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Old 12-15-2019, 09:03 AM   #1
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Furnace Cold Air Return

In reviewing the installation manual on the airstream furnace, I noticed the requirements for 1/2 inch clearance from all materials and basic balancing of hot air exhaust. There is also a requirement for the use of only 4 inch duct work. The cold air return is not addressed; is this because the furnace is a sealed unit?
Additionally, has anyone ever successfully used 4 inch louver controlled exhaust at the end of the duct run?
The furnace is in a flying cloud 27 front bedroom.
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Old 12-15-2019, 10:44 AM   #2
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In my opinion, you don't want to restrict the air flow with louvers as the furnace might overheat. The flame is producing a constant amount of heat that must be carried away by the air flow to avoid damaging the furnace (or worse, starting a fire).

Al
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Old 12-15-2019, 12:41 PM   #3
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Quote:
Originally Posted by Al and Missy View Post
In my opinion, you don't want to restrict the air flow with louvers as the furnace might overheat. The flame is producing a constant amount of heat that must be carried away by the air flow to avoid damaging the furnace (or worse, starting a fire).

Al


I donít see the rational of two runs of duct ... one blows 75% of the heat under the dinette table and the remaining run is furthest to delivery and barely has an air flow.
There are no obvious obstructions ... in a forced air environment such as a home there would be duct balancing using louvers or in line duct work louver.
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Old 12-16-2019, 03:45 PM   #4
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Lots of posts on this if you use the search function. Here is one I just found with Airforums Search. http://www.airforums.com/forums/f44/...ow-162159.html

The solutions are not necessarily as straight forward as one might think.
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Old 12-16-2019, 04:20 PM   #5
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If your 27FB is like my 2013 25FB, the cold air return has no duct, it just sucks air in from the interior of the trailer through the arch-shaped opening in the streetside bench.


My furnace pumps air out through four ducts: to the dinette, to the closet/hallway area, to the bedroom, and into the floor through a hole right next to the furnace. One of the ducts going forward has a tee that feeds a smaller flex hose that runs across to the bathroom.
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Old 12-16-2019, 04:32 PM   #6
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On my 2014 25' rear bedroom twin, the furnace pumps most of the heat to the dinette as that is closest to the furnace. I blocked off about half of that vent to push more heat to the rear of the trailer. It seems to work well with no problems for 5 years.
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Old 12-16-2019, 05:53 PM   #7
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Quote:
Originally Posted by Al and Missy
In my opinion, you don't want to restrict the air flow with louvers as the furnace might overheat. The flame is producing a constant amount of heat that must be carried away by the air flow to avoid damaging the furnace (or worse, starting a fire).

Al




Quote:
Originally Posted by Cispook View Post
I donít see the rational of two runs of duct ... one blows 75% of the heat under the dinette table and the remaining run is furthest to delivery and barely has an air flow.
There are no obvious obstructions ... in a forced air environment such as a home there would be duct balancing using louvers or in line duct work louver.
I mentioned louvers because OP asked bout using a louvered vent at the end of a duct run. I think one would have to be careful to ensure adequate air flow.

Al
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Old 12-17-2019, 07:33 PM   #8
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Lots to consider. I had read numerous links on the issue.
IMHO the bigger issue is the placement of the furnace in the FB model. In a perfect set up the furnace would be centered in the AS thereby ensuring a better balance of heat distribution.
When I take on my remind next year Iíll have a better understanding of the approach I will take in furnace ductwork and flow.
Much appreciative of the input.
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Old 12-17-2019, 07:54 PM   #9
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The furnace must have the prescribed exit ducts as listed in the manual. Pretty sure yours is four 4" ducts. I ran a fifth to the rear of the trailer and added a register which closes one of the two in the living room. A much better balance.
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Old 12-17-2019, 08:44 PM   #10
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Search for a thread called, "not enough heat in the back" for a thorough discussion.
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Old 12-18-2019, 06:04 AM   #11
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Quote:
Originally Posted by dznf0g View Post
Search for a thread called, "not enough heat in the back" for a thorough discussion.


Thanks
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