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My case might help someone. I got the error "negative coil bypass factor calculated" when I hardsized Gross Rated Total Cooling Capacity but forgot to hardsize Rated Air Flow Rate. The cooling capacity and the air flow rate of DX coils should be both autosized or both hardsized.

   ** Warning ** Sizing: Coil:Cooling:DX:VariableRefrigerantFlow "33F_PLANT_ROOM_5 VRF COOLING COIL": Rated air volume flow rate per watt of rated total cooling capacity is out of range.
   **   ~~~   ** Min Rated Vol Flow Per Watt=[4.027E-005], Rated Vol Flow Per Watt=[1.648E-005], Max Rated Vol Flow Per Watt=[6.041E-005]. See Input Output Reference Manual for valid range.
   ** Severe  ** Coil:Cooling:DX:VariableRefrigerantFlow "33F_PLANT_ROOM_5 VRF COOLING COIL" -- negative coil bypass factor calculated.
   **   ~~~   **  Environment=WUHAN ANN CLG 1% CONDNS WB=>MDB, at Simulation time=07/21 24:00 - 24:10
   **  Fatal  ** Coil:Cooling:DX:VariableRefrigerantFlow "33F_PLANT_ROOM_5 VRF COOLING COIL" Errors found in calculating coil bypass factors
   ...Summary of Errors that led to program termination:
   ..... Reference severe error count=105
   ..... Last severe error=Coil:Cooling:DX:VariableRefrigerantFlow "33F_PLANT_ROOM_5 VRF COOLING COIL" -- negative coil bypass factor calculated.
   ************* Warning:  Node connection errors not checked - most system input has not been read (see previous warning).
   ************* Fatal error -- final processing.  Program exited before simulations began.  See previous error messages.