In article , MNRebecca wrote:
On Feb 10, 10:43=A0am, "Bob F" wrote:

A couple elbows shouldn't matter unless you have a lot of piping getting =
there.

Like 12 to 14 feet? The furnace is not against an external wall.
It's in an interior room surrounded by a basement addition. The
intake and exhaust pipes run about a dozen feet or so across the
basement ceiling before breaking through an external wall. Still okay
to add some extension and a few elbows outside?

If you're really concerned about that, add an adapter just outside to
transition to the next larger size of pipe, and make the extensions and elbows
in the larger size.