Originally Posted by j54mark
For my own education, could someone who has been there and done that tell me what "modification" is required to replace the furnace in an '88 Airstream? I would have expected that to be an NT30, and a new NT30 is an exact fit. I thought.
Not trying to accuse anyone of anything, just looking to expand my knowledge.
The furnace lives in side a metal housing, which has 2 parts, spot welded together. The upper part is the furnace enclosure. It sits tightly inside a cutout in the inner skin. The lower part is shallow, and the ducts are connected to it.
Furnace replacement requires for the furnace cassette to be slipped out of the housing, and then ultimately housing removal.
The upper part of the housing needs to be separated fro the lower part. ( chisel, or small die grinder, or in my case, both.
Now you have essentially a steel pedestal, 3 in high, with an open front, and ducts connected to the sides.
The new furnace goes on top, and depending on the installation, provisions must be made for the new furnace to discharge air into the old "pedestal" or manifold, if you will. Either by cutting holes in the top, or by creating a duct the will channel the hot air from the furnace into the front of the manifold.
I hope this explanation makes sense. It's obvious once you look at it, but hard for me to explain.
I did not replace my furnace, but removed it due to it being rusted out. I did save the front cover and reinstalled the lower part for future use.
Do not throw these parts away if you remove your furnace. They will be needed to make a new installation easier.