Knowledgebase
Changes to heating/cooling setback temperature makes no difference to results
Posted by Andy Tindale on 24-Jan-07 12:35 PM
Heating/cooling setback temperatures can be used to keep occupied spaces conditioned to avoid frost and/or overheating during periods when the building is not occupied. The setpoint and setback temperatures you define on the Activity tab under the Environmental Control header are used together with the heating/cooling schedules set on the HVAC tab to create thermostat schedules for EnergyPlus heating/cooling devices.  When the value of the schedule you select is equal to 0.5, a setback temperature is used, as described in 'Defining setpoint temperature schedules' in the program help. When using 'Schedules' timing model option, Schedule values are interpreted as follows: 
  • 0 - system is off
  • 0.5 - setback setpoint temperature used
  • 1.0 - standard setpoint temperature used

If the heating/cooling schedule you are using to describe the operation of your HVAC system does not have value 0.5 then any setback temperatures you define on the Activity tab will not be used.

Try using one of the standard ASHRAE 'heating/cooling with setback' schedules e.g. 'Office_Heat_Setback' which has a value of 0.5 during unoccupied times... or create your own custom schedules.
 
It is always a good idea to look at hourly results on the Simulation screen to check how and when heating and cooling systems are operating before using daily, monthly or annual results. This will allow you to check that your setback and setpoint temperatures are being maintained.