The BULLDOG System’s straightforward design derives maximum efficiency from existing principles. The heating cycle consists of a high efficiency fan drawing air over a simple hot water coil. This is the same mechanism employed by common fan coil units. However, because water loop temperature is scheduled to outdoor air temperature, maximum heat output is available when it is most needed (ie. – when it is coldest outside). As the outdoor air temperature rises, loop water temperatures are lowered providing sufficient heating capability year round while maintaining lowest possible heating costs.