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A-Merry-Can · 01-22-2008, 03:29 PM

I'm not sure I follow the illustration? I think getting the cold air out higher in the trailer would definitely help, but when I duct it, the air flow is dramatically reduced, which negates the effect.

JP

malconium · 01-22-2008, 07:47 PM

JP,

I think Cursh is suggesting a duct seperate from the AC unit and with its own fan to move cold air to the top. I like the idea. You could have more than one such duct too depending on how much room you can find and where your hot spots are. The duct could perhap just be a boxed in area in your cabinetry too rather than an actual duct. There are no heat issues involved so you could make it out of whatever you want. I remember seeing some units (designed for large warehouse spaces) that hang from the ceiling. They have a fan up at the top with a flexible fabric tube that dangles down to near the floor level. The fan sucks air in at the top and pushes it down the tube to be released at the floor. The unit helps with either heating or cooling too.

Malcolm

Cursh · 01-23-2008, 08:03 AM

Thanks malcolm - exactly what I was talking about.

Again - the work computer (in a design firm) only has paint (what gives)

I did my best with what I had. =(

NorCal Bambi · 01-23-2008, 08:18 AM

Cursh, This is an interesting idea. I'm now thinking of a portable unit that could be set up only when it's needed. i.e. some aluminum clothes dryer tubing with a fan. Any ideas on tubing size and fan size? There is even some cloths dryer tubing thats more flexable and compresses to a smaller size. I'm going to try this during this up coming summer.
Thanks Don

Aerowood · 01-23-2008, 08:40 AM

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.

Cursh · 01-23-2008, 08:45 AM

I don't think the size of the tube matters as long as its matched with an appropriate fan.

smaller tube+stroger fan= good pull.

I'm sure their is a zen like middle ground that would be ideal

Aerowood · 01-23-2008, 09:47 AM

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.

Cursh · 01-23-2008, 10:01 AM

I'm sorry - I think we are talking about slightly different things.

I was proposing an independent vent system to pipe the cold air on the floor up to the top of the camper.

[floor vent] ==> [tube upward] ==> [fan] ==> [head height vent]

I don't see where the evaperator fits in, but that being said I have zero experience with heating and air.

Aerowood · 01-23-2008, 11:32 AM

Thats cool Cursh I see where you are going now. I was talking about ducting to route the conditioned air to anywhere in the trailer.

malconium · 01-23-2008, 06:42 PM

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.

Malcolm

Zeppelinium · 01-23-2008, 07:35 PM

Quote:

Originally Posted by malconium

...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.

Zep

Jim & Susan · 01-23-2008, 09:01 PM

Nice job debating this issue, fellas. I have nothing to contribute of any substance, just interested in seeing the outcome.

Jim

malconium · 01-24-2008, 07:53 PM

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.

Malcolm

Zeppelinium · 01-24-2008, 08:31 PM

Malcolm,

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.

Zep

Cursh · 01-25-2008, 06:46 AM

I am going to preface this by saying that I am a little timid about posting this up, because I feel like Malcolm is crazy enough to do it . . .

Why not run vents from the shroud behind the exterior walls?

It seems like (from pictures) that you could run tubing in the walls back down to the floor (feel like this would get a more complete circulation

I mean - you would have to pull some walls . . .

just saying =P

might be one of the worst ideas I have had on this forum :shrug: just tossing it out there

A-Merry-Can · 01-25-2008, 07:51 AM

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

Cursh · 01-25-2008, 08:18 AM

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.

fastrob · 01-25-2008, 09:38 AM

Quote:

Originally Posted by A-Merry-Can

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

malconium · 01-25-2008, 10:57 AM

I forgot to mention earlier that there are fans available called duct fans that are specifically designed to be installed either inside a duct or inline with a duct. In the link below are some that are listed at Home Depot. As you can see they are readily available. The fact that an AC unit pretty much needs shore power (or a generator) meas that it would be perfectly fine for the duct fan to run on 110 power. Metal ducting is pretty readily available as are vents and grills for the ends. It would be pretty simple to install a duct with vents at both ends and a duct fan in the middle. All we have to do is find room for it. You can see from the link that Home Depot carries them in sizes as small as 4" diameter.

Search Results for duct fan

Malcolm

P.S. I probably don't want to pull my inner skins to install tubing at this point.

A-Merry-Can · 01-25-2008, 03:59 PM

Quote:

Originally Posted by fastrob

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

especially these LONG term projects. I foolishly thought I'd have my 18 footer done in 6 months, then we got pregnant with baby #1, and I bought a trade wind to camp in while I was restoring the 18 footer....

THEN, a friend made me an offer on another 19 footer (globe trotter) that I couldn't refuse, AND WE GOT PREGNANT WITH BABY #2... oh, and I bought a FeatherCraft boat.... ha!

I'm still planning (hopefully not FUTILELY) to have the 18 footer at least camp-able by April... I have a lot on at the moment! the bottom line... NO MORE PROJECTS for me until I wrap up at least one trailer and a boat. haha!

Now I'm definitely inspired to fit the water tank and finish the bed installation this weekend on the little trailer... but WILL i have time?

JP