CondenserLoop Coincident sizing is larger than NonCoincident sizing
My model is the same as this post, but let me post a different question.
I have a problem with Coincident
plant sizing for CondenserLoop. I tried both Coincident
sizing and NonCoincident
sizing, but the weird thing is that the autosized condenser loop (Cooling towers and condenser water pumps) by Coincident
sizing is much larger than that by NonCoincident
sizing. It does not happen in PlantLoop (chillers and chilled water pumps). I think my Coincident
sizing settings are appropriate.
Below are the sizing results of cooling towers. Autosized condenser water flow rate by Coincndent
sizing is 0.164097m3/s, which is more than 2 times larger than the autosized condenser water flow rate of 0.072678m3/s by NonCoincident
sizing. Does anyone know why?
I think the "Initial" values in the html file are the correct ones which are autosized by Coincident
sizing. The "Design" values are incorrect. However, this is not just a reporting issue. I also ran annual simulations. The pump end use with Coincident
sizing became much larger than that with NonCoincident
sizing NonCoincident
sizing. EnergyPlus uses the "Design" values.
Is this a bug? Or am I missing something? My settings related to Coincident
sizing are as follows. Any suggestions would be appreciated.
SimulationControl,
Yes, !- Do Zone Sizing Calculation
Yes, !- Do System Sizing Calculation
Yes, !- Do Plant Sizing Calculation
Yes, !- Run Simulation for Sizing Periods
No, !- Run Simulation for Weather File Run Periods
Yes, !- Do HVAC Sizing Simulation for Sizing Periods
1; !- Maximum Number of HVAC Sizing Simulation Passes
Sizing:Parameters,
1.25, !- Heating Sizing Factor
1.15; !- Cooling Sizing Factor
Sizing:System,
VAV_3, !- AirLoop Name
Sensible, !- Type of Load to Size On
autosize, !- Design Outdoor Air Flow Rate {m3/s}
autosize, !- Central Heating Maximum System Air Flow Ratio
30, !- Preheat Design Temperature {C}
0.0033, !- Preheat Design Humidity Ratio {kgWater/kgDryAir}
11, !- Precool Design Temperature {C}
0.008, !- Precool Design Humidity Ratio {kgWater/kgDryAir}
15, !- Central Cooling Design Supply Air Temperature {C}
22, !- Central Heating Design Supply Air Temperature {C}
Coincident, !- Type of Zone Sum to Use
No, !- 100% Outdoor Air in Cooling
No, !- 100% Outdoor Air in Heating
0.008, !- Central Cooling Design Supply Air Humidity Ratio {kgWater/kgDryAir}
0.008, !- Central Heating Design Supply Air Humidity Ratio {kgWater/kgDryAir}
DesignDay, !- Cooling Supply Air Flow Rate Method
0, !- Cooling Supply Air Flow Rate {m3/s}
, !- Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}
, !- Cooling Fraction of Autosized Cooling Supply Air Flow Rate
, !- Cooling Supply Air Flow Rate Per Unit Cooling Capacity {m3/s-W}
DesignDay, !- Heating Supply Air Flow Rate Method
0, !- Heating Supply Air Flow Rate {m3/s}
, !- Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}
, !- Heating Fraction of Autosized Heating Supply Air Flow Rate
, !- Heating Fraction of Autosized Cooling Supply Air Flow Rate
, !- Heating Supply Air Flow Rate Per Unit Heating Capacity {m3/s-W}
ZoneSum, !- System Outdoor Air Method
1.0, !- Zone Maximum Outdoor Air Fraction {dimensionless}
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity ...
I tried changing
Maximum Number of HVAC Sizing Simulation Passes
from 1 to 2, 3, 4 and 5, but the results did not change at all.