Don's Roadtrek furnace return air project.

[rv-n-agin]

This project fixes the problem of poor furnace air circulation in the RT Independent model when the rear bed is down in the bed position.

Step 1 is to determine how many sq. in. opening is needed.



The furnace air return has 8 one half by three inch slots that total 24 sq. in. or a 4"x6" hole.



The Suburban furnace register has 3 slots 1/2 in. by 8 in. which totals 12. sq in. to provide return air.
Conclusion: try for 24 sq. in. and anything over 12 sq. in. should work.



There is a 11 in. space between the furnace and the tub/shower that needs holes in both sides for the new air passageway. (Future project idea: use some of this space for extra storage)



After the hole is cut in the tub wall it is evident that there is plenty of clearance around the tub for sufficient air flow.



The next step is to cut the hole in the other partition and then block off the old return air path.



I didn't see any clearance specs.but I held my hand on the furnace after it ran for 20 minutes and it was not hot to the touch so I dared to temporarily use wood blockers. I will change to metal now that I know this works.



This is where the new return air grill will be.



The hole is cut and then the new register is applied.



It is a 6 by 10 inch flat return air register, - plenty big but that is the smallest they had at Home Cheapo. They didn't have brown so I'll have to paint it.
(Added benefit: A minute or two and a screwdriver makes this a good hiding place for an envelope of valuables)



The last picture shows a butane lighter flame drawing towards the opening with the furnace running.

Before this improvement the furnace would run for 5 to 10 minutes before any noticable heat could be felt above the bed but now it is almost immediate, a very noticable improvement!

"Thanks Markopolo for adding the pictures for me"

[markopolo]

Now I think I understand more about my furnace Thanks Don.

So, before your modification, return air was drawn from the space behind the cabinetry and warm air was pumped into the area between the bed(s) which is partially blocked by the tub in your Roadtrek. Was it drawing in some of the warm air and heating it again?

Now, return air is drawn from middle of your van. The warm air is still pumped into the area between the bed(s) but it is drawn out of that area because it is helped by where your new return air intake is.

On my '04 190P there is a hinged door (maybe 4"x20") under the raised toilet 'floor'. It's in the middle of the van on the same side as the furnace. It's probably there to access the plumbing. If that area is open to the area where the return air vents are I could achieve more efficient heating by opening that door when heating. I'll take a look at it.

I know the area behind the cabinetry on that side is open (not sealed) along the side of the van. The open area at the head of the beds (at the rear doors) must be the "source" for the return air - except when I block it with my pillow

[markopolo]

There's a Suburban Furnace Technical Information download here:

http://classbforum.com/phpBB2/viewtopic.php?t=287

The furnace parts are explained. Very handy to have for reference.

[rv-n-agin]

So, before your modification, return air was drawn from the space behind the cabinetry and warm air was pumped into the area between the bed(s) which is partially blocked by the tub in your Roadtrek. Was it drawing in some of the warm air and heating it again?

Now, return air is drawn from middle of your van. The warm air is still pumped into the area between the bed(s) but it is drawn out of that area because it is helped by where your new return air intake is.

Thats right. If you look at the 2nd picture of the Suburban register grill, you can see that the the air return slots on the sides are only inches away from the front where the warm air exits. That works OK in a large open space but not very well in the small space under the bed where it heats the same air over and over again without satisfying the thermostat.