Intake and discharge tube closure detector for combustion device of forced intake and discharge type

摘要

An orifice is disposed in an intake tube for developing a pressure difference across the orifice, i.e., portions of the intake tube which are positioned upstream and downstream of the orifice. An upstream connection pipe and a downstream connection pipe have respective ends connected to the intake tube and opening into the intake tube respectively upstream and downstream of the orifice, and respective opposite ends connected to a pressure sensor. The pressure sensor detects the pressure difference between the pressure of combustion air in the upstream connection pipe and the pressure of combustion air in the downstream connection pipe. If a change from a pressure value prior to combustion, which is a pressure value detected by the pressure sensor when the combustion fan is stopped before a burner starts burning a fuel gas, to a pressure value in combustion, which is a pressure value detected by the pressure sensor while the fuel gas is being combusted by the burner, becomes smaller than a threshold value, then the combustion of the fuel gas by the burner is stopped.