Originally Posted by
Bob Harper
. May just be an unproven theory that has become urban legend.
I tend to go with the urban legend side of this.
If equipment manufacturers would just install real post purge circuits in their furnaces that ran anywhere from 3-5 minutes after the burner shut down the rusting issues in induced draft equipment would almost disappear.
The rest of the cases in induced draft equipment would normally be taken care of by firing that equipment at it's proper rate.
There are some other factors that go along with atmospheric equipment & those pesky drafthoods.