I am trying to model an office building with different type of HVAC systems. some of the zones are serving by 2 HVAC system. I believe that till now the system modeling is fine. But I keep getting this error message that I don't know how to fix. It seems that one of the zones is too cold.

What is the cause for this error?

PsyRhoAirFnPbTdbW: RhoAir (Density of Air) is calculated <= 0 [-5.22382]
pb =[100487.00], tdb=[-340.17], w=[1.0000000E-005].
   **   ~~~   **  Routine=CorrectZoneHumRat, During Warmup, Environment=INCH'ON ANN CLG 1% CONDNS DB=>MWB, at Simulation time=08/21 12:10 - 12:20

I am trying to model an office building with different type of HVAC systems. some of the zones are serving by 2 HVAC system. I believe that till now the system modeling is fine. But I keep getting this error message that I don't know how to fix. It seems that one of the zones is too cold. Would you please help!!

What is the cause for this error?

PsyRhoAirFnPbTdbW: RhoAir (Density of Air) is calculated <= 0 [-5.22382]
pb =[100487.00], tdb=[-340.17], w=[1.0000000E-005].
   ** *   ~~~   ** *  Routine=CorrectZoneHumRat, During Warmup, Environment=INCH'ON ANN CLG 1% CONDNS DB=>MWB, at Simulation time=08/21 12:10 - 12:20