> We have propane so I
> don't recall what
> the 'wrong' fuel was
Probably natural gas. It is normally used at a lower pressure than
propane/LPG, and so requires a larger orifice.
You've already gotten good suggestions on what to look for; only thing I can
add is anything that would keep the chimney from 'drawing' properly. Maybe
a bird's nest inside or possibly it was built wrong in the first place. If
you can't find anything else, Google for "chimney draft problems" and read
through a few articles.
'Normally' natural gas or propane/LPG is mixed with air first, and the
resulting blue flame is sootless. But a fireplace burner needs to produce
some soot to produce pretty yellow flames (the yellow is from the carbon
particles glowing), so it's important that the chimney suck them away.
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