Gas and Oil Home Heating Furnaces - Chimney/Furnace sizing

About 10 years ago a new gas furnace (about 78% efficient) was installed in a 30 year old house. Recently a representative from a hearing and cooling company told me that at the time the new furnance was installed a metal chimney liner should also have been installed. I was told the new furnace was much more efficient than the old one thus the fire brick would not heat up sufficiently, during the spring and fall, causing condensation to form on the chimney brick. This condensate (acidic) would run back to the furnace and also carbon monoxide could be retuned to the furnace. I was advised to install a metal chimney liner to resolve these problems. Does the above sound reasonable.

Thanks,

Ron

If the chimney does not go up the outside of the house & it has a ceramic (tile) liner but is otherwise sized properly, you most likely don't have to have a metal liner. A metal liner is preferable but not a "must have" unless the chimney is unlined, goes up the outside of the house, or is way oversized.