vertical runs. The vent configuration
in Figure 3 was shown to us by a
A Failing-Furnace Mystery
by J.D. Ned Nisson
A very high-efficiency condensing
furnace was installed in the basement
of a single-story house. The two-inch
PVC flue pipe was run up into the
attic, horizontally about 15 feet, then
up and out through the roof.
When the furnace was fired up, it
ran for a while but then shut down.
After a period of time it could be
fired up again, but then would shut
down again. The manufacturer, seeking
to avoid a bad reputation for the
appliance, replaced the furnace with a
new unit but the problem persisted.
What was wrong?
The new, high-efficiency, directvent