I am replacing an old oil furnace with a new high efficiency natural gas furnace. The plenum on the oil furnace is 19"x20" and the outlet on the new furnace is only 16"x14". Can I adapt the larger plenum to fit the new furnace and will this be an issue.
Also any ideas on how to adapt the sheet metal plenum would also be helpful.
Yes, you can do this if the plenum is larger than the funace (but not the other way around). The furnace manufacturer may make a transition adapter for the furnace but I suspect you'll need a custome fabricated transition to match up the dimensions exactly.