NT30-K Furnace replacement
My trailer is the 1988 Airstream 25' Excella.
I have just completed the replacement of the NT30-K with the Suburban NT30-SP. The new model fit into the space of the old version very nicely. I did need to enlarge the opening in the inner wall for the furnace housing and cut two holes in the outer skin of the trailer for the intake/exhaust pipes. On the outside, I left the 2 holes (on the right) of the old unit covered with the old plate, for appearance, after plugging those holes. With the furnace in place, I then located the points for the 2 new holes and found that the location of the third hole of the old unit (on the left) was mis-aligned. I used a piece of 1/8" thick aluminum sheet, 6" x 8", to cover that hole, then cut the 2 holes for the new unit. Tools used: Small Dremel hand tool; hand drill; hand held jig saw with fine tooth blade. Used plumber's putty for the exhaust cover plates.
As the propane gas outlet is located on the opposite side of the new furnace, I used a piece of hose (made for propane) to make that connection. The hose is 22" long which assures it will not touch any part of the hot furnace housing. Be sure to test all new gas connections for leaks!
I also had to trim the wood cabinetry a little to permit the heat duct tubes to connect to the furnace duct outlets without undue stress. This is to the right of the furnace, inside that compartment.
I am favorably impressed with the performance of the new furnace: quiet, lots of heat, and starts quickly. I urge you to read the installation instructions very carefully and follow them to the letter!