Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
You should look at these plots of data during the design days. Set Run Simulation for Sizing Periods to Yes if not already set.
SimulationControl, Yes, !- Do Zone Sizing Calculation Yes, !- Do System Sizing Calculation Yes, !- Do Plant Sizing Calculation No, !- Run Simulation for Sizing Periods Yes, !- Run Simulation for Weather File Run Periods
Check the averaging window used for sizing. If you leave this field blank the averaging window will equal 15 minutes. Try using 4 time steps in the averaging window to dampen peak loads.
Timestep, 4; (15 minutes)
Sizing:Parameters, 1.25, !- Heating Sizing Factor 1.15, !- Cooling Sizing Factor ; !- Timesteps in Averaging Window
1.18.5.1.3 Field: Timesteps in Averaging Window The number of load timesteps in the zone design flow sequence averaging window. The default is 1, in which case the calculated zone design flow rates are averaged over the load timestep. The zone design air flow rate calculation is performed assuming a potentially infinite supply of heating or cooling air at a fixed temperature. Thus the calculated design air flow rate will always be able to meet any load or change in load no matter how large or abrupt. In reality air flow rates are limited by duct sizes and fan capacities. The idealized zone design flow calculation may result in unrealistically large flow rates, especially if the user is performing the sizing calculations using thermostat schedules with night setup or setback. The calculated zone design flow rates are always averaged over the load timestep. The user may want to perform a broader average to mitigate the effect of thermostat setup and setback and prevent the warm up or cool down flow rates from dominating the design flow rate calculation. Specifying the width of the averaging window allows the user to do this. For example, if the load calculation timestep is 15 minutes and the user specifies the Timesteps in Averaging Window to be 4, the zone design air flows will be averaged over a time period of 1 hour. Specifying 8 would result in averaging over a 2 hour period.
| | 2 | No.2 Revision |
You should look at these plots of data during the design days. Set Run Simulation for Sizing Periods to Yes if not already set.
Check the averaging window used for sizing. If you leave this field blank the averaging window will equal 15 minutes. Try using 4 time steps in the averaging window to dampen peak loads.
1.18.5.1.3 Field: Timesteps in Averaging Window The number of load timesteps in the zone design flow sequence averaging window. The default is 1, in which case the calculated zone design flow rates are averaged over the load timestep. The zone design air flow rate calculation is performed assuming a potentially infinite supply of heating or cooling air at a fixed temperature. Thus the calculated design air flow rate will always be able to meet any load or change in load no matter how large or abrupt. In reality air flow rates are limited by duct sizes and fan capacities. The idealized zone design flow calculation may result in unrealistically large flow rates, especially if the user is performing the sizing calculations using thermostat schedules with night setup or setback. The calculated zone design flow rates are always averaged over the load timestep. The user may want to perform a broader average to mitigate the effect of thermostat setup and setback and prevent the warm up or cool down flow rates from dominating the design flow rate calculation. Specifying the width of the averaging window allows the user to do this. For example, if the load calculation timestep is 15 minutes and the user specifies the Timesteps in Averaging Window to be 4, the zone design air flows will be averaged over a time period of 1 hour. Specifying 8 would result in averaging over a 2 hour period.
