wording from current production cheapo unit warranty document, says nothing about subsequent owners.
That applies to these modern furnaces. You'll notice the OP has a 25 year old G20.
I work for the largest Lennox dealer in North America, I can tell you that Lennox has changed the terms if the warranty on the G20. They're not putting through HX warranty claims for homeowners who are not the original owner anymore.
The warranty certificate for the G20 doesn't say anything about subsequent owners, as the warranty contract is between Lennox and the original purchaser.
Will a pro then be able to conclusively confirm if they are cracks then? I actually have insurance through my utility company. Maybe I should just have the utility company come out and check... They will cover replacement of the part or just pay me a max amount if the cost is too high for repair. Any thoughts for best way to go about this?
read the policy from your utility company, the one in my area does not cover HX.
it is their "easy out", first thing they look at on service call is the HX. if its cracked they just red tag it and shut it off. they don't have to fix it then.