Abstract: 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.

Abstract: An air-conditioning system has an air-conditioning unit and a controller which includes a timer setting unit for establishing data including at least one time zone in the time of one day and an operation status in the time zone for the air-conditioning unit. The controller also has a memory for storing the data established by the timer setting means, and operation control unit for controlling operation of the air-conditioning unit according to the data stored by the memory. The timer setting unit includes a first setting unit for establishing the data altogether for all days of the week, a second setting unit for establishing the data for a plurality of groups divided from the days of the week, and a third setting unit for establishing the data individually for the days of the week. The first, second, and third setting units are selected by the timer setting unit to establish the data. Each time new data is established by either one of the first, second, and third setting units.

Abstract: A space heater for heating air from within a room with a heat exchanger connected to a burner and discharging heated air into the room has a room temperature sensor for detecting a room temperature and a controller for controlling the burner with a freeze prevention temperature set to prevent indoor facilities from being frozen. When the detected room temperature drops to or below the freeze prevention temperature, the controller operates the burner and controls the burner with a lower limit for an amount of heat in the burner with which no moisture condensation occurs in the heat exchanger.