I Have Two Furnaces And Would Like To Know If I Can Connect One Furnace To The Other To Draw Heat From Front Of Building To The Rear Furnace By Using Fan Switch Only. The Front Area Is A Great Room Heated Primarily By A Wood Fireplace. I Want To Take The Heat From The Front Area And Deliever It To The Rear Area Of The House. I Would Like To Know If I Can Use A Duct Run From One Cold Air Return To The Other Cold Air Return And Use The Fan Switch Only On Both To Circulate Warm Air From The Front To The Rear Of House. Any Input Would Be Greatly Appreciated.

Sure you can. All you are going to be using is the blower as a air handler.

You can pick up air from the return in the front of the house by the furnace in the rear of the house by connecting a duct between the two returns but the rear furnace will suck air from the grill closest to it, because it would provide less resistance to air flow, if you block off part of the rear return air grill this will cause the rear furnace to pull more air from the front, but you would not want to run both furnaces with the partial blockage of the rear return grill, this would starve one or both for proper air flow and cause an overheating condition. Good luck, Mike

Be careful if one blower is running pulling air from the other it can get the blower wheel spinning backwards from the one not running, if it tries to kick on while doing this it will give the motor high starting amps or it may start but run backwards.