Patent ID: 8474729

Claim:
A forced draft direct vent type room heater comprising: an outer case, a combustion housing which is provided in the outer case and houses a burner therein, a combustion fan for forced draft direct ventilation, which is provided on the way of any one of an air supply path that supplies air for combustion to the combustion housing and an exhaust path that exhausts a combusted gas from the combustion housing, a main heat exchanger and a supplementary heat exchanger, which are provided in the outer case and are provided on the way of the exhaust path, an air intake and a vent hole which are opened in the outer case, a warm air fan in the outer case for taking in room air from the air intake and sending the air to the inside of the room from the vent hole through a section in which the main heat exchanger and the supplementary heat exchanger are arranged, a drain dish which is provided in the outer case and which makes a drain formed in an exhaust extension tube that is connected to a downstream end of the exhaust path flow into the drain dish itself, and a controller, wherein a first air flow passage that leads to the vent hole in the outer case through a section in which the main heat exchanger is arranged and a second air flow passage that does not pass through the section in which the main heat exchanger is arranged but is led to the vent hole through a section in which the supplementary heat exchanger is arranged are separately formed in the outer case, at least one of a first damper which can freely block the flow of the room air flowing into the first air flow passage due to the warm air fan and a second damper which can freely block the flow of the room air flowing into the second air flow passage due to the warm air fan is provided, and the controller is configured to detect a weak combustion period and to control the at least one of the first damper and the second damper to block the room air from flowing into the first air flow passage or the second air flow passage when the weak combustion period is detected, the weak combustion period being a period wherein a combustion amount of the burner is a predetermined amount or less.