Return Air Tunnel

[DavidInWilmNC]

I'm at the point of removing the floor in my MC-8.  My OTR heat and air work fine for now, so I'd like to keep 'em.  What I'd like to do is to use the center tunnel as a supply instead of the return.  This will keep me from having to have those metal channels along the walls for ducts.  Basically, it'll be set up like a mobile home with a main trunk down the center and individual ducts coming off. 

I'd like to insulate this channel, since it's currently metal on two sides, wood on the bottom, and wood (subfloor) on top.  I've seen duct board that has a long notch cut into it by a 'V' shaped tool.  The V notch has enough left, including the outside covering, that the board is just bent at that point.  It seems like a fairly quick and mostly air-tight solution.  Most of the duct board I've seen is about 2" thick.  This is a bit thicker than I'd like, since I'd prefer to keep the greatest area for air flow possible.  I've also seen this styrofoam board that has a thin cover of foil.  Could something like this work? 

I'm sure some have used this tunnel as a supply duct.  What materials were used?  I'd also like to find some 4" insulated flex ductwork, but most I've seen is uninsulated.  Perhaps this is more of an RV store item.  What's a good source for ductboard (preferably the thin kind). 

So, those of you who work in HVAC, what problems do you see with this plan?  Eventually, I'll probably add one of those two-stage basement heat pumps when the OTR A/C dies. 

Thanks for comments and suggestions.

David

[Ace]

Hey david, you still got that clutch? Man my leg still shakes even when I type this! 

Ace

[DavidInWilmNC]

Hey david, you still got that clutch? Man my leg still shakes even when I type this! 

Ace

Was it heavier than it should be?  I don't have anything to compare it to, 'cept a VW Cabriolet.     It's got the air assist, but maybe I can coax a bit more assist out of it!  Was the clutch on your previous bus much lighter?

David

[Ace]

Not sure what it's supposed to be like in your bus but in my Eagle it was much easier. It also had an air assist on it. My GM was like my eagle if I remember right. I just remember it being as hard as yours but that may be a good thing!

Ace

[Ross]

That's what I did.  The front 4 feet of the tunnel is still return.  I put a divider about 4 feet back and reworked the ducts so the duct on the right going down to the bay is still return and the duct on the left now supplies the center tunnel.  The only difference is that I don't have coach heat anymore.  I just ducted the propane furnace up to the center tunnel.  I used 1" foil backed foam to line the tunnel.

Ross

[Nick Badame Refrig/ACC]

Hi David,

Here are the pics you wanted to see of the 2 heat pumps. Also the construction of the overhead ducts in my 102.

Nick-

[Nick Badame Refrig/ACC]

And more....

[DavidInWilmNC]

Thanks for posting, Nick.  The installation sure looks good.  What material did you use to fabricate your ducts? 

David

[Nick Badame Refrig/ACC]

David,

The overhead trunk is fabricated of 28ga. galvinized metal and insulated with foil-bubble-bubble-foil, wrap. It's a little hard to

see the main trunk with all the tek-foil all over the ceiling. The lowered ceiling is also in the view. The final termination is accomplished with

12-Hi Volocity Space-Pak vents.  The system is very quiet and proforms way better then expected...

Nick-

Thanks for posting, Nick. The installation sure looks good. What material did you use to fabricate your ducts?

David

[buswarrior]

David,

Couyld you insulate the exterior of the tunnel down in the bays instead of taking up valuable interior space?

I like your idea of reversing the use.

just thinking through the keyboard....

happy coaching!
buswarrior