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Lennox Pulse Furnaces

Posted by Charles Rue on December 28th, 2002 06:31 PM
In reply to Pulse by David Keim on December 14th, 2002 02:01 PM [Go to top of thread]

1 of 3 people found this post helpful

I had the leaking heat exchanger syndrome on my
1990 vintage Pulse 21. The leakage on mine was at
the brazed joints on the tubes of the finned
condensing portion (lower section). According to
Lennox, this was due to an incompatible brazing
material/flux which was susceptible to corrosion.
(the joints on mine looked like a corroded flash-
light battery!
Also, the quality of the welds on the entire heat
exchanger (and other furnace parts such as the air
decoupler box)was extremely poor. There were large
blobs of weld slag, spatter, and pieces of painted
-over welding wire stubs. Your comments about the
normal vibration causing leaks are noteworthy in
that the replacement exchanger was beefed-up thru
the addition of stay rods welded across the inside
of the gas-side decoupler section. There was also
a replacement gas pressure valve and spring
assembly installed in the main gas valve which
resulted in much quieter operation (and presumably
lower combustion dynamics and cyclical stresses
on the stainless steel exhanger. Stainless steel
has a strong propensity to work-harden and crack
under vibration and/or thermal stress.

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