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-   -   Ducted AC?- Crazy idea? (http://www.airforums.com/forums/f427/ducted-ac-crazy-idea-89158.html)

VeggieBullet 03-26-2012 07:08 AM

Ducted AC?- Crazy idea?
 
2 Attachment(s)
Hi everybody.
We were brainstorming about the best ways to optimize the cooling of the AS.
Thanks to the "Best Fan Out There" we are for sure installing a Fantastic Fans (Model we are not sure yet.)
We were also researching on the forum about the best AC Systems and obviously it seems like 2 units for the 31ft is the way to go.
We like the Split Systems like Cantrell & SmokeLessJoe.
Now Just wondering is it will be a little crazy to run a ducted system from the Amstrong?:brows:
There is plenty of flexible ducts for boats but we were thinking may be running rectangular or oval ducts thru the ceiling using something like this.
Please any inputs.

DKB_SATX 03-26-2012 07:19 AM

If you don't mind the look of a surface duct you could do that pretty easily, but I think it would be very difficult to run duct through the ceiling. There's not a lot of space between the inner and outer skins, there are ribs you'd have to get through, and you'd be displacing insulation so the outer part of the duct would be near or even touching the outer skin, so the ducts would be hot on a sunny day and you'd be fighting that in addition to trying to cool the main volume of the trailer.

VeggieBullet 03-26-2012 07:29 AM

clearance
 
Quote:

Originally Posted by DKB_SATX (Post 1124897)
If you don't mind the look of a surface duct you could do that pretty easily, but I think it would be very difficult to run duct through the ceiling. There's not a lot of space between the inner and outer skins, there are ribs you'd have to get through, and you'd be displacing insulation so the outer part of the duct would be near or even touching the outer skin, so the ducts would be hot on a sunny day and you'd be fighting that in addition to trying to cool the main volume of the trailer.

Thanks for the reply.
Most likely the idea is to run the ducts thru the ceiling unless my wife will come up with some cool design to make the ducts a kind of invisible?
Wondering how much is the clearance between the inner skin and the outer?

vswingfield 03-26-2012 07:40 AM

Quote:

Originally Posted by VeggieBullet (Post 1124902)
Thanks for the reply.
Most likely the idea is to run the ducts thru the ceiling unless my wife will come up with some cool design to make the ducts a kind of invisible?
Wondering how much is the clearance between the inner skin and the outer?

Two inches. Not nearly enough for a good duct even if you remove all the insulation and the ribs. It will blow through the open trailer much better than it would through a two inch duct. Even if there was a way to run the duct.

In the south, you want as much cool air movement as possible. Restricting it is not a good idea.

VeggieBullet 03-26-2012 08:05 AM

Air Flow
 
Quote:

Originally Posted by vswingfield (Post 1124904)
Two inches. Not nearly enough for a good duct even if you remove all the insulation and the ribs. It will blow through the open trailer much better than it would through a two inch duct. Even if there was a way to run the duct.

In the south, you want as much cool air movement as possible. Restricting it is not a good idea.

Hi vswinfield.
If it is 2 inches between skins is probably 1 to 1.5 inches between ribs?
Found that metal air ducts are sold from 1'. Rather use the metal ducts and insulate them vs the flexible hoses to avoid air flow restriction.
We were also thinking that IF the air ducts can be done that the use of computer fans or silenced blower will avoid the restriction of the airflow.
Just thinking out loud : wouldn't the theory of 4 vents distributed over the trailer with the assistance of fans or blowers at every vent work better than a 1 point of cold air in a big trailer?

Melody Ranch 03-26-2012 08:26 AM

I would try to run a 4" supply thru the back areas of the cabinet structures. My 21' Sovereign had a nice ducting for the heat built like that and it worked well, did not take up space and looked great.

VeggieBullet 03-26-2012 08:35 AM

1 Attachment(s)
Quote:

Originally Posted by Melody Ranch (Post 1124923)
I would try to run a 4" supply thru the back areas of the cabinet structures. My 21' Sovereign had a nice ducting for the heat built like that and it worked well, did not take up space and looked great.

Hi Melody Ranch
That was actually the other idea.
Since we are planning on gutting the trailer out for a major renovation that would be the other option.
Just wondering at this point if is doable.
Surprise that none has done it? may be to early for the Airstreamers of the west coast?
We are pretty sure that someone already have this system somewhere.
But if it can be run thru the ceiling may be thru the back of the new structures and using something like this in the highest points?

TG Twinkie 03-26-2012 08:39 AM

It takes a significantly larger duct to move cold air efficiently as compared to hot air. I would think Smokeless Joe's idea with multiple inside units would be a better approach. The refrigerant lines would be much smaller than air ducts.

TouringDan 03-26-2012 09:07 AM

I have done some difficult duct work jobs in homes, but I don't think that ducted a/c in an Airstream is going to work. It just takes up too much of the precious volume in the Airstream. I would first try a couple of Fantastic Endless air fans to keep the cool air distributed throughout the Airstream. You could also run the funace fan all the time. This will circulate the air through the one or two cold air return ducts for the furnace. If this is not adequate, than add a second air conditioner on top. Smokeless Joe's idea is probably the best if you want to truly have two or more sources of cold air blowing. I suspect you could hide the refrigerant lines between the floor and the belly pan.

Dan

VeggieBullet 03-26-2012 09:19 AM

Quote:

Originally Posted by TouringDan (Post 1124941)
I have done some difficult duct work jobs in homes, but I don't think that ducted a/c in an Airstream is going to work. It just takes up too much of the precious volume in the Airstream. I would first try a couple of Fantastic Endless air fans to keep the cool air distributed throughout the Airstream. You could also run the funace fan all the time. This will circulate the air through the one or two cold air return ducts for the furnace. If this is not adequate, than add a second air conditioner on top. Smokeless Joe's idea is probably the best if you want to truly have two or more sources of cold air blowing. I suspect you could hide the refrigerant lines between the floor and the belly pan.

Dan

Hi Dan.
Great that an HVAC Tech showed up to help whit this naive ignorance:lol:
1)Based on TGWinkie's input : What would be the minimum size of duct that we will need to run to have a good airflow?
2) Will the use of fans or blower at the vents help the air flow?
Thanks again

tpi 03-26-2012 10:12 AM

Even if you could duct the 2" space how do you get the ducts through the structural ribs? Opening a space through them would severely weaken them and more than one would be affected.

I'm in the camp that recommends two roof AC units if one isn't adequate. If there's an issue with my 25, it isn't distribution, it is overall BTU capacity of the AC unit. If I was adamant about a ducted system, my direction would be a split system with the ductwork incorporated into the upper cabinetry.

Jammer 03-26-2012 12:07 PM

Hi Veggie

It's great to have ideas but at some point you have to evaluate them.

The Armstrong A/C does not have the blower capacity to support ductwork. A larger fan would be required and will not fit.

If we look at what would be involved in running A/C from the front to the bedroom you would be looking at a minimum of 4 4" ducts if you were to use round duct. Maybe a 3x12 rectangular duct would do the job.

TouringDan 03-26-2012 12:35 PM

VeggieBullet

I am not an hvac tech, but I am an engineer and a home inspector that has installed some duct systems in homes that typical hvac contractors were not interested in messing with.

I like the KISS principle. To cool the bedroom area I would hang an Endless Air fan near the top of the door going into the bedroom and have it pull the cool living room air into the bedroom; the warm bedroom air would then exit the bedroom at the floor level. Also try having the fan at the floor level. See which location works better. Also make sure the bedroom curtains are closed to minimize the heat infiltration into the bedroom.

To answer your question about minimum size duct, I don't know; it depends.

By running your furnace fan you are pulling air from where ever the register is located (bathroom or bedroom) and blowing it out the furnace outlet grill. No extra fan is needed for circulation. We have a 2 level home. We run the furnace fan constantly in the summer time to keep the temperature level uniform. If we do not do this the upstairs is about 4 degrees warmer than the downstairs.

Running the furnace fan and other fans and keeping the drapes and curtains closed costs little or nothing and will improve the operation of the air conditioning system. Hope this helps.

Dan

nvestysly 03-26-2012 01:42 PM

I sure hope the idea of a ducted system gains traction. It seems apparent that ducting will not fit within the shell but there's got to be a better solution than a noisy A/C unit running in the kitchen/living room. I think this problem deserves significant attention from Airstream.

I wish you good luck in your endeavors to find a solution. In a large trailer, even with two rooftop A/C units the noise is a problem in my mind. I've been in SOB's (yes I know they're not the same as an Airstream) with ducted A/C and I don't even realize the unit is running. Go into an Airstream - supposedly a premium rig (at least it has a premium price) - and you can't even hold a conversation or listen to the radio or TV. What gives? Is Airstream listening?

So... keep posting ideas. SmokeLessJoe may be onto something. We have a dual evaporator in our tow vehicle and it works great for cooling down the rear area when needed. There's a solution out there - just needs to be implemented.

Lucius


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