The board had a current fault code of five flashes burner failed to light exceeded maximum number. stored fault code was 10 flashes pressure switch open five times during one heat demand. I could hear water in the combustion motor flue on fire up. It sounded like a bong. I found the drain for the flue was pinched under the connector box, and the drain was not angled properly. I remedied the pinch and drain angle and test of the unit repeatedly to duplicate a fault. The unit did not fault, the units operating properly The 2 inch flue is angled slightly downhill. If this problem reoccurs the 2 inch flu will need a section replaced.