Help with floor ducted furnace, lack of air flow

[fairlaniac]

We have a seasonal travel trailer at a site in Delaware. We went down from PA this weekend to winterize. Spent the night Saturday only to realize over night the furnace wasn't operating properly. the unit would kick in and it sounded normal with the fan motor but there was very little air flow from the floor ducts. The registers were warm but no real air flow. So I assumed since I heard the fan motor that I might have a blockage. The furnace is under the sink counter. I didn't take time to resolve or dive into the issue as we had to leave early to come home. So I took these pictures. It's all I can see from three vantage points. I'll assume by what I see is there must be a opening on the bottom of the unit that lines up with a hole in the floor to the duct work? Are these fastened to the floor or just sitting there? The one end is against the inside wall of the trailer which is the exhaust to the outside. Then it sits on the floor. I'd like to plan on pulling the unit out but I'm not sure what to expect? Are there any diagrams with typical floor duct installation that I could look at? We bought the trailer used and there are not manuals for any appliances. So I'm not even sure of the manufacturer of this? I know I'm not providing much info but that is all I got from the limited time available. Thanks!

[joshuajim]

My Wildwood had poor flow. Fortunately, FR used rectangular metal ducts for the runs. I pulled the registers which were spaced every 4 to 5 feet and with a mirror and flashlight I was able to look down the line. I found 2 problems. First, where the plenum under the heater attached to the duct, they did not fully cut our the opening where the duct attached resulting in about a 40% blockage. Then further down the line the pedestal base for the table as directly over the duct and crushed it down to about 50%. GREAT design!

After remedying both those heater now works good.

[Edd505]

Remove the floor duct & put your phone down. Take a picture and see what you can see.

[time2roll]

dougrainer wrote:
If you have a blockage, the furnace burner would short cycle and you would hear it cut on and off. Doug

Yes mine did this. Fan would run continuous but if you really paid attention the burner would cycle on and off every 30 to 90 seconds.

My ducting had a few issues. First the short section from furnace to main line protruded 40% into the main line and blocked airflow. Secondly the short section collapsed during installation and was restricted. Flashlight and mirror found these issues.

Used a hole saw to open the metal protruding into the main line. Used some square aluminum that I perforated for air flow as a scaffold to prop open the collapsed section.

Helped some but the real solution was to pop out two of those knock-outs and add two more 4" ducts direct to the living area. Now I get tons of massive heat compared to before. Burner runs continuous until heat gets to the thermostat. Far less furnace fan run time.

[dougrainer]

If you have a blockage, the furnace burner would short cycle and you would hear it cut on and off. Doug

[dougrainer]

fairlaniac wrote:

Dusty R wrote:

fairlaniac wrote:
On the way home I had a thought. I should have removed one of the block off discs to verify air is pushing from the unit. That thought came after 2 hours of driving:)

Those block off discs, are knock out plugs, and once removed will not stay back in.

Be very careful what you use to push down a duct as it is quite likely you could poke a hole in it.

Dusty

Actually the plugs are discs that have an indexing tab and twist to lock.

That is my concern about poking in the duct work. I assume to access the duct work you must pull up the floor? Lets not go there yet 😄

Sorry, those are KNOCK OUT PLUGS. The Indexing tabs are used for the 4 inch metal collar that HAS a Tab to go into and turn to lock it in. You can knock them out, but NOT NEEDED for your problem. If you do knock them out just use metal foil tape to reinstall and block the hole. It is a whole lot easier to take the furnace loose and lift it up to see what and how the furnace is connected to the in floor duct assbly. Doug

[RAS43]

You should be able to remove the floor registers and run the scope thru the duck work that way. You would not need to tear out the floor as the duckwork is below the floor and should be accessible from under the trailer.

[SageCrispin]

Don't you just pull up your floor vents to get into the ducts? Mine are screwed down, but other than that they lift right up for cleaning. If that photo is similar to your RV, the one vent is near enough to the "T" to see in there. My endoscope is like a stiff wire, so can be bent and fed around corners. You may have to get one similar.

[TUCQUALA]

If you can get to the screw hidden behind the cabinet reinforcement, and remove the end cover, you will have wide open access to the entry under the furnace. That may be the first area for blockage or duct being disconnected.

[fairlaniac]

midnightsadie wrote:
you could drill a hole in the duct work ,use camera then buy a plastic plug for the hole.

How would you access any of the ductwork? As seen in the picture at the top of the post, the furnace unit sits over an opening (I assume) and feeds the below floor level ducts.

[midnightsadie]

you could drill a hole in the duct work ,use camera then buy a plastic plug for the hole.

[fairlaniac]

Dusty R wrote:

fairlaniac wrote:
On the way home I had a thought. I should have removed one of the block off discs to verify air is pushing from the unit. That thought came after 2 hours of driving:)

Those block off discs, are knock out plugs, and once removed will not stay back in.

Be very careful what you use to push down a duct as it is quite likely you could poke a hole in it.

Dusty

Actually the plugs are discs that have an indexing tab and twist to lock.

That is my concern about poking in the duct work. I assume to access the duct work you must pull up the floor? Lets not go there yet 😄

[wrktfsh]

I used a 35 dollar WiFi endoscope from amazon to ferret out the problem with a weak a/c vent. Turned out that tape sealing the plenum got pushed over that run.

[Dusty_R]

fairlaniac wrote:
On the way home I had a thought. I should have removed one of the block off discs to verify air is pushing from the unit. That thought came after 2 hours of driving:)

Those block off discs, are knock out plugs, and once removed will not stay back in.

Be very careful what you use to push down a duct as it is quite likely you could poke a hole in it.

Dusty

[fairlaniac]

Here is picture I found on the internet that is very similar to my trailer. The red line indicates where the duct runs down the center of the trailer and the 90 degree dashed line heads to the furnace under the sink/counter. No sure the easiest way to get the scope in the register opening, down and around to the furnace other than the wire I mentioned in the post above.