Dura-Vent GS for Venting Propane

psd_3

I live in NH and am considering a 40K BTU (propane) direct vent fireplace insert. Every propane/gas stove I've seen, free standing or FP insert, calls for an aluminum gas liner (Dura-Vent GS or equivalent). These units are rated as 72-85% efficient (AFUE) and I would think that condensation in an outside chimney would be a serious issue. For oil/gas fired heating equipment, a stainless liner (AL29-4C) would be surely specified. When I mention stainless as a consideration, the folks in the stove shops look at me like I have two heads and say that the code requires Aluminum. The typical installation uses 2 colinear flex liners (intake and vent) from the stove manifold directly to the chimney top. Any condensation that forms is likely to run back down into the stove and would corrode the manifold. Seems sort of dangerous.

Am I being too cautious? Any experience would be really appreciated.

Dale

87%

AS long as you stay less than 87% you don't condense. There is a safety factor so the non condensing stuff is at 82% or less, I would go with what the fireplace manufacture specifies, following the directions is usually safest. I have never heard of a fireplace insert that had too much effeciency. Typical non condensing stuff uses b vent which of course is aluminum in the center. What you are doing must require a larger annular air space.