data to say which is better, just Dometic wants way to much $$ for a replacement cover. I do like the Camco for helping to keep sideways blowing rain out of the fridge though. This wind driven rain has to be just right to be head on into the side of the cover to show up, but it is possible as you can see by eye straight through the Dometic, or the older ones anyway. I really do not like the new redesigned ones that they are forcing a base change to even use. The molding quality is poor compared to what they use to make. Dometic is not the same company with higher quality as it used to be 10 years ago from what I have seen.

Thanks

John

Is this white insulation in the way of the vent? If so that is a choke point.