heating system Upgrade

[Frisbeekev]

I will be pulling my underbelly covering on the camper off to check out a potential leak in my water tank. While I was under there I wanted to try and upgrade the slinky type ducts running from my furnace to the floor heat registers to metal residential style heat ducts. I was also wanted to add more floor insulation. The hope in this is to have more efficient heat in the front bedroom and rear bunk room. as it is a long run from the furnace to the floor register in the bunkroom for the slinky duct.

My questions are this. How hard is it to pull the underbelly and then put it back on when finished.

Has anyone changed the floor ducting from the slinky style to the metal pipe style? How was the process did it work?

If no one has done it, is there reason to think it wouldn't work?

Finally, is there room under there to add unsulation under the floor like what you would see in a house?

Thanks.

[chuckster57]

Your biggest hurdle will be routing the duct work as the slinky style goes through the cross members. I have taken down 75% of the underbelly, trick is to start at the attached end and only put in 2 screws before switching to the other side.

[jasin1]

It’s gonna add some weight and I don’t know if you would be happy. You would have to tape all of the connections including the individual spinning sections of adjustable elbows.
It’s a lot to ask for a completely rigid duct system to be pounded down the highway and not break adjustable elbows or other connections.
It would probably have a lot of vibrations transmitted through the floor when the furnace is running also..just my opinion
I would replace any damaged existing ducts or all of them if you choose with a high quality metal foil flex duct and secure all the connections while making the runs as straight as possible and the turn as smooth and long as necessary to avoid kinks.
It would be no fun to replace with all rigid and have a connection break loose and have to pull bottom off of trailer again

[jasin1]

And I would be wary of installing residential insulation in the floor. If you get another leak or road water gets in there it will be soaking and rot the floor out or cause mold

[Frisbeekev]

Originally Posted by jasin1

And I would be wary of installing residential insulation in the floor. If you get another leak or road water gets in there it will be soaking and rot the floor out or cause mold

Great tips. I will look into a more rigid flex line and make smooth runs turns and transitions. As for insulation that is a great point. Maybe some foam insualtion board would work better. Probably better than nothing.

[chuckster57]

Grand Designs uses paper faced insulation in the underbelly of Solitudes. It does soak up water or hydraulic fluid pretty good.

[JRTJH]

Part of the "meandering flexible ducting" is "unintended laziness at the factory" but part of it is also used to deliver radiant heat (leaked through the ducting) around the valves and holding tanks. What looks like a "mess of extra ducting" is really a predictable heat loss in specific areas of the underbelly.

Remember, there's no way a 2" forced air heat duct, routed even "midway in a 30' trailer belly" is going to heat all of that space, especially when you consider the amount of free air entering the space through all those holes in the uninsulated frame rails....

Granted, the factory could do a better job and improved quality of ducting would be more durable, but don't eliminate all of the "meandering" if you're planning to use your trailer in the winter. You may find "extremely cold floors and frozen valves as a result....

As for spun fiberglass insulation. I'd steer far, FAR away from that. Any moisture will soak into the insulation, lay there and mold, create not only a health hazard but also a "rot hazard" that's in an area you won't see, until it's too late.....

If anything, on the newer trailers, Keystone is adding a "mylar faced bubble wrap sheeting between the coroplast and the crossmembers. The space between the rails is 72", I'd consider some 8' wide bubble wrap, lay it in place and extend it up the inside of the frame rails on each side. That would seal many of the frame rail holes (keeping the air through the holes below the actual underbelly space) and improve (reduce) the air infiltration through the underbelly and into the trailer above the floor.

[rhagfo]

Originally Posted by jasin1

It’s gonna add some weight and I don’t know if you would be happy. You would have to tape all of the connections including the individual spinning sections of adjustable elbows.
It’s a lot to ask for a completely rigid duct system to be pounded down the highway and not break adjustable elbows or other connections.
It would probably have a lot of vibrations transmitted through the floor when the furnace is running also..just my opinion
I would replace any damaged existing ducts or all of them if you choose with a high quality metal foil flex duct and secure all the connections while making the runs as straight as possible and the turn as smooth and long as necessary to avoid kinks.
It would be no fun to replace with all rigid and have a connection break loose and have to pull bottom off of trailer again

Well I would think it is entirely doable, and likely worth the effort. Properly screwed together and seams sealed, the smoother runs of rigid ducting would be worth the effort.

As to pulling down and putting the underbelly covering back up, I got sheets of 1/4" corplast and installed, has worked great.

[jasin1]

Originally Posted by rhagfo

Well I would think it is entirely doable, and likely worth the effort. Properly screwed together and seams sealed, the smoother runs of rigid ducting would be worth the effort.

As to pulling down and putting the underbelly covering back up, I got sheets of 1/4" corplast and installed, has worked great.

I think John actually had a good point about heating the underbelly with the residual heat from the path the ducts take ... for me when running ducts for 35 years in homes I wouldn’t have thought of that. ...Rv’s are different that’s for sure
If you decide to use rigid duct I would at least use flexible connectors at the furnace so you don’t transfer vibrations and noise throughout the entire trailer

[Steveo57]

I've dropped the underbelly on mine and cleaned things up in there. It's not a bad job. While you're in there seal up every little hole and opening in the floor and frame. The ducting was pretty well routed. You'd be surprised how well that little 2" duct does keeping things warm. I've put remote thermometers in the underbelly and it warms right up when you turn on the furnace. I added a layer of reflectix on top of the coroplast because mine had nothing.