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# Revision history [back]

That equation is a correct representation of the zone heat balance. All of the components of the heat balance are available as Output:Variables. My guess is that dividing the zone into two parts has changed the timing of when transmitted solar gains become a load. Start with these outputs for the two cases, and then you can add more detail once you know what area to focus on:

Output:Variable,*,Zone Air Heat Balance Internal Convective Heat Gain Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Surface Convection Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Interzone Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Outdoor Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance System Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance System Convective Heat Gain Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Air Energy Storage Rate,hourly; !- HVAC Average [W]


Also, try a case with a winter design day with no solar and constant temperature and see if the loads agree.

That equation is a correct representation of the zone heat balance. All of the components of the heat balance are available as Output:Variables. My guess is that dividing the zone into two parts has changed the timing of when transmitted solar gains become a load. Start with these outputs for the two cases, and then you can add more detail once you know what area to focus on:

Output:Variable,*,Zone Air Heat Balance Internal Convective Heat Gain Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Surface Convection Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Interzone Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Outdoor Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance System Air Transfer Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance System Convective Heat Gain Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Zone Air Heat Balance Air Energy Storage Rate,hourly; !- HVAC Average [W]


Also, try a case with a winter design day with no solar and constant temperature and see if the loads agree.

4. The bottom floor (Surface 21) has an outside boundary condition of "Ground". There is no Site:GroundTemperature:BuildingSurface object, so the default temperatures of 18C are applied to the outside of this surface. So, this surface has a very different temperature dynamic that the rest of the surfaces. Changed this to be adiabatic. With this (and all of the above changes), the loads are now 5.17 for the single-zone case, and 5.37 for the two-zone case.