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option 1: Two seperated furnances and seperated control * y$ l" m5 q% E (for big house > 3000 ft) 4 d$ O* I* M& ~" yoption 2: One furnance with Zone Control device p1 ]3 Z# t" T+ a# x1 l, _9 v (three zones or fours zone will be good) - total efficiency will be higher g# j6 ], k: R$ b3 T; k- ^" ]
: Y- G9 E% b- y! U, {! UTotal cost is not big difference.