Marketing InformationCounterflow/horizontal furnaces can be mounted horizontally where height restrictions are para-mount. For instance in a basement crawl space or attic. Most furnaces draw cold air in at the bottom and warm air is released out the top. In certain situations, this is not practical and a counterflow or (downflow) furnace is needed. In a counterflow furnace, cold air is drawn in from the top and warm air is released out the bottom. The OD6 comes with a factory standard PSC blower motor but can be upgraded to the optional ECM blower motor for quieter start up, greater efficiency and more comfortable operation due to infinite fan motor speeds.