Cameo 36FWS Furnace Return Duct Mod to Improve Airflow

I purchased a 2011 Cameo 36FWS in 2018. I immediately noticed that the airflow out the furnace floor ducts was very weak and it took a long time to heat up the camper. I ended up using the electric fireplace and a space heater in 2019.

Upon looking at the furnace setup it was obvious what the problem was: insufficient cold air return ducting to the furnace. Carriage put the furnace in the basement storage area. There is a return duct from the living area to the basement/storage area, and they attempted to seal it off using insulation. This was woefully ineffective as the furnace would pull air not only from the living area, but from the entire basement and storage areas. The basement area is not sealed very well with openings around the slide mechanism and probably other areas with air leaks. The storage area will leak air through the door seals and other siding and construction joints. With those air leaks the furnace is pulling cold outside air into the basement/storage area, as well as return air from the living area.

The furnace needed a dedicated return duct. I considered 2 options. 1. Build a duct passage from the return grill that is under the steps or 2. Use duct boots and flex ducting from the return grill. Both options need an air box around the furnace. I decided on option 1 as I would have had to order the duct boots. In hindsight, it probably would have been easier to do option 2.

I constructed a box around the furnace. I used aluminum angle attached to the hot furnace box. I built a wood frame for the areas away from the hot furnace box. I used fiberglass aluminized duct board for the walls around the furnace, and plywood for the duct from the grill opening under the stairs. The construction was tricky with a lot of trial and error as the duct had to go around the sewer storage pipe and RV structure. Granted, I am not much of a woodworker so it took a while to design and build. The duct was sealed with metal duct tape, expanding foam, and caulk. I also found much air leakage around the furnace duct boots and the end plate, so I sealed those with metal duct tape.

The result was a significant increase in air flow coming out of the ducts and thus heating was much better. The heating in the basement is probably better also, as now no cold air is being drawn in through the slide drive, door and other leaks.

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[Expired MemberTopics - 40Replies - 107Total - 147]

More pictures.

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[CLOC-AdminKeymaster]

Peter,

Thanks for the Info.  I just was thinking the same thing about the air flow coming out the vents.  Looks like a new project this summer.  Photos very helpful.

B.W.Gentry
Owner/Admin
2007 Carri-Lite XTRM5
Breckenridge, TX

[John LaPlanteParticipantTopics - 0Replies - 11Total - 11]

Wow! Very nice!  I’ve been forever frustrated with our 36FWS furnace performance too. With hookups we rely on the electric fireplace plus an electric space heater in the bedroom.

For dry camping, I went to the trouble of plumbing a blue flame propane heater mounted to the backside of the kitchen counter which faces the living room.  Super efficient!  But you have to be careful to crack windows, etc – can deplete oxygen.

This looks like a good project for me too!  But it is kind of hard to see where the return goes in the photos, I’ll need to open up our storage and have a look

 

[Expired MemberTopics - 40Replies - 107Total - 147]

Here is a simple sketch. This is a view from the front looking toward the back of the RV. The is not to scale and is missing some features that you will have to figure out as you do the build. I will do the other two views (side-view, top-view) later. Hope this helps.

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[Expired MemberTopics - 40Replies - 107Total - 147]

Here is a view looking down from above. This is a sketch from memory, so many proportions are not correct. Again, the details need to be figured out when you look at your particular setup.

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[expired-memberBlockedTopics - 86Replies - 191Total - 277]

I’ve changed everthing over to 4″ metal ducting and 4″x10″ registers. All 5  registers blast air now.

The bottom of our trailer is insulated with 2″ XPS foam.

The register in the kitchen that was blowing warm into the return air intake was removed.

The return air wasn’t changed to keep the air flow as high as possible and warm air circulating in the basement so the water pipes don’t freeze.

At temps below 20F we insulate along the bottom of the slides with 1/2″ foam.

The best change I made was adding a Propex 2800 furnace. It uses approx 2/3 less power.  Our trip this weekend the first night it was 30F.  The Propex kept the inside at 65F. The next night is was 23F with the Propex running continuously it was 55F inside.

[Expired MemberTopics - 40Replies - 107Total - 147]

Alloy. I found the basement plenty warm after the return duct mod. There is still a lot of heat coming off the flex duct. I assume lots of heat off your metal duct too. ALong with the XPS I would think that basement would stay plenty warm. Do you put foam over the slide rack opening; that would help too?

[expired-memberBlockedTopics - 86Replies - 191Total - 277]

The metal duct and adding new ducts inceases the air flow so the furnace is more efficent.

One of the new ducts runs though the back storage compartment which keeps it warmer.

1/2 foam is fitted around the slide racks also goes along the bottom of the front slide.

 

[rjoney55ParticipantTopics - 2Replies - 4Total - 6]

I would like to know how you were able to access the area with all of the ductwork?

[rjoney55ParticipantTopics - 2Replies - 4Total - 6]

Peter, how did you remove the walls to gain access to the Furnace Lines?

[rjoney55ParticipantTopics - 2Replies - 4Total - 6]

Peter, how did you remove the walls to gain access to the Furnace Lines?

[Expired MemberTopics - 40Replies - 107Total - 147]

rjoney55 wrote:

Peter, how did you remove the walls to gain access to the Furnace Lines?

Sorry for the late reply. The only walls that I needed removal were the thin walls in the big storage compartment tht separate the storage area from the part where the furnace, slide motor, and converter are. Fortunately the compartment is big enough for me to fit inside it.

This is now the 4th year with this mod and it has been great.

[Author]

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