Abstract: A radiant wall oven with a heating chamber and hot air chamber separated by a radiant wall, an air heating chamber, supply and return ducts between the air heating chamber and hot air chamber and blower means for circulating hot air through the ducts is provided with a radiant wall temperature control comprising two cascaded closed loop controls. The first compares the radiant wall temperature with a first setpoint value to generate the difference as a second setpoint value for the second, which compares the temperature of the supply duct with the second setpoint value to control a heat source such as a burner. Under certain conditions, the air heating chamber is vented to atmosphere.

Abstract: A direct gas-fired heating and ventilating system for industrial and commercial buildings and the like comprises a direct gas-fired burner, fresh air dampers, fresh air bypass dampers and recirculation dampers.