Crushed Heating Duct Work

lharsh

Member
We recently purchased a 2006 3655RD Bighorn and found that the heating ductwork is crushed. All of the tin had collapsed top to bottom. We managed to wedge the section in the kitchen and feed PVC piping (cut in half to hold up ductwork) , but the section from kitchen into the living room is so collapsed we are considering cutting through the floor to that section of ductwork in order to repair the problem. Has anyone experienced this problem and how did you fix it. Thought we'd ask before we embark on such drastic action. Pat and Linda
 

cookie

Administrator
Staff member
Pat and Linda, welcome to the forum. A great place to gather and share information on your Bighorn.
Just curious why you would cut through the floor to access the duct work. You can remove the Coroplast underbelly material by removing some screws. If there are obstructions in the way, such as the axles you can cut the material with a razor knife. But be careful not to go too deep and risk cutting a wire or a tank. You can then repair the cut by putting a board on the inside and screw the two sides of the cut to it and then tape it with something like Gorilla Tape.
Now that you own a Bighorn check out the WI rally in the Dells next August. You can find it on the right side of the Portal Page. You may also consider The North American Rally in WY next June.
Another thing you might want to look into is the Heartland Owners Club. Also on the Portal Page.

Peace
Dave
 

Rickhansen

Well-known member
Where do you have metal duct?

There is a sheet metal plenum on the furnace and there is sheet metal diffuser about 4" deep right at each of the the floor registers. Everything in between is flexible duct, much like cheap dryer vent, through the basement/belly.
 

lharsh

Member
The ductwork is aluminum sheeting spanning one section of the aluminum floor supports that run the length of the unit and that is the heat duct for the kitchen and living room. This aluminum has no support ribs pressed into it. My friend has a 2007 Bighorn and his is built the same way except the aluminum has support ribs (maybe 5 to 6 inch squares) pressed into the sheet for rigidity.

How does this ductwork become so buckled, from bottom up and top down? The top and bottom were actually touching in places to where the only opening for heat to get through was a slight opening on each side.
 

RollingHome

Well-known member
It almost sounds like your coach experienced a negative pressure which sucked the duct together. One thing comes to mind... leak test. RV dealers seal a RV outside/inside as best they can. Then they put a high powered fan on a roof vent and positively pressurize the coach. They then apply soapy water on areas prone to leaking. Leaks will bubble and then they seal the leaks. However, "IF" a RV tech put the fan on up-side down it would create a negative pressure and perhaps your ducks were sucked in at this time. Perhaps a previous owner used a powerful fan similarly. I know my explanation sounds farfetched, but I have actually seen similar scenarios in industry. I watched a semi truck driver suck the sides of a tanker in when he forgot to vent while filling a large fuel tank. I also saw what happened when an electric motor turned the wrong direction (incorrectly 3 phased motor) and a large duct collapsed. Even though the actual pressure or suction is low on a gauge or monometer per square inch, when one multiples the square inch surface area the forces are tremendous once they are localized. For example, a 3 psi (positive) pressure on a semi trailer tanker equates to 50,000+ pounds of breakaway thrust at the man hole cover. A couple of inches of water column pressure (negative) on your coach could suck in the ducts if the ducks where the weakest links for air to enter in a negative pressure scenario. It’s one idea based on experience, maybe other posters will think of something else. I don't know how to fix it but... here's goofy idea, could you pressurize it to make it pop out ? My logic is, if it collapsed in the manner I suggested what would happened if the process were reversed ? I don't know if a leak test done for an extended period of time would fix it or not. Call a RV dealer and ask how much to leak test your coach, then tell them to leave the blower on extra long... Maybe others will come up with a better idea. Let us know anymore info or the end results - good luck.
 

lharsh

Member
Thanks for your replies. What Tom says makes perfect sense to us. We can also see where someone had tried to repair the ductwork as the sections were either cut or separated from one another and they had put aluminum duct tape over the separation. We can also see other cuts in the ductwork, perhaps when vents were installed? We are going to attempt to do what Dave suggested. Going at it from underneath.
 

JohnDar

Prolifically Gabby Member
Thanks for your replies. What Tom says makes perfect sense to us. We can also see where someone had tried to repair the ductwork as the sections were either cut or separated from one another and they had put aluminum duct tape over the separation. We can also see other cuts in the ductwork, perhaps when vents were installed? We are going to attempt to do what Dave suggested. Going at it from underneath.

Since you're going to crawl into the Belly of the Beastie, you might consider taking some of the strain off the flimsy duct work at the registers. I did this to our bedroom vent, both to support it better across the ceiling of the basement and remove three feet of excess that drooped behind the basement wall. Bends, especially tight ones, in soft flex-hose are big flow restrictors. This is an adjustable elbow from any big box store.

View attachment 16624
 

Rickhansen

Well-known member
The ductwork is aluminum sheeting spanning one section of the aluminum floor supports that run the length of the unit and that is the heat duct for the kitchen and living room. This aluminum has no support ribs pressed into it. My friend has a 2007 Bighorn and his is built the same way except the aluminum has support ribs (maybe 5 to 6 inch squares) pressed into the sheet for rigidity.

How does this ductwork become so buckled, from bottom up and top down? The top and bottom were actually touching in places to where the only opening for heat to get through was a slight opening on each side.

Thanks for the clarification. Our BH is not ducted that way, so I can't offer any insight.
 

traveler44

Well-known member
I removed a floor register and pulled about six feet of extra flex duct out of mine. The extra length was causing it to crimp shut in places. This was at one of the ducts to the livingroom. It must be easier to install with the extra length when they build. Tom
 

70vette

Member
I have a 30c roadwarrior the short duct working running to main duct was not sealed. And only had a 5 x 3" hole cut in main duct.
 
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