I have an american standard freedom 80. The first burner is allowing flames to leak out of the back of the burner which triggers the open high heat device. What is causing this?
Pictures would help.
If this happens before the main blower comes on then...
you are probably talking about the gas backing out of the venturi opening of the burner because of a dirt/scale/rust obstructed burner diffuser.
Turn off the furnace power, remove the burners and wash them out.