1#feinet2001: U& i2 Z0 f# C4 r" P! I
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option 1: Two seperated furnances and seperated control8 S2 q, j( {! I5 h& A5 Q' Z
(for big house > 3000 ft)* m$ ]( D; d9 i
option 2: One furnance with Zone Control device " T6 \ q2 u0 S' n (three zones or fours zone will be good) - total efficiency will be higher 6 m; }4 X; i0 X6 Y 2 F# q2 c- S5 X8 L: WTotal cost is not big difference.