furnace duct work, only coming out of 1 vent strong

[al7601]

I know its the summer but I'm trying to prepare. Our new to us 2008 Jayco 311 LGT furnace has 5 ducts coming out of it to 6 vents but only the one closest to the furnace is blowing strong. the other vents have heat coming out of them and I confirmed there are no holes or leaks around the vent leaving the furnace. Each duct has strong heat coming out of them but once they reach the exit end its very weak. I confirmed air coming out by placing a lit lighter in front of each exit vent. My guess is that I have to cut open the underbelly to inspect the duct work. Most of the screws holding the underbelly are rusted or strip easy. Is cutting the underbelly and placing it back a difficult job? I plan on using gorilla tape to put it back in place.

[time2roll]

My ducting in the floor was crushed. Poor airflow was an indicator but the real issue is inadequate airflow for the furnace to operate properly. Mine would cycle the burner due to overheating. The high limit switch does this and should not.

I did everything to get the duct propped open and clear. In the end the solution was to add two more 4" round ducts through the cabinet. Makes an amazing difference. Burner now runs continuous until the thermostat is happy.

I looked down the ducting with mirrors and removed the furnace itself to inspect that area. My ducting is between a double floor and I have no belly cover so no real access. Not sure you would even have access if you removed the plastic cover.

[CavemanCharlie]

2Macs wrote:
Try to baffle the ducts with the strongest air flow by using steel wool as the baffle material. It will re-direct air flow to the weak ducts. I had the same problem with my TT and the dealers's service department did not resolve the issue to my satisfaction.

I think you can purchase outlet duct diffusers that have a way to adjust the flow .

[2Macs]

Try to baffle the ducts with the strongest air flow by using steel wool as the baffle material. It will re-direct air flow to the weak ducts. I had the same problem with my TT and the dealers's service department did not resolve the issue to my satisfaction.

[CavemanCharlie]

On my 22 Foot TT it has 3 ducts. One right by the furnace and 2 at each end of the camper. By removing drawers and a couple of panels I can see all the ducts. It blows most of the air out of the duct near the furnace. This makes since if you think about it. That duct is closer and has the shortest distance and the least resistance to air flow. If your furnace is keeping the TT warm I would not start cutting anything. If it works don't mess with it.

Now, on the other hand, if next winter you are having problems you may have to fix it like the other members above have said. But, don't cut anything just yet. Wait until it gets cold and see how well it works.

[dodge_guy]

Probably crushed tubes. on my trailer I had a similar issue, but my duct work is built into the floor. the bunkroom you could almost roast a turkey and the kitchen duct had next to nothing coming out of it. I closed off the bunkroom vent by 70% which forced the heat out the other vents. it takes a bit of work but now the entire trailer is comfortable.

[Halmfamily]

On our fiver I cut out about six feet of flexible duct at the heater. There was about 6-8 of excessiy duct for each run at the heater and it looked like a pile of spaghetti. Once all trimmed and runs were now straight we had good air velocity at each vent.

[bobndot]

x2 possible crushed tubes.

It seems like you have to rip out the old screws and re-drill new ones next to the old ones. When all is done, tape the seams to cover the old holes.

Another option that some have done is do away with the underbelly. If you do not use the TT in cold weather. Its not a bad idea because you can do easy visual inspections of plumbing and water tanks. You can also close off the underbelly heat duct adding more heat flow to the cabin.
Mice tend to nest in underbellies if you do not do a good job of sealing them up which is difficult to do due to sewer and gas pipes. Use steel wool, spray foam and tape after cleaning the surface.

Here is some other info that might be of help:

https://www.amazon.com/Mobile-Belly-Bottom-Repair-Fix-Underbelly/dp/B00BJ5SPO8

thread with PICS on an underbelly fix (I'm sure Jayco owners forum also has the same )
http://www.crossroadsowners.com/forums/f12/replace-underbelly-2786.html

[westend]

I'd bet you have a few crushed or bent ducts underneath. From posts on here about heating and cooling, folks efforts to improve upon it, and the fact that trailers are poorly made, a good inspection and overhaul of the ductwork would be high on my work list, if I had that situation. There is also no guarantee that the ductwork is laid out correctly. A mfg might try to overcome Winter's effect on tanks and subfloor comfort by pushing a large percentage of available forced air into the underbelly.

The removal and replacement of any underbelly material has been covered on the Forum. A search will turn up some threads about it. IIRC, Forum member LarryJM did a really good job on his underbelly area.