Air Return for LP Furnace

[KirbyRVA]

Thanks for the suggestions! I have sent this over to one of our production/customer service reps and here was what he sent me:

"I understand his concern with the cooling system as it is drawing air from the ceiling so you will get air back through the return to the furnace, but to compare the system to a home system is not a far comparison as in a home the heating and cooling are using the some fan and they also have the advantage of using a ducted return right back to the furnace and are able to pull air from each room that they are returning heat to and this allows the system to heat more efficiently by pulling and returning to the same space with the ducted returns. In our set up the turn on the furnaces are not ducted so we have to allow air to return to the furnace by creating openings at the bottom of the steps, cabinets and pantry areas. The basement area where the furnace is located does heat up rather quickly as the furnace get rather hot and also the radiant heat from the flex ducting is also a reason we need these opening to allow the furnace to not over heat. The pantry is right there and if we were to use this as the only area to return air we have to consider that if the pantry door is closed there would be less air that would get to the furnace."

Megan, thanks for this explanation. Let me acknowledge some flaws in the reasoning. First, the Suburban furnace has a limit switch that serves to prevent overheating of the furnace. If that switch becomes defective, it will not allow the burner to light so it is truly an overheating fail safe.
Secondly, in my 384GK, even with the opening under the steps, the furnace has to eventually suck its return air under the closed pantry door and through the small space under the box in the bottom of the pantry. So, the current design restricts return air when the panty door is closed (which it is most of the time) even with the opening under the steps.

Finally, based on my temperature measurements of the air coming into the living area from under the steps, the amount of heat produced in the basement area (even with the small duct opening and any heat radiating from the furnace and the ductwork) is still much cooler than the desired living area temperature.

I believe a better solution in this floor plan would be to create a larger opening in the face of that box in the pantry (install a grill that can be closed during cooling season) and a similar opening with grill in the bottom of the pantry door. Close the space under the steps and allow both the heating cooling systems to more adequately heat/cool the coach.