Dometic furnace combustion air

[Defulmmt]

After reviewing the diesel and propex installations I started wondering where the combustion air comes from on my 2021 dometic heater. I have a direct vent propane heater in my shop and the combustion air shares an engineered vent with the exhaust. I don’t think that the Dometic has that design.

Does the combustion air come from the cabin interior?

 

[veryactivelife]

Yes it does.

Well shame on me, I jumped a little too fast on this one. The combustion air intake is from the outside, I stand corrected. Sorry folk.

Dean

 

[Vic Harder]

Yes it does.

Whoa, I did not know that. On Propex furnaces the combustion air comes from outside.

 

[craig333]

This is pretty interesting. I have the Suburban furnace. It also takes in outside air.

Suburban furnaces installed in recreational vehicles are classified as Direct Vent Sealed Combustion Furnaces. A forced draft furnace utilizes a sealed combustion chamber which is vented to the outside atmosphere. The intake air for combustion is also taken from outdoors and is completely isolated from the room air. A motor is used to drive an impeller wheel to draw intake air into the chamber to support combustion and force the exhaust gases through the furnace chamber to the outside atmosphere. A second impeller wheel (driven by the same motor yet totally isolated from the combustion air) is used to circulate room air across the furnace chamber where it is heated. The blower then forces the hot air into the living area either through a duct system or through a front grille on the furnace cabinet on direct discharge models.

If the dometic units are using inside air it would certainly explain why I get different results.

 

[veryactivelife]

Whoa, I did not know that. On Propex furnaces the combustion air comes from outside.

I just edited my comment. combustion air on the Atwood/Dometic furnace does come from the outside.

 

[ski3pin]

I just edited my comment. combustion air on the Atwood/Dometic furnace does come from the outside.

Bingo. Thanks for the correction.

 

[Defulmmt]

I don’t understand how the Dometic accomplishes this. I’ve read the installation and operating manuals and they do not refer to combustion air intake. The manuals diagrams don’t identify any intake combustion venting and the only apparent venting is the exhaust vent. Is this vent engineered such that it also supports combustion intake?

 

[Jon R]

The outer part of this concentric air vent pulls in the combustion air. The center vent is the hot exhaust.

 

[ski3pin]

The outer part of this concentric air vent pulls in the combustion air. The center vent is the hot exhaust.

correct.

 

[Defulmmt]

Thanks, I just took it apart, cleaned the exhaust tube and reassembled. I looked inside the chamber that houses the exhaust tube and noted there is an impeller in the ceiling of that housing, for the intake combustion air?

I’ve had my issues with the Dometic, but this is an advantage over routing exhaust and intake combustion pipes.