During my annual furnace maintenance service a crack was found in the heat exchanger. I was told I MUST replace the furnace, and the technician turned off the gas & removed a section of the supply pipe. In searching for info I found several references to furnaces being "prematurely" replaced as a result of "acceptable" heat exchanger cracks.
This is a 1981 furnace, so I'm resigned to do the replacement, but my curiosity is aroused! I'm near Ottawa in Canada, so a reliable furnace is essential. Still, what constitutes an "acceptable" crack? Who makes the rules for "acceptable", or is this decided by emissions testing in the furnace compartment or at the registers. This particular hairline crack is just above the big openings where air is drawn into the combustion chamber, so I'm doubtful that there is any real risk from THIS crack... but a strong indicator that the rest of the heat exchanger is now suspect.
Thanks for any insight.