Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
It depends on what load scenario you want to calculate. I think the usual meaning of a design day "load calculation" is to evaluate the load imposed by the design day's weather conditions. In that case the schedules for the design day should not include night setup or setback but be flat throughout the day and night. The schedules can be defined separately between the design periods and the regular run period so you can have it both ways.
Calculating the loads imposed by recovery from setback or setup is not a completely unreasonable thing to do, but the problem is under-defined unless also given a timeframe for how long the recovery is expected to take. For example if the HVAC operation schedule starts up a half hour before the occupancy schedule picks up, then a half hour averaging window might be appropriate. The longer the averaging window the more likely the system won't be oversized and it seems that an hour usually works out okay.
| | 2 | No.2 Revision |
It depends on what load scenario you want to calculate. I think the usual meaning of a design day "load calculation" is to evaluate the load imposed by the design day's weather conditions. In that case the thermostat schedules for the design day should not include night setup or setback but be flat throughout the day and night. The schedules can be defined separately between the design periods and the regular run period so you can have it both ways.
Calculating the loads imposed by recovery from setback or setup is not a completely unreasonable thing to do, but the problem is under-defined unless also given a timeframe for how long the recovery is expected to take. For example if the HVAC operation schedule starts up a half hour before the occupancy schedule picks up, then a half hour averaging window might be appropriate. The longer the averaging window the more likely the system won't be oversized and it seems that an hour usually works out okay.
