Three inefficient atmospheric gas fired unit heaters supply heat to the bay areas. When the gravity vented unit heaters are not running, conditioned air continuously leaves the building through the heater’s flue. These units suffer major standby losses from the draft hood and gravity vent.
Condensing unit heaters use outside air and employ a secondary heat exchanger to capture the latent heat of the water vapor in the exhaust system, and have seasonal efficiencies around 90% or greater. Condensing unit heaters also include an electronic intermittent ignition device (IID) and a draft inducer motor with sealed exhaust, almost eliminating standby losses.