1#feinet2001! F- h1 U8 n, v7 R7 W) D( x+ o
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option 1: Two seperated furnances and seperated control ' M: I& [# Z R0 M5 A (for big house > 3000 ft)2 u8 ~/ k9 W% t
option 2: One furnance with Zone Control device , v! t0 Y9 W' D( T! Y% p (three zones or fours zone will be good) - total efficiency will be higher 9 P1 k) l/ y# i$ @, m9 l0 Y/ V4 j+ b/ f. ]1 {, j) @( W+ |# s5 C N
Total cost is not big difference.