Suburban NT-22 Furnace
The special thing about an RV furnace is the sealed
combustion chamber. In other words, the
air that feeds the flame comes from the outside as opposed to the cabin’s
interior, and the burned fuel gas is exhausted outside. Due to the compactness of the design, a
dedicated fan blade blows air through the combustion chamber. This forced air also minimizes hot spots, and
increases thermal efficiency. Cabin air
is warmed by another fan blade blowing air across the outside of the heat
exchanger. One motor spins both fan
blades.
Furnaces in 1967 were incredibly simple compared to
modern day furnaces. Only two
relatively simple repairs were necessary to bring my furnace back online: Cleaning the pilot light jet, and addressing
an old recall notice:
From the Internet:
Suburban initiated a recall for all furnaces made from 1966 through 1977: Campaign : 77E-012 initiated summer of 77 Campaign : 81E-015 initiated winter 81-82 The
furnaces were models NT-17, NT-20, NT-22 and NT-30 manufactured between 1966
& 1970 The serial numbers were 0064881 and lower. Also furnaces made between 1970 & 1977
except those with an "M" suffix, The serial numbers are: 0064881
through 0715865. The recall
specifies:" if the model and serial number of your furnace falls within
those noted, have it inspected unless you are VERY SURE the Suburban recall
has already been completed on your unit.
The furnaces in question have a rubber-like crossover tube that could
crack. Extremely dangerous carbon monoxide
would then be expelled into the interior.” |
The first interesting thing about this recall is that
I never found a serial number on either my original, 1967 NT-22, or the 1972
NT-22 parts furnace a friend gave me.
But, after inspection, I found my furnace would have been subject to the
recall. The parts furnace would not
have been:
I do not know if Suburban relocated the combustion
chamber blower just so they could incorporated a metal crossover tube. But that is one of many subtle differences
between the two units pictured above.
The second interesting thing was crossover tube’s
function. The tube directs outside air
from the blower into the combustion chamber.
A leaky tube would only allow cold outside air to be forced into the
interior. I suppose if the tube split
& fell off, there could be a concern about not enough air feeding the
flame. The furnace would probably get
hot enough to trip the over-temp sensor.
But the tube has such a short run (2-3 inches), that even then I am not sure
there would be a concern.