Troubleshooting unmet hours in OpenStudio

Basic checks:

1. Look at hours unmet per zone table in eplusout.htm file
   • Make sure that the zone with the problem is not a slave zone on a single-zone VAV system.
   • Check your thermostat setpoint schedules for this zone to make sure values are reasonable
2. Check that design days are for the same location as the weather file
   • Open the .osm in a text editor to look at this.
3. Check the tolerance for reporting unmet hours
   • Try 2F and re-run. If tolerance is too tight, you can get false alarms.
4. Check design/sizing temperature for each plant loop.
   • This is found by clicking the dashed line in the center of a plant loop.
5. Check the operational temperature in the plant loop's setpoint manager.
   • It should match up with the design/sizing temperature for that loop.
   • If you size the loop for 180F water but tell it to operate at 150F, the equipment won't be big enough during peak times.
6. Check design/sizing heating and cooling supply air temperatures for air loop.
   • This is found by clicking the dashed line in the center of the air loop.
7. Check the operational temperature in the air loop's setpoint manager.
   • It should match up with the design/sizing temperature for that loop.
   • If you size the loop for 55F supply air but tell it to operate at 60F, the equipment might not be big enough during peak times.
8. Check that sizing design day thermostat is using a constant setpoint schedule with no setback.
   • This is a 90.1 requirement. If your design day has a setback, your system will be oversized in an attempt to be able to go from setback to setup in a single timestep.
   • Equipment that is significantly oversized might not operate properly at low load conditions.

More detailed checks:

Use the BCL Measure "Add Output Variable" to request timeseries data and inspect these data in ResultsViewer to see what's going on.

1. Examine the zone temperatures and their thermostat setpoints
   • See how much the system is missing setpoint by
   • A shoulder time when transitioning between setback and setup is common
   • You might need to schedule your HVAC on a bit earlier to overcome this
2. Examine the unmet hours per zone
   • See what times of day/year the unmet hours occur
3. Check sizing factor (safety factor) in model.
   • This is found on the Simulation Setting tab

Other resources:

• IES VE has a very good guide that conceptually holds true for most simulation engines.
• Trane has a guide for Trace 700.

Troubleshooting unmet hours in OpenStudio

Basic checks:

1. Look at hours unmet per zone table in eplusout.htm file file

   • Make sure that the zone with the problem is not a slave zone on a single-zone VAV system.

   • Check your thermostat setpoint schedules for this zone to make sure values are reasonablezone

2. Check that design days are for the same location as the weather file file

   • Open the .osm in a text editor to look at this.

3. Check the tolerance for reporting unmet hours hours

   • Try 2F and re-run. If tolerance is too tight, you can get false alarms.

4. Check design/sizing temperature for each plant loop.

   • This is found by clicking the dashed line in the center of a plant loop.

6. Check the operational temperature in the plant loop's setpoint manager.

   • It should match up with the design/sizing temperature for that loop.
   • If you size the loop for 180F water but tell it to operate at 150F, the equipment won't be big enough during peak times.
7. Check design/sizing heating and cooling supply air temperatures for air loop.
   • This is found by clicking the dashed line in the center of the air loop.
8. Check the operational temperature in the air loop's setpoint manager.
   • It should match up with the design/sizing temperature for that loop.
   • loop. If you size the loop for 55F supply air but tell it to operate at 60F, the equipment might not be big enough during peak times.
9. Check that sizing design day thermostat is using a constant setpoint schedule with no setback.
   setback.
   • This is a 90.1 requirement. If your design day has a setback, your system will be oversized in an attempt to be able to go from setback to setup in a single timestep.
   • Equipment that is significantly oversized might not operate properly at low load conditions.

More detailed checks:

Use the BCL Measure "Add Output Variable" to request timeseries data and inspect these data in ResultsViewer to see what's going on.

1. Examine the zone temperatures and their thermostat setpoints setpoints

   • See how much the system is missing setpoint by
   • A shoulder time when transitioning between setback and setup is common
   • You might need to schedule your HVAC on a bit earlier to overcome this

2. Examine the unmet hours per zone zone

   • See what times of day/year the unmet hours occur

3. Check sizing factor (safety factor) in model. model.

   • This is found on the Simulation Setting tab