I have been kicking around using a helper fan or two also, so much so that I already have the fans. Using duckwork from a dryer vent is not such a good idea. the internal ribbing will cause turbulance and a high air flow resistence greatly reducing the cfm flow. I found this out the hard hard way when I was running duckwork for my woodshop dust collector system. Ductwork with a complety smooth interier with sweeping corners will give the best performance.Thin wall PVC or ABS will work quite well in this application, and can be wraped with insulation for less heat transfer. There is also flexable duckting used in the avaition industry called scat tubing that is smooth on the interior and used for this application. It is also spendy. I,m sure McMaster-Carr also has some neat ducting.
The size of the tube does matter in referance to the amount of airflow across the evaperator. To little airflow across the evaperator will cause the coolent going thru the evaperator to not become fully vaporized, liquid coolent can enter the compresser causing it to "slug" shutting down the system or damaging the compresser.
How would the portable unit vent its heat to the outside? Are you visualizing something that has a connection to the outside? Do you have some web links to some units of the type you are thinking about?
I like the idea of the dryer vent duct. The flexible stuff can really compress down too. I would guess that almost any amount of additional air movement would be a big help. As a rough guess I would suggest that the maximum amount of duct size that seems sensible would be an amount whose cross section area was about the same as that of the AC unit. Of course the amount of air that the fan that goes with the duct moves would be variable too.
It is too bad that ceiling vent fans like the Fantastic models don't have a mode where it makes more sense to use them with the vent closed. If there were some way to get indoor air to the top side of the fan blades then it probably could do a pretty good job of pushing the air down into the living space without any ducting. Or better yet if we could figure out a way to get indoor air from the floor level ducted to above the fan blades that would be a great way to go.
...I like the idea of the dryer vent duct. The flexible stuff can really compress down too. I would guess that almost any amount of additional air movement would be a big help. As a rough guess I would suggest that the maximum amount of duct size that seems sensible would be an amount whose cross section area was about the same as that of the AC unit. ...
Just be aware that there is considerable loss due to turbulence along the wall. You can almost imagine that the 1/2" next to the wall doesn't flow any air at all (as an approximation), so you can't squeeze the pipe down to 1" thick and think you're going to get much flow.
I have been thinking a bit more about the notion of turning on a Fantastic vent fan with the vent lid closed. Is there an interlock switch to prevent this? If I did turn on the fan with the vent closed just how much air movement might it cause even though it does not have air coming in on top of it? Could this cause enough air circulation to move the cold air at the floor up higher? What do you guys think? I have three Fantastic fans in my 31' and I would like to consider mounting an AC unit (or two?) down low. I do have an overhead one but I do not even know at this point if it is fully functional. I also don't like the looks of the pod on top although I did spend some time patching the shroud where it had cracked and repainting it.
1. The Fantastic fan has a cutout switch--won't run with the lid closed.
2. The fan is tightly shrouded. I doubt any air will move even if the fan would run with the lid down.
Now, if you wanted to make some side draft channels and mount the fan about 2" lower (I don't know how you'd do that, considering the lip around the fan body), you might be able to make some side inlets that would draw air from right adjacent the ceiling...but you'd bump your head.
I like the idea, though. Maybe some computer pancake fans (4 of them) could be rigged up in a way to do this, but you'd probably have to make some depressions in the ceiling and sacrifice some insulation.
seeing my thread pop up every day is motivating me to get back on the project! hehe! Time to get some measurements for the bed and couch cushions, then start on the bathroom and plumbing...
Sorry - I can't figure out how to edit (I may have abused it or something so it was taken away?) but my last post wasn't exactly clear.
It looks like (in pictures) that there is enough clearance between the fan and the closed shroud that you could vent the fan into the interior walls (into a channel or duct) and have it dump at the floor.
I think that is a more cohesive thought.
thank you.
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2001.5 A4 Avant - (the original Rat Rod B5 Avant)
1967 Safari 22' (like a fish)
Anyone who has never made a mistake, has never tried anything new. ~Albert Einstein
seeing my thread pop up every day is motivating me to get back on the project! hehe! Time to get some measurements for the bed and couch cushions, then start on the bathroom and plumbing...
JP
JP,
It is neat how threads wander, change and develop. You started with one Air Stream now have 3?, a boat and a baby or 2 if I remember correctly.
I admire your work.
How are you doing the air handling (HVAC) in your rigs?
R
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Robert
"Talk is cheap, Airstreams are expensive," Wally Byam.
Buy in haste, repent at leisure; been there, done that.
"You cannot rush quality," fastRob.
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